Thermal modeling of Encapsulated Phase Change Materials (EPCMs) for energy storage applications in a solar chimney

In this paper the thermal performance of Encapsulated Phase Change Materials (EPCMs) is conducted to investigate thermal energy storage for solar chimney applications. The macro-encapsulated paraffin wax RT42 is chosen as the PCM in this study, therefore the main element of the solar chimney is the EPCM container. A two-dimensional horizontally rectangle shaped EPCM capsule is considered in simulations using gas (air) as heat transfer fluid. COMSOL Multiphysics is used in order to numerically solve Navier-Stokes and energy equations in the considered system. Energy storage into rectangular EPCM containers constructed of stainless steel, is simulated for various flow conditions of the heat transfer fluid and various sizes of capsules. The research is carried out with three different heat fluxes of 500 W/m2, 600 W/m2 and 700 W/m2. Results show that the air flow rate and melting rate for heat flux of 700 W/m2 is slightly higher than those for the heat fluxes of 600 W/m2 and 500 W/m2. Furthermore regardless of air flow rate, the air outlet average temperature for the case of 700 W/m2 is the lowest amongst three cases, and then followed by 600 W/m2 and for 500 W/m2. The peak thermal efficiencies of the solar chimney are observed to be about 80% for all cases at the early ventilation period. 500 W/m2 however drives the highest minimum efficiency of 63%.