Performance of SrBr2·6H2O based seasonal thermochemical heat storage in a novel multilayered sieve reactor

Abstract

The salt hydrate-based thermochemical heat storage (TCHS) system, based on a reversible solid-gas chemical reaction, is currently a key technique used to store heat for later discharge. Strontium bromide hexahydrate (SrBr2·6H2O) is one of the most promising candidate materials in seasonal heat storage for residential heating due to its lower desorption temperature. This study develops and numerically investigates a novel multilayered sieve reactor that can promote dehydration and hydration reactions. This paper focuses on the interaction between the porous reactive salt beds and the vapor in an open system. The required time to totally dehydrate and hydrate the salt beds are approximately 1180 min and 940 min, respectively. The effects of various operating conditions such as input temperature, inlet velocity, and relative humidity of fluid on charging and discharging are studied, as well as the influence of thermal conductivity, permeability and kinetic factors. For instance, the reaction kinetic factor Rkin = 1.0 × 10−4 is a threshold in this model. The optimized salt beds reduce dehydration time by 11.4% (130 min). High volumetric thermal powers are obtained for the multilayered sieve reactor, although the values decrease with the degree of conversion. The results indicate that the thermal efficiency η, thermal coefficient of performance (COPth), and exergy coefficient of performance (COPex) of charging are 85.2%, 72.4%, and 21.3%, respectively, and the corresponding values for discharging are 94.5%, 71.5%, and 21.1%, respectively, for the model studied.