CFD modeling of macro-encapsulated latent heat storage system used for solar heating applications

Abstract

Abstract This paper attempts to address and generalize the impact of elementary heat transfer aiding to phase transition of phase change material (PCM) enclosed within a thin cylindrical macro-encapsulate. A transient, three-dimensional solver with user-defined functions is modeled to study the solidification and melting characteristics of PCM aided by conduction heat transfer and external convection effects within a solar air heater system (SAHS). The conservative equations are discretized using Finite volume method (FVM). The effect of convection between the macro-encapsulate and the working fluid is captured by interface modeling. The present analysis is divided into two segments, namely, phase change assisted by conduction heat transfer alone and combined conduction-convection effects. The obtained results suggest that with conduction assisted heat transfer, only 27% of the PCM portion from the bottom of the macro-encapsulate has undergone complete melting. During the discharging cycle, as the bottom part of PCM gets solidified quickly, the heat contained within the upper regions cannot escape easily through the bottom face of macro-encapsulate. However, in the combined mode, over 70% of the PCM has undergone complete melting within the stipulated time. In addition, during the discharging cycle there was no entrapment of stored heat within the macro-encapsulate in the combined mode.