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Research Papers: Forced Convection

Effect of Pin Density on Heat-Mass Transfer and Fluid Flow at Low Reynolds Numbers in Minichannels

[+] Author and Article Information
N. K. C. Selvarasu

Department of Mechanical Engineering, Virginia Polytechnic Institute and State University, 114-I Randolph Hall, Mail Code 0238, Blacksburg, VA 24061

Danesh K. Tafti1

Department of Mechanical Engineering, Virginia Polytechnic Institute and State University, 114-I Randolph Hall, Mail Code 0238, Blacksburg, VA 24061dtafti@vt.edu

Neal E. Blackwell

 U.S. Army RDECOM CERDEC, Fort Belvoir, VA 22060-5816

1

Corresponding author.

J. Heat Transfer 132(6), 061702 (Apr 02, 2010) (8 pages) doi:10.1115/1.4000949 History: Received December 23, 2008; Revised December 14, 2009; Published April 02, 2010; Online April 02, 2010

Previous investigations on the performance of straight pins, pins with tip clearance, and profiled fins showed that closely packed cylindrical pin fins are very competitive with the modified pins. Therefore, the objective of this paper is to investigate the effect of pin density on performance. Steady/time-dependent calculations are performed to investigate the effect of pin density on friction and heat transfer. Pins packed at distances of SD=1.1, 1.2, 1.3, 1.4, 1.5, 2.0, 2.5, and 3 pin diameters (D) are investigated for 10ReD600. Two performance measures are used to compare the different pin fin densities. The first measure is to maximize heat transfer capacity for a given pumping power compared with a plane channel. The second measure used is based on entropy generation minimization (EGM), where the objective is to reduce the total irreversibility of the pin fin array to obtain an optimal spacing. Based on the performance measure of maximizing heat capacity, it is shown that for plain channels operating in the laminar range using denser pin packing has distinct advantages with SD=1.1 providing the best augmentation. However, the augmentation in heat capacity becomes relatively independent of the pin density for a channel operating in the turbulent regime. Based on the EGM method, at ReD>200, SD=1.3, 1.4, and 1.5 are the most suitable, with the least entropy generation observed at SD=1.4. At ReD<200, SD=1.1, 1.2, and 1.3 are also suitable for keeping entropy generation low.

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Copyright © 2010 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Schematic of a pin fin array

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Figure 2

Validation of the current study—NuD versus ReD

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Figure 3

Validation of the current study—f versus ReD

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Figure 4

Variation in friction factor ratio with ReH for all SD values

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Figure 5

Variation in heat transfer coefficient with ReD

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Figure 6

Variation in thermal conductance with ReD

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Figure 7

Increase in thermal conductance compared with plane channel for the same pumping power for higher density configurations

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Figure 8

Increase in thermal conductance compared with plane channel for the same pumping power for lower density configurations

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Figure 9

Entropy generation number for SD=1.5, B=0.00001

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Figure 10

Variation in irreversibility distribution ratio with Reynolds number for all SD values

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Figure 11

Total entropy generation rate Ns versus pin finned channel Reynolds number ReD

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Figure 12

Total entropy generation rate Ns versus plane channel Reynolds number ReH,ch

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