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1
EFFECTS OF OPERATING CONDITIONS
ON A HEAT TRANSFER FLUID AEROSOL
A Thesis
by
PASSAPORN SUKMARG
Submitted to the Office of Graduate Studies ofTexas A&M University
in partial fulfillment of the requirements for the degree of
MASTER OF SCIENCE
August 2000
Major Subject: Chemical Engineering
2
ABSTRACT
Effects of Operating Conditions on a Heat Transfer Fluid Aerosol.
(August 2000)
Passaporn Sukmarg, B. Eng., Khon Kaen University
Chair of Advisory Committee: Dr. Sam Mannan
Heat transfer fluids (HTFs) are extensively used in the chemical process
industry and are available in wide ranges of properties. Aside from their importance,
Factory Mutual Engineering and Research has reported 54 fires and explosions and
$150 million losses due to fires involving HTFs during a recent 10-year period [Febo
and Valiulis, 1995]. The vapors of these fluids are flammable above their flash points
and can cause explosions. To prevent explosions due to loss of vapor, heat transfer
fluids are used as hot liquids at elevated pressures. If loss of containment does occur,
the liquid will leak under pressure and may disperse as a fine aerosol mist.
Though it has been recognized that aerosol mists can explode, very little is
known about their flammability. Therefore, research is critically needed to measure
aerosol properties and the flammability of fluid aerosols. This research is the first part
of a study of heat transfer fluid aerosols. This part of the study focuses on dispersion
and formation of heat transfer fluid aerosols from process leaks. To simulate industrial
leaks, aerosol formation from a plain orifice into ambient air is studied by measuring
liquid drop sizes and size distributions at various distances from an orifice.
Measurements are made over ranges of temperature, pressure and orifice diameters.
Aerosol drop size distributions of a HTF are measured by a non-intrusive
method of analysis using a Malvern Laser Diffraction Particle Analyzer (Malvern laser).
The Malvern laser employs the principle of Fraunhofer diffraction, which is light
scattering. The Malvern does not require any standard to calibrate, but the laser tube
must be aligned frequently to assure that the detector receives the maximum light
3
intensity. The Malvern software converts light intensity information from the detector to
drop size distributions.
HTF used in this research was an alkylated aromatic received from an industrial
source. The measurements were made in the horizontal direction along the center-line
of the HTF spray. The effects of pressure, temperature and orifice size on fluid spray
atomization and aerosol drop size distributions were studied at various distances from
the orifice. Trends of drop size distributions were analyzed with respect to pressures,
temperatures, and orifice sizes. The results of this research will be used in industry to
help predict the behavior of fluid releases from leaks, and the information will improve
the safety of heat transfer fluid handling and process safety design.
4
DEDICATION
To my parents, Yonchoke and Surang Sukmarg, for all their love and support.
5
ACKNOWLEDGEMENTS
I would like to express my sincere gratitude to my advisor Dr. Sam Mannan for
giving me this opportunity to work on such an interesting topic and all his support
during my graduate study. I am grateful to Dr. Ken Kihm for his valuable guidance and
help. I would like to thank Dr. David Ford for serving on my committee and Dr.
William Marlow for initial help. This work would not have been completed without all
the help I received from Dr. William Rogers and Mr. Randy Marek, especially during
the construction of the apparatus. I am also thankful to Kiran Krishna, my wonderful
teammate, for all his help. Finally, I would like to thank my parents, my loving sister,
and all my friends for their support.
6
TABLE OF CONTENTS
Page
ABSTRACT… … … … … … … … … … … … … … … … … … … … … … … … … … … … iii
DEDICATION… … … … … … … … … … … … … … … … … … … … … … … … … … … v
ACKNOWLEDGEMENTS… … … … … … … … … … … … … … … … … … … … … … vi
TABLE OF CONTENTS… … … … … … … … … … … … … … … … … … … … … … … vii
LIST OF TABLES… … … … … … … … … … … … … … … … … … … … … … … … … .. x
LIST OF FIGURES… … … … … … … … … … … … … … … … … … … … … … … … … xi
LIST OF SYMBOLS… … … … … … … … … … … … … … … … … … … … … … … … .. xiv
LIST OF ABBREVIATIONS… … … … … … … … … … … … … … … … … … … … … . xvi
CHAPTER
I INTRODUCTION… … … … … … … … … … … … … … … … … … … … .. 1
Aerosol Formation… … … … … … … … … … … … … … … … … … … … . 2Static DropFormation… … … … … … … … … … … … … … … … ........................ 3Breakup of a Drop… … … … … … … … … … … … … … … … … … ..................... 3Drop Breakup in Flowing Air… … … … … … … … … … … … … ........................ 4Spray Breakup Regime… … … … … … … … … … … … … … … … ...................... 6Characteristics of Atomization for a Plain.Orifice… … … … … … … ................ 10Droplet Size Models… … … … … … … … … … … … … … … … … .................... 11
Literature Review… … … … … … … … … … … … … … … … … … … … ... 12
II EXPERIMENTAL METHODOLOGY… … … … … … … … … … … … . 15
Experimental Arrangement.… … … … … … … … … … … … … … … … ... 15Apparatus… … … … … … … … … … … … … … … … … … … … … … … ... 15
Fluid Cell… … … … … … … … … … … … … … … … … … … … … ....................... 16Positioning System… … … … … … … … … … … … … … … … … … .................... 18Exhaust System… … … … … … … … … … … … … … … … … … … ..................... 19Camera and Micro-flash… … … … … … … … … … … … … … … … .................... 19Malvern Laser Diffraction Particle Analyzer......… … … … … … ...................... 20
Experimental Procedure and Measurement… … ....… … … … … … … ... 28Calibration, Alignment, and Experimental Error… … … … … .… … … .. 29
Malvern Laser… … … … … … … … … … … … … … … … … … … ........................ 29Pressure Transducer… … … … … … … … … … … … … … … … … ...................... 30Thermocouple… … … … … … … … … … … … … … … … … … … ....................... 31Orifice… … … … … … … … … … … … … … … … … … … … … … ........................ 31
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CHAPTER Page
III EXPERIMENTAL RESULTS… … … … … … … … … … … … … … … … 32
Study I: The Effect of Injection Pressure on Atomization with Orifice:0.20 mm… … … … … … … … … … … … … … … … … … … … … 32
Temperature 80 °C… … … … … … … … … … … … … … … … … … … ................. 32Temperature 100 °C… … … … … … … … … … … … … … … … … ....................... 36Temperature 120 °C… … … … … … … … … … … … … … … … … ....................... 36Temperature 150 °C… … … … … … … … … … … … … … … … … ....................... 37Temperature 190 °C… … … … … … … … … … … … … … … … … ....................... 40
Study II: The Effect of Temperature on Atomization with Orifice: 0.20 mm… ..… … … … … … … … .… … … … … … … … … .… ... 41
Pressure 1034 kPa (150 psig)… … … … … … … … … … … … … … ..................... 42Pressure 2068 kPa (300 psig)… … … … … … … … … … … … … … ..................... 43Pressure 3447 kPa (500 psig)… … … … … … … … … … … … … … ..................... 44
Study III: The Effect of Injection Pressure on Atomization withOrifice: 0.36 mm… … … … … … … … … … … … … … … … … 45
Temperature 80 °C… … … … … … … … … … … … … … … … … … … ................. 46Temperature 100 °C… … … … … … … … … … … … … … … … … ....................... 46Temperature 120 °C… … … … … … … … … … … … … … … … … ....................... 48
Study IV: The Effect of Temperature on Atomization with Orifice:0.36 mm… ..… … … … … … … … … … … .… … … … … … … .. 49
Pressure 1034 kPa (150 psig)… … … … … … … … … … … … … … ..................... 49Pressure 2068 kPa (300 psig)… … … … … … … … … … … … … … ...................... 49Pressure 3447 kPa (500 psig)… … … … … … … … … … … … … … ..................... 51
Study V: The Effect of Orifice Size on Atomization… … … … … … … . 51
IV CONCLUSIONS AND RECOMMENDATIONS… … … … … … … .... 57
Conclusions… … … … … … … … … … … … … … … … … … … … … … … 57The Effect of Injection Pressure… … … … … … … … … … … … … ..................... 57The Effect of Temperature… … … … … … … … … … … … … … … ..................... 58The Effect of Orifice Size… … … … … … … … … … … … … … … ...................... 58
Recommendations… ..… … … … … … … … … … … … … … … … … … … 59
LITERATURE CITED… … … … … … … … … … … … … … … … … … … … … … … ... 60
APPENDIX
A EXPERIMENTAL DATASHEETS… … … … … … … … … … … … … ............................ 64
B PHOTOGRAPHS OF SPRAYS… … … … … … … … … … … … … … … .......................... 89C PRESSURE TRANSDUCER CALIBRATION… … … … … … … … … .......................... 100
D THERMOCOUPLE CALIBRATION… … … … … … … … … … … … … ........................ 103
8
E EXPERIMENTAL PROCEDURE… … … … … … … … … … … … … … ......................... 105
F HEAT TRANSFER FLUID PROPERTIES (ALKYLATED
AROMATIC MIXTURE)................................................................................................. 108
VITA… … … … … … … … … … … … … … … … … … … … … … … … … … … … … … ... 110
9
LIST OF TABLES
TABLE Page
-1 Drop size models for plain-orifice atomizers… … … … … … … … … .… .. 11
II-1 Interpretation of Log. Diff number… … … … … … … … … … … … … .… . 27
III-1 Conditions of experiments for orifice size of 0.20 mm… … … … … … .… 32
III-2 Conditions of experiments for orifice size of 0.36 mm… … … … … … … . 45
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LIST OF FIGURES
FIGURE Page
I-1 Flammability diagram at constant pressure… … … … … … … … … … .… 1
I-2 Classification of modes of disintegration… … … … … … … … … … … .… 5
I-3 Rayleigh regime breakup… … … … … … … … … … … … … … … … … … 6
I-4 Comparison of (a) idealized jet breakup with (b) actual breakup asindicated by high-speed photographs… … … … … … … … ......… … .… . 7
I-5 Low velocity liquid jet with air friction… … … … … … … … … … … … .. 8
I-6 First wind-induced regime… … … … … … … … … … … … … … … … … .. 9
I-7 Second wind-induced regime… … … … … … … … … … … … … … … … .. 9
I-8 Fully-developed atomization regime… … … … … … … … … … … … … .. 10
I-9 Mechanism of jet atomization for a plain orifice… … … … … … … … … 10
II-1 Schematic of experimental apparatus… … … … … … … … … … … … … . 16
II-2 Fluid Cell… … … … … … … … … … … … … … … … … … … … … … … … 16
II-3 Schematic of the Fluid Cell… … … … … … … … … … … … … … … … … . 17
II-4 Positioning system for the Fluid Cell… … … … … … … … … … … … … .. 19
II-5 Exhaust system… … … … … … … … … … … … … … … … … … … … … … 20
II-6 Collection chamber… … … … … … … … … … … … … … … … … … … … . 20
II-7 Fraunhofer diffraction in a single slit… … … … … … … … … … … … … .. 22
II-8 Diffraction particle analyzer to measure droplet sizes andconcentrations… … … … … … … … … … … … … … … … … … … … … … .
22
II-9 Ring diode (detector element geometry)… … … … … … … … … … … … 23
II-10 The Fraunhofer diffraction pattern of a single slit (Airy function)… … 24
II-11 Lens cut off (vignetting) distance… … … … … … … … … … … … … … .. 28
III-1 Histogram pattern I from the Malvern laser software… … … … ............ 33
III-2 Histogram pattern II from the Malvern laser software… … ................... 34
III-3 Effect of injection pressure on atomization @ 80 °C (orifice:0.20 mm)… … … … … … … … … … … … … … … … … … … … … … … … .
35
11
FIGURE Page
III-4 Effect of injection pressure on atomization @ 100 °C (orifice:0.20 mm)… … … … … … … … … … … … … … … … … … … … … ............. 35
III-5 Effect of injection pressure on atomization @ 120 °C (orifice: 0.20 mm)… … … … … … … … … … … … … … … … … … … … … … … … .. 38
III-6 Light intensity curve, pattern I… … … … … … … ...........… … … … ..… … 39
III-7 Light intensity curve, pattern II… … … … … … … .......… … … … ..… … .. 39
III-8 Light intensity curve, pattern III… … … … … … … .............… … … … … . 40
III-9 Effect of injection pressure on atomization @ 150 °C (orifice: 0.20 mm)… … … … … … … … … … … … … … … … … … … … … … … … .. 41
III-10 Effect of temperature on atomization @ 2068 kPa (300 psig) (orifice:0.20 mm)… … … … … … … … … … … … … … … … … … … … … … … … . 42
III-11 Effect of temperature on atomization @ 1034 kPa (150 psig) (orifice:0.20 mm)… … … … … … … … … … … … … … … … … … … … … … … … . 43
III-12 Effect of temperature on atomization @ 2068 kPa (300 psig) (orifice:0.20 mm) after the application of function “Kill Data”… … … … … … .. 44
III-13 Effect of temperature on atomization @ 3447 kPa (500 psig) (orifice:0.20 mm)… … … … … … … … … … … … … … … … … … … … … … … … . 45
III-14 Effect of injection pressure on atomization @ 80 °C (orifice: 0.36 mm)… … … … … … … … … … … … … … … … … … … … … … … … . 47
III-15 Effect of injection pressure on atomization @ 100 °C (orifice: 0.36 mm)… … … … … … … … … … … … … … … … … … … … … … … … .. 47
III-16 Effect of injection pressure on atomization @ 120 °C (orifice: 0.36 mm)… … … … … … … … … … … … … … … … … … … … … … … … .. 49
III-17 Effect of temperature on atomization @ 150 psig (orifice: 0.36 mm)… 50
III-18 Effect of temperature on atomization @ 300 psig (orifice: 0.36 mm)… 50
III-19 Effect of temperature on atomization @ 500 psig (orifice: 0.36 mm)… 51
III-20 Effect of orifice size on atomization @ 150 psig and 80 °C… … … … … 52
III-21 Effect of orifice size on atomization @ 150 psig and 100 °C… … … … . 52
III-22 Effect of orifice size on atomization @ 150 psig and 120 °C… … … … . 53
III-23 Effect of orifice size on atomization @ 300 psig and 80 °C… … … … … 53
12
FIGURE7 Page
III-24 Effect of orifice size on atomization @ 300 psig and 100 °C… … … … . 54
III-25 Effect of orifice size on atomization @ 300 psig and 120 °C… … … … . 54
III-26 Effect of orifice size on atomization @ 500 psig and 80 °C… … … … … 55
III-27 Effect of orifice size on atomization @ 500 psig and 100 °C… … … … . 55
III-28 Effect of orifice size on atomization @ 500 psig and 120 °C… … … … .. 56
13
LIST OF SYMBOLS
Ap Projected area, m2
bn Constant in Fourier series expansion
CD Drag coefficient
d Jet diameter, m
d0 Diameter of a circular tube, m
Dd Diameter of a drop, m
Es Potential surface energy
F The focal length of the lens L2
g Acceleration due to gravity, m/s2
Io The intensity at the center of the pattern
J1 The first-order spherical Bessel function
Jo The zero-order spherical Bessel function
L Light intensity
md Mass of a drop, kg
Pa Pressure of air, N/m2
Pi Pressure inside a drop, N/m2
Q Volumetric flow rate, m3/s
q Potential growth rate of the disturbance
s Radial distance in the detection plane measured from the optical axis
UL Velocity of the liquid, m/s
Ur Relative velocity, m/s2
λ Wavelength of disturbance, m
σ Surface tension, kg/s2
ρa Density of air, kg/m3
ρG Density of gas, kg/m3
ρL Density of the liquid, kg/m3
µL Dynamic viscosity of liquid, kg/m s
14
ν Kinematic viscosity, m2/s
γ Dimensionless wave number = 2πd/λ
15
LIST OF ABBREVIATIONS
cm centimeter
m meter
mW milliwatt
nm nanometer
mL milliliter
Re Reynolds number
SMD Sauter mean diameter (ratio of mean volume to mean surface area)
We Webber number
HTF Heat transfer fluid
16
CHAPTER I
INTRODUCTION
Heat transfer fluids (HTFs) are generally synthetic liquids with high boiling
points and high molecular weights. They are widely used in industry, particularly in
heat exchangers. Because these liquids generally have high flash points, industrial
personnel often interpret that HTFs are non-flammable and also non-combustible.
