Experimentation on Pool Boiling With Sodium Dodecyl Sulfate

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1 International Journal of Engineering Researc and Development e-issn: X, p-issn: X, Volume 12, Issue 12 (December 2016), PP Experimentation on Pool Boiling Wit Sodium Dodecyl Sulfate D.CH.N.S.Krisna 1 *, V Ravi Kumar 2 ** *Pg Student, Asrce, Tanuku, ** Assistant Professor, Asrce, Tanuku, Abstract : We ave so many applications related to Pool Boiling. Te Pool Boiling is mostly useful in arid areas to produce drinking water from impure water like sea water by distillation process. It is very difficult to distill te only water wic aving ig surface tension. Te surface tension is important factor to affect eat transfer enancement in pool boiling. By reducing te surface tension we can increase te eat transfer rate in pool boiling. Over te past few decades, researcers ave investigated different passive enancement tecniues to increase te eat transfer coefficient and te critical eat flux. Tey ave used different working fluids, e.g., water, aueous surfactant solutions, refrigerants, alcools, binary mixtures. From so many years we are using surfactants in domestically. It is proven previously by experiments tat te addition of little amount of surfactant reduces te surface tension and increase te rate of eat transfer. Tere are different groups of surfactants. From tose I ave experimenting wit anionic surfactant Sodium Dodecyl Sulfate (SDS), wic is most uman friendly to test te eat transfer enancement. Te effects, of bot SDS concentration, and te excess temperature ΔT on eat transfer performance, are studied. Te experimental results sow tat a small amount of surface active additive enances te eat transfer coefficient considerably iger, and tat tere is an optimum additive concentration for iger eat fluxes. Beyond tis optimum point, furter increase in additive concentration makes lower. Keywords: Pool Boiling, Distillation, Sodium Dodecyl Sulfate. I. INTRODUCTION Boiling is a liuid-to-vapor pase cange process just like evaporation, but tere are significant differences between te two. Evaporation occurs at te liuid-vapor interface wen te vapor pressure is less tan te saturation pressure of te liuid at a given temperature. Boiling, on te oter and, occurs at te solid-liuid interface wen a liuid is brougt in contact wit a surface maintained at a temperature T s sufficiently above te saturation temperature T sat of te liuid. Te boiling process is caracterized by te rapid formation of vapor bubbles at te solid-liuid interface tat detac from te surface wen tey reac a certain size and attempt to rise te free surface of te liuid. Bubbles owe teir existence to te surface-tension σ at te liuid-vapor interface due to te attraction force on molecules at te interface toward te liuid pase. Boiling is classified as pool boiling and flow boiling, depending on te presence of bulk fluid motion. Boiling is called pool boiling in te absence of bulk fluid flow and flow boiling in te presence of it. In pool boiling, te fluid is stationary, and any motion of te fluid is due to natural convection currents and motion of te bubbles under te influence of buoyancy. In flow boiling, te fluid is forced to move in a eated pipe or over a surface by external means suc as a pump. Pool and flow boiling are furter classified as sub-cooled boiling or saturated boiling, depending on te bulk liuid temperature. Boiling is said to be sub-cooled wen te temperature of te main body of te liuid is below te saturation temperature T sat and saturated wen te temperature of te liuid is eual to T sat. One important field of application of boiling and evaporation is in desalination of seawater, wic is becoming essential in some arid regions. Small amount of certain surfactant additives are known to drastically cange te boiling penomena of water. It is most desirable tat employing surfactant additives in liuids can develop and mature into an enancement tecniue for boiling eat transfer. Generally, it is believed tat small amount of surfactant can increase boiling eat transfer. Te extent of enancement as been found to be dependent on additive concentrations, its type and cemistry, wall eat flux, and te eater geometry. II. LITERATURE REVIEW Te mecanism of pool boiling eat transfer as been studied for a long time since it is closely related wit te designs of more efficient eat excanger and eat removal systems. To determine te reuired eat transfer surface area as well as to evaluate te system performance during postulated accidents, overall eat transfer coefficients applicable to te system are needed. Since pool boiling eat transfer coefficient is factor in determining overall eat transfer coefficients troug te eat excanging tubes of te passive eat excangers, many researcers ave studied about it. Wit its ability to transfer large amounts of eat wit relatively small temperature differences, nucleate boiling as attracted considerable researc attention. Tis mode of eat 45

