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 degC. 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 degC and 5 degC, respectively. In addition, the refrigerating capacity of 1.19 kW is achieved even when the hot air temperature is as low as 210 degC, 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 degC and 10 degC, respectively, and the data are higher than the required refrigerating capacity. However, for refrigerating temperatures of 15 degC and 18 degC, the refrigerating capacity experimentally obtained could meet the requirement only when a truck is utilized for long distance transportation.