However, the potential hazards of combustible fluid aerosols have been recognized as
early as 1955 by Jacob Eichhorn. In his paper, he included the interesting diagram
shown below.
Figure I-1. Flammability diagram at constant pressure [Eichhorn, 1955]
Figure I-1 shows a region of vapor flammability with solid lines, meaning that
this region is known and predictable. We can see that this region is in between two
concentrations, high and low. If the concentration of fuel vapor in air is higher or lower
than the upper and lower limits respectively, the potential of fire is low. Bulk liquids are
This thesis conforms to the style and format of the AIChE Journal.
17
non-flammable below their flash points because the concentration of vapor in air at
equilibrium is not high enough. The operating ranges of heat transfer fluids is based on
this knowledge and therefore plant personnel are often not aware of the potential of fire
and explosion of liquids at temperatures below their flash points. As Eichhorn
suggested, there exists another flammability region called “Mist Flammability Region.”
Because this region is not well defined, the author did not use solid lines to designate
this region. So far no one has determined a formula to predict the solid lines for this
mist flammability region. But the most important conclusion from this diagram is that
there exists a potential for fire or explosion of mists or aerosols of combustible liquid at
temperatures below the flash point.
Mists or aerosols consist of both liquid and gas phases. Surface area per unit
volume, or specific surface area, of the liquid in an aerosol is much larger than the bulk
liquid specific surface area. The more surface area of contact with air, the less time that
is required for heat transfer in the phase. An ignition source can heat a liquid drop in an
aerosol to its flash point in microseconds causing fire and explosion. The explosion of
an aerosol release can be much more severe than a vapor release because the liquid
drops in an aerosol have a much larger enthalpy than vapor occupying the same volume.
An aerosol release can develop rapidly and cloud a large area in a few seconds
[Eichhorn, 1955].
Aerosol FormationAn aerosol fire and explosion can occur when the aerosol disperses into an
environment with enough oxygen and in the presence of an ignition source. Aerosol
formation can occur in many ways, such as flashing of a hot liquid [Brown and York,
1962] or atomization. In this research the intention was to study aerosol formed from
leaks in pressurized containers and process lines or fluids atomized through a plain
orifice. Aerosol drop sizes formed from this process were expected to have wide ranges
depending on operating conditions such as temperature and pressure and the size of the
leak. Before discussing the detail of atomization, it is important to understand some of
18
the fundamentals about drop formation and jet breakup (a jet in this case means a
narrow stream of liquid, forced out of a small opening).
Static Drop FormationConsider a liquid being slowly emitted from a vertical circular tube of diameter
d0. A drop of liquid forms and drops down when the gravitational force overcomes the
surface tension force of the liquid. The mass of the drop formed is determined by
equating these two forces as follows [Lefebvre, 1989]:
gd
m od
σπ= (I-1)
Assume a spherical drop and substitute for the mass of the drop by
6
3d
dD
mπ= (I-2)
Then the size of the drop is3/16
=
gd
DL
od ρ
σ(I-3)
Breakup of a Drop
Force Balance;
Surface tension force = Pressure force
Then PDD dd ∆= 2
4πσπ (I-4)
ai PPP −=∆ ; Pi > Pa (I-5)
From (I-4)dD
P σ4=∆ (I-6)
PaPi
19
The drop will be stable if Equation (I-6) is satisfied. If air pressure (Pa)
increases, the pressure inside the drop (Pi) must increase for the drop to be stable.
However, if the air pressure increases more than the internal drop pressure can match,
the drop will break. The resulting smaller drop will have an increased pressure
difference between itself and the air. The higher Pa and the increased pressure difference
due to the smaller drop will increase Pi resulting in a stable drop.
Drop Breakup in Flowing Air
Normally, drop breakup in flowing air is caused by the interaction among
aerodynamic, surface tension, and viscous forces [Lefebvre, 1989]. The ratio of
aerodynamic and surface tension forces, called Webber number, can determine whether
the drop is stable.
forcetensionSurfaceforcecAerodynami
numberWebber = (I-7)
σπρ
d
rapD
DUAC
We2/2
= (I-8)
CD = drag coefficient
Ap = projected area, 2
4 dDπ
Ur = relative velocity
Then σ
ρ dr DUWe = (I-9)
Usually, We ~ 10-13 indicates drop stability.
When the liquid is forced through an orifice in the form of a jet, the jet will
break or disintegrate because of jet instability. In 1936 Ohnesorge [Lefebvre, 1989]
proposed jet disintegration criteria, which since then have been commonly used. The
20
criteria indicate three regimes of jet breakup depending on the value of Reynolds
number and a dimensionless number Z or the Ohnesorge number (Oh), which has the
expression
0/ dOh LL σρµ= (I-10)
µL = dynamic viscosity of liquid, kg/ms
ρL = density of liquid, kg/m3
σ = surface tension, kg/s2
d0 = orifice diameter, m
In a more recent work, Reitz [1978] studied Ohnesorge’s work [1936] and
attempted to resolve some of the uncertainties of each Ohnesorge regime. Reitz
suggested new regimes of jet disintegration: Rayleigh Regime or Drip Flow Regime,
First Wind-Induced Regime, Second Wind-Induced Regime, and Fully Developed
Atomization Regime. Figure I-2 shows each regime as a function of Ohnesorge’s
number and Reynold’s number.
Figure I-2. Classification of modes of disintegration [Reitz, 1978]
21
Spray Breakup Regime
1. Rayleigh Regime
Figure I-3. Rayleigh regime breakup [Faeth, 1990]
This regime characterizes the atomization of very low velocity-jets or drip
flows, as shown in Figure I-3 and does not create an aerosol. However the mechanism
of this regime is a very important fundamental for other breakup regimes. The name of
this regime came from a mathematician, Lord Rayleigh, who in 1878 introduced a
mechanism and mathematical equations of drop breakup in this regime. He studied the
case of liquid jet collapse by comparing the jet surface energy of disturbed condition
with that of undisturbed condition. He then derived an equation to calculate the
potential energy of the disturbed condition as follows:
( ) 222 12 ns bn
dE −+= γπσ
(I-11)
Es = potential surface energy
d = jet diameter
σ = surface tension
bn = constant in Fourier series expansion
γ = dimensionless wave number = 2πd/λ
λ = wavelength of disturbance
n = any positive integer (including zero)
22
If Es is positive the liquid jet is stable, but if Es is negative the liquid jet becomes
unstable. When n >> 1, the disturbances are nonsymmetrical and Es is always positive,
according to equation (I-11). When n=0, γ < 1 and λ > 2πd, the system is not stable,
because Es is negative. Moreover from this equation it can be interpreted that λmin =
2πd. If the wavelength of the disturbance is less than λmin, the surface forces will
overcome the disturbance and the spray will remain stable. If the wavelength is greater
than λmin, the surface tension forces will increase the disturbance, which will lead to jet
disintegration.
Figure I-4. Comparison of (a) idealized jet breakup with (b) actual breakupas indicated by high-speed photographs [Lefebvre, 1989]
Figure I-4(a) shows an idealization of Rayleigh jet disintegration. Rayleigh
predicted that first the liquid comes out from the tube in the form of a cylinder and then
breaks into a shorter cylinder. Each short cylinder becomes a drop later on. He also
proposed that all broken drops had uniform size, and the gaps between drops are equal.
However, high-speed photographs proved a different result, as shown in Figure I-4(b).
The photograph showed that the jet had a dumb-bell shape before breaking up into a
drop. The gravitational force tries to pull the liquid down or break the liquid cylinder
into a drop, but the viscous and surface forces of the liquid prevent that from happening.
23
Moreover, the drops formed usually coalesce with each other, so the jet consists of
consecutive large and small drops. Eventually, each drop becomes spherical to
minimize surface energy. In this regime, drop diameters normally are larger than the jet
diameter.
Rayleigh assumed that bn in equation (I-11) is proportional to exp(qt), where q is
the exponential growth rate of the disturbance. From his mathematical analysis, he
showed that q for the fastest growing disturbance is5.0
3max 97.0
=
dq
Lρσ (I-12)
Also, he suggested that the wavelength that would cause qmax is as follows
dopt 51.4=λ (I-13)
The jet breaks into a cylinder if the cylinder length equals the wavelength of
outside disturbance, and then the cylinder finally becomes a drop.
32
6451.4 dDdd ππ =×
Hence
dDd 89.1= , (I-14)
where Dd is the drop diameter.
Once the velocity of the liquid jet increases, the friction force between the
surface of the liquid column and air becomes important. In this case, the wavelength (λ)
of the disturbance is longer which increases its instability. A pictorial representation of
this friction is shown in Figure I-5.
Figure I-5. Low velocity liquid jet with air friction [Elkotb, 1982]
24
2. First Wind-Induced Regime
In this regime, the exit velocity of the liquid jet is greater than in the first
regime. The friction force between the surface of the liquid column becomes much
greater and so does the wavelength (λ) of the disturbance. The liquid cylinder twists and
its instability increases. This regime could create drops with diameters about the same
as the jet diameter. A sketch of this regime is shown in Figure I-6.
Figure I-6. First wind-induced regime [Elkotb, 1982]
3. Second Wind-Induced Regime
The friction force at the surface of the liquid jet is so great that breakup occurs at
the surface near the nozzle exit yielding a wide range of drop sizes. First the liquid
column breaks into many large ligaments. Then the large ligaments break further until
they become spherical drops. Drop diameters created in this regime can be much
smaller than the jet diameter. This regime has a moderate potential to create aerosol.
The mechanism of this regime is represented in Figure I-7.
Figure I-7. Second wind-induced regime [Faeth, 1990]
4. Fully-Developed Atomization Regime
25
The exit velocity in this regime is faster than in other regimes. Because of a very
high friction force, the surface of the liquid jet breaks into very fine drops at the nozzle
exit. As shown in Figure I-8, the liquid core is very short, and where the liquid core
ends, the spray contains only aerosol. The jet in this regime has a very high potential to
create aerosol. Aerosol drop sizes in this regime are much smaller than the jet diameter.
Figure I-8. Fully-developed atomization regime [Faeth, 1990]
The stages of jet breakup mechanism for a plain orifice [Elkotb, 1982] are discussed below.
Characteristics of Atomization for a Plain Orifice
Figure I-9. Mechanism of jet atomization for a plain orifice [Elkotb, 1982]
1. The jet spreads out into a cone with an angle depending on the liquid
velocity and the orifice size.
26
2. As shown in Figure I-9, the jet splits into layers with various velocities. The
center of the spray has the highest velocity. The velocities of the outer layers
are affected by the center layer. Therefore, the outermost layer has the
lowest velocity and the inner layers have higher velocities.
3. Small waves occur in each layer.
4. The surface of each layer breaks into ligaments due to interactions among
drag, surface tension, and viscous forces.
5. Ligaments in (4) break further until they are stable, normally in a spherical
geometry.
6. Drops in (5) break further into more stable drops.
7. Drops coalesce.
Drop Size ModelsThe background above shows that operating conditions for heat transfer fluids
are very important because they affect the properties of the liquid and determine the
spray regimes and whether the spray has potential to create aerosol. Moreover,
according to the regime, we could determine roughly the drop size of aerosol as
compared to the diameter of the jet.
Table I-1. Drop size models for a plain-orifice atomizers [Lefebvre, 1989]
Investigators ModelsMerrington and Richardson
L
Lo
Ud
SMD2.02.1500 υ=
Harmon 052.078.015.015.0648.007.03.03330 −−−−= GGLLL UdSMD ρµσρµ
Tanasawa and Toyoda
( )
×+
= −
5.0
25.01 331147
ddUSMD
L
L
GL σρ
µρσ
Hiroyasu and Katoda 135.0131.0121.02330 −∆= LA PQSMD ρElkobt ( ) 54.006.0737.0385.008.3 −∆= LALL PSMD ρσρυ
UL = velocity of the liquid, m/s
27
d = discharge orifice diameter, mµ = dynamic viscosity, kg/m sν = kinematic viscosity, m2/sρ = density, kg/m3
σ = surface tension, kg/s2 ∆ PL = injection pressure differential across nozzle, PaQ = volumetric flow rate, m3/s
Table I-1 shows models of Sauter Mean Diameter (SMD) prediction from
various researchers. Unfortunately, each model gives very different SMD predictions,
perhaps because jet breakup is a random process, and aerosol drops from jet breakup are
of many sizes. The aerosol drops after being formed can break into smaller drops,
coalesce with each other and become larger in size, evaporate and/or rain out. These
scenarios are dependent upon the initial aerosol drop size, so it is important to
understand how aerosols are formed. The drop sizes of aerosols created by atomization
are dependent on the properties of the liquid, especially viscosity and surface tension,
and other conditions such as orifice size. Many researchers studied atomization through
plain orifices and developed various models. Table I-1 lists some of the models that
have been developed.
Literature Review
Aerosols of hydrocarbons or combustible liquids including heat transfer fluids
can explode even at temperatures below their flash points. Detail of explosion hazards
have been discussed in several papers [Eichhorn, 1955; Vincent and Howard, 1976;
Bowen and Shirvill, 1994; Febo and Valiulis, 1995].
