Performance improvement of packed bed thermochemical heat storage by enhancing heat transfer and vapor transmission

Thermochemical heat storage (TCHS) has the advantages of high storage density and low heat loss, which is attracting much attention in energy storage. But the reaction process is usually restricted by the poor heat transfer and vapor transmission of reaction beds. In present paper, to enhance the TCHS performance, the dehydration process of Ca(OH)₂/CaO in a cylindrical reactor is numerically studied. Metal foam and vapor channel are used to enhance heat transfer and vapor transmission, respectively. Then the relative importance of enhancing heat transfer versus vapor flow and the combined effect of the two are analyzed under different conditions. The results show that improving both heat transfer and vapor transmission simultaneously can achieve synergetic enhancement effect, the heat storage rate can be enhanced up to 6.6 times and the heat storage density is only reduced by 18.06%. Besides, it is found that the relative importance of heat transfer and vapor flow enhancement mostly depends on the height-diameter ratio and porosity of reaction beds. When the porosity is small or height-diameter ratio is large, enhancing vapor flow is more effective, otherwise, enhancing heat transfer is more effective.