Numerical investigation of a latent cold storage system using shell-and-tube unit

Abstract

The use of cold thermal storage systems in low-temperature industrial applications is considered one of the most promising ways of improving energy efficiency and reducing the use of power during peak periods. In this study, the thermal performance of a shell-and-tube cold storage system under realistic operating conditions is investigated numerically. The proposed model is developed based on energy balances and then validated using existing experimental data from the literature. Glycol/water is used as the heat transfer fluid (HTF) and the phase transition phenomena in the phase change material (PCM) is simulated using the enthalpy–porosity approach. The influence of several design and operating parameters, including the HTF mass flow rate, HTF temperature, PCM type, and volume, on the cold storage performance during the crystallization process is presented and analyzed. The numerical results show that increasing the HTF mass flow rate accelerates the PCM crystallization process. However, the delivery periods of constant thermal power and constant HTF outlet temperature are reduced. The HTF inlet temperature has a significant effect on the cold storage performance, and the complete charging period is reduced by approximately 37% when the HTF inlet temperature is reduced from −4 °C to −7 °C. Increasing the number of tubes in the cold storage unit is concluded to significantly improve the thermal performance of the system, and using water/ice as a cold storage medium is more suitable than using the commercial PCMs RT2-HC and RT4-HC. Finally, the proposed numerical model for cold storage systems can be successfully used to design and simulate their realistic operation under different conditions.