Experimental Study On The Absorption Heat Transformer For Recovering The Low-temperature Waste Heat

Absorption heat transformers (AHT) are devices that can increase the temperature of moderately low-enthalpy waste heat to a higher level, which can be taken good use of. The AHT can be operated by inputting any low-enthalpy thermal energy, such as waste heat and solar energy, other than mechanical energy, electrical energy and high temperature thermal energy. Thus AHT can be a promising device for energy saving.Considering that there had been a lot of moderately low-enthalpy waste heat discharged during the processes of geothermal resource utilization, a scheme using absorption heat transformer to recover geothermal waste heat was proposed in this paper. The geothermal water at about 50℃which comes out of heating system one is taken as the driving heat source of the AHT. After the thermal cycling of the system, the temperature of the recycling water in the heating system two is raised. A 10kW experimental AHT system was designed and set up, and experiments about the waste heat recovery scheme were carried out under different working conditions. The impact of major working parameters such as temperatures of each component inlet and mass flow rate, on the performance of the AHT system was analyzed. Based on the experimental data, thermal resistance and heat transfer coefficient of each component in different working conditions were derived using empirical formulas. The tendency of the main heat resistance and the total coefficient of heat transfer along with the factors affecting them are investigated. Some equations of main factors that affect the system's COP were concluded, such as the temperature and mess flow rate of cooling water in condenser, temperature and mess flow rate of the waste heat water in generator inlet and temperatures of the water in condenser and evaporator inlet, through which the system's COP can be derived. The difference of the results between the experiment and the computational model were analyzed and the reason why the difference occurred was discussed. Based on the experiments and investigations of different heating systems, it can be understood that in specific conditions, the AHT system for district heating can be more competitive in energy saving and environment protecting compared with other systems such as water source heat pumps and gas boiler and so on.