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A numerical study of the non-absorbable effects on the falling liquid film absorption

Numerische Studie über die Einwirkung von nicht absorbierbaren Stoffen auf die fallende Flüssigkeitsfilmabsorption

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Abstract

A numerical study for the simultaneous heat and mass transfer in a falling liquid film absorption process with the presence of non-absorbable gases is presented. Water vapor mixed with air as the non-absorbables being absorbed into a falling smooth aqueous lithium chloride film flow was chosen as the model problem for the study. The finite difference numerical calculation was proceeded by marching downward from the top end, owing to the parabolic type energy and concentration equations for both liquid and gas phases. The results indicate that the local non-absorbable gas concentration is much higher at the gas-liquid interface than that in the ambient, hence the local vapor pressure is lowered there such that the absorption driving potential of the vapor pressure difference is reduced. The resulting reduction of the absorption rate due to the presence of the non-absorbables suggests that its effect must be carefully considered in the application of absorption heat pump design. The present study can provide some useful information for this purpose.

Zusammenfassung

Hier wurde eine numerische Studie der Wärmeund Stoffübertragung in einem Absorptionsprozeß eines fallenden Flüssigkeitsfilms in Anwesenheit von nicht absorbierbaren Gasen dargestellt. Ein Wasserdampf-Luft-Gemisch, das in Anwesenheit von nicht absorbierbaren Gasen von einer fallenden glatten flüssigen Lithium-Chlorid-Filmströmung absorbiert wird, wurde als das Modellproblem für diese Studie gewählt. Die numerische Berechnung mit dem Finite Differenzenverfahren wurde schrittweise vom obersten Ende nach unten durchgeführt. Die Berechnung bezieht sich auf den parabolischen Typ der Energie- und Konzentrationsgleichungen für die Flüssigkeits- und Gasphasen. Die Ergebnisse weisen darauf hin, daß die lokale nicht absorbierbare Gaskonzentration bei der Gasflüssigkeitsphase sehr viel höher ist als in der Umgebung. Weiter ist der lokale Dampfdruck so erniedrigt worden, daß sich das Absorptionsbewegungspotential des Dampfdruckunterschiedes reduziert. Die resultierende Reduzierung der Absorptionsrate, die auf die Anwesenheit der nicht absorbierbaren Stoffe zurückzuführen ist, verlangt eine sorgfältige Einbeziehung ihere Einflüsse auf die Gestaltung der Absorptionswärmepumpen. Diese Arbeit kann einige nützliche Informationen für diesen Zweck geben.

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Abbreviations

C :

absorbent concentration in weight fraction of salt

C a :

nonabsorbables concentration in molar fraction

\(C_{a_\infty } \) :

C a at inlet and infinity

C in :

C at film inlet

c p :

specific heat of liquid

c p g :

specific heat of gas

D :

species diffusivity for LiCl-H2O

D g :

species diffusivity for air-water vapor

g :

gravity

h o :

film thickness

H a :

heat of absorption

k :

thermal conductivity of liquid

k g :

thermal conductivity of gas

L :

transformation constant

\(\dot M_{abs} \) :

water vapor mass absorption rate

P v :

water vapor pressure

Re :

film Reynolds number=ϱV 0 h 0/μ

T :

film temperature

T in :

film temperature at inlet

T g :

gas temperature

T w :

wall temperature

T ∞ :

gas temperature at inlet and infinity

u :

velocity inx-direction

U :

=1.5V 0

V 0 :

mean film velocity=ϱg h 20 /3µ

x :

coordinate parallel to the wall

y :

coordinate normal to the wall in the film region

y g :

coordinate normal to the wall in the gas region

\(\bar y\) :

transformedy g

μ :

dynamic viscosity

ϱ :

liquid density

ϱ g :

gas density

References

  1. Grigor'eva, N. I.; Nakoryakov, V. E.: Exact solution of combined heat and mass transfer problem during film absorption. Inzh.-Fiz. Zh. 33 (1977) 893

