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research-article

Numerical investigation of natural convection heat transfer from an array of horizontal fins in non-Newtonian power-law fluids

[+] Author and Article Information
Jacob Koshy Mulamootil

Department of Mechanical Engineering, Indian Institute of Technology Kharagpur, Kharagpur-721302, India
jkmkoshy@gmail.com

Sukanta K. Dash

Department of Mechanical Engineering, Indian Institute of Technology Kharagpur, Kharagpur-721302, India
sdash@mech.iitkgp.ernet.in

1Corresponding author.

ASME doi:10.1115/1.4037537 History: Received December 27, 2016; Revised June 08, 2017

Abstract

Natural convection heat transfer from an array of horizontal rectangular fins on a vertical flat plate in non-Newtonian power-law fluids has been studied. The underlying physical principles affecting heat transfer were studied using comprehensive solutions obtained from numerical investigations. Heat transfer to the power-law fluid was found to depend on the fluid rheology (power-law index) and significantly on the geometric parameters (inter-fin spacing, fin length) as well. The dependence was quantified using the Nusselt number (Nu) and fin effectiveness (Q/Q0). The present study shows that compared to a fin analyzed in isolation, the spatial arrangement of multiple fins relative to one another in an array does have a significant effect on the flow field around subsequent fins in power-law fluids. Therefore the average heat transfer coefficient of the natural convection system is affected significantly. The variation of Nu with the dimensionless fin length (l/L), dimensionless inter-fin spacing (S/L) and fluid power-law index (n) was plotted. The dependence was found to be counter intuitive to expectations based on studies for natural convection from vertical flat plates to power-law fluids. In the present study involving fins, shear-thinning fluids (n<1) show a decrease in heat transfer and shear-thickening fluids (n>1) show an enhancement in heat transfer for higher l/L values. The results of the study may be useful in the design of natural convection systems that employ power-law fluids to enhance or control heat transfer.

Copyright (c) 2017 by ASME
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