UNIVERSITI TEKNOLOGI MARAFAKULTI KEJURUTERAAN KIMIA
THERMOFLUIDS LABORATORY (CGE536)
NAME : MUHAMAD ADNAN BIN ZAINAL ABIDIN (2015208916)GROUP : 3EXPERIMENT : LAB 6 : FILM BOILING CONDENSATIONDATE : 3RD MAY2016PROG/CODE : EH2433BNo Title Allocated Marks
(%)Marks
1 Abstract 52 Introduction 53 Objectives 54 Theory 55 Procedures/Methodology 106 Apparatus 57 Results 108 Calculation 109 Discussion 2010 Conclusion 1011 Recommendations 512 References 513 Appendices 5
TOTAL 100
Remarks:
Checked by: Rechecked by:
Date: Date:
1
ABSTRACT
This Film and Dropwise Condensation Unit is used to observe the process of heat
transfer during condensation, as well as gather experimental data for a better theoretical
understanding. The unit itself contained bench top unit, with an integrated steam generator
and air extraction system. The main components in the unit are the specially designed
condensers for the observation of both filmwise and dropwise condensation about the
differences of them. In this experiment, we want to study the heat transfer coefficient and
the heat flux. Besides that, we were study the effect of air inside the chamber. Condensation
occurs when vapor changes to liquid state with a large heat-transfer coefficient. Filmwise
condensation occurs on a vertical or horizontal plane when a film of condensate is formed
on surface and flows by action of gravity. Dropwise condensation occurs when small drops
formed on surface. The heat transfer coefficient can be calculated using Nussselt equation. .
Nusselt assumed that the heat transfer that occurs from the vapor through the film and to the
wall is conduction. Since the process is conduction is well known, therefore calculation on
the heat-transfer coefficients can be done. In this experiment, obtained data are for Tsat, Tsurf,
Tin and Tout.
2
INTRODUCTION
Filmwise and Dropwise are two forms of condensation. In filmwise condensation a
laminar film of vapor is created upon a surface. This film can then flow downwards, increasing
in thickness as additional vapor is picked up along the way. In dropwise then flow downwards,
accumulating static droplets below them along the way.
When the rate of condensation is low (e.g., a non-condensable gas is present) or when the
liquid does not "wet" the wall, dropwise condensation occurs. In most engineering components
where condensation is a required part of an industrial process film condensation is expected,
because of the large mass flux of condensed liquid per unit length of wetted area.
Dropwise condensation was first recognized by Schmidt et al. (1930), and much interest
was stimulated by their report that heat transfer coefficient are between 5 and 7 times those
found with film condensation. Over the years there have been a few demonstrations of successful
applications on an industrial scale. This experiment would be used in by any industry which is
trying to increase the efficiency of heat transfer. An example of this is any vapour power cycle
such as the rankine cycle. By increasing the efficiency of the condenser, its operational pressure
can be reduced and the overall efficiency of the cycle can be increased. Dropwise condensation
is difficult to sustain reliably; therefore, industrial equipment is normally designed to operate in
filmwise condensation mode.
In all application, the steam must be condensed as it transfers heat to a cooling medium
which could be cold water in a condenser of generating station, hot water in a heating calorifier,
sugar solution in a sugar refinery and etc. during condensation very high heat fluxes are possible
and provided that the heat can be quickly transferred from the condensing surface into the
cooling medium, the heat exchangers can be compact and effective.
The SOLTEQ Film & Dropwise Condensation Unit (Model: HE163) is designed to help
student to understand several key aspects in condensation topic, in particular the process of
filmwise and dropwise condensation. It allows students to visualize both phenomena and
3
perform a few experiments to demonstrate both concepts and how their applied and give benefit
in industry.
4
OBJECTIVES
1. To demonstrate the filmwise and dropwise condensation.
2. To describe filmwise and dropwise condensation
3. To demonstrate the effect of air on heat transfer coefficient of condensation
4. To demonstrate the filmwise heat flux and surface heat transfer coefficient ay constant
pressure.
5. To determine the dropwise heat flux and surface heat transfer coefficient at constant
pressure.
