Adsorption performance and thermodynamic analysis of SAPO-34 silicone composite foams for adsorption heat pump applications

In the present work, adsorption performances of an innovative composite adsorber, based on SAPO-34-silicone composite macro-cellular foams, are reported. The choice of a foamed structure was assessed to improve the water vapor access towards the embedded zeolite keeping good adsorption heat pump dynamic performance. Depending on zeolite amount used as filler, zeolite/silicone foams evidenced a soft and open cell configuration (low zeolite content) or rigid and closed one (high zeolite content). Morphological analysis evidenced that the cellular structure of the foam is homogeneous and well distributed along the foam cross section. Adsorption tests showed that the adsorbent foamed samples have very effective adsorption capabilities indicating that the porous structure of the filled pure zeolite was not obstructed. SAPO-34 filler contributed actively, with an efficiency above 90%, to the adsorption performances of the composite foam. Starting from experimental equilibrium data, a simple thermodynamic analysis based on energy balances was carried out for air conditioning application. Results of the analysis demonstrated that foam technology can guarantee cooling COP up to 7% higher than that estimated for the typical adsorber solution based on loose adsorbent grains inside an aluminum finned-flat tube heat exchanger, which is very promising for practical application in adsorption heat pumps.