氧化钙-氢氧化钙热化学储热系统放热数值分析

Numerical study on exothermic process of a CaO-Ca(OH)_2 thermochemical heat storage system

热化学储热与显热、潜热储热相比,储热密度高且能够实现常温下季节性储热。基于氧化钙-氢氧化钙热化学储热系统,建立了二维轴对称非稳态气固化学反应模型,对直接传热式氧化钙-氢氧化钙储热装置的放热过程进行了研究,并分析了压力、流量、床体孔隙率、床体高度等参数对放热过程的影响。该模型耦合了气固化学反应、多孔介质内的传热传质和流体流动。模拟结果表明,在反应床内存在一个反应速率较快的区域,随着放热的进行该区域由入口逐渐向出口移动;压力、流量分别是影响出口温度、放热功率的主要因素;改变反应物高度,系统的最大放热功率不变。

Compared to sensible and latent heat storage,thermochemical heat storage has a higher heat storage density,achieving seasonal heat storage at ambient temperature.This paper concerns a CaO-Ca(OH)2 heat storage system.A 2D axisymmetric transient model was developed to study the exothermic process of the system,which is essential for reactor design and operation condition optimization.The effect of different reaction conditions and reaction bed parameters on the exothermic process was investigated systematically.The results indicated a rapid reaction zone in the reaction bed with the exothermic reaction moving from the inlet to the outlet.The outlet temperature was mainly influenced by the steam pressure and the reaction exothermic power was mainly influenced by the flow rate.The results also showed that the height of reaction bed had no effect on the maximum reaction exothermic power.