Experimental investigation of the silica gel-water adsorption isotherm characteristics

In designing adsorption chillers that employs silica gel-water as adsorbent-adsorbate pair, the overriding objective is to exploit low temperature waste-heat sources from industry. This paper describes an experimental approach for the determination of thermodynamic characteristics of silica gel-water working pair that is essential for the sizing of adsorption chillers. The experiments incorporated the moisture balance technique, a control-volume-variable-pressure (CVVP) apparatus and three types of silica gel have been investigated, namely the Fuji Davison Type A, Type 3A and Type RD. As evidenced by the experimental results, the Henry-type equation is found to be suitable for describing the isotherm characteristics of silica gel-water working pair at the conditions of adsorption chiller. The regeneration of adsorbent depends on the correct allocation of temperature as well as the amount of regeneration time. From the experiments, the isotherm characteristics of silica gel-water in the low- to high-pressure regimes and hence, its isosteric heat of adsorption will be determined. Key parameters for optimizing the amount of heat recovery such as the cycle and switching time of chiller can also be implied from the measured results.