Experimental study on discharging performance of vertical multitube shell and tube latent heat thermal energy storage

An experimental investigation on the thermal performance of vertical multitube shell and tube based latent heat thermal energy storage system (LHTES) during discharging process for solar applications at medium temperature (∼200 °C) is presented in this paper. A commercially available organic phase change material (PCM), A164 having melting temperature of 168.7 °C is stored in the shell side and a thermic oil, Hytherm 600 as heat transfer fluid (HTF), is flown through seven tubes. The effects of three operating parameters, such as inlet HTF temperature, mass flow rate and initial PCM temperature on the outlet HTF temperature are investigated during discharging period. The total energy released, discharging efficiency and heat fraction are analyzed to understand the solidification process of PCM in the multitube LHTES. Thermal Performance Index (TPI) is calculated to evaluate the overall thermal performance of the LHTES under different conditions. The results indicate that the energy released and discharging efficiency increase with increasing mass flow rate and initial PCM temperature and with decreasing inlet HTF temperature. The maximum discharge efficiency and TPI is obtained for the initial PCM temperature of 210 °C with the inlet HTF temperature of 100 °C and the mass flow rate of 0.097 kg/s in this study. Heat fraction is found to be maximum for high mass flow rate, low inlet HTF temperature and higher initial PCM temperature.