A novel topology optimization of fin structure in shell-tube phase change accumulator considering the double objective functions and natural convection

Shell-tube phase change accumulator (STPCA) has been widely applied in renewable energy generation and energy-saving building field. However, due to the low thermal conductivity of phase change material (PCM), its structure needs to be carefully designed to obtain the best heat release and storage rate. Most of the traditional design schemes are trial and error method, which has long design cycle, low efficiency, and difficulty in obtaining the optimal structure. In this contribution, we firstly adopt the topology optimization methods to obtain novel fins in STPCA considering natural convection. Then, we compared the difference between different objective functions and demonstrated the superiority of topology optimization. In addition, we have further studied fin design under double objective functions with different weight ratios and analyzed the synergistic effects on the objective functions. The results have shown that after natural convection has been considered in the topological optimization process, it can help obtain a better structure, and the generated fins can better enhance the performance of STPCA. For the case of single objective function, the conclusions are as follows: the maximum average temperature can be used to obtain the faster melting speed, while the minimum temperature difference can be used to obtain the best temperature uniformity. The conclusions of using double objective function are as follows: when the weight ratio of the maximum average temperature and the minimum temperature difference is 0.6: 0.4, the field synergy angle is smallest, and the performance of STPCA is further improved. This contribution can provide a guidance for STPCA design and enhance its thermal storage performance.