FORCED-CONVECTION HEAT-TRANSFER IN MICROENCAPSULATED PHASE-CHANGE MATERIAL SLURRIES - FLOW IN CIRCULAR DUCTS

The heat transfer characteristics of microencapsulated phase change material slurry flow in circular ducts are presented in this paper. The energy equation is formulated by taking into consideration both the heat absorption (or release) due to the phase change process and the conductivity enhancement induced by the motion of the particles. The heat source or heat generation function in the energy equation is derived from solutions for freezing or melting in a sphere. The correlation for the effective conductivity of the slurry is obtained based on available analytical and experimental results. The governing parameters are found to be the particle concentration, a bulk Stefan number, the duct/particle radius ratio, the particle/fluid conductivity ratio, and a modified Peclet number. For low temperature applications, it is found that the dominant parameters are the bulk Stefan number and concentration. The numerical solutions show that heat fluxes about 2-4 times higher than single phase flow may be achieved by a slurry system.