Ln(P) Pc Heating and Pressurization A Ln(P) Pc Desorption and Condensation B PE PE –1/T Desorber TH QH Desorbed Vapor Condenser QC TC TH QH Desorber Desorbed Vapor Condenser –1/T QC TC TM QM Throttling Valve TE TM QM Throttling Valve QE TE QE Ln(P) Pc D Ln(P) Pc Cooling and Depressurization C PE Adsorption and Evaporation –1/T Adsorber TH QH QC QM Throttling Valve Absorbed Vapor Evaporator QE TE Condenser TC PE –1/T Adsorber TH QH QC QM Condenser TC TM TM Throttling Valve Absorbed Vapor Evaporator QE TE Figure 1: Basic adsorption refrigeration system. A. Heating and pressurization. B. Desorption and condensation. C. Cooling and depressurization. D. Adsorption and evaporation.29 Advanced Adsorption Cycle Since the efficiency of the basic adsorption refrigeration cycle is low, and the cooling output is not continuous, many advanced adsorption refrigeration cycles (such as the heat recovery cycle, mass recovery cycle, thermal wave cycle, forced convective thermal wave cycle, etc.) have been developed to improve efficiency and practicability. The heat recovery cycle is an advanced adsorption cycle used in a system with two or more adsorbers. Figure 2 shows the heat recovery system on the P-T diagram. After the adsorption 18 ASHRAE Journal phase and desorption phase are finished in the adsorbers, the heat from the hot adsorber is transferred to the cold adsorber by circulating heat transfer fluid between them in a closed loop. The experimental results show that the COP of the system will increase by up to 25% with the heat recovery cycle.21,22 The mass recovery cycle uses refrigerant mass recovery between two adsorbers to effectively increase cooling output and COP of the system. Figure 3 presents a diagram of the mass recovery cycle of an adsorption system. In the end of the desorption−adsorption phase, the high-pressure adsorber ashrae.org September 2011