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Research Papers: Evaporation, Boiling, and Condensation

Evaporating Liquid Film Flow in the Presence of Micro-Encapsulated Phase Change Materials: A Numerical Study

[+] Author and Article Information
Yasmin Khakpour

Multi-Scale Heat Transfer Laboratory,
Department of Mechanical Engineering,
Worcester Polytechnic Institute,
Worcester, MA 01609
e-mail: ykhakpour@alum.wpi.edu

Jamal Seyed-Yagoobi

Multi-Scale Heat Transfer Laboratory,
Department of Mechanical Engineering,
Worcester Polytechnic Institute,
Worcester, MA 01609
e-mail: jyagoobi@wpi.edu

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received February 18, 2014; final manuscript received August 15, 2014; published online November 18, 2014. Assoc. Editor: Giulio Lorenzini.

J. Heat Transfer 137(2), 021501 (Feb 01, 2015) (9 pages) Paper No: HT-14-1081; doi: 10.1115/1.4028808 History: Received February 18, 2014; Revised August 15, 2014; Online November 18, 2014

This paper numerically investigates the heat transfer characteristics of a mesoscale liquid film slurry flow containing micro-encapsulated phase change material (MEPCM) in the presence of evaporation. The two-phase evaporating liquid film flow is modeled using one-fluid volume-of-fluid (VOF) formulation. During the evaporation process of the base fluid, the concentration of MEPCM in the slurry film increases as it flows along a heated plate, resulting in a continuous variation of its effective thermal properties. The effect of MEPCM on the evolution of the liquid film thickness under different operating conditions is presented. It is shown that the MEPCM suppresses the rate of decline in the liquid film thickness, which results in a higher heat transfer coefficient compared to that of pure liquid film under similar operating conditions. This study also provides an understanding towards delaying of the dry-out condition in slurry liquid film flow evaporation compared to that of the pure fluid.

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References

Figures

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Fig. 1

Schematic of 2-D representation of the numerical domain (not to scale)

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Fig. 2

Variation of the specific heat of PCM with temperature [27]

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Fig. 6

Variation of the Peclet number along the channel for q"w=400 W/m2

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Fig. 7

Variation of liquid film thickness along the channel for q"w=400 W/m2: (a) effect of MEPCM inlet concentration, ξ and (b) effect of liquid inlet mass flux, G

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Fig. 3

Variation of slurry's specific heat with temperature for the case of pure R134a, 5% and 15% MEPCM slurry

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Fig. 5

Temperature distribution and interface profile for q"w=400W/m2 and Gin = 10 kg/m2 · s for (a) pure R134a and (b) ξin = 15% MEPCM slurry

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Fig. 4

Comparison of current numerical model and Nusselt theory for falling film evaporation [38] for the evolution of liquid film thickness and local average heat transfer coefficient

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Fig. 8

Variation of evaporation heat transfer coefficient along the channel for q"w=400 W/m2: (a) effect of MEPCM inlet concentration, ξ and (b) effect of liquid inlet mass flux, G

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Fig. 9

Variation of average heat transfer coefficient with liquid film inlet temperature for pure R134a and MEPCM slurry at ξ = 15%

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Fig. 10

Variation of MEPCM concentration along the channel for various applied heat fluxes

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