Thermally-driven hybrid vapor absorption cycle: Simultaneous and flexible use of steam generation heat pump and refrigeration applications

For flexible use of a thermally driven absorption system for heating and cooling effects, a hybrid absorption cycle, which contains a sub-heat pump and a sub-refrigeration cycle, is proposed. Each sub-cycle shares a generator and a condenser, and the flow rate of the solution and the refrigerant entering each sub-cycle is adjusted by the general operating conditions, such as the heating source temperature and flow rate of the working fluid. The proposed hybrid absorption cycle introduced the solution distribution ratio to easily adjust the amount of the solution flow rate entering each sub-cycle, and as a result, the flexible control of the desired heating and cooling capacities was simultaneously achieved. We first proposed the experimental investigation using the pilot-scale hybrid absorption system for simultaneously producing 120 °C steam of approximately 110 kg/h and 8 °C cooling effect. The experimental analysis validified the steady-state theoretical model, and the theoretical simulation characterized the operating characteristics, such as the variations in three pressure levels, the circulation ratios, and the system performance in terms of the practical operating conditions and the defined solution distribution ratio. It was noted that the decrease in the solution distribution ratio, i.e., more amount of the solution entering the sub-refrigeration cycle than entering the sub-heat pump cycle, contributed the decrease in the COP of the sub-refrigeration cycle from 0.74 to 0.72, but brought about the increase in total COP from 0.53 to 0.60. It was concluded that all the parameters considered greatly influenced the heat transfer characteristics of the hybrid absorption cycle, and the heating and cooling effects could be flexibly controlled by the solution distribution ratio. The present study provides comprehensive and valid data for the further experimental investigations to determine main parameters that affect the performance characteristics of the proposed hybrid absorption cycle.