Experimental analysis of phase change material slurry through porous channel

Among the emerging heat transfer technologies of today are fluid additives based on micro-encapsulated phase-change materials (MPCM). Unfortunately, very small particles do not produce a strong mixing effect in the liquid, thus missing out on a source of efficiency in the heat transfer process. Also, particles flowing far from the channel heat exchange surfaces do not efficiently participate in heat transfer. In this study, phase change material slurry is used in conjunction with porous media (metal foam) to improve the heat transfer rate. The experimental results show that addition of porous media increases the heat transfer rate significantly. Enhancement in heat transfer happens mainly due to the departure of un-melted particles from center of the channel toward the heated surface area by mixing processes in the porous channel. Experimental tests for various wall heat fluxes, inlet velocities and particle concentration are carried out. Also the effect of porous media structure on heat transfer enhancement and mixing phenomena is studied. Heat transfer enhancements are compared for two cases of (1) micro-size flow circulation inside the pores and (2) large scale mixing effects by inserting baffles in the channel. The results show that small circulations of flow due to the porous media has dominant effect on the heat transfer rate compared with the large-scale circulations happening by baffles.