| Because the area of new construction in our country is increasing,the area connected to the urban central heating pipe network system has also increased,and now under the premise that the pipe network and heat source have been basically improved,how to ensure the heating effect of the new building has become the primary problem.Large temperature difference absorption heat pump system can effectively reduce the return water temperature,heat utilization is achieved by widening the temperature value between supply and return,and effectively improving the heating effect of the new heating area,so the large temperature difference absorption heat pump system has been widely used and developed in the first station of cogeneration in recent years.But the application of large temperature difference absorption heat pump system in the heat exchange station is not common,and the relevant operating technology is not mature enough and the unit adjustment method is single.In this project,heat exchange efficiency is used as an evaluation index,and the operation mode of the large temperature difference absorption heat pump system used in the heat exchange station is adjusted to achieve efficient operation.At present,the common large temperature difference absorption heat pump system is divided into heat enhancement heat pump and heating type heat pump,this thesis mainly studies the heat enhancement heat pump system,is the use of high temperature heat energy drive,the temperature of the low temperature heat source to medium temperature.The large temperature difference absorption heat pump system can reduce the return water temperature on the primary side to below the return water temperature on the secondary side,make full use of the functional force of the high temperature heat source on the primary side,drive the large temperature difference absorption heat pump system to produce heating effect,effectively avoid the problems of large heat transfer temperature difference and irreversible loss caused by the operation of conventional plate heat exchange units,and improve heating efficiency and heat energy utilization rate.Its coefficient of performance is greater than 1,generally 1.5-2.5.In this project,the method of separate research of absorption unit and temperature drive heat exchanger is adopted.Firstly,according to the maximum heat load that the absorption unit can provide in the actual project,the heat load ratio is used to define the early cold,late cold and severe cold period of the heating season.Secondly,aiming at the problem of low heat exchange efficiency due to unreasonable adjustment mode during the operation of the system,a mathematical model is established,and the primary and secondary adjustment methods of the system are simulated by Matlab software in the initial cold period,the final cold period(when the absorption unit is used for heat supply)and the severe cold period when the heat load ratio is 0.7-1.0(starting the combined heating of the absorption unit and the temperature drive heat exchanger).Finally,combined with the actual engineering project to carry out experimental research,when the outdoor ambient temperature is different in the early cold period,on the basis of the quality adjustment of the primary side of the system to change the flow rate in stages,the secondary side of the system is respectively adopted three adjustment methods: quality adjustment,quantity adjustment and quality-quantity interadjustment,and multiple sets of experimental data including primary and secondary side flow and inlet and outlet temperature are recorded,and compared and analyzed with the simulation data to verify the feasibility of the model.Finally,the model is used to simulate and study the operation regulation mode of the system during the severe cold period of the heating season,and then the operation and regulation mode of the system is reasonably optimized.The results show that the heat exchange efficiency of the secondary side of the system during the initial cold period and the final cold period is significantly lower than that of the quality regulation and quality-quantity adjustment taking the large temperature difference absorption heat pump system as the research object,without considering the loss of heat during transportation.When the heat load ratio is 0.4-0.7,the secondary side of the absorption unit adopts two methods: quality adjustment and quality-quantity regulation,and the water supply temperature range of the primary side is 85-96°C;when the heat load ratio is 0.7-1.0,the large temperature difference absorption heat pump system is used,and the water supply temperature of the primary side,the flow rate of the incoming temperature drive heat exchanger on the secondary side and the actual flow ratio are analyzed through simulation research,the heat exchange ratio of the absorption unit and the temperature drive heat exchanger,the water supply temperature of the secondary side of the warm drive heat exchanger and the water supply temperature of the secondary side of the unit.It is concluded that the operation of the system is affected by the concentration and crystallinity of lithium bromide solution.When the water supply temperature on the primary side is 110°C,and the ratio of the flow rate of the temperature drive heat exchanger on the secondary side to the actual flow is 20%,the heat exchange efficiency of the system is higher. |