5
THEORY
Mechanism of Condensation
Condensation of a vapor to a liquid and vice versa, both involve a change of a fluid with
large heat-transfer coefficients. Condensation occurs when a saturated vapor such as steam
makes a contact with a solid whose surface temperature is below the saturation temperature, to
form a liquid such as water.
When a vapor condenses on a surface, for example vertical or horizontal tube or other
surface, a film of condensate is formed on the surface and flows over the surface because of
gravity. It is this film of liquid between the surface and the vapor that produce the main
resistance of heat transfer. This is called filmwise condensation.
Another type of condensation is dropwise condensation. Dropwise condensation occurs
when small drops are formed on the surface. These drops grow and mix together, and the liquid
flows from the surface. Large areas of tube are devoid of any liquid and are exposed directly to
the vapor during condensation. Very high rates of heat-transfer occur on these bare areas. The
average heat transfer coefficient for dropwise condensation is five to ten times larger than the
filmwise coefficient.
Dropwise condensation can be promoted by making the surface non-welting by coating.
However, dropwise condensation is difficult to maintain in industrial applications because of
oxidation, fouling and degrading of coating, and finally film condensation occurs. Therefore,
condenser designs are often based on the assumption of filmwise condensation.
Film-condensation coefficients for vertical surfaces
Film type condensation on a vertical wall or tube can be find analytically by assuming
laminar flow of the condensate film down the wall. The film thickness is zero at the top of the
6
wall or tube. It increases in thickness as it flows downward as a result of condensation. Nusselt
assumed that the heat transfer from the condensing vapor at Tsat, through this liquid film, and at
the wall at Tw, was by conduction. Equating this heat-transfer by conduction to that from
condensation of the vapor, final expression can be obtained for the average heat-transfer
coefficient over the whole surfaces.
7
APPARATUS
Equipment Prefer:
SOLTEQ MODEL: HE 163 (Film and Dropwise Condensation Unit)
8
PROCEDURE
General Start-up
1. The main switch is ensured in its off position.
2. The power regulator knobs are turned fully anti-clockwise to set the power to minimum.
3. Valves V1 to V6 are checked to ensure its closed.
4. The chamber is filled with distilled water until the water level stays between the hater and
baffles plates. The heater is ensured fully immersed in the water throughout the
experiment. The chamber is filled with water through the drain valve with the vent valve,
V4 opened. Then the vent valve V4 is closed.
5. The water flow rate to the condenser is adjusted by controlling the control valve
according to experimental procedure.
6. The main switch and the heater switch are turned on. The heater power is set by rotating
the power regulator clockwise to increase the hater power.
7. The water temperature reading is observed where the water temperature should increase
when its start heat-up.
8. The water is heated up to boiling point until the pressure reaches 1.02-1.10 bar.
Immediately valve V1 is opened and follow by valve V5 for 1 minute to vacuum out the
air inside condenser. Then both valve V1 and V5 is closed.
9. The system is let to stabilize. Then all relevant measurement is taken for experimental
purposes. Adjustment is made if required.
General shut-down
1. The voltage control knob is turned to 0 Volt position by turning the knob fully anti-
clockwise. The cooling water is kept flowing for at least 5 minutes through the condenser
to cold them down.
2. The main switch and power supply are switch off. Then, the power supply cable is
unplugged.
3. The water supply is closed and the cooling water connection tubes are disconnected if
necessary. Otherwise, the connection tubes are leaved for next experiment.
4. The water inside the chamber is discharged using the discharge valve.
9
A) Demonstration of filmwise and dropwise condensation
1. The basic procedure is followed as written in the general set-up. The equipment by make
sure connected to the service unit.
B) The filmwise heat flux and surface heat transfer coefficient determination at constant
Pressure
1. Cooling water is circulated through the filmwise condenser starting with a minimum
value of 0.1 LPM.
2. The heater power is adjusted to obtain the desired pressure at 1.01 bar.
3. When the condition is stabilized, the steam (T sat) and surface temperature (T surf ) , T ¿ (T1)
and T out (T2), and flowrate are recorded.
C) The dropwise heat flux and surface heat transfer coefficient determination at
Constant pressure
1. Cooling water is circulated through the dropwise condenser starting with a minimum
value of 0.4 LPM.
