Experimental and numerical analysis of thermal flow in open-cell porous metal during Darcy-Forchheimer transition regime

Abstract

A numerical analysis of pressure drop and heat transfer for open-cell porous media is performed using a three-dimensional conjugate heat transfer model. Porous metal with a pore density of 20 pores per inch (PPI) and porosity of 95.7% is used in the present numerical simulation. Real microstructure of the open-cell porous metal is constructed using stacked images obtained by X-ray computed tomography method. Computed thermal-fluid characteristics are compared directly with the experimental pressure drop and unit overall thermal resistance values. The flow through porous metal can be divided into the Darcy regime and the Forchheimer regime. The thermo-fluidic characteristics in the Darcy regime and the Forchheimer regime are investigated numerically. The flow separation is not observed in the Darcy regime, but the wake region occurs in the Forchheimer regime because of the flow separation on the ligament surface. The contribution of the total drag acting on the walls (top & bottom) is very small, namely, less than 5% compared to the total drag on ligaments. The total drag force coefficient of ligaments tends to converge at high Reynolds number. This is because the pressure drag force is dominant due to the wake effect in the Forchheimer regime. Local Nusselt number is large near the upstream side of the ligament and very low in the wake region. Average Nusselt number increases with Reynolds number. In the Forchheimer regime, wakes developed behind ligaments increase the pressure loss and decrease the heat transfer performance.