Experimental and analytical investigation of solidification and melting characteristics of PCMs inside cylindrical encapsulation

Phase change materials encapsulated inside cylindrical enclosures are analyzed for solidification and melting process. Analytical solutions for finding the interface locations at various time steps are obtained. Transient interface positions and complete phase change time is predicted by two models for solidification and by three models for melting. To validate the analytical results, experiments are carried out to find the transient positions of the front. The agreement was found to be good for model with conduction and heat generation in solidification process, but in melting the model with conduction, convection and heat generation gives a better prediction. Validated analytical model is extended to study the phase change behavior and heat transfer characteristics inside PCM. Presence of heat generation increases the total solidification time of the cylinder, though it accelerates melting. Total solidification time depends on Stefan number and heat generation parameter β, whereas complete melting time depends on equivalent thermal conductivity. This paper also analyzes the behavior of three paraffins, 60% n-tetradecane + 40% n-hexadecane, n-tetradecane, and n-pentadecane. Since the model considered the influence of heat generation, analytical predictions are also helpful in applications such as nuclear fuel freezing, microwave thawing, and vacuum freeze drying.