Performance assessment of a novel diffuser for stratified thermal energy storage tanks – The nonequal-diameter radial diffuser

Abstract

Owing to their simple structure, easy installation, low cost, and excellent thermal stratification, radial diffusers have been widely used in large-scale stratified thermal energy storage (TES) tanks. The current work proposes a novel nonequal-diameter radial diffuser. The short baffles for the top diffuser and bottom diffuser are above and below, respectively. On the one hand, the new diffuser design is beneficial to thermal stratification. On the other hand, it can reduce the cost of the radial diffuser. The thermal stratification and cost analysis of the proposed nonequal-diameter radial diffuser is performed based on the computational fluid dynamics. Moreover, the influence of the structural parameters on the diffuser performance is analyzed. The research results demonstrate that the nonequal-diameter radial diffuser has nearly the same thermal stratification performance as the equal-diameter radial diffuser and can significantly reduce the cost (37.5% when the diameter of the short baffle is 2/3 that of the long baffle). The thermal stratification performance of the stratified TES tank is optimized when the diameter ratio of the long baffle and the tank is 1/3, the diameter ratio of the short baffle and the long baffle is 1/3, and the distance between the two baffles is as small as possible. The research results are of considerable significance to the design, operation, and optimization of stratified TES tanks.