Analysis of thermodynamic performance of cascaded latent heat storage using variable diameter capsules

In this paper, four models are developed to study the thermodynamic performance of a cascaded latent heat storage packed bed filled with three different diameter spherical capsules. The effects of equal and variable capsule diameters on the thermodynamic performance of 3-stage cascaded packed bed are compared. The results show the packed beds with variable diameter capsules has an advantage on heat storage capacity and exergy storage capacity. Exergy storage capacity of packed beds with variable diameter capsules (373-7-6-5) is higher 4.15 %, 7.36 % and 10.68 % than that of the packed beds with equal diameter capsules (373-05, 373-06 and 373-07), respectively. Heat storage capacity of packed beds with variable diameter capsules is higher 1.98 %, 5.76 % and 8.43 % than that of the packed beds with equal diameter (373-05, 373-06 and 373-07), respectively. In addition, the packed beds with equal diameter and variable diameter capsules have the similar thermodynamic performance at the same average capsule diameter. This work has important guiding significance for the thermodynamic performance optimization of cascaded latent heat storage system.