Experimental and Numerical analysis of melting of PCM inside a spherical capsule

Abstract

The aim of this study is to analyze heat transfer performance of a spherical capsule using paraffin wax as PCM placed in a convective environment during the melting process. In the melting process, hot water enters the test vessel and flows over the spherical capsule which gets heated resulting in the melting of PCM. Experiments were carried out with heat transfer fluid temperature ranging from 70 to 82 °C for a capsule of radius 49 mm. A model for phase change using enthalpy method and finite difference formulation has been developed. The predicted results are compared with the experimental results and are found to be in good agreement. The model was then used to investigate the effect of capsule radius and the Stefan number on the thermal performance of the capsule i.e. the instantaneous heat flux, molten fraction and time for complete melting. Among different radii of the capsules analyzed, it is found that the shorter time for complete melting and higher time averaged heat flux occurs in the capsules of smaller radii and for higher Stefan number.