Aerosols can be created in several ways such as flashing liquid [Brown and
York, 1962], pressure atomization, air-blast atomization, and air-assist atomization
[Lefebvre, 1989]. However, this research focused on HTF aerosols formed from a leak
in pressurized containers or process lines. In an experiment, pressure atomization with a
plain orifice is used to simulate such a leak. In 1991, Johnson from Quest Consultants,
performed an experiment, which was very similar to this research, but tested water,
chlorofluorocarbon-11 (CFC-11), chlorine, methylamine, and cyclohexane instead of
28
HTF and used a Insitec PCSV-P (Particle-Counter-Sizer-Velocimeter; probe version)
particle analyzer instead of a Malvern Laser. Research by Richer [1994] focused on
potential of fire and explosion of hydrocarbon fluid aerosols. Richer also used a
Malvern Laser to measure drop size distributions. However, the samples used, and the
type of orifices was different from this research. Moreover, Richer measured drop sizes
with respect to time and studied the decay of aerosol drop sizes in a confined space. The
decay of drop sizes involves behavior such as evaporation, condensation, and the
settling down of drops by gravity. For this research, the initial drop size distributions of
aerosols formed from atomization were measured at various operating conditions. The
intention was to focus on process safety aspect of aerosols and the use of drop size data
in aerosol models. Moodie and Ewan’s work [1990] also has a safety-related purpose.
They studied jets of superheated Freon-11 discharging to atmosphere. Schmidli et al.
[1990] also studied vapor, aerosol, and pool formation upon rupture of vessels
containing superheated liquid. The amount of research conducted in this area clearly
indicates its importance.
The process of creating aerosol in this research is the same as the process of
atomization in diesel engines, and much atomization literature is relevant to this work.
Much previous research has attempted to understand the structure of sprays in diesel
atomization or drop breakup [Elkotb, 1982; Hiroyasu, 1991; Huh et al., 1991; Huh et
al., 1994; Lin and Hudman, 1994; Samenfink et al., 1994]. Some work focused on just
one section of the spray, for example the dense spray or near-injector region [Felton et
al., 1985; Ruff et al., 1989; Solomon et al., 1985; Takahashi et al., 1994].
The effect of orifice size on spray characteristics has been studied by
Ramamurthi and Nandakumar, 1994. The effect of fluid viscosity and surface tension
on spray drops also has been studied by Tabata et al., 1985. Moreover, effect of
propellant on the disintegration mechanism was studied by Namiyama et al., 1985. For
a complete understanding of aerosol formation, drop evaporation must be considered
[Yule et al., 1982; Faeth, 1983; Gong et al., 1992]. Many books discuss the basic
mechanism of spray breakup [Lefebvre 1989].
29
In this research, a laser diffraction particle-analyzing (LDPA) technique using
the Malvern Laser (2600-C) measured drop size distributions of HTF aerosols. This
technique uses the principle of Fraunhofer diffraction theory [Barth, 1984; Richer,
1994; Watson and Tech, 1985]. Some researchers have used imaging techniques to
study mechanism of spray breakup [Shimazaki et al., 1994; Iki et al., 1994].
Measurement techniques of the Malvern Laser have been discussed in several articles
[Lefebvre, 1989; Miles et al., 1989; Kihm et al., 1994].
30
CHAPTER IIEXPERIMENTAL METHODOLOGY
This work focused on aerosol formation from a leak in a pressurized container,
and experiments were designed to emulate industrial process leaks. Initial drop size
distributions of HTF aerosol were measured by a laser diffraction technique, using a
Malvern Laser Diffraction Particle Analyzer (2600-C). This chapter includes the
experimental arrangement, apparatus, experimental procedure and measurement, and
calibration and experimental errors.
Experimental Arrangement
The experiment was designed to emulate aerosol formation from a leak in a
pressurized container and to measure aerosol drop size distributions. The fluid cell,
which is described later in this chapter, was the pressurized container. A plain orifice
was used to imitate a leak. Drop size distributions of a HTF aerosol were measured by a
non-intrusive method using a Malvern Laser Diffraction Particle Analyzer. Because this
is a light scattering method, the lab environment must be as dark as possible so that the
aerosol does not scatter light from sources other than the laser beam. Moreover, the
closed lab environment ensured that the air was quiescent and hence did not interfere
with aerosol formation. The spray was emitted from the pressurized Fluid Cell in a
horizontal direction (x direction). After the measurements, the entire spray was
collected by an exhaust system. Care was taken to ensure that the exhaust system was
adequate to remove all aerosol. The schematic of the arrangement is shown in Figure II-
1.
Apparatus
The experimental system is composed of the Fluid Cell, positioning system,
exhaust system, and Malvern laser.
31
MalvernReceiver
MalvernLaser
Fluid Cell
Nitrogen Tank
ExplosionProof Blower
CollectionChamber
StorageVessel
Mist Separator
Computer
Printer
Spray
Orifice
Figure II-1. Schematic of experimental apparatus
Fluid Cell
Figure II-2. Fluid Cell
The Fluid Cell, as shown in Figure II-2, is made of stainless steel by Parr and
has a working pressure limit of 13100 kPa (1900 psi). The polytetrafluoroethylene
gasket on the lid has an upper limit temperature of 350 °C. The cell capacity is 1000
x
32
mL, the inside diameter is 10 cm (4 inches) and the inside depth is 13.3 cm (5.32
inches). Figure II-3 shows the schematic of the Fluid Cell. On the top of the Fluid Cell,
there are 2 outlet ports and 1 inlet port.
P
TC
TC
PT
Fluid Cell
OrificeFill
Legend
On/Off Valve
Control Valve
P Pressure Gauge
PRV
Pressure Relief Valve
Thermocouple
Pressure Transducer
TC
PRV
PT
Figure II-3. Schematic of the Fluid Cell
The fill line, a 0.9375 cm (3/8 inch) inside diameter flexible metal host (model:
SS-6BHT-36) from Swagelok, transferred heat transfer fluid from a 1 gallon glass
container into the Fluid Cell. The needle valve (model: SS-1RF4) from Swagelok at the
fill line has a working pressure of 34474 kPa (5000 psig) at 38 °C (100 °F).
The spray line was comprised of a 0.625 cm (¼ inch) diameter tube, 35.3 cm
long with one 90-degree turn to transport HTF from the Fluid Cell to the nozzle. Each
nozzle was made from a brass plug from Swagelok, because this material is softer than
stainless steel and easier to drill. Various sizes of simple round holes to form plain
orifices were made by drilling at the end of each nozzle. The pressure transducer and
33
thermocouple were calibrated and installed very closely to the nozzle for accurate
measurements of the fluid entering the nozzle. The pressure transducer (model:
THE/0713-18TJA) from Sensotec was made of stainless steel. The pressure range is
3550 kPa (500 psia) with a 10.0 volt supply and an output of 3.0 mV/V. The transducer
was connected to a power supply (model: LMC-0-32) from Lambda Electronics
Corporation and a volt meter (model: 181 Nano-voltmeter) from Keithley. The pressure
transducer was calibrated to determine an equation to convert voltage data into pressure
data (see Appendix C).
The stainless steel needle valve (model: SS-1RS4) with 0.025 cm (¼ inch)
fitting from Swagelok on the spray line was used to control the flow rate of the spray.
The valve has working pressure of 34474 kPa (5000 psig) at 38 °C (100 °F).
On the vent line, a Swagelok pressure relief valve (model: SS-4R3A1) was
installed to prevent an overpressure. A needle valve from Swagelok with working
pressure of 34474 kPa (5000 psig) at 38 °C (100 °F) was for the nitrogen line. The
nitrogen line was a Swagelok thermoplastic hose with 0.625cm (¼ inch) tube adapters
on both sides. A 2000 psi pressure gauge was installed adjacent to a Swagelok on-off
valve (model: SS-4P4T) to measure pressure in the fluid cell. A thermocouple from
Omega also was installed to measure the temperature of the HTF in the Fluid Cell.
HTF in the Fluid Cell and in the spray line was heated by two strip heaters,
which can heat up to 232 ° C. The heaters (Volt:120, Watts: 313, Amps: 2.61, model
SRT051-120) from Omegalux were controlled by temperature controllers (model:
CN76000) from Omega. A thermocouple was placed at each heater in a control circuit
with a temperature controller.
Two thermocouples, one on the spray line and the other in the Fluid Cell, were
calibrated and connected to temperature indicators.
Positioning System
The Fluid Cell was placed on the positioning system, as shown in Figure II-4.
Because the Malvern laser was fixed, the nozzle was moved for measurements along the
34
horizontal line (x direction). The positioning system can move the Fluid Cell in two
orthogonal directions, x and y. Direction x allows measurements of drop size
distributions at distances horizontally from the nozzle. Direction y allows measurements
of drop size distributions in the radial direction from the nozzle.
Spring Lock
Top Plate
Lock for TopPlate
Base Plate
Scale
Scale on Top
y
x
Figure II-4. Positioning system for the Fluid Cell
Exhaust System
The exhaust system, shown in Figure II-5, is composed of a collection chamber,
made of an acrylic plastic and a mist separator. At the end of the collection chamber
shown in the Figure II-6 is a 7 cm diameter hose, which was connected to the mist
separator, shown in Figure II-5. The mist separator separates the two phases of the
spray. Collected liquid, after passing through the inlet, drops to the bottom. The vapor
and aerosol phases are pulled through a filter by a 1 HP-explosion proof blower (model:
PW 11 and spec: 35E 353-498, RPM: 3450, Volt: 115/230, and Amp: 12/6, Madison
Manufacturing Company), which was located outside the building. The filter was
polyester filter felt and could separate particles as small as 5 micron, so particles larger
than 5 micron, cannot pass through the filter. The particles smaller than 5 micron can
pass through the filter and are carried by air out of the building.
35
Camera and Micro-flash
The camera used to photograph the sprays was a Cannon (model: FX2) with a
macrolens F3.8 and a micro-flash illumination of 1 microsecond.
29.75"
2"
15"
2.5"
7.5"Filter
Mist Separator ( front view )
Inlet
Drain
Outlet
Outlet ( out side the building,front view )
Inlet (front view )
Metal sheet
8"
Can
Host
Fan
8"
0.5"
top view
Figure II-5. Exhaust system
75 cm
10 cm
Ø 7 cm Spray
Figure II-6. Collection chamber
Malvern Laser Diffraction Particle Analyzer
The Malvern laser uses Fraunhofer diffraction or light scattering principle,
which is widely used in drop size measurements. The advantages of this method are that
36
it is non-intrusive, practical and simple to use, and does not require any conducting
media. However some of the disadvantages of this method are non-direct analysis and
limitations of the Fraunhofer diffraction principle. Fraunhofer diffraction principle can
be applied to particles as small as 5 µm with errors less than 20%.
1. Fraunhofer DiffractionWhen a beam of light encounters a particle, it is reflected, refracted, diffracted
or absorbed. There are two types of diffraction, near field diffraction or Fresnel
diffraction and far field diffraction or Fraunhofer diffraction. We can differentiate these
two types of diffraction based on the smaller of the two distances between the light
source and the slit or between the slit and the screen, R. For Fraunhofer Diffraction R >
a2/λ [Hecht, 1998], where a is the width of the slit, and λ is the wavelength. When light
passes through a slit, the central part of the beam will pass through the slit (Σ) directly
without any deviation. The part of the beam that hits the edges will deviate due to
diffraction. Now the wave fronts from the two edges of the slit are different from the
wave front from the center, so interference occurs among them. If the distance between
the light source and the screen is large enough or infinite, the interference will fade
away. Without any interference, the majority of light passing through the slit will fall on
the screen at one point, as shown in Figure II-7. Lens L1 or the beam expander must be
placed after the light source to shorten the distance between the light source and the slit
causing the front wave of light to be straight. The same function is applied to lens L2,
which helps the beam to focus on one point. Lens L2 has another important function in
the Malvern laser, which will be discussed later.
The Malvern laser includes a 2 mW Helium-Neon laser tube and a detector. The
laser tube creates a collimated and monochromatic beam of red light with wavelength of
780-662 nm, and is expanded by lens L1 to around 18 mm in diameter. When particles
pass through this beam, they scatter the laser light. Smaller particles scatter at larger
angles. The scattered light falls on a ring-diode in the detector, as shown in Figure II-8.
The unscattered light passes through a pin-hole in the middle of the ring-diode. The ring
37
diode has hemisphere geometry as shown in Figure II-9. The first ring is the closest ring
to the pin-hole in the middle. It is divided into 31 rings of various radii. Each ring
detects a particular size range. The light intensity on each ring, indicates the number of
particles in that size range. The schematic of light scattering is shown in Figure II-8
[Malvern Laser Manual, 1993].
Figure II-7. Fraunhofer diffraction in a single slit [Hecht,1998]
Figure II-8. Diffraction particle analyzer to measure drop sizes and concentrations [Malvern Laser
Manual, 1993]
38
Figure II-9. Ring diode (detector element geometry) [Malvern Laser Manual, 1993]
The Fraunhofer principle can be extended to spherical drops. The light intensity
of the diffraction pattern for a disk or a spherical drop of radius r is described by the
Airy function as follows [Barth, 1984]
( ) 212
=
xxj
II o (II-2)
Frsx
λπ2= (II-3)
Io = Intensity at the center of the pattern
j1 = First-order spherical Bessel function
s = Radial distance in the detection plane as measured from the
optical axis
F = Focal length of the lens L2
From Figure II-10, a very high peak is seen at the center of the detector and
many comparatively smaller peaks appear around the highest peak. These small peaks,
which result from interference of diffracted light, decrease in amplitude at greater
distances from the center.
39
Figure II-10. The Fraunhofer diffraction pattern of a single slit (Airy function)
[Hecht, 1998]
As mentioned earlier, the focal length of the lens L2 is important because it
determines the range of the particles to be measured. Let us consider Figure II-8.
Because different particle sizes will result in different scattering angles, a lens with a
fixed focal length must be arranged so that all the light scattered by the drops will be
captured.
Integrate Equation (II-2) to obtain the light energy within a circle of radius, s, on
the detector. Then
( ) ( )xJxJL o21
21 −−= (II-4)
Jo = the zero-order spherical Bessel function
For the light falling between two radii s1 and s2, owing to a single particle, the light
energy is
40
( ) ( ) ( ) ( ) 221
21
21
222,1 ][][ sososs xJxJxJxJrCL −−−= π (II-5)
C = optical constant that depends on the power of the light source and
on the detector sensitivity
Therefore for N particles, Equation (II-5) becomes
( ) ( ) ( ) ( ) }][]{[ 221
21
21
22
12,1 sosoii
M
iss xJxJxJxJrNCL −−−= Σ
=π (II-6)
where the size distribution is divided into M size classes.
