Many studies related to latent heat thermal energy storage (LHTES) and performance of phase change materials (PCM) are focused on melting and solidification processes. Investigating and understanding the influence of various parameters on PCMs based thermal energy storage is the key to developing innovative and efficient energy storage systems. The aim of this study is to experimentally compare and assess the performance of phase change material based copper heat exchanger (PCM-HX) in different modes of operation. This PCM-HX is designed to be used in systems where thermal energy can be stored up to 90 °C and an organic PCM RT82 was selected as the energy storage medium. This study focuses on the pressure impact on the PCM melting (charging) and solidification (discharging) processes. Two different modes of operation were analysed: Open and Closed. In the case of an Open mode, the storage tank of PCM-HX was open to the atmosphere (pressure control valve open), in the case of Closed mode the storage tank was closed (pressure control valve closed). PCM charging and discharging processes were conducted and the PCM-HX performances were tested at different pressure inside the storage tank.

The paper presents an experimental study of the influence of heat transfer fluid (HTF) mass flow rate on phase change materials (PCM) behaviour. The experimental study was performed on a specially designed test bench. Research object – PCM based thermal energy storage unit which consists of a stainless steel tank with dual circuit tube-fin copper heat exchanger. The tank (storage volume) was filled with phase change material RT82. The experiment was carried out using three different mass flow rates of HTF: high – 0.25 kg/s, medium – 0.125 kg/s, low – 0.05 kg/s. The analysis showed that in the case of high and medium mass flow rates the melting/solidification process highly depends on the temperature of inlet HTF. Influence of mass flow rate is higher in the case of low mass flow rate.