Adsorption performance of composite adsorbent for adsorption refrigeration

Adsorption performance of adsorbents for the adsorption cooling cycle was discussed. Adsorption isotherms and adsorption rate of water or ethanol on composite adsorbents prepared by the authors (named M4-0132, M1-0001, M1-9906 and M2-0003 respectively), were tested. The results of fitting to the micro-pore filling theory equation and calculation of characteristic adsorption work based on these pairs were presented. The results showed that the amount of water adsorbed by composite adsorbents was as high as 2 times that by silica gel and 2.5 times that by 13X molecular sieve, respectively, and characteristic adsorption work calculated was 2.55-4.78 kJ·mol^-1, only 12%-29% of that on 13X molecular sieve. The values of adsorption rate of water on composite adsorbents were higher than that on silica gel. Analysis for ethanol adsorption on composite adsorbent, M1-0001, showed occurrence of capillary condensation, which resulted in a considerably higher ethanol uptake than on activated carbon at higher relative vapor pressure. The characteristic adsorption work of ethanol on composite sorbents was 2.55-4.78 kJ·mol^-1, merely 10%-20% of that on activated carbon. Based on comprehensive estimate of adsorption properties, including adsorption loading, characteristic adsorption work and adsorption rate etc., M4-0132 and M1-0001 composite adsorbents were more preferred for the adsorption cooling process, and the preferable type of isotherm for adsorption cooling cycle appeared to be the V type of Brunauer classification.