Sometimes it is more convenient to write the equation above in terms of particle weight
(W).
ρπ 343rW
N ii = (II-7)
ρ = density of the particle
Then equation (II-7) becomes
( ) ( ) ( ) ( ) }][]{[ 22
12
12
12
12,1 soso
i
iM
iss xJxJxJxJ
rW
KL −−−
= Σ
=(II-8)
K = a constant containing the optical constant C and density
The size distribution or weight distribution is obtained as follows:
1. Estimate an initial set of 31 W’s from the raw data or calculate from an assumed
functional form of the size distribution.
2. Calculate Ls1,s2 again, using W’s in 1, from Equation (II-8).
3. Apply least square to Ls1,s2 from the measurements. The Ls1,s2 calculated from 2 set
of W’s that make the lowest least-square error is selected.
Some of the functional forms of the size distribution are
Model Independent
( )[ ]210 jj LDLogLogD −Σ= (II-9)
Where Dj the measured data
Lj the data calculated from the estimated volume distribution
41
Log-normal
)ln()ln(2)/ln(
exp)ln(2
12
xdxx
dW
−=
−
σσπ(II-10)
Normal
dxxx
dW
−−=−
2
2
)(2)(
exp)ln(2
1σσπ
(II-11)
Rosin-Rammler
dxx
x
x
xdW
−
= −−
−σ
σ
σ
σ exp1
(II-12)
In each case x represents drop diameter, and W is the weight fraction.
In the Malvern laser software, two size distribution models are are Model
Independent and Rosin-Rammler. In this research the Rosin-Rammler model was
selected because it is simple and it agrees reasonably well with the experimental data
[Barth, 1984]. Moreover, Lefebvre [1989] has suggested that this model is currently the
most widely used.
Function Log. Diff in the Malvern laser indicates the accuracy of the model. The
number shows the quality of fit between the measured light energy distribution and the
distribution calculated by the algorithm. The following guide in Table II-1 may be
applied.
Table II-1. Interpretation of Log. Diff number [Malvern Laser Manual, 1993]
Log. Diff Interpretation
Log. Diff > 6 Model not appropriate or experiment incorrectly performed.
5.5 < Log. Diff > 6 Poor fit. May be adequate for trend analysis only.
5 < Log. Diff > 5.5 Adequate fit but look for evidence of systematic misfitting.
5 < Log. Diff > 4 Good fit. Well presented sample.
Log. Diff < 4 Very unlikely with measured data but normal with analytic data.
42
However the Fraunhofer diffraction theory has some limitations, as discussed by
Barth (1984)
2. Limitations of Fraunhofer Diffraction
2.1 Theoretical: Fraunhofer diffraction theory usually yields errors up to
20 % with particles smaller than 5 µm.
2.2 Concentration: Fraunhofer diffraction assumes that no multiple
scattering occurs. Care should be taken to avoid measurement when
the concentration of the aerosol is too high because multiple light
scattering will occur. Felton’s experiments [1981] showed that when
aerosol concentration exceeded about 50%, multiple scattering has a
significant effect on the size distribution. However, if the aerosol
concentration is too low, the Malvern laser measures too few
particles, and the Malvern laser statistical average will bias toward
smaller size distributions. The aerosol concentration should not be
lower than 5%. Nevertheless, the ideal obscuration or concentration
should be about 20-30%.
2.3 Vignetting: This limitation will result when the particles are too far
away from the receiving lens. The diffracted light from the beam
may be cut off by the receiving lens’ finite aperture, as shown in the
Figure II-11. This research employed only 300 mm focal length lens,
for which the cut-off distance is 400 mm from the detector.
43
A = Lens cut-off distance
Figure II-11 Lens cut off (vignetting) distance [Malvern Laser Manual]
2.4 Averaging: Fraunhofer diffraction instrument is categorized in the class
of “Ensemble Averagers (EA’s)”. With this class it cannot give
“absolute” concentrations like single particle optical counter (SPOC),
but this method is faster and good for statistical analysis because the
sum of signals from all particles measured will be taken into account.2.5 Beam Steering: In a high temperature environment, thermal gradients in the hot air
refract the laser beam.
Experimental Procedure and MeasurementHTF is filled into the Fluid Cell and heated to the test temperature. Two strip-
heaters, each controlled by temperature controller, were used, one for the Fluid Cell and
the other for the spray line. The Fluid Cell was pressurized by nitrogen gas. The spray
was emitted after the system attained thermal equilibrium. The detector of the Malvern
laser was aligned on a daily basis. The pin-hole at the ring-diode in the Malvern laser
detector was aligned so that the laser beam passes exactly through it. A reticle with 46.5
micron particle size distribution was used to check the alignment. Focal length of the
lens used in this research was 300 mm because a particle size range of 5.8 to 564
micron was expected. Sample measurement was done by averaging data collected from
44
500 sweeps per experimental test. A high number of sweeps has an advantage in
statistical analysis because a larger sample size gives a better representation of the
entire spray.
The data were analyzed by the Malvern laser software using the Rosin-Rammler
model. The analysis was focused on the Sauter Mean Diameter (SMD) data. By
definition, SMD is the ratio of drop surface area to drop volume. SMD data were used
because the surface area and the volume of drop are important information for aerosol
dispersion models. In the future, the behavior of drop evaporation, and condensation or
heat transfer among drops and ambient media will be studied. SMD provides more
meaningful data for these studies.
The detailed experimental procedure is provided in Appendix E.
Calibration, Alignment, and Experimental Error
To document accuracy of the experimental data, calibration and alignment are
required. Calibrations were performed for a pressure transducer, and thermocouples,
and alignments were performed for the Malvern laser.
Malvern laser
The signal from the ring diodes can be transferred to the Malvern laser software
and calculated without any standard. However, the laser beam must be aligned properly
because the entire laser beam is expected to pass through the pin hole at the center of
the diode. To do this, the diode detector must be adjusted in the x and y directions to
allow the maximum light intensity to fall on the pin-hole. While adjusting the position
of the detector, the optimum position yields the maximum synchronizer voltage. This
position can be confirmed again by measuring the particle size distribution of the
reticle. The exact size of each particle was determined by an electron microscope and
particle size distribution was calculated [Barth, 1984]. The reticle used had a reported
size distribution of 46.5 ± 4.7 micron and during the alignments, only deviations less
than 10% from the reported value were accepted. The alignment of the Malvern laser
45
was conducted on a daily basis. Nevertheless the nominal uncertainty of particle size
distribution measurements were in the range of 20 micron.
Pressure Transducer
The advantage of a pressure transducer over a Bourdon’s pressure gauge is that
it is more responsive to pressure fluctuations. It does not give direct readings, but the
voltage from the transducer must be sent to a voltmeter. These voltage data were
transformed to pressure data using a pressure calibration equation The Sensotec
pressure transducer was calibrated using a digital pressure gauge (1500 psi with PM
Indicator, SN; 40928) from Heise, which has a read out error of 0.1 %, and a vacuum
pump. The digital gauge permitted direct pressure readings. The transducer was
connected to a power supply, which was set for an input of 10 volts, a voltmeter, and a
nitrogen tank as a pressure source. The digital pressure gauge was connected between
the nitrogen tank and the transducer. At each set pressure, Vin and Vout from the
voltmeter were recorded. An equation was fit to the Vout/Vin versus pressure data to
transform Vout/Vin data read from the experiment, into the pressure data. (See Appendix
C)
The total uncertainty of the pressure data read from the pressure transducer is
the sum of
1. The uncertainty of the pressure gauge Heise: ± 1.5 psia
2. The Sensotec pressure transducer: ± 0.25 psia
3. The error of the fit: very small ~ ± 0 psia
Therefore the total uncertainty of the pressure data is in the order of ± 1.75 psia.
Thermocouple
Sample fluid temperatures were measured at the nozzle using a thermocouple.
Another thermocouple is used to measure the fluid temperatures in the Fluid Cell. Each
thermocouple was calibrated over the range of the experimental temperature, using a
mercury thermometer. The difference in temperatures between the thermocouple and
46
the mercury thermometer was taken to be the error of the thermocouple reading. The
error curves for the nozzle thermocouple is shown in Appendix D.
The total uncertainty of the temperature data read from the thermocouple at the
nozzle is the sum of
1. The uncertainty of the mercury thermometer: ± 0.5 °C
2. The uncertainty of the fit (maximum): ± 1.4 °C
Therefore the total uncertainty of the temperature data is in the order of ± 1.9 °C
OrificeFor the 0.20 mm and 0.36 mm orifices, the total uncertainty is the sum of
1. Drill tolerance by measurement of drill: ± 0.0051 mm
2. Drill measurement: ± 0.0051 mm.
3. Hole drilling: +0.0051 mm, – 0.0000 mm (Note that the drilled hole always is larger than
the drill diameter.)
Therefore the total uncertainty of the orifice is + 0.015 mm, – 0.010 mm. This
uncertainty value confirms the use of two digits past the decimal place.
47
CHAPTER IIIEXPERIMENTAL RESULTS
The objective of this research was to measure the effects of operating conditions
on HTF aerosols. Two operating conditions, pressure and temperature were studied.
Another important factor that would affect the SMD of HTFs is the size of the leak or in
this case, the orifice size. This analysis was based on the droplet size distribution data,
histograms, and the light intensity curve from the Malvern laser.
Study I: The Effect of Injection Pressure on Atomization with Orifice: 0.20 mmThe effect of pressure on SMD of a HTF aerosol was studied at 3 pressures:
1034 kPa (150 psig), 2068 kPa (300 psig), and 3447 kPa (500 psig). The experiments
were conducted with these three pressures at temperature of 80, 100, 120, 150, and 190
°C. Table III-1 lists the experimental conditions.
Table III-1 Experimental conditions for orifice size of 0.20 mm80 °C 100 °C 120 °C 150 °C 190 °C
1034 kPa (150
psig)
2068 kPa (300
psig)
3447 kPa (500
psig)
48
Temperature 80 °CAt 1034 kPa (150 psig), the spray was not fully developed or mature, meaning
that the extent of atomization was low, as shown in Appendix, Figure B-1. Therefore
the SMD at this condition is very large, and the range of SMD was between 202 and
349 micron. The spray was composed of non-spherical droplets or ligaments and hence
was not mature. As the Malvern data analysis is based on spherical droplets, the
measurement of particle SMD was not very accurate at this condition, which is evident
also in the histograms. At all distances, the histograms did not show complete bell-
shaped curves. The bell-shaped curves were truncated at the large droplet region,
indicating that, a lot of large droplets and ligaments appeared, that exceeded the 300
mm focal length of the lens. The pattern of the histogram is shown in Figure III-1.
Obscuration at distances far from the nozzle was very low because gravitational force
dominated the spray.
Figure III-1. Histogram pattern I from the Malvern laser software
49
Considering Appendix, Figure B-2 and Figure B-3, at 2068 kPa (300 psig) and
3447 kPa (500 psig), the spray seemed to be well developed after the distances 300 mm
and 180 mm, respectively. However, according to the histograms and light intensity
curves, the spray was not mature until 341 mm and 191 mm from the nozzle for 2068
kPa (300 psig) and 3447 kPa (500 psig), respectively. The histogram of both conditions
before the sprays became mature appeared like Figure III-1. After the sprays became
mature the histograms showed a complete bell-shaped curve, as shown in Figure III-2.
The obscuration and Log. Diff appeared normal for both pressures. For the mature
spray, the droplet size distribution ranged from 68 to 84 micron at 2068 kPa (300 psig)
and from 57 to 72 micron at 3447 kPa (500 psig). Note that the SMD for the mature
spray at 3447 kPa (500 psig), condition remained the same for all distances. However at
2068 kPa (300 psig), SMD increased a little at the end. This may be because the
droplets coalesced with each other resulting in larger droplets. Another interesting point
was that the SMD at 2068 kPa (300 psig) and 3447 kPa (500 psig) were very similar,
but they were very different from the SMD at 1034 kPa (150 psig).
These results agreed with the expected trend. Higher pressures cause more
atomization, resulting in smaller droplet sizes. The effect of injection pressure at this
condition is shown in Figure III-3.
50
Figure III-2. Histogram pattern II from the Malvern laser software
0
50
100
150
200
250
300
350
400
0 50 100 150 200 250 300 350 400 450
Distance from the nozzle (mm)
150 psig 300 psig 500 psig
Figure III-3. Effect of injection pressure on atomization @ 80 °C (orifice: 0.20
mm)
51
0
50
100
150
200
250
300
350
0 50 100 150 200 250 300 350 400 450
Distance from the nozzle (mm)
150 psig 300 psig 500 psig
Figure III-4. Effect of injection pressure on atomization @ 100 °C (orifice:
0.20 mm)
Temperature 100 °C
At 1034 kPa (150 psig), the spray was not mature, so the Malvern’s
measurement of droplet size distribution was not very accurate. The range of SMD was
from 131 to 331 micron. All histograms showed incomplete bell-shaped curves at this
condition, as shown in Figure III-1, and many large droplets and ligaments were
observed. The obscuration for all measurements was quite low, especially after 191 mm
from the nozzle. Although the spray seemed to break after 191 mm from the nozzle,
because of low pressure the droplet sizes remained large and separated from each other.
At 2068 kPa (300 psig) the spray became mature at 241 mm from the nozzle,
judging from the histograms. The SMDs in this region range from 56 to 67 micron. In
this case, the measurements should be very accurate, because the Malvern laser is most
efficient with obscurations between 30-50%. Also the Log. Diff values fell in an
accurate range. At this condition the spray broke into finer droplets than at 1034 kPa
(150 psig) resulting in higher obscurations.
52
At 3447 kPa (500 psig), the histogram was a bell-shaped curve, as shown in
Figure III-2, starting at 141 mm from the nozzle. In this case we would analyzing the
data starting from the distance 141 mm from the nozzle. The SMD in this region ranged
from 35 to 44 micron. The SMDs decreased and then increased because of coalescence.
According to the obscuration and Log. Diff data, the measurements should be very accurate.
At this condition, the spray created finer droplets than at 2068 kPa (300 psig) resulting in higher
obscurations.
These results agreed with the expected trend. Higher pressures cause more
atomization, resulting in smaller droplet sizes. The effect of injection pressure at this
condition is shown in Figure III-4.
Temperature 120 °C
At 1034 kPa (150 psig), the photographs (Appendix, Figure B-4) showed that
the spray broke into spherical droplets at a distance of 300 mm from the nozzle.
However, the measurements from the Malvern laser still exhibited moderately large
SMDs. The results should be reliable from the measurements at 391 mm from the
nozzle because of the complete bell-shaped curve of the histograms. The lowest SMD at
this condition was 85 micron.
