Research On Low Temperature Waste Heat Recovery Performance Of Coupled Absorption-Compression Warming Heat Pumps

China is a major energy consumer,with the industrial sector accounting for around 45%of energy consumption.Due to the constraints of manufacturing processes and technology,a very large proportion of energy ends up in the environment in the form of industrial waste heat,and the impact of heat recovery is not ideal.Among the many waste heat recovery technologies,another type of absorption heat pump,which can improve the quality of heat energy so that heat energy can be used more efficiently,is an effective way to address the problem of low temperature waste heat recovery.Traditional type Ⅱ absorption heat pumps mostly use cooling tubes to cool the condenser,because the circulating cooling water is strongly disturbed by the ambient air temperature,it cannot continuously discharge low-temperature water to cool the condenser,resulting in a high condensing temperature of the system,limited temperature rise capacity,and cannot effectively recover low-quality waste heat below 50℃.In response to the above-mentioned problems,a combined absorption and compression heat pump system is proposed in this paper,which utilizes the low-quality waste heat as a source of kinetic heat and then realizes the deep recovery of the low-quality waste heat.First,an absorption-compression heat pump test system based on the cooling-heat pump heat cycle principle and heat transfer calculations was constructed,and an absorption-compression heat pump system simulation model was designed.The results of the model were verified experimentally and the results showed that the difference between the simulated and experimental values was 2.45%～10.53%.Secondly,the effects of low-temperature heat source temperature,condensing temperature,absorber inlet temperature,supply water flow rate and low-temperature heat source flow rate on the system heat supply and the performance coefficient were analyse for the experimental system and the simulation model,and the changes in the performance coefficient for each parameter under different operating conditions were compared.The results show that the COP of the system increases with increasing the water inlet temperature of the low-temperature heat source,increasing the water flow rate of the low-temperature heat source,increasing the supply water flow rate,decreasing the absorber inlet temperature and decreasing the condensing temperature.The lower the condensation temperature,the lower the temperature of the low temperature waste heat recovered by the absorption heat pump system;if the condensation temperature is 3℃,the existing low temperature heat source temperature is 40℃.The lower the condensation temperature,the lower the temperature of the low temperature waste heat recovered by the absorption heat pump system.It is therefore possible to use another type of lithium bromide absorption heat pump,which uses a low temperature waste heat of 40℃to 50℃as the heat source.If the condensing temperature is 3℃,the absorber inlet temperature is 45℃ and the low-temperature heat source temperature is 50℃,the system can achieve a hot water supply temperature rise of 70℃and a hot water supply temperature rise of 25℃;a reduction of 1℃in the condensing temperature increases the heat supply by 0.7 kW～1.4 kW;with the combined system,a COP factor of 0.40～0.47 and a heat production capacity of 9.5 kW～20.6 kW can be achieved.Hot water supply with temperature rise from 10℃to 25℃.Finally,based on the test results and simulations,the characteristics of the coupled system were analysed and a system benefit analysis was carried out.The results show that:when the low-temperature heat source is constant,by changing the condensing temperature to supply hot water,a temperature increase of 28.7℃can be achieved;when the condensing temperature is 3℃,the bottom temperature of the low-quality waste heat used in the system is 37℃,and for every 1℃decrease in the condensing temperature,the heating temperature increases by 1.2℃,and the temperature of the low-quality waste heat used in the system decreases by about 0.6℃,which can achieve the efficient recovery of low-quality waste heat;if the student is taken as the target The results show that the combined heat pump system has a strong economic advantage and can reduce SO₂ emissions by 44.88 t,CO₂ emissions by 1498.13 t,NOx emissions by 22.44 t and dust emissions by 204.4 t per year during the heating period,which is a good environmental benefit.