Experimental study of a two-stage adsorption freezing machine driven by low temperature heat source

A novel two-stage adsorption freezing machine, which is powered by the heat source with the temperature below 100 °C was developed. The composite adsorbents of CaCl2 and BaCl2 developed by the matrix of expanded natural graphite were chosen as adsorbents. The performance of the system was tested, and the results showed that the system can generate the refrigerating power at −15 °C for the coolant temperature of 25 °C when the temperature of heat source is as low as 75 °C. For the heat source of 85 °C and the coolant temperature of 25 °C, the optimal coefficient of performance (COP) and specific cooling power (SCP) at −15 °C refrigeration are 0.127 and 100 W kg−1, respectively. COP and SCP increased with the increasing heat source temperature and decreased with the decreasing evaporating temperature; the influence of evaporating temperature is not as significant as that of the regeneration temperature.

► A novel two-stage adsorption freezing machine was developed.
► Two different types of salts were chosen as adsorbents.
►  Optimal cycle time for the cycle with three levels of pressure was studied.
► The heat source temperature can be as low as 75 °C for -15 °C freezing output.
► Reasonable performance for freezing conditions is gotten for 85 °C heat source.