Numerical study of the effect of graphene nanoparticles in calcium chloride hexahydrate -based phase change material on melting and freezing time in a circular cavity with a triangular obstacle

Abstract

In the present paper, the effect of graphene nanoparticles (NPs) in Calcium Chloride Hexahydrate (CaCl2.6H2O)-based Phase Change Material (PCM) on its melting and freezing time is investigated. The simulations are performed on a novel geometry involving a two-dimensional tube with a triangular obstacle. In PCM charging mode, the internal obstacle is hot and the outer walls are cold. In the PCM discharge mode, the internal obstacle is cold and the outer walls are assumed to be hot. A number of rectangular-shaped fins with a length of 0.5 to 1.5 mm are placed on the obstacle. To solve the equations and determine the melting and freezing fronts, the finite element method is used by employing COMSOL Multiphysics software. The enthalpy method is employed to simulate the melting front. The variable is the length of the fins at different solution times and its effect on the melting and freezing times as well as the Nusselt number is studied. The results demonstrate that an increment in the length of the fins reduces the melting time of PCM (charge time) and the freezing time of PCM (discharge time). An enhancement in the fin length causes a higher percentage of molten material in the charge mode and a higher percentage of frozen material in the discharge mode at a specific time from the starting time of solution. The addition of a 1.5-mm fin to the obstacle increases the solid PCM by 26% in the PCM discharging mode and 56% of the molten material in the PCM charging mode at 400 ss.