At 2068 kPa (300 psig), considerable atomization was observed from
photographs in Appendix, Figure B-5. The photographs showed the mature aerosol
region after the distance 240 mm from the nozzle. The histograms suggested that
measurements were accurate after a distance of 241 mm from the nozzle. Also, the
obscuration and Log. Diff values were in the accurate range. The smallest SMD
measured by the Malvern laser was 60 micron.
At 3447 kPa (500 psig), substantial atomization was observed. The photographs
in Appendix, Figure B-6 showed the mature region after a distance of 180 mm from the
nozzle. The histograms have complete bell-shaped curve as in Figure III-2, suggesting
accurate measurements after a distance of 191 mm from the nozzle. Also, the
53
obscuration and Log. Diff values were in the accurate range. The smallest SMD
measured by the Malvern laser was 39 micron.
These results agree with the expected trend. Higher pressures cause more
atomization, resulting in smaller droplet sizes. The effect of injection pressure at this
condition is shown in Figure III-5.
Temperature 150 °C
At 1034 kPa (150 psig), the range of SMDs were from 119 to 148 micron. Again
the spray was not mature at this condition as shown in Appendix, Figure B-7. Notice in
Figure III-4 that the drop size range was relatively narrow or the SMDs at all conditions
were the same. The light intensity curve showed that at all distances, laser light of very
high intensity fell onto the first two ring diodes. Near the nozzle, a high light intensity
was detected on the outer rings, ring 19-20, because some atomization to very fine
droplets occurred. At the farther distance, more light intensity fell on ring 10-15,
meaning larger droplets were detected. However when the SMDs were calculated, a
large number of large droplets plus some of the small droplets would yield the same
value as some amount of large droplets plus a large amount of small droplets. The type
of light intensity curve is shown in Figure III-6, and Figure III-7, and Figure III-8.
54
0.00
30.00
60.00
90.00
120.00
150.00
180.00
210.00
0 50 100 150 200 250 300 350 400 450
Distance from the nozzle (mm)
150 psig 300 psig 500 psig
Figure III-5. Effect of injection pressure on atomization @ 120 °C (orifice:
0.20 mm)
At 2068 kPa (300 psig), as observed from photographs in Figure B-8 in
Appendix B, page 96, the spray appeared mature after a distance of 180 mm from the
nozzle. The SMD at a distance of 191 mm from the nozzle was as low as 39 micron and
increased after that, perhaps because of droplet coalescence. The measurement was
believed to be accurate after a distance of 141 mm from the nozzle, because the
histograms showed a complete bell-shaped curve, as shown in Figure III-2, and the
obscurations were in the working range of the Malvern laser. The Log. Diff values were
a little high, but they were still within the acceptable range.
55
Figure III-6. Light intensity curve, pattern I
Figure III-7. Light intensity curve, pattern II
56
Figure III-8. Light intensity curve, pattern III
At 3447 kPa (500 psig), the spray appeared mature after a distance of 141 mm
from the nozzle, as in Appendix, Figure B-9. The SMD went down to as low as 35
micron at a distance of 191 mm from the nozzle and increased after that. From Figure
III-9, it was noticed that the results of 2068 kPa (300 psig) and 3447 kPa (500 psig)
conditions were not very different, perhaps because the droplets were approaching
stable droplet sizes.
Temperature 190 °C
Experiments at this temperature were conducted only at 2068 kPa (300 psig)
because of the beam steering effect. From photographs in Appendix, Figure B-10, the
spray appeared mature after 180 mm from the nozzle, and the histograms showed
complete bell-shaped curves as in Figure III-2, after 341 mm from the nozzle. However,
from Figure III-10 the result at this condition did not agree with the expected trend.
57
Also, the histograms showed complete bell-shaped curves even farther than at 150 °C.
However, the light intensity curves showed very high peaks in the first two ring diodes.
We believe that this was caused by the beam steering effect. Due to this effect, drop size
data taken in this condition are not reliable.
0
20
40
60
80
100
120
140
160
180
0 50 100 150 200 250 300 350 400 450
Distance from the Nozzle (mm)
150 psig 300 psig 500 psig
Figure III-9. Effect of injection pressure on atomization @ 150 °C (orifice:
0.20 mm)
Study II: The Effect of Temperature on Atomization with Orifice: 0.20 mm
Although 5 temperatures were studied in this experiment, only 4 temperatures
will be discussed here. At 190 °C, the large difference in temperature between the spray
and the surrounding air causes a gradient in the refractive index along the path of the
laser, which results in a steering or shifting of the laser beam. The beam impinges on
the first and second ring diodes producing a bias to the large droplet count with an
increase in the SMD. The evidence of this effect could be seen in the light intensity
58
curve. Unlike sprays of other temperatures, the 150 °C-spray gave high light intensity at
the first ring diodes, as shown in Figure III-8. This intensity was not because of the
presence of many large drops, and photographs at this condition in Figure B-7 indicated
otherwise. Hence, the high light intensity detected at the first ring diodes was caused by
the beam steering effect.
Pressure 1034 kPa (150 psig)
In spite of the fact that all sprays at 1034 kPa (150 psig) were not mature, as
discussed in Study I, we still observed the trend, as shown in Figure III-11. As the
temperature increases, the SMD decreases because at higher temperatures, the liquid
surface tension and viscosity are lower causing higher atomization. However, the result
at 150 °C did not agree with this trend because of the beam steering effect.
0
50
100
150
200
250
300
350
0 50 100 150 200 250 300 350 400 450
Distance from the nozzle (mm)
80 °C 100 °C 120 °C 150 °C 190 °C
Figure III-10. Effect of temperature on atomization @ 2068 kPa (300 psig) (orifice:
0.20 mm)
59
0
50
100
150
200
250
300
350
400
0 50 100 150 200 250 300 350 400 450
Distance from the nozzle (mm)
80 °C 100 °C 120 °C 150 °C
Figure III-11. Effect of temperature on atomization @ 1034 kPa (150 psig) (orifice:
0.20 mm)
Pressure 2068 kPa (300 psig)
As shown in Figure III-10, the sprays at all temperatures mature after a distance
of 200 mm from the nozzle. The trend, of SMD decreasing as temperature increases,
was as expected. However, at the distance greater than 200 mm, the SMDs were too
close together to be resolved by the Malvern laser, perhaps because the effect of
pressure is more significant than the effect of temperature. The effect of beam steering
was very significant at 190 °C, and the SMD at this condition was larger than expected.
Also the light intensity showed very high peak at the first ring, as shown in Figure III-8.
The function “Kill Data” was applied to only the data in the range of 241 mm to 441
mm from the nozzle to correct data in the mature spray region. The “Kill Data” function
was applied only to the first Malvern laser detector ring diode, as the light intensity was
abnormally high in this ring. To have light intensity in ring one much higher than ring
two was abnormal because the light intensity curve should have the characteristic bell-
60
shap. Also killing data from the second detector ring diode did not improve the data
because the SMD did not change much and the Log. Diff value was poorer than after
killing data of only the first ring. Figure III-12 shows effect of temperature on
atomization at 2068 kPa (300 psig) with the application of function “Kill Data.” After
applying the function “Kill Data” to the first ring, the SMDs of 190 °C were still larger
than the SMDs of 150 °C, but very close to each other. At the distance 441 mm from the
nozzle the SMD of 190 °C was actually smaller than the SMD of 150 °C.
0.00
50.00
100.00
150.00
200.00
250.00
300.00
350.00
0 50 100 150 200 250 300 350 400 450
Distance from the nozzle (mm)
80 °C 100 °C 120 °C 150 °C 190 °C
Figure III-12. Effect of temperature on atomization @ 2068 kPa (300 psig) (orifice:
0.20 mm) after the application of function “Kill Data”
Pressure 3447 kPa (500 psig)
Considering Figure III-13, the trend in the mature spray region at 3447 kPa (500
psig) was hardly seen. The pressure was so high that it overcame the temperature effect.
Also the SMDs of each temperature were too close to each other to distinguish because
of the limitation in the accuracy of the Malvern laser measurement.
61
0
20
40
60
80
100
120
140
160
180
200
0 50 100 150 200 250 300 350 400 450
Distance from the nozzle (mm)
80 °C 100 °C 120 °C 150 °C
Figure III-13. Effect of temperature on atomization @ 3447 kPa (500 psig) (orifice:
0.20 mm)
Study III: The Effect of Injection Pressure on Atomization with Orifice: 0.36 mm
To study the effect of pressure on droplet size of HTF aerosol, three pressures,
1034 kPa (150 psig), 2068 kPa (300 psig), and 3447 kPa (500 psig), were selected. The
experiments were conducted with these three pressures at temperature of 80, 100, and
120 °C. Temperatures 150 and 190 °C were not considered because of the beam
steering effect. Table III-2 shows the experiments that were conducted.
Table III-2. Conditions of experiments for orifice size of 0.36 mm80 °C 100 °C 120 °C
1034 kPa (150 psig)
2068 kPa (300 psig)
3447 kPa (500 psig)
62
Temperature 80 °C
At 1034 kPa (150 psig), the photographs in Figure B-1 showed that the spray
was not mature, so the drop size measurements from the Malvern laser were not
accurate. The SMDs range from 173 to 412 micron, and the droplet size decreases at
greater distance from the nozzle. The trend was similar to that of orifice size 0.20 mm,
or as the pressure goes up the SMD goes down.
At 2068 kPa (300 psig), the photographs in Figure B-4 showed a high degree of
atomization after 300 mm from the nozzle, and the histogram showed a complete bell-
shaped curve or a mature spray region after the distance 441 mm from the nozzle.
However, according to the histograms, the spray was still composed of many large
droplets and ligaments. Therefore, the drop size measurements were not accurate
because the Malvern assumes spherical droplets.
At 3447 kPa (500 psig), the spray up to 291 mm was composed of many large
drops. The measurements after this distance were not reliable because of the very high
obscuration. When the obscuration is higher than 50%, there exits multiple light
scattering, where the laser light ray is scattered by more than one drop resulting in lower
SMDs.
Figure III-14 shows the effect of injection pressure on atomization at this
condition.
Temperature 100 °C
This temperature showed the expected trend for the pressure effect that as
pressure increases the drop size decreases.
At 1034 kPa (150 psig), the spray again was not mature. None of the histograms
at each measurement showed a complete bell-shaped curve and the obscurations were
too low. The SMDs ranged from 144 to 342 micron.
63
0
50
100
150
200
250
300
350
400
450
0 50 100 150 200 250 300 350 400 450
Distance from the nozzle (mm)
150 psig 300 psig 500 psig
Figure III-14. Effect of injection pressure on atomization @ 80 °C (orifice: 0.36
mm)
0
50
100
150
200
250
300
350
400
0 50 100 150 200 250 300 350 400 450
Distance from the nozzle (mm)150 psig 300 psig 500 psig
Figure III-15. Effect of injection pressure on atomization @ 100 °C (orifice:
0.36 mm)
64
At 2068 kPa (300 psig), the spray was still not very mature, so the experimental
results were not accurate. However, the obscuration at this pressure was higher than at
1034 kPa (150 psig), from which could be concluded that more atomization occurred at
this condition.
At 3447 kPa (500 psig), the spray seemed to be mature after 141 mm from the
nozzle. The obscurations after 341 mm from the nozzle were high enough for the
multiple scattering phenomena. The Log. Diff values indicate that the SMD values
obtained are of greater accuracy. The SMD decreased to 34 micron at 341 mm from the
nozzle.
Figure III-15 shows the effect of injection pressure on atomization at this
condition.
Temperature 120 °C
The trend was normal for the pressure effect that as pressure increases the drop
size decreases. At 1034 kPa (150 psig) the spray was not mature because the spray was
composed of many large droplets or ligaments according to histograms. The SMDs
ranged from 139 to 296 micron.
At 2068 kPa (300 psig), the spray seemed mature after 341 mm from the nozzle.
The SMDs decreased to 48 micron at 441 mm from the nozzle. Both obscurations and
Log. Diff values were in the acceptable ranges. Here the results were reliable in the
mature spray region.
At 3447 kPa (500 psig), the measurements were made only until 191 mm from
the nozzle. This was because the degree of atomization was high resulting in high
obscurations and may result in inaccurate measurements. The lowest SMD at this
condition was 39 micron.
Figure III-16 shows the effect of injection pressure on atomization at this
condition.
65
0
50
100
150
200
250
300
350
0 50 100 150 200 250 300 350 400 450 500
Distance from the nozzle (mm)
Sau
ter
Mea
n D
iam
eter
(mic
ron)
150 psig 300 psig 500 psig
Figure III-16. Effect of injection pressure on atomization @ 120 °C (orifice: 0.36 mm)
Study IV: The Effect of Temperature on Atomization with Orifice: 0.36 mm
As temperature increases, the SMD is expected to decreases.
Pressure 1034 kPa (150 psig)
The SMDs at all temperatures were not very far apart. The results, as shown in
Figure III-17, exhibit the expected trend: as the temperature increases, the drop size
decreases. However, as mentioned in Study III, all of the sprays at 1034 kPa (150 psig)
were not mature, and hence the measurements were not accurate.
Pressure 2068 kPa (300 psig)
Consider Figure III-18. The results also showed the expected trend: as the
temperature increases, the SMD decreases. The measurements at all temperatures were
accurate after 441 mm from the nozzle.
66
0
50
100
150
200
250
300
350
400
450
0 50 100 150 200 250 300 350 400 450 500
Distance fron the nozzle (mm)80°C 100°C 120°C
Figure III-17. Effect of temperature on atomization @ 150 psig (orifice: 0.36 mm)
0
40
80
120
160
200
240
0 50 100 150 200 250 300 350 400 450 500
Distance from the nozzle (mm)
80°C 100°C 120°C
Figure III-18. Effect of temperature on atomization @ 300 psig (orifice: 0.36 mm)
67
0.00
20.00
40.00
60.00
80.00
100.00
120.00
140.00
160.00
0 50 100 150 200 250 300 350 400 450
Distance from the nozzle (mm)80°C 100°C 120°C
Figure III-19. Effect of temperature on atomization @ 500 psig (orifice Size:
0.36 mm)
Pressure 3447 kPa (500 psig)
Consider Figure III-19. The results showed that the SMDs for the 80 °C spray
were larger than those for the 100 °C spray. This result agrees with the expected trend.
Measurements were made up to only 191 mm from the nozzle because the degree of
atomization was high resulting in high obscurations and inaccurate measurements
Study V: The Effect of Orifice Size on Atomization
Two orifice sizes, 0.20 mm and 0.36 mm were prepared for this study.
According to equation (I-14) ,89.1 dD = a larger drop size is expected from a larger
nozzle. The result at 1034 kPa (150 psig), as shown in Figure III-20, Figure III-21, and
Figure III-22, will not be discussed here because the sprays are not mature resulting in
inaccurate drop size measurement.
