Thermally Developing Forced Convection and Heat Transfer in Rectangular Plate-Fin Passages Under Uniform Plate Temperature

Abstract

Laminar forced convection inside plate-fin passages is of interest in the design of a low-Reynolds-number heat exchanger apparatus. Heat transfer to thermally developing, hydrodynamically developed forced convection inside tubes of rectangular cross section with various aspect ratios has been well studied and documented in various books, but for plate-fin ducts there has not been much work done. A typical plate-fin passage is comprised of two horizontal plates and two vertical fins. The main assumption in this study is that the plate is under uniform temperature conditions and the heat fluxes on two fins are distributed in a skew-symmetric manner. Heat conduction in the fin and convection in the fluid are analyzed simultaneously as a conjugate problem. Various duct aspect ratios from 0.125 to 4.0 are considered, and the fins have different conductance parameters from 0 to infinitely large, representing materials from polymers to pure copper. The Nusselt numbers in the developing region, the thermal entry length, and the fully developed values for these passages are obtained, which can be used in estimation of heat transfer performance in plate-fin compact heat exchangers with fins of various thermal conductivities and thicknesses.