2 transfer is encountered in many different applications ranging from energy conversion systems, to refrigeration and air- conditioning, to cemical termal processing tat employs bot Newtonian and non-newtonian liuids[1]. Among te different enancement tecniues investigated, te use of additives for liuids appears to be uite viable and attracted some researc. Small amount of certain surfactant additives are known to drastically cange te boiling penomena of water. Te surfactant effect as generated a lot of interest for many years. It is most desirable tat employing surfactant additives in liuids can develop and mature into an enancement tecniue for boiling eat transfer. Generally, it is believed tat small amount of surfactant can increase boiling eat transfer. Te extent of enancement as been found to be dependent on additive concentrations, its type and cemistry, wall eat flux, and te eater geometry. Surfactant is a generic term for a surface-active agent, wic literally means active at surface. It is fundamentally caracterized by its tendency to adsorb at surfaces and interfaces wen added in low concentrations to aueous system. Te study of te saturated pool boiling of a surfactant solution sows a significant enancement of eat transfer. Generally, it is believed tat small amount of surfactant can increase boiling eat transfer. Te extent of enancement as been found to be dependent on additive concentrations, its type and cemistry, wall eat flux, eater geometry as reviewed recently by Wasker and Manglik (2000). Wu and Yang (1995) reported experimental data on te effect of surfactants on nucleate boiling in water wit nine different additives[6][7]. Te enancement of eat transfer was related to depression of te static surface tension. Small concentrations of surfactant additives reduces te surface tension reduces considerably and its level of reduction depends on te amount and type of surfactant presented in te solution. Te activation of nucleation sites, bubble growt and bubble dynamics influence te boiling eat transfer coefficient by Wen DS (2000) [5]. Frost and Kippenan (1997) investigated boiling of water wit various concentrations of surfactant Ultra wet 60L. Tey observed tat te increase of eat transfer being related to te reduction in te surface tension [3].Te effect of surfactants and polymeric additives on te pysical properties of aueous surfactant and polymeric solutions as reviewed recently by Ceng L (2007)[8]. Te measurement results of surface tensions and viscosities by aueous surfactant and polymeric solutions sow te variation of pysical properties and interfacial properties affected by concentrations of surfactant and polymeric solutions. Hetsroni G (2000) studied experimentally te saturated nucleate pool boiling of aueous Habon G solutions on te surface of electrically eated constantan plate. Tey ave concluded tat te eat transfer coefficient can be enanced by te addition of Habon G, depending upon its concentration[4]. Te eat transfer increases wit increasing te solution concentration and reaces a maximum value at a certain solution concentration, and ten decreases wit furter increasing te solution concentration. Te effect of bot te surface tension and te kinematic viscosity of aueous Habon G solutions can explain te features of boiling eat transfer of te solutions. By Conducting an Experiment on Pool Boiling eat transfer wit Sodium Dodecyl Sulfate(SDS), we may get grater Heat Flux results. In Pool Boiling, a little amount of SDS can drastically increase te Heat Flux nearly undred times. By using SDS in power plants we may get best rate of steam generation. And in sea water desalination and polluted water desalination we may get best eat transfer rates and can produce large uantity of drinking water in minimum time. III. 3.1 Experimental Setup: Te experimental setup consists of a Power Supply Euipment, Pool Heater, Beaker, Termocouples. EXPERIMENTATION Power Supply Euipment: Te power supply euipment consists of a Voltmeter, Ammeter and Temperature Indicator. Te Voltmeter is of maximum 240 Volts, and Ammeter is of maximum 4.05 Amperes. Te voltmeter and ammeter are used to set te constant power supply. 46

