Heat transfer correlations for open-cellular porous materials

Abstract

A general correlation for volumetric heat transfer coefficient between stream of air and open-cellular porous materials was derived utilizing experimental data obtained by several researchers. The derived correlation is written in form of h v = ( A/ D s 2− n ) u n . Here, h v denotes the volumetric heat transfer coefficient, A is the constant, n is the velocity exponent, u is the mean fluid velocity and D s is the equivalent strut diameter of Dul'nev's unit cell for open-cell foam. The parameters, A and n, were determined by a least-square fit of the expression to the above-mentioned experimental data to give A = 13.0 and n = 0.791. Moreover, from the h v− u correlation thus determined, the following Nusselt vs. Reynolds number heat transfer correlation was proposed: Nu s = 0.124( Re s Pr) 0.791, where Nu s represents the Nusselt number defined by h v D s 2/ k f, Re s denotes the Reynolds number defined by uD s/ ν f, Pr is the Prandtl number, k f is the thermal conductivity of fluid and ν f is the kinetic viscosity of fluid. It is found that this correlation approximates 78.1% of the available experimental data with an error of less than ± 40%.