    Google Scholar 

  2. Nakoryakov, V. E.; Grigor'eva, N. I.: Combined heat and mass transfer during absorption in drops and films. Inzh. Fiz. Zh. 32 (1980) 111

    Google Scholar 

  3. Nakoryakov, V. YE.; Burdukov, A. P.; Bufetov, N. S.; Grigor'eva, N. I.; Dorokhov, A. R.: Coefficient of heat and mass transfer in falling wavy liquid films. Heat Transfer-Soviet Research 14 (1982) 6

    Google Scholar 

  4. Nakoryakov, V. E.; Bufetov, N. S.; Grigor'eva, N. I.: Heat and mass transfer in film absorption. Fluid Mech.-Soviet Research 11 (1983) 97

    Google Scholar 

  5. Andberg, J. W.: Non-isothermal absorption of gases into falling liquid films. M. S. thesis, Uni. of Texas at Austin (1982)

  6. Nakoryakov, V. YE.; Bufetov, N. S.; Grigor'eva, N. I.: Heat and mass transfer in film absorption. Fluid Mech.-Soviet Research 11 (1983) 97

    Google Scholar 

  7. Grossman, G.: Simultaneous heat and mass transfer in film absorption under laminar flow. Int. J. Heat Mass Transfer 26 (1983) 357

    Google Scholar 

  8. Grossman, G.; Heath, M. T.: Simultaneous heat and mass transfer in absorption of gases in turbulent liquid films. Int. J. Heat Mass Transfer 27 (1984) 2365

    Google Scholar 

  9. Grossman, G.: Analysis of diffusion-thermo effects in film absorption. Heat Transfer (1986) 1977

  10. Goff, H. L.; Ramadance, A.: Modeling the coupled heat and mass transfer in a falling film. Heat Transfer (1986) 1971

  11. Grossman, G.: Heat and mass transfer in film absorption. Handbook of Heat and Mass Transfer, New York: Gulf Publishing 1986

    Google Scholar 

  12. Yang, R.; Chen, J. H.: A numerical modeling of a liquid absorbent absorption process. 8th Annual Meeting and Workshop, Solar Energy Society of R.O.C.

  13. Nakoryakov, V. E.; Grigor'eva, N. I.: Combined heat and mass transfer in nonisothermal absorption on the initial portion of a downflowing film. Teore. Osn. Khim. Tek. 14 (1980) 483

    Google Scholar 

  14. Grossman, G.: Simulation and analysis of high efficiency absorption system for solar cooling: Part IV. Film absorption heat and mass transfer in the presence of noncondensables. Final Report for DOE Contract, DE-AC03-85SF15894, Technion-Israel Inst. of Technology (1987)

  15. Minkowycz, W. J.; Sparrow, E. M.: Condensation heat transfer in the presence of non-condensables, interfacial resistance, superheating, variable properties and diffusion. Int. J. Heat Mass Transfer 9 (1966) 1125

    Google Scholar 

  16. Rose, J. W.: Condensation of a vapor in the presence of a non-condensing gas. Int. J. Heat Mass Transfer 12 (1969) 233

    Google Scholar 

  17. Al-Diwany, H. K.; Rose, J. W.: Free convection film condensation of steam in the presence of non-condensing gases. Int. J. Heat Mass Transfer 16 (1973) 1359

    Google Scholar 

  18. Slegers, L.; Seban, R. A.: Laminar film condensation of steam containing small concentrations of air. Int. J. Heat Mass Transfer 13 (1970) 1941

    Google Scholar 

  19. Bird, E. B.; Stewart, W. E.; Lightfoot, E. N.: Transport phenomena. New York: Wiley 1960

    Google Scholar 

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Authors and Affiliations

  1. Institute of Mechanical Engineering, National Sun Yat-Sen University, Taiwan, R.O.C.

    R. Yang & J. H. Chen

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  1. R. Yang
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  2. J. H. Chen
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Yang, R., Chen, J.H. A numerical study of the non-absorbable effects on the falling liquid film absorption. Wärme- und Stoffübertragung 26, 219–223 (1991). https://doi.org/10.1007/BF01590252

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