Heat transfer correlations for open-cellular porous materials

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 hv = (A/Ds2−n)un. Here, hv denotes the volumetric heat transfer coefficient, A is the constant, n is the velocity exponent, u is the mean fluid velocity and Ds is the equivalent strut diameter of Dulʹnevʹs 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 hv−u correlation thus determined, the following Nusselt vs. Reynolds number heat transfer correlation was proposed: Nus = 0.124(ResPr)0.791, where Nus represents the Nusselt number defined by hvDs2/kf, Res denotes the Reynolds number defined by uDs/νf, Pr is the Prandtl number, kf is the thermal conductivity of fluid and νf 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%.