THERMODYNAMIC ANALYSIS OF A FIXED-BED REACTOR FOR THE THERMOCHEMICAL ENERGY STORAGE SYSTEM Ca(OH)2/CaO

In recent decades, thermochemical heat storage has been considered as a promising candidate to make long-term storage and long-distance transportation of thermal energy possible. Especially, the thermochemical heat storage system Ca(OH)(2)/CaO is thought as one of the most potential thermochemical processes for storing middle- and high-temperature thermal energy. In this study, we have investigated the heat and mass transfer characteristics of a three-dimensional fixed-bed reactor with a direct wall heat exchanger using a finite element software. The effect of the porosity, wall temperature, and reaction kinetics on the reactor performances was investigated in detail. Also, the entropy generation due to heat transfer, mass transfer, and chemical reaction during the dehydration/hydration process occurring in the porous reactant were studied. The results indicated that increasing the heat conductivity of the bed can enhance the reaction performances dramatically for both dehydration and hydration processes. A lower porosity, higher wall temperature, and higher reaction rate can have an obvious positive influence on the dehydration reaction. The reaction rate almost has no effect on the entropy productions of reaction and mass transfer during the energy storage process. The entropy generation due to heat transfer process and chemical reaction plays an important role during both dehydration and hydration processes. The results might provide the guidelines on designing or selecting the heat exchanger of a reactor for thermochemical energy storage.