Using PCMs to store solar energy

Abstract

This paper focuses on results of an experimental investigation to study the melting and solidification processes of paraffin wax, a phase change material (PCM), used to store heat energy in a shell-helical coiled tube heat exchanger system. The PCM is stored in a cylindrical space which also contains a coiled tube through which the heat transfer fluid HTF (water) flows. Different paraffin waxes (Ributherm RT25, RT 28, and RT35) have been used as PCMs because of their high energy storage density, availability and relatively low cost. A series of experiments were conducted to test the rate of heat absorption and release of the paraffin waxes. Results indicate that the heat transfer stored using PCMs is dependent on the circulation flow rate of the water in the helical coiled tube. The performance of the system when using a shell-single concentric helical coil heat exchanger is found more effective when compared to the one using a shellsingle straight pipe heat exchanger.