IJE Transactions A: Basics Vol. 21, No. 2, June 2008 - 113POOL BOILING HEAT TRANSFER IN WATER/AMINES SOLUTIONSS. A. Alavi Fazel*Department of Engineering, Science and Res earch Campus, Islamic Azad Unive rsity P.O. Box 14515-775, Tehran, Iran [email protected]A. A. Safekordi Department of Chemical and Petroleu m Engineering, Sharif University of Technol ogy P.O. Box 11365-8639, Tehran, Iran [email protected]M. Jamialahmadi Department of Chemical and Petroleum Eng ineering, The University of Petroleum Indus try P.O. Box 63431, Ahvaz, Iran [email protected]*Corresponding Author(Received: September 24, 2007 – Accepted in Revised Form: January 30, 2008) Abstract In this investigation, nucleate boiling heat transfer coefficients were experimentally measured during pool boiling of mixtures, consisting of water/Monoethanolamine and water/Diethanolamine on a horizontal heating rod, under atmospheric pressure. The experiment was carried out up to 205 kW.m -2 heat flux over a wide range of concentrations. These experiments include, measurement of pool boiling heat transfer coefficient and also visual information. Applicability of the existing main correlations is briefly discussed, with the present experimental data. The major predictions(over and/or under) were observed in some parameter range by the existing correlations. In this investigation the correlations of Fujita et al and Inoue et al, which are structurally the same but have different tuning parameters were modified for this system and the average error has been significantly reduced. Keywords Pool Boiling, Heat Transfer Coefficient, Amine Solutions, Correlations ﺪﻩﻴﻜ ﭼﯽ ﻴ/ ﻴ/ ﯼ ﺪﻩ ﯼ ﻴﮔ ﻩ ﺪﯽﮏ ﯼﯽﮔ ﺪ ﻴ. ﯽ ﯼﻩ ﺪﯽ ﻴ ﻩﮔ ﻴﮐ. ﯼ ﻴﭽ ﺪ. ﻴ ﯼ ﺪﮑﻩ ﺪﯽ. ﯽ ﺪ ﻴﮐﯽ ﯼ ﻩ. ﮑﮑ ﻴ ﻩ ﯼ ﯼ ﻴﯽﮑ ﻴ ﻴ ﯼ ﯼﻩ ﺪ. 1. INTRODUCTION Nucleate pool boiling of pure and liquid mixtures are involved in many chemical and petrochemical applications such as; multicomponent distillation, air separation, refrigeration and power cycles. Forexample, preferential evaporation of more volatile component inside the evaporator, and preferential condensation of non-volatile component in condenser, would provide a higher thermal driving force in condensers and also evaporators, in comparison with pure liquids. Consequently, using
(Received: September 24, 2007 – Accepted in Revised Form: January 30, 2008)
Abstract In this investigation, nucleate boiling heat transfer coefficients were experimentallymeasured during pool boiling of mixtures, consisting of water/Monoethanolamine andwater/Diethanolamine on a horizontal heating rod, under atmospheric pressure. The experiment wascarried out up to 205 kW.m-2 heat flux over a wide range of concentrations. These experimentsinclude, measurement of pool boiling heat transfer coefficient and also visual information.
Applicability of the existing main correlations is briefly discussed, with the present experimental data.The major predictions(over and/or under) were observed in some parameter range by the existingcorrelations. In this investigation the correlations of Fujita et al and Inoue et al, which are structurallythe same but have different tuning parameters were modified for this system and the average error has been significantly reduced.
Keywords Pool Boiling, Heat Transfer Coefficient, Amine Solutions, Correlations
ه د ي ك ي ی چ ي/ ی/ ه ی د ه گ ي ی ک ی د د گ ی ي .
ی ی ه ي ی د ه . ک ي گ
ی ي.د چ ي
ی د ه ک ی . ی د
د ک ي ی
یه ي ک ک . ه
یی ي يي ک ی ی ی
ه .د
1. INTRODUCTION
Nucleate pool boiling of pure and liquid mixturesare involved in many chemical and petrochemicalapplications such as; multicomponent distillation,air separation, refrigeration and power cycles. For
example, preferential evaporation of more volatilecomponent inside the evaporator, and preferentialcondensation of non-volatile component incondenser, would provide a higher thermal drivingforce in condensers and also evaporators, incomparison with pure liquids. Consequently, using
solution refrigerants instead of pure solution, couldsignificantly increase the thermal efficiency of therefrigeration cycles. This wide range of applications in boiling phenomenon is because of high heat transfer coefficient between heatingsurface and boiling liquid due to three implicatedmechanisms including:
• Free convection• Severe micro-convection flow induced by
bubble dynamics• Latent heat from vaporization consequences
of bubble generation.
Needless to say that at very high heat flux,radiation mechanism could also develop and
extend significantly, although not considered inthis investigation. Design, operation andoptimization of the equipments which are involvedin boiling phenomenon, necessitates an accurate prediction of the boiling heat transfer coefficient between surface and the boiling liquid. Predictably,the temperature of heating surface is a strongfunction of the heat transfer coefficient for anygiven bulk temperature and heat flux.
