Experimental investigation of a MnCl2/CaCl2-NH3 two-stage solid sorption freezing system for a refrigerated truck

A MnCl2/CaCl2-NH3 two-stage solid sorption freezing system consisting of a MnCl2 sorption bed, a CaCl2 sorption bed, an evaporator and a condenser is established for a refrigerated truck, for which the required refrigerating capacity is 1.13 kW at a refrigerating temperature of −5 °C. Composite adsorbents of MnCl2 and CaCl2 developed by expanded natural graphite treated with sulfuric acid are utilized. The sorption/desorption process and the resorption process are coupled in the two-stage cycle. The experimental results show that the maximum refrigerating capacity of 1.25 kW and COP (coefficient of performance) of 0.143 are obtained at a resorption time of 120 min when the hot air and refrigerating temperatures are 230 °C and −5 °C, respectively. In addition, the refrigerating capacity of 1.19 kW is achieved even when the hot air temperature is as low as 210 °C, and such a result can satisfy the requirement for transporting fresh goods. The refrigerating capacity is 1.32 kW when the hot air and refrigerating temperatures are 270 °C and −10 °C, respectively, and the data are higher than the required refrigerating capacity. However, for refrigerating temperatures of −15 °C and −18 °C, the refrigerating capacity experimentally obtained could meet the requirement only when a truck is utilized for long-distance transportation.