Pergamon Int. Comm. HeatMass Transfer, Vol. 28, No. 5, pp. 617-630, 2001 Copyright © 2001 Elsevier Science Ltd Printed in the USA. All rights reserved 0735 - 1933/01/S-see front matter Plh S0735-1933(01)00266-4 SECOND LAW ANALYSIS OF RECTANGULAR CHANNELS WITH SQUARE PIN-FINS O. N Sara, S. Yaplcl, M. Ytlmaz Faculty of Engineering, Ataturk University. 25240 Erzurum, Turkey T. Pekdermr Department of Mechanical and Chemical Engineenng, Heriot-Watt University Edinburgh EHI4 4AS, UK (Communicated by J.W. Rose and A. Briggs) ABSTRACT This paper presents heat transfer and friction characteristics, and the second law analysis of the convective heat transfer through a rectangular channel with square cross-sect~onal pin- fins attached over a fiat surface. Various clearance ratios (C/H) and interfin distance ratios (S~/D) were used, and optimum pin-fin arrays that minimize entropy generation were determined. It was found that Nu number based on the projected area decreased with increasing S.~/D and C/H, whereas Nu based on the total heat transfer area increased with increasing S~/D and with decreasing C/H. The friction factor was found to decrease with increasing Sx/D and C/H. Smaller entropy generation numbers were obtained at lower Reynolds number, tugher clearance ratio, and higher inter-fin spacing ratio. © 2001 Elsevier Science Ltd Introduction Heat exchanger fins are frequently employed in heat exchange devices to mcrease the heat transfer rate between the heat-exchange surface and the surrounding fluid. Extended (or finned) surface enhances heat transfer rate by increasing surface area and by inducing turbulent mixing of flow. Applications of fins include the cooling of turbine blades in gas turbine engines, the cooling of electronic components, and various other heat exchange devices used in aerospace, aircraft, chemical processing plants etc. Various types of heat exchanger fins, ranging from relatively stmple shapes, such as rectangular. cylindrical, annular, tapered or pin fins, to a combination of different geometry, have been used. These fins may protrude from either a rectangular or cylindrical base. Many studies have been conducted on the thermal and friction characteristics of the heat exchanger fin arrays. Babus'haq et al. [ 1 ], Naik et al. [2], Sparrow et al. [3], Yell [4], and Kadle [5] etc. investigated experimentally the thermal and hydraulic 617