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Research Papers: Heat Transfer Enhancement

Transient Thermal Response of Pin-Fin Sandwich Panels to Hot Jet Impingement

[+] Author and Article Information
S. S. Feng

SV Laboratory, School of Aerospace, School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an 710049, People’s Republic of China

T. J. Lu1

SV Laboratory, School of Aerospace, Xi’an Jiaotong University, Xi’an 710049, People’s Republic of Chinatjlu@mail.xjtu.edu.cn

T. Kim

SV Laboratory, School of Aerospace, Xi’an Jiaotong University, Xi’an 710049, People’s Republic of China; School of Mechanical, Industrial, and Aeronautical Engineering, University of Witwatersrand, Private Bag 3, Johannesburg WITS 2050, Republic of South Africa

1

Corresponding author.

J. Heat Transfer 133(6), 061901 (Mar 10, 2011) (11 pages) doi:10.1115/1.4003555 History: Received August 19, 2010; Revised January 19, 2011; Published March 10, 2011; Online March 10, 2011

The transient thermal response of a sandwich panel with pin-fin core subjected to nonuniform impinging jet heating was investigated theoretically and experimentally. Forced convection flow passing through the sandwich channel was employed to remove heat imposed nonuniformly on the pin-fin sandwich. A semi-empirical model was developed to predict the transient thermal fields in the front and back facesheets of the sandwich, in the pin-fins, and in the forced convective flow. Transient heat transfer measurements were conducted to validate the model with hot air impinging jet heating. The temperature history of the sandwich was predicted under two different boundary conditions: (1) continuous and (2) cyclic heating from a flame impinging jet. Heating by the flame impinging jet was modeled by prescribing heat flux distribution expressed with an exponential function. For continuous heating, systematic parametrical studies were carried out to examine the effects of convection Reynolds number, fin pitch, fin thickness, and facesheet thickness on the maximum facesheet temperature. For cyclic heating, the thermal performance of the sandwich as a function of heat flux intensity was quantified. It was demonstrated that pin-fin sandwiches are capable of thermally managing nonuniformly distributed heat fluxes having high intensities, either continuously or cyclically imposed.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic of a pin-fin sandwich panel with its front facesheet heated nonuniformly by a normally impinging hot jet and its back facesheet exposed to surroundings (natural convection and radiation), the sandwich is cooled by forced convective flow across the pin-fins

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Figure 2

Heat balance of convective flow in a representative pin-fin unit cell

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Figure 3

Measured and predicted transient responses of (a) front facesheet temperature at impinging center and (b) fluid temperature at exit of pin-fin channel

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Figure 4

Nonuniform heat flux distribution of typical flame jet (11)

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Figure 5

Predicted temperature distributions on front surface (z=0) of pin-fin sandwich panel S-A subjected to continuous exposure of nonuniform heat flux (Fig. 4) at ReDh=4.2×104

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Figure 6

Predicted temperature distributions on back surface (z=2Hb+Hfin) of pin-fin sandwich panel S-A subjected to continuous exposure of nonuniform heat flux (Fig. 4) at ReDh=4.2×104

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Figure 7

Transient response of maximum temperature on front facesheet of pin-fin sandwich panel for selected Reynolds numbers: (a) S-A, (b) S-B, and (c) S-C

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Figure 8

Effect of facesheet thickness on maximum front facesheet temperature

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Figure 9

Transient heat flow in sample S-A at ReDh=1.2×105: (a) variation of Qst,ft/Qin, Qst,bk/Qin, Qst,fin/Qin, Qconv,ft/Qin, Qconv,bk/Qin, Qconv,fin/Qin, and Qamb/Qin with time and (b) variation of total heat storage (Qst/Qin) and total heat release (Qrelease/Qin) with time

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Figure 10

Thermal response of sample S-C subjected to cyclic heating, with B=5, C=2.6, qmax=1.0×106 W/m2, and ReDh=1.2×105

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Figure 11

Maximum temperature Tm and cooling time Δt plotted as functions of heat flux intensity qmax for sample S-C at selected ReDh values

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