Boiling of liquid mixtures should be investigateddifferently from pure liquids, because of additionalinteracting mechanisms, which turns it in to a morecomplicated circumstance. For mixtures, selectiveevaporation of the more volatile component(s)establishes a concentration gradient, during bubbleformation at the vapor-liquid interface. Accordingly, back diffusion of the more volatile component(s)from vapor inside the bubble to the vapor-liquidinterface, establishes a mass transfer andconsequently a heat transfer resistance. This phenomenon directly affects the amount of heattransfer and also could affect the bubble dynamics;as a result the boiling heat transfer coefficient wouldtrim down significantly. Great number of experiments in the literature confirm that the heattransfer coefficients of mixtures, were less than theinterpolated heat transfer coefficients between purecomponents, decreasing more at higher heat flux.Heat transfer coefficients are reduced significantlyin rising ranges of boiling [1,2]. This means withmatching amount of heat trnasfer and bulk temperature, higher surface temperature on the boiling surface, for liquid mixtures in comparisonwith, pure liquids would establish.
Many investigations on pool boiling for pure andalso liquid mixtures have been performed in the past few decades. The ultimate objective is tofundamentally derive a model which describes the boiling phenomenon in the absence of any tuning parameter or any simplifications; however theexisting position is still far-off from the target, because of the great sophistication and intricacy of the boiling phenomenon, especially for liquidmixtures.
For boiling of liquid mixtures, Schlünder [3]has derived a semi-theoretical model includingonly one tuning parameter based on SF6-CF2Cl2 mixtures. In this model, the mass transfer coefficient has been considered equal to 2E-4 m/sobtained from physical and chemical absorption
and in falling film vaporization. This correlationcorresponds particularly well with theexperimental observation that, the heat transfer coefficient is less dependent on heat flux densityand the pressure. Jungnickel [4] measured the boiling heat transfer on a horizontal copper platefor refrigerant mixtures and proposed a newcorrelation with a unique definition for ideal boiling heat transfer coefficient. Stephan, et al [5]equation is the most popular empirical correlationwhich has an inclusive tuning parameter. For boiling liquid mixtures with high heat solutions,Stephan, et al [5] correlation, over-predicts the dataover all fraction ranges, which has the samecharacteristic as Schlünder [3] Correlation [6].These authors proposed that wall superheat for binary mixtures boiling could be determined by thesum of ideal wall superheat and excess wallsuperheat. Inoue, et al [6] measured the pool boiling heat transfer coefficients of ammonia/water mixture and its pure components on a horizontal platinum wire (diameter of 0.3 mm, 37 mm length)at pressure of 0.4 and 0.7 MPa. The wire washeated using a direct electric current. Based on the boiling range, the temperature difference betweendew and bubble points at a given concentration, asa parameter in reducing the available drivingtemperature, these authors have developed a newmodel including a tuning parameter which isimplicitly independent of mixture's physical properties. This tuning parameter is discussed inthis paper. Thome, et al [7] proposed another predicting correlation based on this assumptionthat the bubble point temperature near the heating
surface is not constant. Fujita, et al [8,9] used avertical tube to measure the boiling heat transfer of binary mixtures of CF3CH2F/CHCl2CF3 and theyhave proposed two different correlations. Thesecorrelations which are founded on a model that thedrop of effective temperature difference is a mainreason for heat transfer reduction in mixtures. Theyassumed that the bubble point temperature close tothe heating surface is variable as a function of heatflux. They determined this function in reference totheir heat transfer data of seven different kinds of binary mixtures including aqueous, organic, non-azeotropic, and azeotropic mixtures. Thereafter they made the influence of heat flux dimensionless,in order to extend their correlation to a wider use[8]. Fujita, et al [9] also showed this diminution is
most considerable in mixtures with higher glidingtemperature. The larger the decrease for higher heat flux condition and higher mole fractiondifference │Y-X│, the larger the boiling rangewould be. Calus, et al [10] reported data on boilingunder free convection for isopropanol/water andacetone/water binary mixtures and for the three pure components. They used a nickel/aluminumalloy wire 0.315 mm in diameter as anexperimental heating element. They had proposeda new correlation including mass and heatdiffusivity coefficients. Unal [11] proposed acorrelation based on an empirical procedure of dimensional analysis that allowed him to obtain anew correlation. Vinayak, et al [12] have obtainedheat transfer coefficient data in nucleate pool boiling of acetone/isopropanol/water andacetone/MEK/water systems. They have developeda correlation involving thermal and massdiffusivity coefficients. A summary of mainexisting correlations for pool boiling heat transfer coefficient for liquid mixtures and pure liquids aregiven in Table 1 and Table 2 respectively. Theexperimental development of the experimentresearch for nucleate boiling mixture has also beenreviewed by Fujita, et al [1].
Clearly, the effect of all influential parameterssuch as liquid and vapor and heating surface physical properties including heat of vaporization,surface tension, relative volatility and contactangle are still not well understood. For any givencorrelation, a number of effective parameters areignored for some reasons. All developed modelhas satisfactory performance in a specific
constricted range of parameters. Some models arelimited to less parameter and some arecomplicated with more involved variableshowever it has been shown that involving more parameters would not necessarily enhance themodel performance at all.
One of the objects in the present study is tomeasure and compare the nucleate boiling heattransfer coefficient of binary solutions, includingMonoethanolamine/water and Diethanolamine/water over a wide range of concentrations and heat fluxesat atmospheric pressure. It is worth knowing that,there hasn't been any previously publishedexperimental data in the literature over the last twodecades for neither Water/Monoethanolamine nor water/Diethanolamine solutions. This investigation
is focused Inoue, et al [6] and Fujita, et al [8,14]correlations which have similar basis, but differenttuning parameters. The measured boiling heattransfer coefficients are correlated to thementioned equations. It is shown that a minor modification could significantly reduce theestimating error, at least for the above binaryliquids in which water-as a non-wetting phase-onstainless steel heating surface is the more volatilecomponent.
