Performance Research On An Absorption Heat Pump System Driven By Multi-heat Sources

Vapor compression heat pump systems consume precious electric energy, and refrigerants commonly used will cause severe damage to the ozone layer and global warming. Absorption heat pump systems driven by thermal energy and using environment-friendly refrigerants which can not only greatly ease the power shortage but also can meet demand for energy conservation and environment protection are welcomed. Traditional absorption systems and some improved absorption systems are mostly driven by a single heat source and the driven heat source temperatures are different. It is difficult for low-temperature solar thermal and geothermal as well as a large amount of industrial waste heat to be used in a system. This thesis proposed a multi-heat sources driven absorption heat pump system. High pressure and low pressure generators are coupled by an ejector. The system is capable of efficiently using waste heat and low grade solar thermal energy which can not be used in the conventional single-effect absorption system in a relatively simple structure.Theoretical researches on the performance of the multi-heat sources driven absorption heat pump cycle have been taken. The effects of generation pressure on the cycle cooling/heating performance were evaluated. The simulation results showed that to get optimal performance, the high and low generation pressure and entrainment ratio of the ejector should be optimized. The optimized parameters also were analyzed under different working conditions. Under cooling conditions, if the high generation pressure deviates from the optimal value5KPa the COP remained above0.9, indicating a better performance of this system. The COP of multi-heat sources driven absorption cycle was above0.9, which was20%higher than that of the conventional single-effect cycle, when the heat load ratio of exhaust heat and solar thermal energy is over3.5. Great increase of energy efficiency was achieved.Under the same waste heat and solar thermal energy conditions, cooling capacity/heating capacity generated by multi-heat sources driven absorption heat pump can be more than the sum cooling/heating capacity which was generated by a traditional single effect cycle and a traditional double-lift cycle. But the system equipment could be greatly simplified by using multi-heat sources cycle. Great decrease of initial cost for making the system was achieved.The entire cycle can be seen as hot gas driven sub-cycle and solar thermal energy driven sub-cycle. The maximum heat load ratio values of hot gas load and solar thermal energy were calculated theoretically. The result showed that they varied under different working conditions.An experimental setup of the multi-sources driven absorption heat pump system was designed and built. Experimental study of cooling and heating performance of the system was carried out. The hot gas inlet temperature of high pressure generator, solar hot water inlet temperature of low pressure temperature generator Ⅱ, chilled water outlet temperature of evaporator (cooling conditions), air-conditioning water outlet temperature of condenser (heating conditions) are independent variables. The influences of these independent variables on the key internal operating parameters, such as generation temperature, evaporating temperature, condensing temperature and the performances of cycle including cooling capacity/heating capacity and coefficient of performance of the system have been investigated. Experimental studies showed that the cooling capacity and heating capacity of theoretical results were in good agreement with experimental results. When the hot gas temperature was213℃and the chilled water temperature was6℃, cooling capacity of12.5kW was achieved with a coefficient of performance of0.78. In heating phase, heating capacity of26.6kW was achieved with a coefficient of performance greater than1.7when the temperature of hot water was43.5℃. The above results showed that an efficient and full use of waste heat was realized, providing important basis for the design and wide applications of the multi-heat sources driven absorption heat pump system.