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Research Papers: Evaporation, Boiling, and Condensation

A Semi-Empirical Model for Condensation Heat Transfer Coefficient of Mixed Ethanol-Water Vapors

[+] Author and Article Information
Yang Li

State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi’an City 710049, P.R. China

JunJie Yan1

State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi’an City 710049, P.R. China

JinShi Wang

State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi’an City 710049, P.R. Chinayanjj@mail.xjtu.edu.cn

GuoXiang Wang

Department of Mechanical Engineering, University of Akron, Akron, OH 44325-3903gwang@uakron.edu

1

Corresponding author.

J. Heat Transfer 133(6), 061501 (Mar 02, 2011) (11 pages) doi:10.1115/1.4003433 History: Received October 04, 2009; Revised January 05, 2011; Published March 02, 2011; Online March 02, 2011

A semi-empirical model describing the heat transfer characteristics of the pseudo-dropwise condensation of binary vapor on a cooled vertical tube has been formulated. By ignoring the thin film always present on the condensation surface and the intensification of mass transfer caused by the Marangoni effect, the heat transfer characteristics of pseudo-dropwise condensation are tentatively formulated. The model involved an analysis of the diffusion process in the vapor boundary layer along with the heat transfer process through the condensate drops. This model was applied to the condensation of the saturated binary vapor of ethanol and water, and was examined using experimental data at vapor pressure values of 101.33 kPa (provided by Utaka and Wang, 2004, “Characteristic Curves and the Promotion Effect of Ethanol Addition on Steam Condensation Heat Transfer,” Int. J. Heat Mass Transfer, 47, pp. 4507–4516), 84.52 kPa and 47.36 kPa. Calculations using the model show a similar trend to the experimental measurements. With the change of the vapor-to-surface temperature difference, the heat transfer coefficients revealed nonlinear characteristics, with the peak values under all ethanol mass fractions of binary vapor. The heat transfer coefficients increased with decreasing ethanol mass fraction.

Copyright © 2011 by American Society of Mechanical Engineers
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References

Figures

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Figure 18

Sensitivity analysis of the heat transfer calculation to the radius of the smallest drop (We∞=10%)

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Figure 1

A schematic diagram of the experimental apparatus

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Figure 2

Dimensions of the test tube

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Figure 3

Condensation heat transfer coefficients

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Figure 4

Transformation of the condensate modes

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Figure 5

Transformation of the condensation modes with respect to ethanol mass concentration and vapor-to-surface temperature difference

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Figure 6

Schematic diagram for pseudo-dropwise condensation of binary vapor

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Figure 7

Drop size distribution of pseudo-dropwise condensation

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Figure 8

Comparison of Eq. 10 with the observed radius of the largest drop

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Figure 9

Comparison of Eq. 11 and observed radius of the largest drop

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Figure 10

The error of Eq. 11 and observed radius of the largest drop

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Figure 11

Liquid-vapor phase equilibrium diagrams for water and ethanol

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Figure 12

Assumed interfacial temperature

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Figure 13

Model condensation heat transfer coefficient (p=101.33 kPa)

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Figure 14

Model condensation heat transfer coefficient (p=84.52 kPa)

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Figure 15

Model condensation heat transfer coefficient (p=47.36 kPa)

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Figure 16

Thermal resistance analysis of the Marangoni condensation

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Figure 17

Sensitivity analysis of the heat transfer calculation to the radius of the smallest drop (We∞=0.5%)

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