68
0
100
200
300
400
500
0 100 200 300 400Distance from the nozzle (m m )
Sau
ter
Mea
n D
iam
eter
(m
icro
n)
0.20 mm 0.36 mm
Figure III-20. Effect of orifice size on atomization @ 150 psig and 80 °C
0
60
120
180
240
300
360
0 100 200 300 400
Distance from the nozzle (mm)
Sau
ter
Mea
n D
iam
eter
(m
icro
n)
0.20 mm 0.36 mm
Figure III-21. Effect of orifice size on atomization @ 150 psig and 100 °C
69
0
100
200
300
400
0 100 200 300 400
Distance from the nozzle (mm)
Sau
ter
Mea
n D
iam
eter
(m
icro
n)
0.20 mm 0.36 mm
Figure III-22. Effect of orifice size on atomization @ 150 psig and 120 °C
At 2068 kPa (300 psig), the results, as shown in Figure III-23, Figure III-24, and
Figure III-25, agree with the trend, except that at temperature 120 °C the SMDs of both
orifices were too close for the Malvern measurement to distinguish.
0
100
200
300
400
0 100 200 300 400
Distance from the nozzle (m m )
Sau
ter
Mea
n D
iam
eter
(m
icro
n)
0.20 m m 0.36 m m
Figure III-23. Effect of orifice size on atomization @ 300 psig and 80 °C
70
050
100
150
200250
300
0 100 200 300 400Distance from the nozzle (mm)
Sau
ter
Mea
n D
iam
eter
(m
icro
n)
0.20 mm 0.36 mm
Figure III-24. Effect of orifice size on atomization @ 300 psig and 100 °C
0.00
60.00
120.00
180.00
240.00
0 100 200 300 400Distance from the nozzle (m m )
Sau
ter
Mea
n D
iam
eter
(m
icro
n)
0.20 mm 0.36 mm
Figure III-25. Effect of orifice size on atomization @ 300 psig and 120 °C
At 3447 kPa (500 psig), the expected trend was very obvious at a temperature of
80 °C, as shown in Figure III-26. Consider Figure III-27. At a temperature of 100 °C,
the SMDs of both orifices were too close for the Malvern measurement to distinguish.
The results at temperature 120 °C, as shown in Figure III-28, indicated that the
obscurations were too high, so the measurements were stopped at 191 mm from the
nozzle.
71
It was also noticed that at the same conditions of temperature and pressure, the
obscuration of sprays from the 0.36 mm nozzle were higher than that from the 0.20 mm
nozzle because more liquid mass was present.
0
20
40
60
80
100
0 100 200 300 400Distance from the nozzle (mm)
Sau
ter
Mea
n D
iam
eter
(m
icro
n)
0.20 mm 0.36 mm
Figure III-26. Effect of orifice size on atomization @ 500 psig and 80 °C
0
30
60
90
120
150
0 100 200 300 400
Distance from the nozzle (mm)
Sau
ter
Mea
n D
iam
eter
(m
icro
n)
0.20 mm 0.36 mm
Figure III-27. Effect of orifice size on atomization @ 500 psig and 100 °C
72
0
50
100
150
200
0 100 200 300 400
Distance from the nozzle (mm)
Sau
ter
Mea
n D
iam
eter
(m
icro
n)
0.20 mm 0.36 mm
Figure III-28. Effect of orifice size on atomization @ 500 psig and 120 °C
73
CHAPTER IV
CONCLUSIONS AND RECOMMENDATIONS
Heat transfer fluids are combustible fluids, which are not generally considered tobe flammable at temperatures below the flash points. However, this is not true for HTFaerosols. This work presents the first measurements of drop size distributions of HTFaerosols, created from leaks in pressurized containers or process lines. The effects ofconditions, such as temperature, pressure, leak size, and the distance from the nozzle onaerosol formation and on the aerosol droplet size distributions are presented. These datawill help industry predict operating conditions that could create aerosols and at whatdistances from the leaks. Moreover, the effect of each operating condition can helpindustry estimate the potential of aerosol formation beyond the present experimentalmeasurements.
ConclusionsThis work demonstrates that, HTF aerosols can form at temperatures below the
fluid flash points, especially at high pressures. Experiments were undertaken to study
the effects of pressure, temperature, and orifice size on HTF aerosols formed from
process leaks. Droplet size distributions were measured by a Malvern Laser Diffraction
Particle Analyzer. Photographs were taken in some cases for visualization of the
atomization.
The Effect of Injection Pressure
The experimental results showed that as the injection pressure increases, the
aerosol droplet size decreases, as expected. As the pressure increases the drop breaks up
further to maintain its stability. Moreover, at higher injection pressures the liquid sprays
have higher velocities, which increases the friction force between the jet surface and the
surrounding air, resulting in greater instability. The results showed also that the pressure
of 1034 kPa (150 psig) for all temperatures and orifice sizes was too low to create a
mature aerosol. These sprays were immature and only moderate atomization occurred at
large distances from the nozzle exit. At all temperatures, the drop size data at 2068 kPa
(300 psig), and 3447 kPa (500 psig) were very similar, ranged around 30 to 70 micron,
and at the mature region both jets had constant droplet sizes. In some cases, especially
with the orifice size of 0.36 mm at 120 °C, the obscuration was too high, greater than
74
70%, indicating that multiple light scattering has a significant effect on drop size
measurements.
The Effect of Temperature
The experimental results supported the expected trend. At temperatures of 80,
100 and 120 °C, the droplet size decreases when the temperature increases. Viscosity
and surface tension of the HTF decrease when the temperature increases so the liquid
stream more easily into drops. However, there were some measurements that we believe
gave inaccurate results. At 150 and 190 °C, the droplet sizes were larger than the
droplet sizes of 120 °C, perhaps because of the beam steering effect (see explanation in
Chapter II, Limitation of FD and in Chapter III). These results could be corrected by the
option “Kill data” in the Malvern software to eliminate the light intensity on the rings
that were affected by the beam steering. The average of the remainder of the data should
provide more accurate drop size measurements.
It should be emphasized that temperatures as low as 80 °C, which is well below
the flash point for the measurement HTF, can create aerosols, especially at pressures
higher than 2068 kPa (300 psig). With the orifice size of 0.20 mm, the SMD can be as
low as 67 micron.
The Effect of Orifice Size
A larger orifice size results in a larger jet diameter, which consequently results
in a higher SMD value (see Chapter I, Breakup of a Drop, and Chapter III). The
experimental results agreed with expectations except at 1034 kPa (150 psig). At this
condition, the sprays were streams consisting of many large drops and ligaments, and
hence the Malvern drop size measurements were not accurate.
Both orifice sizes of 0.20 and 0.36 mm have potential to create aerosol at any
temperature in the range 80 to 190 °C, and for pressures above 2068 kPa (300 psig).
75
Recommendations
This work indicates conditions at which HTF aerosols can be formed, and it also
suggests the aerosol droplet size distributions at each condition. It is obvious that
aerosol formation and droplet size distributions depend upon the fluid properties. To
develop an aerosol model, more droplet size distribution data of various fluids that
represent the range of HTF used in industry are needed. Also, wider ranges of operating
conditions and orifice sizes must be tested. HTF Droplet size distributions are only the
initial data to characterize HTF handling. The drop size data can be used as input for an
aerosol dispersion model. Information about aerosol combustion is also needed for
identifying hazards of aerosol releases. To study flammability, open-air experiments
should be conducted to measure the upper and lower explosive limits of HTF aerosol/air
mixtures as a function of fluid properties.
76
LITERATURE CITED
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Bowen, P.J., and L.C. Shirvill, “Combustion Hazards Posed by the PressurizedAtomization of High-Flash Point Liquid,” J. Loss Prev. Process Ind., 7(3), 233-241(1994).
Brown, R. and J.L. York, “Sprays Formed by Flashing Liquid Jets,” AIChE J., 8(2),149-153 (1962).
Eichhorn, J., “Careful! Mist Can Explode,” Petroleum Refiner, 34(11), 194-196 (1955).
Elkotb, M.M., “Fuel Atomization for Spray Modeling,” Prog. Energy Combust Sci. 8,61-91 (1982).
Faeth, G.M., “Evaporation and Combustion of Sprays,” Progress in Energy andCombustion Science, 9(1-2), 1-76 (1983).
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80
APPENDIX A
EXPERIMENTAL DATASHEETS
81
Date: 01/27/2000
Substance: Heat Transfer Fluid, alkylated aromatic
Orifice Size: 0.20 mm
Pressure: 1034 kPa (150 psig)
Temperature: 80 °CRoom Temperature: 17.5 °C
Table A-1. Data at 80 °C and 1034 kPa (150 psig) for 0.20 mm
orifice size
Distance from thenozzle
Temperature (°C) Pressure Obscuration Log. Diff Droplet Size
x (mm) Nozzle Cell kPa % micron
41 80.1 80.3 1189.543 21.27 4.590 312.00
91 80.1 80.2 1189.971 19.01 3.906 314.81
141 80.6 80.1 1099.854 12.21 2.571 349.38
191 80.9 80.1 1100.042 11.30 3.532 301.05
241 80.7 80.3 1100.651 10.72 3.738 277.14
291 80.4 80.4 1111.504 10.14 4.148 270.33
341 80.3 80.6 1100.487 8.34 4.093 264.26
391 80.4 80.7 1100.675 7.27 3.990 220.81
441 80.4 80.7 1112.049 5.40 4.424 201.64
82
Date: 02/17/2000
Substance: Heat Transfer Fluid, alkylated aromatic
Orifice Size: 0.20 mm
Pressure: 2068 kPa (300 psig)
Temperature: 80 °CRoom Temperature: 24.2 °C
Table A-2. Data at 80 °C and 2068 kPa (300 psig) for 0.20 mm
orifice size
Distance from thenozzle
Temperature (°C) Pressure Obscuration Log. Diff Droplet Size
x (mm) Nozzle Cell kPa % micron
41 79.7 79.7 2067.319 20.61 4.734 328.95
51 81.0 80.5 2067.276 15.71 4.559 318.56
61 81.2 80.8 2078.768 12.92 4.371 328.95
71 81.2 80.8 2090.370 9.93 4.002 301.87
81 81.3 80.8 2090.370 9.46 3.890 292.73
91 81.2 80.7 2090.348 8.17 4.352 250.03
141 81.1 80.3 2067.190 6.94 4.931 127.23
191 81.2 80.3 2078.768 12.09 4.961 119.63
241 81.7 80.7 2078.790 13.76 4.943 86.55
291 81.8 80.1 2090.239 14.04 5.017 72.74
341 81.8 80.1 2090.283 16.74 4.952 68.47
391 81.7 80.2 2090.261 16.37 4.768 67.87
441 81.8 80.2 2078.833 16.45 4.578 83.59
83
Date: 03/23/2000
Substance: Heat Transfer Fluid, alkylated aromatic
Orifice Size: 0.20 mm
Pressure: 3447 kPa (500 psig)
Temperature: 80 °C
Room Temperature: 21.5 °C
Table A-3. Data at 80 °C and 3447 kPa (500 psig) for 0.20 mm orifice size
Distance from thenozzle
Temperature (°C) Pressure Obscuration Log. Diff Droplet Size
x (mm) Nozzle Cell kPa % micron
41 80.8 83.2 3407.055 28.90 4.764 184.82
91 80.1 83.4 3407.193 37.07 5.097 119.26
141 80.7 83.6 3395.741 36.86 5.192 107.74
191 80.8 83.7 3407.020 37.67 2.765 71.57
241 81.0 83.9 3407.020 37.23 4.995 61.08
291 80.9 83.9 3395.741 36.96 4.644 55.40
341 80.8 84.0 3395.568 32.73 4.367 51.35
391 80.7 84.1 3384.322 33.16 4.222 59.64
441 81.2 84.2 3384.391 30.08 3.875 56.60
84
Date: 04/15/2000
Substance: Heat Transfer Fluid, alkylated aromatic
Orifice Size: 0.20 mm
Pressure: 1034 kPa (150 psig)
Temperature: 100 °C
Room Temperature: 22.6 °C
Table A-4. Data at 100 °C and 1034 kPa (150 psig) for 0.20 mm
orifice size
Distance from thenozzle
Temperature (°C) Pressure Obscuration Log. Diff Droplet Size
x (mm) Nozzle Cell kPa % micron
41 103.0 101.0 1037.895 5.40 4.821 331.49
91 102.5 100.8 946.144 19.89 4.431 279.50
141 101.9 100.8 946.154 17.27 4.451 302.03
191 101.8 100.8 946.134 7.07 4.438 316.27
241 102.1 100.9 946.144 3.18 4.478 244.49
291 101.7 100.9 934.677 1.62 4.878 229.54
341 101.7 101.1 946.154 2.19 5.011 163.15
391 101.3 101.2 946.134 4.03 5.324 131.04
441 101.2 101.2 957.622 2.77 5.265 139.31
85
Date: 04/15/2000
