Unsteady Heat Transfer in Cylindrical Encapsulated Phase Change Materials with Buoyancy Effect

In this paper, the effect of buoyancy force on the temperature change of the phase change materials which has been encapsulated in two pipes in a channel, is simulated numerically using Boussinesq approximation. An application of this topic is in air-conditioning, which uses ice in the pipes as PCM for coolant and the aim is calculating the PCM discharging time. The unsteady governing equations including continuity, momentum and energy in the fluid flow and phase change material for laminar flow regime, have been solved by the well-known SIMPLE method. The needed time to phase change material reach the inlet temperature of the fluid flow has been obtained and compared to the results of the lumped temperature assumption. The results show that the discharging time is 4,000 for Gr=5,000 and 70,000 for Gr=200,000. It is 25,000 for kr=0.5 and 34,000 for kr=1.5. Also, it is 11,000 for Cpr=103 and 28,000 for Cpr=104. Finally, it has been concluded that due to the fine mixing of PCM because of buoyancy force, the results are so closed to the results of the lumped temperature assumption for PCM.