3 Fig: 1 Experimental Setup line diagram. Te temperature indicator is used to sow te temperature measurement by reuired number of temperatures marked reader. And termocouples also connected to tis power supply wic converts te temperature measurement to digital form and sows te reading Pool Heater: Te pool Heater of polised stainless steel of lengt 600mm and 3.75mm radius is used. Te eater is connected to te power supply euipment to regulate te amount of power supply Termocouples: Termocouple is used to measure te temperature of matter and transfers it to te digital reader. A termocouple is a temperature-measuring device consisting of two dissimilar conductors tat contact eac oter at one or more spots, were a temperature differential is experienced by te different conductors (or semiconductors). It produces a voltage wen te temperature of one of te spots differs from te reference temperature at oter parts of te circuit. Fig: 2 Termocouple 3.2 Procedure: A beaker of one liter volume is taken and filled wit pure water. A eater is dipped into te water wic is connected to power supply euipment. Two termocouples are attaced to eater surface to measure te temperature of te eater surface. Te power supply is switced on to te eater. Te supplying eat is set to constant at voltmeter reading(v) is set to 120 volts and ammeter reading(i) is adjusted to 2.05 amperes. Fig: 3 Practical Experimental Setup After reacing te saturation temperature bubble formation is started on eater surface. Ten te values of temperatures of eater surface is noted and tabulated. After a certain interval time again te temperature readings are noted and tabulated. Tis process is continued for up to te end of nucleate boiling. 47

4 Te process is repeated for every 10 ppm SDS concentration up to 100ppm and from tat process is repeated for every 100ppm concentration up to 1000ppm and furter te concentration is increased by 500ppm up to 3000ppm. Tabulated all tose readings and calculated te Heat flux( s ) and Coefficient of Heat Transfer (). Te Heat flux is calculated by using Rosenow Nucleate Boiling correlation. 4.1Observations: IV. OBSERVATIONS & CALCULATIONS Table: 1 Experimental values of Pure Water Pure Water Table : 2 Experimental values of 10ppm Concentration 10ppm Table: 3 Experimental values of 50ppm Concentration 50ppm Table: 4 Experimental values of 100ppm Concentration 100ppm Table: 5 Experimental values of 400ppm Concentration 400ppm Table: 6 Experimental values of 500ppm Concentration 500ppm

5 Table: 7 Experimental values of 800ppm Concentration 800ppm Table: 8 Experimental values of 1000ppm Concentration Table: 9 Experimental values of 1500ppm Concentration Table: 10 Experimental values of 2000ppm Concentration Table: 11 Experimental values of 2500ppm Concentration Table: 12 Experimental values of 3000ppm Concentration 4.2 Calculations: Here te power supplied to te pool eater power reuirement to be determined. Assume Water is boiled at 1 tam pressure on a stainless steel tube surface. At C g(ρ l ρ v ) Heat flux s = µ l fg( ) 0.5 ( σ ppm c pl (T s T sat ) C sf fg ρr l n ) (1) fg = Entalpy of vaporization = 2257 KJ/Kg, ρ v = Density of te vapor = 0.6Kg/m 3, µ l =Viscosity of te liuid = 0.282*10 3 Kg/m-s, ppm Q ppm Q ppm ppm

6 σ = Surface tension of te liuid-vapor interface = N/m, Pr L = Prandtl number of te liuid =1.75, ρ l = Density of liuid= Kg/m 3, C pl = Specific eat of liuid = 4220 J/Kg k, n = 1 for water Nucleate Heat flux: s = ( )( ) s = s = W/m 2 eat transfer coefficient = s /(T s -T sat ) = 475.1/( ) =31.67 KW/ m 2 o C Stainless Tube eater Design: Lengt of stainless tube eater (L) = 600 mm Diameter of stainless tube eater (D) = 7.5 mm Surface area of eater (A) = πdl = π = m 2 Maximum Heat flux is given by, max = C cr fg [σgρ v 2 (ρl - ρ v )] (2) Were, C cr = Constant, Wic value depends on te Dimensional Lengt L *, given by (3) L * = L g ρ L ρ v σ Were, L = Caracterstic Dimension of Heater =Radius = 3.75 mm L * = L * =0.478 m ; 0.15<L * <1.2 Terefore, From table, C cr =0.12L *-0.25 C cr = max = ( ) 0.25 = [199.12] 0.25 max = 2.23 MW/m Burnout temperature: Surface Temperature at wic burnout penomenon occurs determined by, g(ρ l ρ v ) nucleate = µ l fg( ) 0.5 c ρl (T s T sat ) ( σ C sf fg ρr n ) (4) l = ( )( ) ( ) 4220(115 T s ) T s = C. V. RESULTS & DISCUSSION 5.1 Variation of Heat Fluxes for Different Concentrations: A Grap is drawn to Heat flux and concentration ere we can observe tat for te pure water te obtained eat fluxes are very low and it is increased wit increase in concentration of te surfactant sodium dodecyl sulfate. Very ig eat fluxes are obtained at 1500ppm and 2000ppm. Fig:4 Grap - Variation of Heat Fluxes for Different concentrations. 50