Substance: Heat Transfer Fluid, alkylated aromatic
Orifice Size: 0.20 mm
Pressure: 2068 kPa (300 psig)
Temperature: 100 °C
Room Temperature: 22.6 °C
Table A-5. Data at 100 °C and 2068 kPa (300 psig) for 0.20 mm
orifice size
Distance from thenozzle
Temperature (°C) Pressure ObscurationLog.Diff
Droplet Size
x (mm) Nozzle Cell kPa % micron
41 101.2 101.4 2092.885 36.05 5.044 259.52
91 101.2 101.4 2081.374 33.75 4.941 151.19
141 100.9 101.5 2092.906 20.11 4.974 136.52
191 100.7 101.6 2047.036 27.69 5.427 112.70
241 100.6 101.6 2081.396 31.63 5.376 67.13
291 100.6 101.6 2047.015 29.61 5.158 64.30
341 100.4 101.6 2081.439 29.31 5.045 65.61
391 100.4 101.6 2069.993 25.17 4.680 56.23
441 100.3 101.5 2069.993 24.81 4.722 59.41
86
Date: 04/15/2000
Substance: Heat Transfer Fluid, alkylated aromatic
Orifice Size: 0.20 mmPressure: 3447 kPa (500 psig)
Temperature: 100 °C
Room Temperature: 22.7 °C
Table A-6. Data at 100 °C and 3447 kPa (500 psig) for 0.20 mm
orifice size
Distance from thenozzle
Temperature (°C) Pressure ObscurationLog.Diff
Droplet Size
x (mm) Nozzle Cell kPa % micron
41 100.3 101.6 3365.835 41.36 5.972 63.88
91 100.1 101.4 3388.770 47.44 6.234 62.94
141 100.1 101.4 3365.801 45.02 4.917 40.59
191 100.3 101.4 3583.720 41.43 4.721 35.23
241 100.1 101.3 3377.268 41.12 4.503 36.85
291 100.2 101.1 3457.541 41.83 4.312 39.15
341 100.2 100.7 3457.576 38.39 4.145 39.57
391 100.2 100.9 3469.008 39.40 4.432 40.62
441 100.3 101.4 3423.104 35.10 4.082 44.17
87
Date: 03/01/2000
Substance: Heat Transfer Fluid, alkylated aromatic
Orifice Size: 0.20 mm
Pressure: 1034 kPa (150 psig)
Temperature: 120 °C
Room Temperature: 23.3 °C
Table A-7. Data at 120 °C and 1034 kPa (150 psig) for 0.20 mm
orifice size
Distance from thenozzle
Temperature (°C) Pressure ObscurationLog.Diff
Droplet Size
x (mm) Nozzle Cell kPa % micron
41 120.5 120.6 1054.461 27.19 5.063 197.31
91 120.4 120.7 1054.552 21.89 5.072 178.54
141 120.5 120.8 1054.564 18.64 5.631 120.20
191 120.5 120.8 1054.564 17.17 5.540 98.61
241 120.7 120.5 1054.564 16.30 5.636 90.43
291 120.5 120.6 1054.552 16.30 5.674 83.26
341 120.6 120.4 1054.541 16.40 5.636 94.93
391 120.3 120.4 1054.495 15.34 5.542 84.60
441 120.5 120.4 1054.541 16.81 5.559 93.66
88
Date: 02/13/2000
Substance: Heat Transfer Fluid, alkylated aromatic
Orifice Size: 0.20 mm
Pressure: 2068 kPa (300 psig)
Temperature: 120 °C
Room Temperature: 22.5 °C
Table A-8. Data at 120 °C and 2068 kPa (300 psig) for 0.20 mm
orifice size
Distance from thenozzle
Temperature (°C) Pressure ObscurationLog.Diff
Droplet Size
x (mm) Nozzle Cell kPa % micron
41 120.2 121.6 2056.916 8.89 6.5120 96.57
51 120.2 120.7 2091.347 37.93 5.4810 112.70
61 120.3 119.7 2091.347 37.45 5.4520 99.04
71 120.9 119.4 2091.325 35.26 5.5530 91.87
81 120.4 121.2 2056.809 21.82 5.7010 44.58
91 120.3 121.8 2068.415 21.83 5.5170 46.68
141 120.4 121.7 2091.456 26.00 5.3850 51.61
191 120.5 121.8 2079.979 30.80 5.2805 59.74
241 120.1 121.4 2079.935 27.03 5.2980 66.09
291 120.4 120.1 2091.456 34.48 5.0420 63.80
341 120.4 120.8 2091.456 32.63 5.0300 63.13
391 120.0 121.3 2079.935 32.87 4.9860 67.50
441 120.2 121.7 2079.935 34.11 4.7960 68.98
89
Date: 03/23/2000
Substance: Heat Transfer Fluid, alkylated aromatic
Orifice Size: 0.20 mm
Pressure: 3447 kPa (500 psig)
Temperature: 120 °C
Room Temperature: 21.5 °C
Table A-9. Data at 120 °C and 3447 kPa (500 psig) for 0.20 mm
orifice size
Distance from thenozzle
Temperature (°C) Pressure ObscurationLog.Diff
Droplet Size
x (mm) Nozzle Cell kPa % micron
41 120.7 120.2 3430.099 49.60 5.669 180.16
141 120.9 119.2 3430.029 49.18 5.703 63.13
191 120.9 121.2 3384.804 55.93 5.602 39.49
241 121.2 121.0 3384.977 55.74 5.329 39.02
291 121.1 120.9 3384.977 53.95 5.064 38.83
341 121.1 121.0 3373.556 52.50 4.802 41.90
391 121.0 121.1 3373.762 50.49 4.610 44.64441 121.0 121.1 3362.238 46.77 4.492 45.35
Date: 02/17/2000
90
Substance: Heat Transfer Fluid, alkylated aromaticOrifice Size: 0.20 mm
Pressure: 1034 kPa (150 psig)
Temperature: 150 °C
Room Temperature: 23.3 °C
Table A-10. Data at 120 °C and 1034 kPa (150 psig) for 0.20 mm
orifice size
Distance from thenozzle
Temperature (°C) Pressure Obscuration Log. Diff Droplet Size
x (mm) Nozzle Cell kPa % micron
41 151.2 151.1 1123.950 5.63 6.064 118.81
91 150.8 151.1 1123.877 17.45 5.310 145.94
141 150.7 151.1 1123.877 21.65 4.965 140.39
191 150.5 151.0 1135.411 24.25 4.810 147.01
241 150.2 150.9 1135.399 24.73 4.837 148.47
291 150.3 150.9 1123.877 24.19 4.978 135.87
341 150.7 150.8 1135.399 22.57 4.976 131.85
391 150.6 150.8 1135.399 23.17 4.935 130.55
441 150.8 150.9 1135.387 22.01 4.947 127.66
91
Date: 02/17/2000
Substance: Heat Transfer Fluid, alkylated aromaticOrifice Size: 0.20 mm
Pressure: 2068 kPa (300 psig)
Temperature: 150 °C
Room Temperature: 24 °C
Table A-11. Data at 120 °C and 2068 kPa (300 psig) for 0.20 mm
orifice size
Distance from thenozzle
Temperature (°C) Pressure ObscurationLog. Diff
Droplet Size
x (mm) Nozzle Cell kPa % micron
41 150.5 150.2 2055.633 21.11 5.631 147.89
51 151.2 151.3 2055.612 26.64 5.451 159.27
61 150.8 151.7 2055.590 28.97 5.414 161.67
71 151.1 151.7 2044.077 29.71 5.405 156.79
81 150.3 151.1 2055.505 33.32 5.403 147.89
91 150.6 150.6 2067.082 28.18 5.430 122.50
121 150.9 150.4 2067.082 33.61 5.283 113.97
141 150.1 150.2 2078.660 27.30 5.873 61.04
191 150.5 150.4 2078.704 26.54 5.730 38.71
241 149.9 150.8 2078.617 30.83 5.682 50.54
291 149.8 150.8 2067.297 29.95 5.558 48.15
341 150.1 150.8 2055.548 30.15 5.439 48.56
391 150.3 151.1 2090.218 30.86 5.252 51.29
441 150.45 150.5 2078.477 31.50 5.250 64.59
92
Date: 02/20/2000
Substance: Heat Transfer Fluid, alkylated aromaticOrifice Size: 0.20 mm
Pressure: 3447 kPa (500 psig)
Temperature: 150 °C
Room Temperature: 18.5 °C
Table A-12. Data at 120 °C and 3447 kPa (500 psig) for 0.20 mm
orifice size
Distance from thenozzle
Temperature (°C) Pressure ObscurationLog.Diff
Droplet Size
x (mm) Nozzle Cell kPa % micron
41 150.2 150.8 3547.019 41.38 6.183 68.93
51 150.6 151.7 3547.019 46.59 6.159 68.59
61 150.7 151.8 3547.055 58.48 4.904 94.65
71 150.7 151.3 3547.127 54.33 6.008 78.34
81 150.4 151.1 3546.982 54.08 5.905 73.81
91 150.7 151.2 3547.037 52.21 5.287 79.72
121 150.6 151.9 3558.588 51.13 5.598 52.97
141 151.1 151.5 3547.019 57.67 5.514 42.20
191 150.7 151.6 3547.019 55.08 5.419 34.76
241 151.0 151.7 3547.019 52.77 5.201 35.16
291 151.1 151.5 3558.552 49.49 5.121 38.49
341 151.2 151.9 3547.019 44.50 5.124 41.32
391 151.0 151.6 3558.588 43.27 4.922 45.32
441 151.1 151.5 3547.091 41.58 4.917 46.05
93
Original data
Date: 02/18/2000
Substance: Heat Transfer Fluid, alkylated aromaticOrifice Size: 0.20 mm
Pressure: 2068 kPa (300 psig)
Temperature: 190 °C
Room Temperature: 22.7 °C
Table A-13. Data at 190 °C and 2068 kPa (300 psig) for 0.20 mm
orifice size
Distance from thenozzle
Temperature (°C) Pressure ObscurationLog. Diff
Droplet Size
x (mm) Nozzle Cell kPa % micron
41 191.1 190.0 2101.099 34.63 5.102 219.23
51 190.6 191.1 2078.509 13.16 6.090 99.50
61 190.3 192.1 2077.840 15.24 5.826 31.93
71 189.9 192.3 2077.732 19.94 5.800 34.02
81 189.9 192.3 2089.176 22.33 5.806 56.06
91 190.1 192.3 2089.154 27.66 5.849 67.27
121 189.8 192.1 2089.046 40.14 5.952 71.68
141 189.9 192.2 2088.092 42.94 4.817 106.66
191 189.8 192.5 2088.049 57.88 5.256 99.53
241 189.7 192.1 2099.617 58.62 5.565 71.52
291 190.0 192.2 2099.595 59.40 5.506 65.31
341 190.8 192.2 2099.595 51.62 6.204 58.50
391 191.1 192.2 2076.546 48.39 6.054 67.50
441 190.1 191.8 2099.508 46.57 5.752 72.49
94
Kill Data
Date: 06/05/2000
Substance: Heat Transfer Fluid, alkylated aromaticOrifice Size: 0.20 mm
Pressure: 2068 kPa (300 psig)
Temperature: 190 °C
Room Temperature: 22.7 °C
Table A-13. Data at 190 °C and 2068 kPa (300 psig) for 0.20 mm
orifice size
Distance from thenozzle
Temperature (°C) Pressure ObscurationLog. Diff
Droplet Size
x (mm) Nozzle Cell kPa % micron
41 191.1 190.0 2101.099 34.63 5.102 219.23
51 190.6 191.1 2078.509 13.16 6.090 99.50
61 190.3 192.1 2077.840 15.24 5.826 31.93
71 189.9 192.3 2077.732 19.94 5.800 34.02
81 189.9 192.3 2089.176 22.33 5.806 56.06
91 190.1 192.3 2089.154 27.66 5.849 67.27
121 189.8 192.1 2089.046 40.14 5.952 71.68
141 189.9 192.2 2088.092 42.94 4.817 106.66
191 189.8 192.5 2088.049 57.88 5.256 99.53
241 189.7 192.1 2099.617 58.62 5.565 71.52
291 190.0 192.2 2099.595 59.40 5.506 52.43
341 190.8 192.2 2099.595 51.62 6.204 54.13
391 191.1 192.2 2076.546 48.39 6.054 56.88
441 190.1 191.8 2099.508 46.57 5.752 60.00
Date: 04/06/2000
95
Substance: Heat Transfer Fluid, alkylated aromaticOrifice Size: 0.36 mm
Pressure: 1034 kPa (150 psig)
Temperature: 80 °C
Room Temperature: 23.7 °C
Table A-14. Data at 80 °C and 1034 kPa (150 psig) for 0.36 mm orifice size
Distance from thenozzle
Temperature (°C) Pressure Obscuration Log. Diff Droplet Size
x (mm) Nozzle Cell kPa % micron
41 80.8 82.7 980.038 37.62 4.862 412.47
91 81.0 82.6 968.576 6.95 5.121 220.55
141 80.4 82.5 980.027 11.44 4.822 282.85
191 80.3 82.3 979.996 19.92 4.581 240.69
241 80.3 82.3 968.545 22.35 4.338 229.20
291 80.4 82.3 968.545 22.36 4.337 213.07
341 80.6 82.2 980.017 25.09 4.384 205.36
391 80.7 82.1 968.576 23.50 4.584 186.94
441 80.6 82.2 968.555 22.90 4.750 173.08
96
Date: 04/06/2000
Substance: Heat Transfer Fluid, alkylated aromatic
Orifice Size: 0.36 mm
Pressure: 2068 kPa (300 psig)
Temperature: 80 °C
Room Temperature: 23.7 °C
Table A-15. Data at 80 °C and 2068 kPa (300 psig) for 0.36 mm orifice size
Distance from thenozzle
Temperature (°C) Pressure Obscuration Log. Diff Droplet Size
x (mm) Nozzle Cell kPa % micron
41 80.3 82.2 2011.508 45.81 6.135 86.88
91 80.2 81.5 2000.088 25.00 5.593 130.90
141 79.7 87.7 1965.744 33.53 4.894 153.03
191 80.2 88.2 1954.222 40.53 4.873 139.03
241 80.3 81.3 1965.683 45.84 4.884 130.85
291 81.1 82.2 1965.724 48.03 4.993 120.68
341 79.8 82.2 1965.724 44.26 5.111 106.49
391 79.8 81.9 1965.622 47.68 5.166 93.13
441 80.7 82.0 1965.724 47.39 5.045 87.64
97
Date: 04/06/2000
Substance: Heat Transfer Fluid, alkylated aromatic
Orifice Size: 0.36 mm
Pressure: 3447 kPa (500 psig)
Temperature: 80 °C
Room Temperature: 23.7 °C
Table A-16. Data at 80 °C and 3447 kPa (500 psig) for 0.36 mm orifice size
Distance from thenozzle
Temperature (°C) Pressure Obscuration Log. Diff Droplet Size
x (mm) Nozzle Cell kPa % micron
41 79.8 82.7 3295.081 40.41 5.608 39.85
91 80.6 82.8 3295.383 38.65 5.705 42.83
141 80.7 83.1 3306.912 46.38 5.843 50.54
191 80.7 83.4 3306.677 36.35 5.799 64.66
241 80.4 83.2 3295.249 66.37 5.572 57.30
291 80.7 83.1 3295.417 68.99 5.551 60.87
341 80.6 82.7 3295.349 70.50 5.347 59.47
391 80.7 81.6 3295.417 69.72 5.516 57.30
441 80.7 81.5 3295.417 70.02 5.532 58.33
98
Date: 04/06/2000
Substance: Heat Transfer Fluid, alkylated aromatic
Orifice Size: 0.36 mm
Pressure: 1034 kPa (150 psig)
Temperature: 100 °C
Room Temperature: 21.0 °C
Table A-17. Data at 100 °C and 1034 kPa (150 psig) for 0.36 mm orifice size
Distance from thenozzle
Temperature (°C) Pressure Obscuration Log. Diff Droplet Size
x (mm) Nozzle Cell kPa % micron
41 100.80 101.10 956.586 47.52 4.973 342.27
91 100.70 101.10 956.586 9.67 4.761 294.86
141 100.60 101.00 945.130 25.69 4.786 258.39
191 100.80 100.90 945.140 32.13 4.685 210.73
241 100.70 100.70 933.735 33.97 4.579 207.08
291 100.60 100.40 945.120 34.25 4.791 186.94
341 100.60 100.40 945.130 32.38 4.843 192.61
391 100.60 100.30 945.110 30.74 5.032 143.69
441 100.60 100.40 945.181 29.36 5.019 152.45
99
Date: 04/06/2000
Substance: Heat Transfer Fluid, alkylated aromatic
Orifice Size: 0.36 mm
Pressure: 2068 kPa (300 psig)
