Ca(OH)₂/CaO 热化学储能过程中变孔隙率影响的多物理场耦合数值模拟研究

The thermochemical energy storage systems based on Ca(OH)₂/CaO system show significant changes in the pore structure in experiments, which has not been considered in most of the existing numerical simulation studies. In this paper, a reaction kinetic model with variable porosity and an unsteady coupling model of”flow-heat-transfer-chemical reaction” are established for this phenomenon. Based on these results, the characteristics of Ca(OH)₂/CaO dehydration reaction process (permeability, pressure, temperature, reaction rate and conversion, etc.) in direct and indirect heat transfer fixed-bed reactors were compared and simulated. The results show that there are obvious differences between the constant porosity model and the variable porosity model, and the variable porosity model can better reflect the characteristics of the actual reaction process. Taking the initial porosity of 0.8 as an example, the conversion rate of the constant porosity model in the direct heat transfer reactor is nearly 19.8% faster than that of the variable porosity model, while the conversion rate of the indirect heat transfer reactor is about 6.1% slower than that of the variable porosity model. The results show that the constant porosity assumption used in previous studies overestimates the performance of direct heat transfer reactors and underestimates the performance of indirect heat transfer reactors.