2. The heater power is adjusted to obtain the desired pressure at 1.01 bar.
3. When the condition is stabilized, the steam (T sat) and surface temperature(T surf ), T ¿ (T3),
T out (T4) and flowrate are recorded.
10
RESULTS
Experiment 1: Demonstration of filmwise and dropwise condensation
Figure 2: (Left) The Filmwise Condensation and (right) The Dropwise Condensation
11
Experiment 2:
Table 1: The filmwise heat flux and surface heat transfer coefficient determination at constant
pressure
Flowrat
e (LMP) Power (P)
Tin
( ̊ C)
Tout
( ̊ C)
Tsat
( ̊ C)
Tsurf
( ̊ C)
ΔTm
( ̊ C) q ɸ U
0.1 185 31.9 32.0 70.4 30.7 38.44 185 45826.11 1192.15
0.2 205 34.3 34.6 69.2 33.3 35.35 205 50780.28 1436.50
0.3 230 34.6 34.9 68.8 33.8 34.05 230 56973.00 1673.22
0.4 259 34.8 34.9 68.5 34.1 33.65 259 64156.55 1906.58
34.4 35 35.9 39.70
10000
20000
30000
40000
50000
60000
70000
Heat Flux vs Tsat-Tsurf
Tsat-Tsurf
Heat
Flu
x
Heat Flux vs. Tsat-Tsurf for filmwise without air
12
34.4 35 35.9 39.70
500
1000
1500
2000
2500
Heat Coefficient vs Tsat-Tsurf
Tsat-Tsurf
Heat
Coe
fficie
nt
Heat coefficient against Tsat-Tsurf for filmwise without air
13
Experiment 3:
Table 2: The dropwise heat flux and surface heat transfer coefficient determination at constant
pressure
Flowrate
(LMP)
Power
(P)
Tin
( ̊ C)
Tou
t
( ̊ C)
Tsat
( ̊ C)
Tsurf
( ̊ C)
ΔTm
( ̊ C) q ɸ U
0.4 347 34.6 35.7 68.8 41.6 33.65 347 85954.92 2554.38
0.8 365 34.9 35.9 72.2 44.2 36.80 365 90413.67 2456.89
1.2 487 35.1 35.9 71.8 45.2 36.30 487 120634.13 3323.25
1.6 588 34.4 36.1 70.2 46.6 34.94 588 145652.71 4168.65
23.6 26.6 27.2 280
20000
40000
60000
80000
100000
120000
140000
160000
Heat Flux vs Tsat-Tsurf
Tsat-Tsurf
Heat
Flu
x
Heat Flux vs. Tsat-Tsurf for dropwise without air
14
23.6 26.6 27.2 280
500
1000
1500
2000
2500
3000
3500
4000
4500
Heat Coefficient vs Tsat-Tsurf
Tsat-Tsurf
Heat
Coe
fficie
nt
Heat coefficient against Tsat-Tsurf for dropwise without air
15
Experiment 4:
Filmwise
Table 3: The effect of air inside chamber for filmwise
Flowrate
(LMP)
Power
(P)
Tin
( ̊ C)
Tout
( ̊ C)
Tsat
( ̊ C)
Tsurf
( ̊ C)
ΔTm
( ̊ C) q ɸ U
0.1 248 33.1 35.1 68.3 33.7 34.19 248 61431.76 1796.79
0.2 275 33.1 33.6 68.9 32.5 35.55 275 68119.89 1916.17
0.3 298 33.1 34.9 69.7 32.1 35.69 298 73817.19 2068.29
0.4 308 33.3 33.4 69.8 31.7 36.45 308 76294.28 2093.12
34.6 36.4 37.6 38.11600
1700
1800
1900
2000
2100
2200
Heat Coefficient vs Tsat-Tsurf
Tsat-Tsurf
Heat
Coe
fficie
nt
The heat coefficient vs Tsat-Tsurf for filmwise with 1% air
16
Dropwise
Table 4: The effect of air inside chamber for dropwise
Flowrate
(LMP)
Power
(P)
Tin
( ̊ C)
Tout
( ̊ C)
Tsat
( ̊ C)
Tsurf
( ̊ C)
ΔTm
( ̊ C) q ɸ U
0.4 323 33.4 34.3 71.3 32.6 37.45 323 80009.91 2136.45
0.8 559 33.4 34.4 70.5 32.6 36.60 559 138469.16 3783.31
1.2 571 33.6 34.5 71.7 32.9 37.65 571 141441.66 3756.75
1.6 685 33.8 34.9 72.3 33.3 37.95 685 169680.46 4471.16
37.9 38.7 38.8 390
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
Heat Coefficient vs Tsat-Tsurf
Tsat-Tsurf
Heat
Coe
fficie
nt
The heat coefficient vs Tsat-Tsurf for dropwise with 1% air
DISCUSSIONS
17
In this experiment we are mostly investigate about the film boiling condensation
by using the SOLTEQ Film and Dropwise Condensation Unit (Model: HE 163). There are 4
objectives that must be accomplished. For the experiment 1, we have to demonstrate the filmwise
and dropwise condensation. From this experiment, we are able to describe the characteristics of
filmwise and dropwise condensation. In filmwise condensation, most materials used in the
construction of heat exchangers are “wettable” and during the condensation a film condensate
spreads over the surface. More vapour condenses onto the outside of this film will increases its
