Performance Estimation of Fatty Acid and Paraffin Wax as Phase Change Materials (PCMs) in Thermal Energy Storage System

In this work, an experimental analysis has been done on thermal energy storage system (TESS) to provide comparative study of two different phase change materials (PCMs)—fatty acid and paraffin wax. Set of experiments have been executed to find out thermal energy storage capacity, heat transfer characteristics during charging and discharging periods and overall efficiency of the system for different mass flow rates (0.5, 1, and 2 LPM), and different inlet temperatures (85 and 90 °C) of water as heat transfer fluid (HTF). The system has been built to conduct experiments with at least two PCMs independently, as well as to investigate the combined (cascade) effect of two PCMs in thermal energy storage. The results indicate that with increase in mass flow rate, charging time reduces and melting rate increases. With increase of heat transfer fluid temperature, melting rate will increase about 28.4%. Out of these two process parameters, input temperature of heat transfer fluid impacts more significant rather than mass flow rate of fluid on PCM melting rate. The overall heat transfer efficiencies are 30%, 17%, and 14% for fatty acid, cascading system, and paraffin wax, respectively, at 90 °C HTF temperature. It was found that fatty acid has superior thermal storage capacity as compare to paraffin wax and cascading arrangement. Novelty Statement The present work is novel in terms of conducting an experimental investigation of cascade arrangement of two PCMs (fatty acid and paraffin wax unmixed) in a thermal energy storage system, uniquely evaluates the effect of varying mass flow rates and inlet temperatures.