2. EXPERIMENTAL APPARATUS ANDPROCEDURE
Figure 1, presents the experimental equipmentused in the present measurements, which is called“Gorenflo pool boiling apparatus”. This boilingvessel is a vertical hollow cylinder of stainlesssteel containing 38 liters of test liquid, connectedto another vertical condenser to condense andrecycle the evaporated liquid. The whole system isheavily isolated, for more controllability andreduction of the heat loss. The temperature of theliquid inside the tank is incessantly monitored andcontrolled to any predestined set point by a thermalregulator, which relates the thermocouples to anappropriate band heater, covering the outside of thetank. Before the experiment begins, the liquidinside the tank is preheated to the saturationtemperature, using the specific mentioned bandheater. The pressure of the system is monitoredand regulated continuously and a safety pressure
TABLE 2. Major Existing Correlation for Prediction of Pool Boiling Heat Transfer Coefficient in Pure Liquids.
Author Correlation Reference
Mostinski ( )⎥⎥⎥
⎦
⎤
⎢⎢⎢
⎣
⎡
⎟⎟
⎠
⎞⎜⎜
⎝
⎛ +
⎟⎟
⎠
⎞⎜⎜
⎝
⎛ +
⎟⎟
⎠
⎞⎜⎜
⎝
⎛ =
10
cPP1.2
cPP0.17
cPP1.80.7q/A0.69
c bPα b = 3.75E-5 [SI Unit] [36]
McNelly0.33
1vρlρ0.31
σlPk
0.69
fgAHlqC
0.225α⎟⎟
⎠
⎞⎜⎜
⎝
⎛ −
⎟⎟
⎠
⎞⎜⎜
⎝
⎛ ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛ = [37]
Boyko-
Kruzhilin
0.5
vρlρg
σ*l;
0.33
*l2vρ2fgH
σPlCsT0.7
vρlρvρ
lk sgT
qfgH
*l
lk 0.082α
⎥
⎥⎥
⎦
⎤
⎢
⎢⎢
⎣
⎡
⎟ ⎠ ⎞⎜⎝ ⎛ −
=⎥⎥
⎥
⎦
⎤
⎢⎢
⎢
⎣
⎡
⎥
⎥
⎦
⎤
⎢
⎢
⎣
⎡
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
−= [35]
Nishikawa m0.125μ pR ;0.9cP/P991
4/5q0.23
cP/PcP/P10.2
p8R 0.9cT0.1M
1/5c31.4P
α =
⎥⎦
⎤⎢⎣
⎡⎟ ⎠ ⎞
⎜⎝ ⎛ −
⎟ ⎠ ⎞
⎜⎝ ⎛ −
⎟ ⎠ ⎞
⎜⎝ ⎛ = ⎟
⎟
⎠
⎞⎜⎜
⎝
⎛
[34]
Gorenflo0C0ρ0k
ρCk WMF;
2/15
aR a0R
WR Fr P1
r Pr 2.5P
0.27r 1.2P pF;3
r 0.3P0.9n;n
0qq
PF(*);WMFWR FqFPF0αα
=⎟⎟
⎠
⎞⎜⎜
⎝
⎛ =
−+
+=−=⎟⎟
⎠
⎞⎜⎜
⎝
⎛ ==
Note: New international standard DIN EN ISO 4287 (10.98)α0 must be determined byexperiments or calculated independently of equation (*).
[33]
relief valve is also installed to prevent anydangerous situation. The test section is a horizontalrod heater with a diameter of 10.67 mm and aheating length of 99.1 mm which can be observedand photographed through observation glasses.This heater consists of an internally heatedstainless steel sheathed rod and four stainless steelsheathed thermocouples with an exterior diameter of 0.25 mm which are entrenched along thecircumference of the heater close to the heatingsurface. Some details of the heating rod are given
in Figure 2. One thermocouple inside the heatingrod was used as a protection trip, to cut off theelectric power if the temperature exceeds themaximum limit. The test heater is manufactured byDrew Industrial Chemicals Company according tospecifications by Heat Transfer ResearchIncorporated (HTRI).
A PC-based data acquisition system was used torecord all measuring parameters. The input power of the heating rod is precisely equal to the heat fluxand could be calculated by the product of electrical
Figure 1 . Schematic diagram of gorenflo pool boiling apparatus.
Figure 2 . A schematic of rod heater.
voltage, current and cosine of the difference between electrical voltage and current. Theaverage of five readings was used to determine thedifference between heating surface and the bulk temperature of each thermocouple. To calculate thereal surface temperature by correcting the minor temperature drops due to small distance betweensurface and thermocouple location, the Forie`sconduction equation is used as follow:
)A/q()k /s() bTthT( bTsT −−=− (1)
In this equation, s is the distance between thethermocouple location and heat transfer surface and k is the thermal conductivity of the heater material. Thevalue of s/k is determined for each thermocouple bycalibration of the test heater. The average temperaturedifference was the arithmetic average of the four thermocouple locations. The boiling heat transfer coefficientα is calculated by following equation:
For each experiment, picture of boiling phenomenawas taken using a high speed camera. A high speedvideo recorder was also used to record theformation and growth of the bubbles at the heattransfer surface. These recordings are used todetermine the frequency of bubble generation,nucleation site density and also the bubblediameter as function of time. In these set of visual recordings, a Canon EOS 300D DIGITALwere used with the following photo specification:F-Stop f/8, Exposure time 1/200 s, ISO-400, Focallength 54 mm and Max. Aperture = 4.970856. Itwas found that the above settings were satisfactoryto freeze the image of the moving bubble and makea sharp stationary picture. However, for muchhigher heating fluxes, because of higher
frequencies of bubble departure, higher frame ratessuch as 1/500 s and some even higher, arerequired which needs more intensive lightingstechniques.
