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Research Papers: Micro/Nanoscale Heat Transfer

# Liquid Single-Phase Flow in an Array of Micro-Pin-Fins—Part I: Heat Transfer Characteristics

[+] Author and Article Information
Weilin Qu1

Department of Mechanical Engineering,  University of Hawaii at Manoa,  Honolulu, HI 96822qu@hawaii.edu

Abel Siu-Ho

Department of Mechanical Engineering,  University of Hawaii at Manoa,  Honolulu, HI 96822

1

Corresponding author.

J. Heat Transfer 130(12), 122402 (Sep 17, 2008) (11 pages) doi:10.1115/1.2970080 History: Received September 11, 2007; Revised March 04, 2008; Published September 17, 2008

## Abstract

This is Paper I of a two-part study concerning thermal and hydrodynamic characteristics of liquid single-phase flow in an array of micro-pin-fins. This paper reports the heat transfer results of the study. An array of 1950 staggered square micro-pin-fins with $200×200 μm2$ cross-section by $670 μm$ height were fabricated into a copper test section. De-ionized water was used as the cooling liquid. Two coolant inlet temperatures of $30°C$ and $60°C$ and six maximum mass velocities for each inlet temperature ranging from 183 to $420 kg/m2 s$ were tested. The corresponding inlet Reynolds number ranged from 45.9 to 179.6. General characteristics of average and local heat transfer were described. Six previous conventional long and intermediate pin-fin correlations and two micro-pin-fin correlations were examined and were found to overpredict the average Nusselt number data. Two new heat transfer correlations were proposed for the average heat transfer based on the present data, in which the average Nusselt number is correlated with the average Reynolds number by power law. Values of the exponent $m$ of the Reynolds number for the two new correlations are fairly close to those for the two previous micro-pin-fin correlations but substantially higher than those for the previous conventional pin-fin correlations, indicating a stronger dependence of the Nusselt number on the Reynolds number in micro-pin-fin arrays. The correlations developed for the average Nusselt number can adequately predict the local Nusselt number data.

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## Figures

Figure 1

Schematic of the flow loop

Figure 10

Variation in local heat transfer coefficient with input heat flux (a) at ztc1–ztc3 for Tin=30°C and Gmax=420 kg/m2 s and (b) at ztc1 for Tin=30°C and all six Gmax

Figure 11

Comparison of the local Nusselt number data with predictions of (a) correlation 9 and (b) correlation 10

Figure 2

Test module construction

Figure 3

Top view of the micro-pin-fin array and schematic of the unit cell

Figure 4

Variation of the measured micro-pin-fin base temperature with input heat flux (a) at ztc1–ztc3 for Tin=30°C and Gmax=420 kg/m2 s and (b) at ztc1 for Tin=30°C and all six Gmax

Figure 5

Variation in average heat transfer coefficient with input heat flux: (a) Tin=30°C and (b) Tin=60°C

Figure 6

Variation in the average Nusselt number with the average Reynolds number

Figure 7

Comparison of the average Nusselt number data with predictions of (a) correlation 1, (b) correlation 2, (c) correlation 3, (d) correlation 4, (e) correlation 5, and (f) correlation 6

Figure 8

Comparison of the average Nusselt number data with predictions of (a) correlation 7 and (b) correlation 8

Figure 9

Comparison of the average Nusselt number data with predictions of (a) correlation 9 and (b) correlation 10

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