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RESEARCH PAPERS: Two-Phase Flow and Heat Transfer

On the Transient Analysis of a V-Shaped Microgrooved Heat Pipe

[+] Author and Article Information
Balram Suman1

Department of Chemical Engineering and Materials Science, University of Minnesota, 151 Amundson Hall, 421 Washington Avenue SE, Minneapolis, MN 55455suman@cems.umn.edu

Nazish Hoda

Department of Chemical Engineering and Materials Science, University of Minnesota, 151 Amundson Hall, 421 Washington Avenue SE, Minneapolis, MN 55455

1

Corresponding author.

J. Heat Transfer 129(11), 1584-1591 (Mar 05, 2007) (8 pages) doi:10.1115/1.2759975 History: Received December 14, 2006; Revised March 05, 2007

In this paper, we present a transient mathematical model for a V-shaped microgrooved heat pipe considering the temporal variations in the fluid flow, and heat and mass transfer, and utilizing a macroscopic approach. Unlike other heat pipe models, the shear stress at the liquid-vapor interface and the disjoining pressure have been used in the momentum balance equation of the model. The sensible heat used by the substrate is also taken into account using a pseudo-lump capacity model. The coupled nonlinear partial differential equations governing the transient fluid flow, heat and mass transfer have been solved numerically. The transient and steady-state profiles for the radius of curvature, liquid and vapor velocity, liquid pressure, and substrate temperature have been obtained. The mathematical model is capable of predicting the time required for the onset of dry out at the hot end, and for a micro heat pipe to reach steady state. The time required to reach steady state is independent of heat input, heat pipe inclination, groove angle, and Qss profile. However, the time required for the onset of dry out at the hot end decreases with increasing heat input, inclination, and groove angle. The model predicted results have been successfully compared to the results from the literature. The general nature of this model and the associated study can be useful for many practical applications in the microscale heat exchange.

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Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

A V-groove showing heat pipe dimensions and flow directions

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Figure 2

Volume element of a V-shaped micro heat pipe with all forces specified

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Figure 3

Variation of the substrate temperature, Ts(°C) with the dimensionless position, X* at different times (s)

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Figure 10

Comparison of the theoretical and the experimental (23) dimensionless steady-state substrate temperature (Ts*) with position X*. The points are the experimental data and the solid lines are the theoretical predictions. The reference temperatures for 0deg and 14.93deg inclinations are 35°C and 32.6°C, respectively.

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Figure 9

Steady-state dimensionless radius of curvature (R*) with the dimensionless position, X* for different values of Hamaker constant

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Figure 8

Variation of the dimensionless vapor velocity, Vg* with the dimensionless position, X* at different times (s)

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Figure 7

Variation of the dimensionless liquid velocity, Vl* with the dimensionless position, X* at different times (s)

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Figure 6

Variation of the dimensionless liquid pressure, Pl* with the dimensionless position, X* at different times (s)

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Figure 5

Variation of the dimensionless radius of curvature, R* with time (s) for different positions, X*=0.32,0.5, and 0.68

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Figure 4

Variation of the dimensionless radius of curvature, R* with the dimensionless position, X* at different times (s)

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