Initially, the entire system including the rodheater and the inside of the tank were cleaned andthe test solution was introduced. The vacuum pump is then turned on and the pressure of thesystem is kept low approximately to 10 kPa for five hour to allow all the dissolved gases especiallythe dissolved air to be stripped from the testsolution. Following this, the tank's band heater wasswitch on and the system's temperature wasallowed to rise to the saturation temperature. Thismodus operandi present a homogeneous conditionthroughout. Then the electric power was slowlysupplied to the rod heater and increased graduallyto a constant predetermined value. Data acquisitionsystem, video equipments including a digitalcamera were simultaneously switched on to recordthe required parameters including the heating rodtemperature, bulk temperature, heat flux and alsoall visual information. All experimental runs werecarried out with decreasing heat flux to shun thehysteresis effect. Some runs were repeated twiceand even thrice to ensure the reproducibility of theexperiments.
Many test solutions have been selected to studythe boiling phenomenon in the past literatures.Each binary system could detect any sub- phenomenon in boiling process. Manyinvestigations are involved in liquids which water is the non-volatile component, such asacetone/water, isopropanol/water, methanol/water
and ethanol/water [15-19]; accordingly themaximum expected boiling temperature for thesesolutions is about 100˚ C. At least one investigator is focused on binary systems with high heatsolution such as water/ammonia [6]. The boiling process in such binary system, could absorb or release the heat of the solution depending on theexothermic of endothermic disposition duringsolving gases in liquid solvents. This heat is notconsidered in any major predictive correlation;nevertheless it is shown that this ignorance couldcause a high deviation of the experimental and predicted values of boiling heat transfer by themajor existing correlations for such systems [6].The test solutions in numerous investigatorsresearch for pool boiling are the refrigerant
solutions because of the wide application of thosesystems in practice [20-32]. Monoethanolamineand Diethanolamine are two liquid solvents whichare used as carbon dioxide and hydrogen sulfideabsorbing agent from sour hydrocarbon gasstreams. This commercial procedure which iswidely used in gas treatment process, involveswater washing and boiling process to remove andrecycle the dissolved gases.
As a result, binary or ternary mixtures of water/Monoethanolamine/Diethanolamine areopenly involved in boiling process. The maindifference of such solutions with other solutionsis the difference in characteristics of Monoethanolamine and Diethanolamine on metalsurface, when bubbles form on heated surfaceduring boiling. Preferential evaporation of water leaves higher concentrations of amines on theheating surface; accordingly, bubble dynamicsand consequently boiling heat transfer coefficientwould be affected.
In this investigation, water, Monoethanolamineand Diethanolamine were selected as pure liquidsto produce binary mixtures. Some physical andcritical constants, of pure selected liquids are givenin Table 3. Table 4 presents some physical properties of water-solution binary mixtures for thesaturation temperature range.
Except for the industrialized usage,water/Monoethanolamine and water/Diethanolamine binary solutions have been selected as test liquidsfor a number of reasons. At first, the bubbletemperatures and pressures of these combinationsare at moderate levels to complete the experiments.
Secondly, phase equilibrium diagrams andthermodynamic properties of these mixtures arewell known and could be easily-and accurately- predicted using an appropriate equation of state.Thirdly, in these binaries, water is the morevolatile component; the wetability of stainlesssteel-as heat transfer surface-to Monoethanolamine
and Diethanolamine are different in comparison to pure water, this means different vapor-liquidcontact angle and consequently different bubbledynamics for those system which water is the less-volatile component. Finally, boiling range of thesemixtures is wide enough to detect a significantvariety of mixture effects. There are also someother minor advantages of the mentioned binarymixtures such as transparency which provides agood condition for gathering visual information. Not interestingly some disadvantages are also
considerable for these binary systems. Highoxidation potential for Monoethanolamine andDiethanolamine should be considered principally,when these liquids are exposed to air. This needsadditional care and extraordinary treatment duringtransportation, the making up of the solution andalso during experiments. Furthermore, relatively
high operating temperatures should be noted as ahard practical condition. Figure 3 and 4 present theXY and XYT diagram for the selected test liquidsrespectively.
3. RESULTS AND DISCUSSIONS
Nucleate boiling phenomenon initiates when vapor bubbles form on the discriminatory points on the
Figure 5 . Experimental and predicted pool boiling heattransfer coefficient for pure water.
heat transfer surface, known as nucleation site. In boiling phenomenon, as discussed earlier, there arefundamental differences between pure liquids andliquid mixtures, due to the difference in bubbledynamics. As stated in the introduction, the boiling phenomenon is integrated with three differentmechanisms including free convection, micro-convection and evaporation. All these mechanismsare directly or indirectly affected by bubbledynamics. Microlayer evaporation is implicatedwith mass transfer between interface and vapor
inside the bubble; on the other hand, micro-convection is related to bubble dynamics. The bubble dynamics would also affect the freeconvection heat transfer by changing the exposedarea of heating surface to the bulk liquid;nevertheless, free convection has a diminutivecontribution in the total amount of transferred heatin comparison to other mechanisms.
