Performance optimization of latent heat storage by structural parameters and operating conditions using Al-based alloy as phase change material

Abstract

Heat storage technology can effectively solve the intermittency and instability of solar radiation and it also plays a vital role in solar thermal power generation. In this paper, Al-based alloys as candidates for high-temperature phase change material (PCM) with different Si/Cu content ratios are prepared. Thermal properties such as melting point, latent heat, specific heat, and thermal conductivity are investigated. A numerical model of phase change heat storage unit (PCHSU) is developed to analyze the heat transfer characteristics. The structural parameters are optimized by the PCM container structure, the surface to volume ratio, and inserted inner ring fins. The operating conditions are optimized by the flow direction, the inlet temperature, and the velocity of the thermal fluid. The results show that Al-5%Si-31.5%Cu (wt. %) has strengths in latent heat, specific heat, and thermal conductivity. The PCM container with a circular structure is superior to that of hexagonal and square structures in heat storage rate and thermal uniformity. The heat storage rate of PCHSU with inner ring finned tube is 6.83% higher than that of the smooth tube, and it has the advantage of inhibiting thermal stress due to the axial temperature uniformity. The horizontal PCHSU is more helpful in stabilizing the state of thermal fluid outlet temperature. Notably, 1023 K and 10 m/s are the optimal inlet temperature and velocity of the thermal fluid. Finally, the heat storage module is analyzed based on the variation of solar radiation intensity. These conclusions provide guidance for the design and optimization of PCHSU for heat storage systems.