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RESEARCH PAPERS: Micro/Nanoscale Heat Transfer

# Convection Heat Transfer in Microchannels With High Speed Gas Flow

[+] Author and Article Information
Stephen E. Turner

Naval Undersea Warfare Center, Newport, RI 02841turnerse@npt.nuwc.navy.mil

Yutaka Asako

Tokyo Metropolitan University, Tokyo, 1920397, Japanasako@ecomp.metro-u.ac.jp

University of Rhode Island, Kingston, RI 02881faghri@egr.uri.edu

1

Corresponding author.

J. Heat Transfer 129(3), 319-328 (Jun 12, 2006) (10 pages) doi:10.1115/1.2426358 History: Received February 22, 2005; Revised June 12, 2006

## Abstract

This paper presents an experimental investigation of convective heat transfer for laminar gas flow through a microchannel. A test stand was set up to impose thermal boundary conditions of constant temperature gradient along the microchannel length. Additionally, thin film temperature sensors were developed and used to directly measure the microchannel surface temperature. Heat transfer experiments were conducted with laminar nitrogen gas flow, in which the outlet Ma was between 0.10 and 0.42. The experimental measurements of inlet and outlet gas temperature and the microchannel wall temperature were used to validate a two-dimensional numerical model for gaseous flow in microchannel. The model was then used to determine local values of Ma, Re, and Nu. The numerical results show that after the entrance region, Nu approaches 8.23, the fully developed value of Nu for incompressible flow for constant wall heat flux if Nu is defined based on $(Tw−Tref)$ and plotted as a function of the new dimensionless axial length, $X*=(x∕2H)(Ma2)∕(RePr)$.

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## Figures

Figure 1

Test stand for microchannel heat transfer experiment

Figure 2

Schematic of the heat transfer manifold, instrumentation, and boundary condition control

Figure 3

Microchannel test section with nine thin film RTDs

Figure 4

Thin film RTD concept: (a) cross-section view showing the side leads sputtered at microchannel depth; and (b) top view showing the resistor pattern and the relative size of the resistors and leads

Figure 5

Calibration data and linear curve fit for RTD 1

Figure 6

Microchannel wall temperature measured by thin film RTDs

Figure 7

Velocity distribution for Test 9; both walls heated, Reout=915, Maout=0.12

Figure 8

Gas temperature contours for Test 9; both walls heated, Reout=915, Maout=0.12

Figure 9

Two-dimensional model prediction of stagnation and bulk temperatures for Test 9; both walls heated, Reout=915, Maout=0.12

Figure 10

Gas temperature contours for Test 9; one side heated, Reout=915, Maout=0.12

Figure 11

Two-dimensional model prediction of stagnation and bulk temperatures for Test 9; one wall heated, one insulated, Reout=915, Maout=0.12

Figure 12

Velocity profiles for Test 10; both sides heated, Reout=1635, Maout=0.32

Figure 13

Gas temperature contour for Test 10; both sides heated, Reout=1635, Maout=0.32

Figure 14

Two-dimensional model prediction of stagnation temperature and bulk temperature for Test 10; two sides heated, Reout=1635, Maout=0.32

Figure 15

Gas temperature contour for Test 10; one side heated, Reout=1635, Maout=0.32

Figure 16

Two-dimensional model prediction of stagnation temperature and bulk temperature for Test 10; one side heated, Reout=1635, Maout=0.32

Figure 17

Two-dimensional model prediction of stagnation and bulk temperatures for Test 1; two sides heated, Reout=473, Maout=0.26

Figure 18

Two-dimensional model prediction of stagnation and bulk temperatures for Test 2; two sides heated, Reout=756, Maout=0.42

Figure 19

Local Mach number for Tests 1–5

Figure 20

Local Mach number for Tests 6–10

Figure 21

Recovery factor plotted against X* for two walls heated boundary conditions

Figure 22

Local Nu plotted against X* for two wall heated boundary conditions

Figure 23

Local Nu plotted against X* for one wall heated, one wall insulated boundary conditions

## Errata

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