To corroborate the validity of the achievedexperimental data in the present experiments,measured boiling heat transfer coefficient for pure
water has been compared to five well knowncorrelations including Gorenflo [33], Nishikawa etal [34], Boyko-Kruzhilin [35], Mostinski [36] andMcNelly [37]. Pure water has been used as the boiling liquid to calibrate the apparatus for somereasons.
• The physical properties of water are wellknown. Consequently, applying any existingcorrelation to water is trouble-free.
• During the boiling of any pure liquid(including water), there isn't an existingconcentration gradient anywhere andaccordingly no mass transfer is presented between the bulk liquid and heatingsurface, to affect the boiling heat transfer
coefficient. This phenomenon happens inmixture boiling.• The boiling heat transfer coefficient for pure
water has been repeatedly and extensivelymeasured by various investigators.
Therefore, the dependability of water, as a standardtest liquid for calibrating the pool boiling apparatuscould be considered logical.
Figure 5 presents the measured and predictedvalue of boiling heat transfer coefficient for purewater by the major existing correlations. A goodagreement could be observed especially by Gorenflo[33] at medium to high heat flux. Needless to saythat in low heat flux, free convection could take alarge contribution of the total heat transfer,consequently, deviation of experimental and predicted value could be expected for anycorresponding correlation. Note that, in thisinvestigation the value of 6,400 W/(m2˚ C) have
Figure 6 . Measured boiling heat transfer coefficient for water/monoethanolamine solution at atmospheric pressure.
Figure 7 . Measured boiling heat transfer coefficient for water/diethanolamine solution at atmospheric pressure.
been used and confirmed as the reference value for boiling heat transfer coefficient of pure boilingwater in Gorenflo [33] correlation. Measured boiling heat transfer for water/Monoethanolamineand water/Diethanolamine are given in Figure 6and Figure 7 respectively. These charts, which areenforced with 3D wire extrapolation, demonstratesthat, the pool boiling heat transfer coefficientsmoothly increases with rising heat flux at anygiven concentration. In addition, the pool polingheat transfer coefficient sharply increases when asmall amount of Monoethanolamine or Diethanolamine is added to pure water; however with increasing the concentration of amines, thisenhancement sharply diminishes and wouldcontinue to decrease smoothly. This enhancement
is significant especially at high heat flux and is not predicted by any existing correlation. It is wellknown that decrease in boiling heat transfer coefficient for mixtures is due to the preferentialevaporation of the more volatile component, at thevapor-liquid interface, during bubble generation.Evaporation of the more volatile component meansincrease in concentration of nonvolatile componentin the vapor-liquid interface and as a result, thelocal bubble temperature increases at this interface,which clearly indicates that the consequence is thediminution in the thermal driving force and boilingheat transfer coefficient.
Table 1 presents that all existing correlation for predicting the pool boiling heat transfer coefficientfor mixtures, could be written as the following
equation:
ϕ+=
11
idαα
(3)
Based on the above definition, the parameter φ is afunction of different parameters, which could beeasily derived from any existing correlation givenin Table 1. Based on the involved parameters,these correlations could be categorized to differentgroups with different complexities.
The ideal boiling heat transfer coefficientαid, is believed as the heat transfer coefficient of animaginary fluid, without any kinetic mixture effect.Two approaches are reported in the literature for calculating this ideal nucleate pool boilingcoefficient [22]. The first one is derived from thecharacterization of an ideal heat transfer coefficientfor the mixture, on the basis of a mole fraction-weighted average of the wall superheat for the purefluids:
∆Tid = x1∆T1 + x2∆T2 (4)
This results in the mole average heat transfer coefficients of the pure components,α1 and α2,which are at the same temperature or pressure asmixture would be as follows, which could beextended to multicomponent systems:
Figure 8 . Performance comparison of different existing correlation for water/Monoethanolamine boiling solution.(Average at heat fluxes between 20 and 350 kW.m-2).
Figure 9 . Performance comparison of different existing correlation for water/diethanolamine boiling solution.(Average at heat fluxes between 20 and 120 kW.m-2).
TABLE 5. The Impact of Boiling Heat Flux on the Calculated Error by Various Correlations forWater/Monoethanolamine Solution, [q] = W.m -2, Average Water Mole Fraction = [0.4 0.9].
Correlation q =5.6 k
q =15 k
q =27 k
q =38 k
q =62 k
q =101 k
q =147 k
q =188 k
q =205 k
Schlünder 17% 21% 15% 15% 16% 17% 14% 15% 17%Stephan, et al 40% 42% 33% 31% 25% 20% 15% 16% 17%Fujita, et al 65% 69% 68% 69% 68% 69% 69% 69% 70%
TABLE 6. The Impact of Boiling Heat Flux on the Calculated Error by Various Correlations forWater/Diethanolamine Solution, [q] = W.m -2, Average Water Mole Fraction = [0.7 0.9].