Temperature: 100 °C
Room Temperature: 21.5 °C
Table A-18. Data at 100 °C and 2068 kPa (300 psig) for 0.36 mm orifice size
Distance from thenozzle
Temperature (°C) Pressure ObscurationLog.Diff
Droplet Size
x (mm) Nozzle Cell kPa % micron
41 100.3 100.3 1964.807 53.18 5.618 222.96
91 100.7 99.8 1941.834 22.55 5.788 49.84
141 100.3 100.1 1941.794 35.94 5.978 70.69
191 100.3 100.8 1999.136 44.86 6.030 70.27
241 100.5 100.6 1976.264 51.54 5.906 79.73
291 100.7 100.7 1805.697 54.02 5.431 109.98
341 100.8 101.0 1930.398 55.91 5.473 107.61
391 100.4 100.7 1976.264 60.75 5.580 79.92
441 100.6 101.0 1930.398 55.05 5.511 73.26
100
Date: 04/06/2000
Substance: Heat Transfer Fluid, alkylated aromatic
Orifice Size: 0.36 mm
Pressure: 3447 kPa (500 psig)
Temperature: 100 °C
Room Temperature: 22.0 °C
Table A-19. Data at 80 °C and 3447 kPa (500 psig) for 0.36 mm orifice size
Distance from thenozzle
Temperature (°C) Pressure ObscurationLog.Diff
Droplet Size
x (mm) Nozzle Cell kPa % micron
41 100.7 100.6 3214.854 46.90 5.966 124.09
91 102.7 100.9 3123.197 43.31 4.689 34.26
141 100.7 101.0 3111.673 49.56 4.915 31.04
191 100.4 101.1 3111.736 56.81 4.925 34.41
241 100.7 101.3 3123.070 61.40 4.182 34.91
291 100.1 100.6 3123.134 65.48 4.797 37.21
341 100.4 100.7 3123.006 70.02 4.848 39.57
391 100.8 100.9 3111.577 72.03 4.871 42.91
101
Date: 04/06/2000
Substance: Heat Transfer Fluid, alkylated aromatic
Orifice Size: 0.36 mm
Pressure: 1034 kPa (150 psig)
Temperature: 120 °C
Room Temperature: 20.0 °C
Table A-20. Data at 120 °C and 1034 kPa (150 psig) for 0.36 mm orifice size
Distance from thenozzle
Temperature (°C) Pressure ObscurationLog. Diff
Droplet Size
x (mm) Nozzle Cell kPa % micron
41 121.4 121.1 945.150 51.33 5.433 296.23
91 120.4 119.7 945.181 18.27 5.591 168.38
141 120.4 119.7 910.989 30.39 5.324 197.26
191 119.8 120.0 1094.646 40.96 5.099 187.62
241 120.4 120.3 1106.415 40.02 5.032 175.25
291 120.5 120.7 1084.067 41.30 5.034 162.38
341 120.6 121.0 1084.067 39.01 5.113 151.97
391 120.6 121.3 1072.620 36.42 5.219 139.47
441 120.1 121.2 1061.137 36.08 5.246 145.94
102
Date: 04/06/2000
Substance: Heat Transfer Fluid, alkylated aromatic
Orifice Size: 0.36 mm
Pressure: 2068 kPa (300 psig)
Temperature: 120 °C
Room Temperature: 20.0 °C
Table A-21. Data at 120 °C and 2068 kPa (300 psig) for 0.36 mm orifice
size
Distance from thenozzle
Temperature (°C) Pressure ObscurationLog. Diff
Droplet Size
x (mm) Nozzle Cell kPa % micron
41 119.9 121.2 2161.354 65.40 5.730 193.23
91 120.7 120.4 2149.666 39.60 5.932 46.16
141 120.8 120.8 2149.578 50.31 5.694 46.13
191 120.6 120.5 2161.064 55.39 5.586 63.27
241 119.8 121.7 2159.569 59.68 5.635 57.59
291 119.8 121.4 2136.656 63.83 5.486 54.98
341 120.8 121.3 2090.830 64.77 5.424 53.98
391 120.7 121.2 2148.069 66.27 5.376 53.95
441 120.7 121.1 2148.157 65.88 5.223 48.19
103
Date: 04/06/2000
Substance: Heat Transfer Fluid, alkylated aromatic
Orifice Size: 0.36 mm
Pressure: 3447 kPa (500 psig)
Temperature: 120 °C
Room Temperature: 20.0 °C
Table A-22. Data at 120 °C and 3447 kPa (500 psig) for 0.36 mm orifice
size
Distance from thenozzle
Temperature (°C) Pressure ObscurationLog.Diff
Droplet Size
x (mm) Nozzle Cell kPa % micron
41 120.0 121.8 3465.727 78.00 5.966 144.64
91 120.8 121.1 3465.762 54.68 5.685 36.66
141 119.7 120.4 3454.270 69.39 5.680 35.73
191 120.9 121.2 3465.727 71.02 5.642 39.55
104
Date: 04/06/2000
Substance: Heat Transfer Fluid, alkylated aromatic
Orifice Size: 0.36 mm
Pressure: 3447 kPa (500 psig)
Temperature: 100 °C
Room Temperature: 22.0 °C
TableA-23. Data at 100 °C and 3447 kPa (500 psig) for 0.36 mm orifice size
Distance from thenozzle
Temperature (°C) Pressure ObscurationLog.Diff
Droplet Size
x (mm) Nozzle Cell kPa % micron
41 100.7 100.6 3214.854 46.90 5.966 124.09
91 102.7 100.9 3123.197 43.31 4.689 34.26
141 100.7 101.0 3111.673 49.56 4.915 31.04
191 100.4 101.1 3111.736 56.81 4.925 34.41
241 100.7 101.3 3123.070 61.40 4.182 34.91
291 100.1 100.6 3123.134 65.48 4.797 37.21
341 100.4 100.7 3123.006 70.02 4.848 39.57
391 100.8 100.9 3111.577 72.03 4.871 42.91
105
APPENDIX B
PHOTOGRAPHS OF THE SPRAYS
106
Figure B-1. Photographs of the spray @ 1034 kPa (150 psig) and 80 °C
107
Figure B-2. Photographs of the spray @ 2068 kPa (300 psig) and 80 °C
108
Figure B-3. Photographs of the spray @ 3447 kPa (500 psig) and 80 °C
109
Figure B-4. Photographs of the spray @ 1034 kPa (150 psig) and 120 °C
110
Figure B-5. Photographs of the spray @ 2068 kPa (300 psig) and 120 °C
111
Figure B-6. Photographs of the spray @ 3447 kPa (500 psig) and 120 °C
112
Figure B-7. Photographs of the spray @ 1034 kPa (150 psig) and 150 °C
113
Figure B-8. Photographs of the spray @ 2068 kPa (300 psig) and 150 °C
114
Figure B-9. Photographs of the spray @ 3447 kPa (500 psig) and 150 °C
115
Figure B-10. Photographs of the spray @ 2068 kPa (300 psig) and 190 °C
116
APPENDIX C
PRESSURE TRANSDUCER CALIBRATION
117
Table C-1. Calibration Data for Sensotec Pressure Transducer
Vin Vout Vout/Vin pressure P(psia) pressure Pg (psig)
10.092 0.0001 9.90874E-06 0 -14.67
10.092 0.0007 6.93612E-05 14.67 0.00
10.092 0.0014 1.38722E-04 24.67 10.00
10.092 0.0019 1.88266E-04 34.37 19.70
10.092 0.0026 2.57632E-04 44.87 30.20
10.092 0.0031 3.07177E-04 54.77 40.10
10.092 0.0050 4.95447E-04 85.57 70.90
10.092 0.0069 6.83723E-04 116.47 101.80
10.092 0.0085 8.42268E-04 144.27 129.60
10.092 0.0104 1.03054E-03 175.07 160.40
10.092 0.0122 1.20890E-03 205.07 190.40
10.092 0.0139 1.37736E-03 233.57 218.90
10.092 0.0158 1.56563E-03 264.67 250.00
10.092 0.0176 1.74399E-03 295.17 280.50
10.092 0.0195 1.93226E-03 325.67 311.00
10.092 0.0213 2.11065E-03 354.97 340.30
10.092 0.0230 2.27910E-03 383.97 369.30
10.092 0.0249 2.46737E-03 415.67 401.00
10.092 0.0267 2.64576E-03 445.17 430.50
10.092 0.0286 2.83404E-03 475.27 460.60
10.092 0.0310 3.07186E-03 515.47 500.80
118
y = 167389x - 12.462R2 = 1
-100
0
100
200
300
400
500
600
0.000E+00 5.000E-04 1.000E-03 1.500E-03 2.000E-03 2.500E-03 3.000E-03 3.500E-03
Vout/Vin
Figure C-1. Calibration of the Sensotec Pressure Transducer (500 psig: TJE/0713-
18TJA)
119
APPENDIX D
THERMOCOUPLE CALIBRATION
120
Table D-1. Temperature calibration data for nozzle thermocouple
Temperature
@ thermometer,
THg (°C)
Temperature
@ nozzle thermocouple,
TTC (°C)
Delta T (°C)
(TTC – THg)
65.0 64.4 -0.6
87.0 87.0 0.0
105.5 105.5 0.0
123.5 123.7 0.2
139.0 139.6 0.6
157.0 158.4 1.4
-1.0
-0.5
0.0
0.5
1.0
1.5
0.0 50.0 100.0 150.0 200.0
TTC (°C)
TT
C -
TH
g (°
C)
Figure D-1. Error curve for the Nozzle Thermocouple when compared to a
Mercury Thermometer.
121
APPENDIX E
EXPERIMENTAL PROCEDURE
122
1. Depressurize the Fluid Cell by opening the valve at the vent line.
2. Check the spring in the pressure relief valve for the correct range of working
pressure.
3. Fill HTF into the glass storage with the desired amount.
4. Open the valve at the fill line and wait until all HTF is transferred into the Fluid
Cell, then close the valve.
5. Attach the test nozzle. Adjust the nozzle so that the spray is straight and the center
of the spray passes through the laser beam.
6. Install the insulation, both on the Fluid Cell and the spray line.
7. Turn on the temperature control box connected to the heater strip to heat the system.
The heating procedure can be very tricky. The set temperature must initially be
determined by trial and error. Set temperature can be adjusted to a much higher
level than the test temperatures to accelerate the heating process. Decrease the set
temperature when the temperature of HTF is close to the test temperature.
8. Pressurize the Fluid Cell to the test pressure and wait until the system comes to
equilibrium.
9. Check the focal length of lens L2. In this case 300 mm is selected (see instruction in
Malvern Laser manual).
10. The Malvern Laser must be aligned on a daily basis. The reticle will be placed at the
focal lens, L2. Move the reticle until the laser beam just passes through the glass
part and not the particle part. Measure the particle size distribution by using the set
zero mode (F3). Then move the reticle again so the laser beam will pass through to
the particle part. By setting the independent model, measure the particle size
distribution using the measured sample and analyze (F5). The exact particle size
distribution for D(v,0.5) should be 46.5 micron. If the error is greater than 5%, the
alignment of the detector must be adjusted.
11. Turn the knots both x and y direction until the synchronizer reaches the maximum
value.
123
12. Repeat (8) again. If the error is still greater than 5%, keep adjusting.
13. Turn on the exhaust system. The exhaust system must be turned on during the
measurements to ensure that aerosol does not accumulate in the laboratory.
14. Now the system is ready to make measurements. Turn off all the lights in the room
and turn on the exhaust system. Measure the background (F3).
15. Open the spray valve to a certain position (this position needs to be fixed every
measurement). Wait until the spray is steady for about 10 seconds.
16. Measure the droplet size distribution with the F5 mode. The measurement is set to
500 sweeps per one time measurement. This step will take 5 seconds.
17. Write down the temperature and pressure data on the data sheet.
18. Close the spray valve and turn on the light.
19. During this time Malvern software will calculate the size distribution.
20. Write down the value of Sauter mean diameter, obscuration, and Log Diff.
21. Save data on disk.
22. For the next measurement, go back to (11).
23. Drain the Mist Separator every day after all the measurements, but not after more
than 10 measurements.
24. Change the filter in the Mist Separator on a monthly basis.
124
APPENDIX F
HEAT TRANSFER FLUID PROPERITES
(ALKYLATED AROMATIC MIXTURE)
125
Alkylated Aromatic Mixture, HTF
Flash Point (ASTM D-92) 173 °C (343.4 °F)
Fire Point (ASTM D-92) 216 °C (420 °F)
Autoignition Temperature (ASTM D-2155) 366 °C (690 °F)
Kinematic Viscosity, at 40 °C 19.0 mm2/ s (cSt)
at 100 °C 3.5 mm2/ s (cSt)
Density at 25 °C 868 kg / m3 (7.25 lb/gal)
Specific Gravity (60 °F/ 60 °F) 0.876
Coefficient of Thermal Expansion at 200 °C 0.000961/ °C (0.000534/ °F)
Average Molecular Weight 320
Pour Point - 54 °C (- 65 °F)
Pumpability, at 2000 mm2 / s (cSt) - 28 °C (- 19 °F)
at 300 mm2 / s (cSt) - 8 °C (17 °F)
Minimum Temperature for
Fully Developed Turbulent Flow (Re= 10000)
10 ft / sec, 1-in tube 67 °C (152 °F)
20 ft / sec, 1-in tube 45 °C (114 °F)
Transition Region Flow (Re= 2000)
10 ft / sec, 1-in tube 24 °C (75 °F)
20 ft / sec, 1-in tube 11 °C (52 °F)
Boiling Range, 10% 340 °C (644 °F)
90% 390 °C (734 °F)
Normal Boiling Point 351 °C (664 °F)
Pseudocritical Temperature 512 °C (953 °F)
Pseudocritical Pressure 13.2 bar (191 psia)
Pseudocritical Density 258 kg / m3 (16.1 lb / ft3)
126
VITA
Passaporn Sukmarg was born in Bangkok, Thailand, on November 11, 1975, the
youngest daughter of Yonchoke and Surang Sukmarg. After completing her schooling
in Rajinee Bon School, she pursued her bachelor’s degree in Chemical Engineering
from Khon Kaen University from 1992 to 1996. Prior to continuing her education, she
worked for Siam Cement Public Ltd. Co. In June 1998, she entered the Chemical
Engineering Department at Texas A&M University to pursue her master’s degree. She
was also employed as a graduate research assistant. She will begin working for Bayer
Corporation in Baytown, Texas on August 1, 2000.
Permanent address: 60/14 Ngamwongwan 15
Ngamwongwan Rd., Muang
Nonthaburee 11000 Thailand