Optimization of evaporation heat transfer in high-porosity porous columns

Compared to pool boiling or flow boiling, the evaporation within porous media can offer a higher heat transfer advantage. In this work, the numerical simulations were conducted on the application of porous columns at hot spots in heat exchanger and an analysis was performed on the transient evaporation of liquid within the porous medium. The thermal performance of porous columns with different porosities and pore sizes were investigated on the basis of the obtained data. It finds that the porous columns tend to experience vapor blockage during the phase change, which will hinder liquid replenishment and result in a deterioration of heat transfer. Moreover, the vapor blockage phenomenon is more pronounced in porous columns with lower porosity and smaller pore size. Six types of porous columns were compared, and it finds that inlet-optimized samples with a relief in vapor blockage exhibits a better thermal performance compared to the conventional ones. After an optimization of outlet, a rapid discharge of vapor within the porous medium column can be achieved, which reduces the difficulty of liquid replenishment and contributes to performance of evaporation heat transfer.