Correlation q = 5.6k
q = 15k
q = 27k
q = 38k
q = 62k
q = 85k
q = 101k
q = 121k
Schlünder 49% 17% 10% 12% 18% 28% 39% 28%Stephan, et al 16% 5% 7% 10% 26% 47% 67% 46%Fujita, et al 70% 77% 79% 79% 79% 77% 75% 83%
TABLE 7. The Average Calculated Error by Vinayak-Balakrishnan [12] Equation as A Function of Both Beat Flux and Concentration. (X = Water Mole Fraction).
Heat Flux
kW.m-2
X =
0.2
X =
0.3
X =
0.37
X =
0.44
X =
0.5
X =
0.56
X =
0.63
X =
0.7
X =
0.77
X =
0.8
X =
0.95.6 n/a n/a n/a 37% 20% 21% n/a n/a 4% n/a n/a
8.6 n/a n/a n/a 31% 15% 15% n/a n/a 19% n/a n/a
11.5 n/a n/a n/a 29% 14% 11% n/a n/a 27% n/a n/a
15 n/a n/a n/a 28% 13% 8% 26% 27% 33% n/a 23%
19.6 n/a n/a n/a n/a 14% 5% 20% 20% 30% n/a 16%
27.6 n/a n/a n/a n/a 14% 4% 13% 12% 29% n/a 9%
32.1 n/a n/a n/a n/a 14% 3% 11% 10% 29% n/a 7%
38.3 n/a n/a n/a n/a 14% 2% 8% 7% 30% n/a 5%
49.1 n/a n/a n/a n/a 14% 1% 5% 4% 30% n/a 5%
62.5 5% 16% n/a n/a 12% 1% 3% 1% 31% n/a 6%
85.2 44% 3% n/a n/a 10% n/a 1% 1% 35% 37% 5%
101.1 n/a 21% 1% n/a 6% n/a 0% 2% 37% 37% 2%
121 n/a 46% 10% n/a 2% n/a n/a 4% n/a 37% 1%
147 n/a n/a 26% 3% n/a n/a n/a n/a n/a 35% 2%
166 n/a n/a 31% 4% n/a n/a n/a n/a n/a 36% 2%
188.62 n/a n/a 27% 1% n/a n/a n/a n/a n/a 41% 1%
205 n/a n/a 21% 2% n/a n/a n/a n/a n/a 43% 3%
idTΔ/ETΔK 11
idαα
+= (6)
Which the definitions of k could be found inTable 1 for the three set of equations. In thisinvestigation, the experimental values of k have been correlated as a function of heat flux for water/Monoethanolamine and water/Diethanolamine binary solution on a stainless steel heating surface
and the following new function have beenachieved:
)q6E646.1(exp1K −−−= (7)
This new equation is correlated to other threementioned equation and the results are allcompared in Figure 14 and 15. Based on Equation 7,the pool boiling heat transfer coefficients are
Figure 10 . The appearance of heat transfer surface during boiling of water/Acetone mixture [q = 90 kW.m-2, X(Acetone = 0.5)].
Figure 11 . The appearance of heat transfer surface during boiling of water/Acetone mixture [q = 42 kW.m-2, X(Acetone = 0.5)].
Figure 12 . The appearance of heat transfer surface during boiling of water/Monoethanolamine mixture [q = 90 kW.m-2, X(Acetone = 0.5)].
Figure 13 . The appearance of heat transfer surface during boiling of water/Diethanolamine mixture [q = 42 kW.m-2, X(Acetone = 0.5)].
recalculated and the average errors aresignificantly reduced. The average errors over water mole fractions between 0.7 and 0.9 aresummarized in Figure 16 and 17 and similar comparison for average heat flux between 15 and205 kW.m-2 are presented in Figure 18 and 19 for water/Monoethanolamine and water/Diethanolaminesolutions.
4. CONCLUSION
Heat transfer coefficient for water/Amine solutions
has been experimentally measured in a wide rangeof concentrations and heat fluxes at atmospheric pressure. Existing correlations to pool boiling of mixtures are correlated to these experimental data.Results from water/Amine solutions concludesthat, the boiling heat transfer coefficients of liquidmixtures are generally less than pure liquids, withthe same physical properties. This phenomenoncould be related to mass transfer and back diffusion, caused by concentration gradientthrough vapor-liquid interface. However, aconsiderable enhancement of boiling heat transfer could be observed at low concentrations of amines
Figure 14 . Experimental and calculated value of k for water/Monoethanolamine boiling system at atmospheric pressure.
Figure 15 . Experimental and calculated value of k for water/Diethanolamine boiling system at atmospheric pressure.
Figure 16 . Calculation error for predicting the boiling heattransfer coefficient for water/Monoethanolamine solution inthe average concentrations of 0.7, 0.77, 0.8 and 0.9 water molefraction.
Figure 17 . Calculation error for predicting the boiling heattransfer coefficient for water/Diethanolamine solution in theaverage concentrations of 0.7, 0.77, 0.8 and 0.9 water molefraction.
at any heat flux. This enhancement could beconnected to the wetability characteristicsof vapor/liquid/solid in boiling and theconsequentially affected, bubble dynamics at thisrange. None of the existing correlations couldestimate this enhancement, but some haverelatively good performance with the rest of theamine concentrations. This investigation is focusedon the correlations of Fujita, et al [8], Fujita, et al[14] and Inoue, et al [6] and the existing tuning parameters are modified. The results present asignificant improvement for boiling heat transfer coefficient of amine aqueous solutions on stainlesssteel heating surface, which water is the morevolatile component.
