Development and experimental investigation of full-scale phase change material thermal energy storage prototype for domestic hot water applications

The paper presents an experimental analysis of the full-scale phase change material (PCM) thermal energy storage (TES) prototype that is designed for use in domestic hot water preparation systems. The PCM-TES prototype is based on the external arrangement of organic PCM and a custom-made compact fin-and-tube type of heat exchanger. The prototype has been designed, constructed, and tested according to the Ecodesign Directive requirements for water heaters and hot water storage tanks. Several parameters have been analysed, including the heat transfer fluid (HTF) temperature and mass flow rate, heat transfer rate, accumulated and released energy, and quantity of domestic hot water (DHW) delivered. Additional attention was paid to the reliability and repeatability of the results. Experimental research allowed to determine the quantity and temperature of DHW at a constant mass flow rate of 0.1 kg/s. The prototype unit showed that it can deliver 99.1 l of hot water at 40 C for up to 15 min and 39 s, while the use of lower temperature DHW (up to 37 C) allows to increase the quantity of hot water delivered up to 156.2 l. Experimental results showed the viability of the prototype, areas for improvement and further possibilities for its optimization. Overall, the study results are relevant for developing latent heat thermal energy storage systems using fin-and-tube heat exchangers in tanks and the feasibility of integrating such systems into DHW systems.