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The aim of the present paper is the experimental characterization of adsorbent materials suitable for practical applications in adsorption refrigeration systems, employing ethanol as refrigerant. Different commercial activated carbons as well as a properly synthesized porous composite, composed of LiBr inside a silica gel host matrix, have been tested. A complete thermo-physical characterization, comprising nitrogen physi-sorption, specific heat and thermo-gravimetric equilibrium curves of ethanol adsorption over the sorbents, has been carried out. The equilibrium data have been fitted by means of the Dubinin – Astakhov equation. On the basis of the experimental data, a thermodynamic evaluation of the achievable performance of each adsorbent pair has been estimated by calculating the maximum COP (Coefficient of Performance) under typical working boundary conditions for refrigeration and air conditioning applications. The innovative composite material shows the highest thermodynamic performances of 0.64–0.72 for both tested working conditions. Nevertheless, the best carbonaceous material reaches COP value comparable with the synthesized composite. The results have demonstrated the potential of the chosen adsorbents for utilization in adsorption cooling systems.

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. © 2014 Elsevier Ltd. All rights reserved.

One of the main limitations for the wide diffusion of sorption systems, either as stand-alone and in hybrid configurations, is the low heat transfer inside the adsorber, as well as the low volumetric cooling power. In this context, the present paper reports the experimental activity on four different advanced configurations for the adsorber, based on microchannel heat exchangers where the gap between the channels is filled with porous structures where zeotypes of SAPO-34 family were synthetized. The porous structures evaluated are high-density fins, two different aluminium foams and compressed chips from the waste of aluminium machining. The sorption dynamic and cooling power density of each structure were measured through a Gravimetric Large Temperature Jump testing apparatus. The results obtained showed that the best-performing configuration is the one with high-density fins, that, for a 90/30/20 degrees C cycle showed a Specific Cooling Power up to 1.1 kW/kg. The other structures exhibit a much slower adsorption process, corresponding to power densities of about 0.3 kW/kg. The results were used for sizing a full-scale adsorber, whose expected Volumetric Cooling Power is 500 kW/m(3). (C) 2020 The Author(s). Published by Elsevier Ltd.