5. NOMENCULATURE
A Area, m2 b A Parameter in Mostinski [36]
Equation b1-b5 Tuning Parameter in Unal [11]
equation.Bo The Ratio of Evaporation Heat
Transfer to Total Heat Transfer C Heat Capacity, J.kg-1.˚ C-1 DAB Diffusivity Coefficient, m2.s-1 F Parameters in Gorenflo [33], see
Figure 18 . Average calculation error of pool boiling heattransfer coefficient for water/Monoethanolamine binarysolution between 15 to 205 kW.m-2.
Figure 19 . Average calculation error of pool boiling heattransfer coefficient for water/Diethanolamine binary solution between 15 to 205 kW.m-2.
g Gravity Acceleration, m.s-2 Hfg Heat of Vaporization, J.kg-1 k Thermal Conductivity, W.m-1.˚ C-1
K See Equations 4, 5 and Table 1K o A Tuning Parameter in Stephan, et
al [5] and Jungnickel, et al [4]equation
l* A parameter in Boyko-Kruzhilin[35] equation
M Molecular Weight, g.mole-1 n See Gorenflo [33] equation
P Pressure, Pa otherwise specifiedq Heat Transfer, WRa Roughness,μmRp Roughness,μms Distance, mT Temperture, ˚ C or k x Liquid Mole Fractiony Vapor Mole FractionΔTE Difference Between Bubble and
Dew Temperature, k α Boiling Heat Transfer Coefficient,
W.m-2.˚ C-1 α Thermal Diffusivity, m2.s-1 β Mass Transfer Coefficient, m.s-1 ρ Density, kg.m-3 σ Surface Tension, n.m-1
φ A Tuning Parameter
Subscripts
0 Reference1,2 Components b Saturation bo Dew Point bi Bubble Pointc Criticalid Ideall Liquidr Reduceds Surface or Saturationth Thermocouplesv Vapor
6. REFERENCES
1. Fujita, Y. and Bai, Q., “Bubble Dynamics and HeatTransfer in Mixture Boiling”, Proc. 12 th Int. Heat
Transfer Conf ., Elsevies SAS, Grenoble, (2002), 1-5.2. Fujita, Y. and Tsutsui, M., “Nucleate Boiling of Two
and Three-Component Mixtures”, International Journal of Heat and Mass Transfer , Vol. 47, (2004),4637-4648.
3. Schlünder, E. U., “Heat Transfer in Nucleate Boiling of Mixtures”, Int. Chem. Eng ., Vol. 23, No. 4, (1983),589-599.
4. Jungnickel, H., Wassilew, P. and Kraus, W. E.,“Investigations on the Heat Transfer of Boiling BinaryRefrigerant Mixtures”, International Journal of
5. Stepha n, K. and Körner, M., “Berech nungdes Wärme-Übergangs Verdampfender Binärer Flussigkeitgemische”, ChmieIng Techn ., Vol, 41,(1969), 409-417.
6. Inoue, T., Monde, M. and Teruya, Y., “Pool BoilingHeat Transfer in Binary Mixtures of Ammonia/Water”,
Int. J. of Heat and Mass Transfer , Vol. 45, (2002),4409-4415.
7. Thome, J. R. and Shakir, S., “A New Correlation for Nucleate Boiling of Binary Mixtures”, AIChESymposium Series , Vol. 83, (1987), 46-51.
8. Fujita, Y. and Tsutsui, M., “Heat Transfer in NucleateBoiling of Binary Mixtures”, Int. J. Heat MassTransfer , Vol. 37, (1994), 291-302.
9. Fujita, Y. and Tsutsui, M., “Convective Flow Boiling of Binary Mixtures in a Vertical Tube, in: ConvectiveFlow Boiling”, Taylor and Francis, Washington, U.S.A.,(1996), 259-264.
10. Calus, W. F. and Rice, P., “Pool Boiling: BinaryLiquid Mixture”, Chem. Eng. Sci ., Vol. 27, No. 9,(1972), 297.11. Unal, H. C., “Prediction of Nucleate Pool Boiling HeatTransfer Coefficients for Binary Mixtures”, Int. J. Heat
Mass Transfer , Vol. 29, (1986), 637-640.12. Rao, G. V. and Balakrishnan, A. R., “Heat Transfer in
Nucleate Pool Boiling of Multicomponent”, Exp.Therm. Fluid Sci ., Vol. 29, (2004), 87-103.
13. Taylor, R. and Krishna R., “Multicomponent MassTransfer”, Wiley, New York, U.S.A., (1993).
14. Fujita, Y. and Tsutsui, M., “Heat Transfer in NucleateBoiling of Binary Mixtures (Development of a HeatTransfer Correlation)”, Jsme International Journal ESeries B: Fluids and Thermal Engineering , Vol. 40,(1997), 134-141.
15. Krupiczka, R., Rotkegel, A. and Ziobrowski, Z., “TheInfluence of Mass Transport on the Heat Transfer Coefficients During the Boiling of MulticomponentMixtures”, Int. J. Therm. Sci ., Vol. 39, (2000), 667-672.
16. Li, J. and Peterson, G. P., “Microscale HeterogeneousBoiling on Smooth Surfaces-From Bubble Nucleation toBubble Dynamics”, International Journal of Heat and
Mass Transfer , Vol. 48, (2005), 4316-4332.17. Wen A, D. S. and Wang, B. X., “Effects of Surface
Wettability on Nucleate Pool Boiling Heat Transfer for Surfactant Solutions”, International Journal of
Heat and Mass Transfer , Vol. 45, (2002), 1739-1747.