7 Heat Flux Varying Heat Flux wit Concentration pure water 50ppm 100pp m 400pp m 800pp m 5.2 Concentration Vs Temperature Difference: A grap is drawn between concentration of SDS and cange in temperature. Here we can observe tat by increasing te concentration of SDS te temperature difference also increased. For pure water te maximum temperature difference is C and for 2500ppm te temperature difference is 25 0 C. Fig: 5 Grap-Concentration Vs Temperature Difference 5.3 Heat Flux Vs Concentration: Te Grap is drawn between Heat Flux and concentration of SDS. Here we can observe tat te Heat Flux is increased wit increase in concentration of SDS. And te minimum eat flux is obtained for pure water and maximum eat flux is obtained for 2500ppm. Fig: 6 Grap-Heat flux Vs Concentration of SDS. 51

8 5.4 Concentration and of Boiling: Te grap is drawn between concentration of SDS and time of bubble formation. From te grap we can observe tat by increase in concentration of SDS te time of bubble formation is decreasing wic means te rate of eat transfer increasing wit concentration and reducing te time of boiling. Fig: 7 Concentration and of Boiling 5.5 of Boiling and Temperature Difference: Te grap is drawn between time of boiling and Temperature difference, ere we can observe tat te time of boiling is decreasing wen te temperature difference increasing. By tis we can said tat depending on concentration time of boiling is decreasing and temperature difference is increasing. Fig:8 of Boiling and Temperature Difference VI. CONCLUSION Experimentation is conducted on Pool Boiling eat transfer wit Sodium Dodecyl Sulfate(SDS).From te results te maximum Heat Flux obtained for pure water is KW/m 2 and maximum Heat Flux for 2500ppm is 2199 KW/m 2, wic means little amount 2.5 grams of SDS increases te Heat Flux nearly undred times. Terefore rate of eat transfer increased drastically by using SDS in pool boiling. By using SDS in power plants we may get best rate of steam generation. And in sea water desalination and polluted water desalination we may get best eat transfer rates and can produce large uantity of drinking water in minimum time. ACKNOWLEDGEMENT Te Autor would like to tank all te persons wo elped me in te completion of my experimental work. Also tanks are extended to ASR College of Engineering, Tanuku, INDIA for support trougout te execution of te experimental work. Nomenclature s = Heat flux, fg = Entalpy of vaporization, ρ v = Density of te vapor, 52

9 µ L =Viscosity of te liuid, σ = Surface tension of te liuid-vapor interface, Pr L = Prandtl number of te liuid, ρ l = Density of liuid, = Specific eat of liuid. C pl REFERENCES [1]. Heat and Mass Transfer by R.K.Raj Put. [2]. Heat Transfer by Yunus A. Çengel, [3]. Frost W, Kippenan CJ. Bubble growt and eat transfer mecanisms in forced convection boiling of water containing a surface active agent Int. J Heat Mass Transfer,1967, vol.10, pp [4]. Hetsroni G, Zakin JL, Lin Z, Mosyak A,Pancallo EA,Rozenblit R. Te effect of surfactants on bubble growt, wall termal patterns and eat transfer in pool boiling Int. J Heat Mass Transfer, 2001, vol.44, pp [5]. Wen DS, Wang BX. Effects of surface wettability on nucleate pool boiling eat transfer for surfactant solutions Int. J Heat Mass Transfer, 2002, vol.45, pp [6]. Wasekar VM, Manglik RM. Pool boiling eat transfer in aueous solutions of an anionic surfactant. Journal of Heat Transfer, Transactions of te ASME, 2000, vol.122, pp [7]. Wu WT, Yang YM, Maa JR. Nucleate pool boiling Enancement by means of surfactant additives Experimental Termal and fluid science 1998, vol.18, pp [8]. Ceng L, Mewes D, Luke A. Boiling penomena wit surfactants and polymeric additives Int. J Heat Mass Transfer, 2007, vol.50, pp