Research On Temperature Rise Characteristics And Dynamic Simulation Of Absorption Heat Transformer Driven By Low-temperature Waste Heat

Absorption heat transformer is a kind of heating heat pump,which has good energy-saving effect in the production process.It can convert low-grade waste heat into high-grade heat without consuming other high-grade energy.In this paper,a thermodynamic model of absorption heat transformer is established.On this basis,the influence of external operating parameters on the temperature rise ability and exergy efficiency of absorption heat transformer is analyzed.The temperature difference and heat exchange network of the heat pump system are optimized,and the dynamic characteristics of the heat pump system are numerically simulated.The temperature of low-temperature residual heat source can be increased by absorption heat transformer,and the heating capacity of heat pump is directly related to the value of waste heat utilization.Therefore,the heating characteristics of low temperature heat source driven heat pump is the main research of this paper.Firstly,the temperature rise ability of parallel mode and series mode under the same design condition is compared under the low temperature residual heat source,and the effects of the initial and final temperature of the residual heat source and the initial temperature of the cooling water on the absorption temperature of the heat pump are analyzed.Then the characteristic curve of the temperature rising capacity of the heat pump with the initial temperature of the residual heat source and the initial temperature of the cooling water was plotted according to the thermodynamic calculation results.Finally,two empirical correlations between the appreciation of the residual heat temperature and the final temperature of the residual heat source,the initial temperature of the cooling water and the concentration difference of the lithium bromide solution are fitted.The maximum relative error of correlation is 4% and 6% respectively,which meets the engineering requirements.In practical engineering,it provides a basis for determining the temperature rise capacity of absorption heat converter.The performance of heat pump unit can be reflected by COP and ECOP.Therefore,the influences of initial temperature of waste heat,final temperature of waste heat and initial temperature of cooling water on COP and ECOP of heat pump are analyzed.Exergy loss of all parts of the heat pump was shown,of which the condenser was the largest exergy loss,while the solution heat exchanger was the smallest exergy loss.Assuming that the weights of ECOP,COP and absorption temperature of the heat pump are equal,the mean value method is used for dimensionless treatment.It shows that the higher the temperature of the heat source,the higher the temperature of the cooling water,the better the overall performance of the heat pump.Higher economic benefit of heat pump can be obtained by reasonable design conditions.Taking the absorption heat transformer of combined power station as the system model,the maximum annual recovery of heat pump as the objective function,the temperature drop of waste heat and the temperature rise of cooling water as the independent variables,the optimization analysis of heat pump design conditions is carried out.The optimal value of waste heat water temperature drop and cooling water temperature rise are obtained,and the dynamic recovery period after optimization is 1.57 years.The influence of pinch temperature difference on pinch temperature,minimum common heating load and minimum common cooling load of heat pump is analyzed by pinch analysis method.The results show that the heat coefficient of the optimized heat pump is 3.2% higher than that before optimization.Absorption heat pump system has many heat transfer components and remarkable dynamic characteristics.Dynamic analysis of heat pump unit can provide guidance for safe and economical operation and optimal design of the unit.Based on the thermodynamic calculation model,the centralized distribution dynamic model of the heat exchange components of absorption heat pump is established The parameter change of each component and system performance change when the inlet temperature of surplus hot water changes are analyzed.It takes 500 seconds for the system to get back to steady state.Without considering the startup mode,the dynamic response of the heat pump system during the startup process are simulated when the system components are at room temperature.