Experimental investigation on a thermochemical sorption refrigeration prototype using EG/SrCl2–NH3 working pair

Abstract

Heat-powered thermochemical sorption refrigeration is a promising technology due to its distinct advantage of energy-saving and the close coincidence of cooling demands with the available solar thermal energy. In this paper, an advanced heat-powered thermochemical sorption refrigeration prototype using SrCl2/NH3 working pair is developed for air-conditioning and deep-freezing process with the utilization of low-grade heat. Expanded graphite (EG) is used as porous matrix to enhance the heat and mass transfer of strontium chloride by preparing EG/SrCl2 composite sorbent. Experimental results showed that the proposed refrigeration prototype can produce the cooling capacity with a refrigeration temperature from 5 to −15 °C by effectively utilizing thermal energy with a temperature below 100 °C. The system COP varies between 0.13 and 0.22 and the SCP ranges from 115 to 185 W kg−1 at the heat sink temperature of 25 °C and the global conversion reaches about 0.42. At the constant heat source temperature, the lower heat sink temperature contributes to the higher global conversion of reactive salt. The sorption reaction platforms of SrCl2/NH3 working pair corresponding to different evaporation temperatures are analyzed during the adsorption–evaporation phase. Potential development is analyzed and proposed for further improving system COP by reducing the mass ratio of metal and reactive salt in the solid–gas reactor and enhancing the global conversion of reactive salt as much as possible with the optimization construction of the reactor and better performance of heat and mass transfer of composite sorbent.