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Research Papers: Multiphase Flows

Analysis of Laminar Falling Film Condensation Over a Vertical Plate With an Accelerating Vapor Flow

[+] Author and Article Information
A.-R. A. Khaled1

Department of Thermal Engineering and Desalination Technology, King AbdulAziz University, P.O. Box 80204, Jeddah 21589, Saudi Arabiaakhaled@kau.edu.sa

Abdulhaiy M. Radhwan, S. A. Al-Muaikel

Department of Thermal Engineering and Desalination Technology, King AbdulAziz University, P.O. Box 80204, Jeddah 21589, Saudi Arabia

1

Corresponding author.

J. Fluids Eng 131(7), 071304 (Jun 23, 2009) (10 pages) doi:10.1115/1.3155992 History: Received August 16, 2008; Revised April 10, 2009; Published June 23, 2009

Laminar falling film condensations over a vertical plate with an accelerating vapor flow is analyzed in this work in the presence of condensate suction or slip effects at the plate surface. The following assumptions are made: (i) laminar condensate flow having constant properties, (ii) pure vapor with a uniform saturation temperature in the vapor region, and (iii) the shear stress at the liquid/vapor interface is negligible. The appropriate fundamental governing partial differential equations for the condensate and vapor flows (continuity, momentum, and energy equations) for the above case are identified, nondimensionalized, and transformed using nonsimilarity transformation. The transformed equations were solved using numerical, iterative, and implicit finite-difference methods. It is shown that the freestream striking angle has insignificant influence on the condensation mass and heat transfer rates, except when slip condition is present and at relatively small Grl/Re2 values. Moreover, it is shown that increasing the values of the dimensionless suction parameter (VS) results to an increase in dimensionless mass of condensate (Γ(L)/(μlRe)) and Nusselt number (Nu(L)/Re1/2). Thus, it results in an increase in condensation mass and heat transfer rates. Finally, it is found that the condensation and heat transfer rates increase as Jakob number, slip parameter, and saturation temperature increase. Finally, the results of this work not only enrich the literature of condensation but also provide additional methods for saving thermal energy.

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic diagram

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Figure 2

(a) Grid with variable thickness and (b) uniform thickness grid

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Figure 3

Effects of m and the dimensionless suction parameter VS on the dimensionless condensation flow rate Γ at the end of the plate

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Figure 4

Effects of x¯ and the dimensionless suction parameter VS on the dimensionless film condensation thickness δ¯(x¯)

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Figure 5

Effects of m and the dimensionless suction parameter VS on the Nusselt number Nu at the end of the plate

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Figure 6

Effect of m on the dimensionless freestream longitudinal pressure gradient

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Figure 7

Effects of m and the slip coefficient parameter BS on the dimensionless condensation flow rate Γ at the end of the plate

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Figure 8

Effects of m and the slip coefficient parameter BS on the Nusselt number Nu at the end of the plate

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Figure 9

Effects of m and the Grashof number Grl on the dimensionless condensation flow rate Γ at the end of the plate

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Figure 10

Effects of the saturated temperature Tsat on the dimensionless condensation flow rate Γ at the end of the plate

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Figure 11

Effects of the saturated temperature Tsat on the Nusselt number Nu at the end of the plate

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