Water vapor adsorption equilibrium and adsorption/desorption rate of porous alumina film adsorbent synthesized with anodization on heat transfer plate

Enhancement of adsorption/desorption rate in an adsorption heat exchanger is effective to enhance the cooling/heating power per unit volume of adsorption chillers and the dehumidifying/humidifying rate of desiccant systems. Since exothermic/endothermic phenomena during adsorption/desorption process decrease adsorption/desorption reaction rate, it is necessary to improve heat transfer performance in the adsorption heat exchanger. Thin film adsorbent synthesized on heat transfer plate is promising to enhance the heat transfer. Porous alumina thin film synthesized with anodization on an aluminum plate was greater than that of conventional particle packed bed of activated alumina. In the present study, adsorption equilibrium and adsorption/desorption rate of water vapor in the film were measured to discuss the advantage of the film adsorbent. The parameters in BET equation were determined and Polanyiʹs potential theory was examined. In addition, adsorption/desorption rate of water vapor was also measured and the effective diffusivity was identified with adsorbent temperature. These results were compared with those of particle packed bed of activated alumina. In addition, we estimated the adsorption/desorption rate on the heat exchanger. Consequently, the uptake of adsorbed amount in a cycle and the cooling effect in adsorption refrigeration cycle of the film adsorbent was superior to those of the particle bed.