A consolidated calcium chloride-expanded graphite compound for use in sorption refrigeration systems

A consolidated composite reactive bed for refrigeration sorption systems made from expanded graphite powder impregnated with CaCl2 was produced and tested. The composite material was compressed under a pressure of 10 MPa to enhance its heat transfer properties. Experimental results showed that this material could incorporate 0.90 kg of NH3 per kg of salt and that the agglomeration phenomenon was avoided. The blocks with apparent density of 0.56 g cm−3 and 35% of expanded graphite ensured a good refrigerant mass transfer with a negligible pressure drop between the inner and outer part of the blocks. However, the heat transfer still need some improvements, as the temperature difference inside the blocks could reach 15 °C during the decomposition phase. The average specific cooling power during the synthesis phase was 306 and 194 W per kg of salt at the average evaporation temperatures of −2.7 and −18.3 °C, respectively. The calculated coefficient of performance under different generation temperatures and global conversions ranged from 0.28 to 0.46, and it was not very sensitive to the increase of the generation temperature.