Adsorption cooling utilizing the “LiBr/silica - ethanol” working pair: Dynamic optimization of the adsorber/heat exchanger unit

Owing to encouraging energy saving potential, adsorption heat transformers are considered as promising alternative to compression systems. However the enhancement of their specific power is required for their broader dissemination. This paper aims at the dynamic optimization of the Ad-HEx (adsorber/heat exchanger) unit operating with the novel working pair “LiBr/silica - ethanol”, which is characterized by high sorption difference under typical conditions of ice making and air conditioning cycles. The comparative investigation of various Ad-HEx configurations, namely thin beds of loose sorbent grains located on a flat metal plate and loaded into finned flat-tube heat exchangers was carried out. The effects of the adsorbent grain size, Ad-HEx geometry were explored in detail, and the main factors affecting sorption dynamics were revealed. The intra-particle diffusion of ethanol vapor and heat transfer between the support and the sorbent bed were shown to affect the sorption rate for flat sorbent bed configuration. For the configurations based on finned flat-tube heat exchangers, additional effects of the inter-particle diffusion or/and residual air were detected. On the base of the main findings obtained the practical recommendations on optimization of the Ad-HEx unit were formulated in order to enhance the specific cooling power of the adsorptive chiller.