Effect of fluid direction and reactor structure on heat storage performance of Ca(OH)₂/CaO based on shell-tube thermochemical energy storage device

The flow direction of the heat transfer fluid (HTF) and reactor structure inside the shell-tube heat exchanger has a significant impact on the heat transfer performance of the shell-tube reaction device. In this study, a comprehensive 3D multi-physics coupled model of a shell-tube fixed bed thermochemical energy storage (TCES) device is developed. The investigation delves into the influence of HTF flow direction and reactor structural design on a plethora of critical parameters including temperature distribution, steam pressure distribution, reaction extent, reaction time, heat transfer power, heat transfer efficiency, and heat storage efficiency within the reactor. The result indicates that the flow direction of HTF has an impact on the homogeneity of the reaction in the tube, and the countercurrent and concurrent flow can realize the gradient and homogeneous occurrence of the reaction in the tube, respectively. Both lessening the outer diameter of the device and increasing the diameter of the heat storage material filling tube can improve the average heat exchange efficiency and the average heat storage efficiency. Compared with the basic case (Basic case A), the optimized (Case D) heat storage device volume decreased by 13.38 %, the energy stored amount increased by 24.14 %, heat storage time shortened by 8.04 %, and heat storage efficiency increased by 32.14 %. Additionally, the inlet temperature and velocity still have an obvious influence on the thermal performance of the reactor after structural optimization. These research findings guide for improving the heat and mass transfer effect and working performance of the shell-tube fixed bed Ca(OH)₂/CaO reactor.