Numerical modeling of heat transfer in open-cell micro-foam with phase change material

The heat transfer behavior of micro-foam impregnated with phase change material (PCM) was investigated. Both microscopic and macroscopic modeling approaches were considered. An open-cell PCM/micro-foam structure under constant heat flux was modeled using an ideal micro-foam structure based on a cubic unit cell with spherical micro-pores arranged in a BCC lattice. Results from direct numerical simulations (DNS) which take into account the intricate foam geometry were compared with those from one- and two-temperature volume-averaged simulations. The enthalpy-porosity method was used for phase change and conjugated heat transfer was applied at the PCM/micro-foam interface. The DNS simulations provided insight into the complicated heat transfer and a three-dimensional PCM melting front and temperature distribution was observed. Along with serving as a benchmark for the less computationally expensive volume average methods, the DNS results were also used to extract thermo-physical parameters such as effective thermal conductivity and interstitial heat transfer coefficients. These coefficients were subsequently used in the volume averaged simulations. The choice of the effective thermal conductivity of the PCM/micro-foam structure was found to be crucial in matching the temperature profile and liquid PCM volume fraction results from volume averaged simulations and DNS. Effective thermal conductivity values based on the nonlinear Progelhoff model with power factor derived from DNS were found to provide an improvement over the more widely used value based on the arithmetic mean.