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Research Papers: Evaporation, Boiling, and Condensation

A Study on Gas–Liquid Film Thicknesses and Heat Transfer Characteristics of Vapor–Gas Condensation Outside a Horizontal Tube

[+] Author and Article Information
Huijun Li

e-mail: hj_li009@sina.com

Wenping Peng

e-mail: wenpingpeng@gmail.com

School of Energy Power
and Mechanical Engineering,
North China Electric Power University,
HeBei 071003, China

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received December 4, 2012; final manuscript received July 27, 2013; published online November 7, 2013. Assoc. Editor: Ali Ebadian.

J. Heat Transfer 136(2), 021501 (Nov 07, 2013) (10 pages) Paper No: HT-12-1646; doi: 10.1115/1.4025501 History: Received December 04, 2012; Revised July 27, 2013

Noncondensable gases deteriorate heat transfer in the condensation process. It is therefore necessary to study vapor–gas condensation heat transfer process and analyze main factors influencing the process. Based on the double-film theory and the Prandtl boundary layer theory, this investigation developed a mathematical model of gas–liquid film thicknesses and local heat transfer coefficient for studying laminar film condensation in the presence of noncondensable gas over a horizontal tube. Induced velocity in the gas film, gas–liquid interfacial shear stress, and pressure gradient were considered in the study. Importantly, gas–liquid film separations were analyzed in depth in this paper. It obtained the distributions of gas–liquid film thicknesses, local heat transfer coefficient, condensate mass flux, and gas–liquid interfacial temperature along the tube surface, and analyzed the influences of bulk velocity, total pressure, bulk mass concentration of noncondensable gas and wall temperature on them, providing a theoretical guidance for understanding and enhancing vapor–gas condensation heat transfer. Gas film thickness and gas–liquid film separations have certain effects on vapor–gas condensation heat transfer. The average dimensionless heat transfer coefficients are in agreement with the data from related literatures.

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References

Figures

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Fig. 1

Physical model and coordinate system

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Fig. 2

Schematic diagram of gas–liquid film separations

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Fig. 3

Calculation scheme flowchart

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Fig. 4

The distributions of some physical quantities along the wall in the different total pressure, wall temperature and mass concentration of air with gas–liquid film nonseparating. (a) Gas film thickness, (b) liquid film thickness, (c) local heat transfer coefficient, (d) condensate mass flux, and (e) gas–liquid interfacial temperature.

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Fig. 5

The distributions of some physical quantities along the wall in the different total pressure, wall temperature and mass concentration of air with only gas film separating and liquid film nonseparating. (a) Gas film thickness, (b) liquid film thickness, (c) local heat transfer coefficient, (d) condensate mass flux, (e) gas–liquid interfacial temperature.

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Fig. 6

The distributions of some physical quantities along the wall in the different total pressure, wall temperature and mass concentration of air with gas–liquid film separating. (a) Gas film thickness, (b) liquid film thickness, (c) local heat transfer coefficient, (d) condensate mass flux, (e) gas–liquid interfacial temperature.

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Fig. 7

Dependence of average dimensionless heat transfer coefficients on F and Wnc,b

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