18. Yanga, C., Wua, Y. and Yuana, X., “Chongfang Ma,Study on Bubble Dynamics for Pool Nucleate Boiling”,
International Journal of Heat and Mass Transfer ,Vol. 43, (2000), 203-208.
19. Vinayak Rao, G. and Balakrishnan, A. R., “HeatTransfer in Nucleate Pool Boiling of Multicomponent”,
Exp. Therm. Fluid Sci ., Vol. 29, (2004), 87-103.20. Wang, W. J., Zhao, L. X. and Zhang, C. L.,
“Generalized Neural Network Correlation for FlowBoiling Heat Transfer of R22 and its AlternativeRefrigerants Inside Horizontal Smooth Tubes”,
International Journal of Heat and Mass Transfer ,Vol. 49, (2006), 2458-2465.
21. Zhao, Y. H., Diao, Y. H. and Takaharu, T.,“Experimental Investigation in Nucleate Pool Boiling of Binary Refrigerant Mixtures”, Applied Thermal
Engineering , Vol. 28, (2008), 110-115.22. Taboas, F., Valle`S, M., Bourouis, M. and Coronas, A.,
“Pool Boiling of Ammonia/Water and its PureComponents:Comparison of Experimental Data in theLiterature with the Predictions of StandardCorrelations”, International Journal of Refrigeration ,Vol. 30, (2007), 1-11.
23. Zhang, L., Gong, M., Zhang, Y., Li, P., Wu, J. andXu, L., “Nucleate Pool Boiling Heat Transfer Measurements of HC170/HFC23 System”, International Communications in Heat and Mass Transfer , Vol. 34,(2007), 277-284.
25. Zhaohu, S., Maoqiong, G., Zhijian, L. and Jianfeng,W., “Nucleate Pool Boiling Heat Transfer Coefficients of Pure HFC134A, HC290, HC600Aand Their Binary and Ternary Mixtures”, International
Journal of Heat and Mass Transfe r , Vol. 50,(2007), 94-104.26. Jungnickel, H., Wassilew, P. and Kraus, W. E.,“Investigations on the Heat Transfer of BinaryRefrigerant Mixtures”, Int. J. Refrig ., Vol. 3, (1980),129-133.
27. Gorenflo, D., “State of the Art in Pool Boiling HeatTransfer of New Refrigerants”, International Journal
of Refrigeration , Vol. 24, (2001), 6-14.28. Fujita, Y. and Tsutsui, M., “Experimental Investigation
in Pool Boiling Heat Transfer of Ternary Mixtureand Heat Transfer Correlation”, Experim ental Thermal and Fluid Science , Vol. 26, (2002), 237-244.
29. Barthau, G. and Hahne, E., “Nucleation Site Density
and Heat Transfer in Nucleate Pool Boiling of Refrigerant R134a in a wide Pressure Range”, In 3 rd European Thermal Sci. Conf. Heidelberg , Germany,Vol. 2, (2000), 731-736.
30. Barthau, G. and Hahne, E., “Nucleation Site Densityand Heat Transfer in Nucleate Pool Boiling of Refrigerant R134a in a wide Pressure Range”, In 3 rd
European Thermal-Sciences Conference , Heidelberg,Vol. 2, (2000), 731-736.
31. Gorenflo, D., Chandra, U., Kotthoff, S. and Luke, A.,“Influence of Thermophysical Properties on PoolBoiling Heat Transfer of Refrigerants”, Internat ional
Journa l of Ref rigeration , Vol. 27, (2004), 492-502.
32. Kedzierski, M. A., “A Semi-Theoretical Model For Predicting Refrigerant/Lubricant Mixture Pool BoilingHeat Transfer”, International Journal of Refrigeration ,Vol. 26, (2003), 337-348.
33. Gorenflo, D., “Pool Boiling”, In VDI Heat Atlas,Chapter Ha, Germany, (1993).
34. Nishikawa, K. and Fujita, Y., “Nucleate Pool BoilingHeat Transfer and its Augmentation”, In J. P. Hartnett,T. F. Irvine Jr. (Eds.), Advances in Heat Transfer ,Academic Press, New York, U.S.A., Vol. 20, (1990), 1-82.
35. Boyko-Kruzhilin, “Perry’s Chemical EngineeringHandbook”,Ver 6 , (1997), 419.
36. Mostinski, I. L., “Application of The Rule of Corresponding States for Calculation of Heat Transfer and Critical Heat Flux”, Teploenergetika , Vol. 4,(1963), 66.
37. McNelly, M. J., “A Correlation of Rates of HeatTransfer to Nucleate Boilingo Liquids”, J. Imperial College Chem. Eng. Soc ., Vol. 7, (1953), 18-34.
38. Thome, J. R. and Shock, M. R. A. W., “Boiling of Multicomponent Liquid Mixtures”, In J. Thome, R. A.W. Shock (Eds.), Advances in Heat Transfer , Vol. 16,(1984), 59-156.
39. Palen, J. W. and Small, W., “A New Way to DesignKettle and Internal Reboilers”, Hydrocarbon Process ,Vol. 43, No. 11, (1964), 199-208.
![Evening star. (Washington, D.C.). 1936-03-03 [p A-12].](https://static.documents.pub/doc/80x56/61f4ba02a87e7616cc77d859/evening-star-washington-dc-1936-03-03-p-a-12.jpg)
