Enhancing efficiency: the role of reactor geometry in thermochemical heat storage with zeolite 13X

The successful application of thermochemical heat storage (TCHS) in real-world heating, ventilation, and air conditioning (HVAC) systems requires overcoming challenges related to low heat and mass transfer rates and high pressure drops. Also, as the system is scaled up, radial non-uniformities in temperature and mass transfer become more pronounced due to the mismatch between inlet duct and reactor diameters, which can significantly degrade zeolite utilization efficiency. This study investigates how reactor geometry influences heat and mass transfer efficiency, as well as fluid flow dynamics, in a TCHS system using zeolite 13X-water pair. We analyzed the effects of varying key geometric parameters, reactor inlet duct diameter (d), bed height (H), and bed diameter (D) on critical performance metrics including reactor outlet temperature, zeolite 13X consumption homogeneity (P(%)), and pressure drop. Our findings reveal that reducing the D/d ratio from 3 to 1 significantly enhanced the uniformity of zeolite consumption, leading to an 8.62% reduction in discharging time. Additionally, reducing the H/D ratio from 2 to 0.5 resulted in an 89.5% decrease in pressure drop, due to shorter flow paths and reduced flow resistance. While changes in reactor geometry did not alter the total heat released, they led to an 89.3% reduction in energy consumption, attributed to both shorter discharging times and reduced flow resistance. By quantitatively decoupling the geometric effects of the D/d ratio on flow uniformity and the H/D ratio on pressure drop, this study provides fundamental design guidelines essential for the successful scale-up of TCHS systems for practical applications.