thickness and causes the flow downward and drip from the lowest points. The heat given up by
the vapour during condensation is conducted through the film. During filmwise condensation a
layer of condensate covers the cool surface and this will cause the resistance to the transfer of
heat. However, for the dropwise condensation the material used in the construction is “non-wet
table” .When the steam condenses, a large number of spherical forms on its surface. These beads
become larger and then the trickle downwards. The moving bead gathers all the static beads
along its downward path, becomes larger, accelerates and leaves a virtually bare surface in its
trail.
For experiment 2 and 3, theoretically there is a big difference from the graph for the
dropwise and filmwise condensation based on its heat transfer coefficient and temperature
difference. For dropwise there is a relatively larger area heat transfer coefficient that proposes a
larger value of heat transfer during condensation. As for filmwise there is a smaller value of heat
transfer and the larger area on the graph that shows the larger margin of heat transfer value are at
larger heat transfer value. But for the errors that has occur, they didn’t match for the desirable
data.
For experiment 4, theoretically, the clear difference between both heat transfer coefficient
and temperature difference for filmwise and dropwise condensation is for dropwise with the
present of air there is a larger value of heat transfer coefficient at a small temperature difference
rather than for filmwise that shows a smaller value of heat transfer coefficient and at a larger
difference of temperature. The analysis for the data collected is that heat flux shows a clear
difference due to the presence of air. With the presence of air the heat flux value is smaller.
Dropwise condensation is far more efficient for condensation process due to the specifications
18
for each plate surface. However, we are not able to achieve the desired outcome due to some
errors.
The errors involve that effect the results is due to fluid involve for the process of
condensation to occur. The impurities that contain within the fluid involve has effect the density
and boiling temperature that occur at a much lower temperature. Thus condensation occurs at a
less precise order and resulting in impairment data.
19
CONCLUSION
For experiment 2 and 3, we have concluded that the dropwise condensation heat flux and
surface heat transfer coefficient at constant pressure occur at a relatively larger value at smaller
temperature difference than for filmwise condensation. Thus efficient condensation
For experiment 4, we have demonstrated the effect of air on heat transfer coefficient of
condensation for dropwise and filmwise, it concluded that dropwise has a more stable and larger
heat transfer value for condensation process thus a more efficient condensation process.
RECOMMENDATIONS
1. Avoid error in taking readings and make sure eyes of observer are parallel to the meniscus
2. Make sure the valve were close tightly when the film condensation equipment is turn off.
3. Make sure all the valve close at the beginning of the experiment
4. Allow the cooling water to flow at the end of the experiment before the equipment is shut
down to avoid the cracking of cylindrical tube.
20
REFERENCES
1) Aksan, S. N. and Rose, J. W. (1973). Dropwise condensation—the effect of thermal
properties of the condenser material. Int. J. Heat Mass Transfer, 16, 461-467.
2) Blackman, L. C. F., Dewar, M. S. J. and Hampson, H. (1957). Compounds for promoting
dropwise condensation of steam. J. Appl. Chem., 7, 160-171.
21
Appendices
22
23