Research On Key Technologies Of High Temperature Heat Pump

As a green energy-saving technology,air-source heat pumps are widely used in various heating fields such as industry,food,and building.In the heating temperature range of60～80℃,most of the current medium and high-temperature air-source heat pumps still use the old normal temperature heat pump unit accessories.Aiming at the problems caused by this phenomenon,such as the mismatch of the working fluid components of the heat pump system and the unsatisfactory energy saving benefits of the heat pump.This thesis conducts in-depth research on key technologies such as the selection of medium and high-temperature heat pump refrigerants and the optimization of system heat exchanger performance to achieve the purpose of improving the energy-saving benefits of heat pumps.In addition,in order to enable heat pump technology to achieve high-temperature heating above 100°C,expand the application field of heat pump technology.This thesis combines air-source heat pump technology with electromagnetic induction steam generation technology to form a high-temperature heat pump steam generator to provide high-temperature steam above100°C,achieving high-temperature heating while achieving green and energy-saving effects.The research is mainly divided into two parts: air-source heat pump heat exchange mechanism and key technology research on energy-saving benefits,and combined electromagnetic induction heating method to produce high-temperature steam.First,the cyclic performance of the high-temperature heat pump mixed working fluid system is studied.By establishing a system thermodynamic model of the circulating working fluid,the appropriate mixed working fluid components are screened and the optimal ratio is determined to achieve the energy-saving effect of the heat pump unit.Next,the heat pump system evaporator was analyzed by numerical simulation.The effect of the fin structure on the heat transfer performance of the heat exchanger is studied,orthogonal experiment and response surface method are used to optimize heat exchanger structure.Finally,the hightemperature heat pump steam generator scheme was designed,and the system prototype was built to verify the feasibility of the system scheme.The main contents of this thesis are as follows:1.Determined the overall plan of the high-temperature heat pump steam generator.Design the system work plan according to the actual heating demand and related technical standards.First,75～80℃ medium-high temperature hot water is produced by the air-source heat pump,and then this part of the hot water is heated to above 100℃ by the electromagnetic induction heating device.Design the overall scheme of the system,and use Solid Works to establish the system model.2.Screen suitable mixed working fluid components and determine their optimal ratio.Establish a cycle thermodynamic model of mixed working fluid system at the high condensing temperature.Select suitable working fluid components from the six pure working fluids,and pair them with R22 and R134 a respectively,and study the optimal mix of mixed working fluids while ensuring that the compressor discharge temperature and condensing pressure are within a reasonable range.And discuss the cycle performance of the heat pump system under the set conditions.Finally determined the optimal mixed working fluid ratio: R22/R142b(55%/45%),R134a/R142b(70% 30%).The heating energy efficiency coefficient COP when the circulating temperature rises to 60℃ in summer is 3.2and 2.9 respectively.3.Research and Optimization of Heat Exchange Mechanism of Finned Tube Evaporator.Numerical simulation analysis of finned tube evaporator using CFD technology to study the influence of fin structure on air-side flow resistance characteristics and heat transfer factors,use orthogonal experiment and response surface method(RSM)to optimize the structure.Finally optimized fin structure parameters:fin spacing 1.5mm,fin corrugation width 6.7mm,fin corrugation height 0.9mm,tube longitudinal spacing 23.65 mm.4.Installation and feasibility verification of high-temperature heat pump steam generator.According to the determined scheme,the high-temperature heat pump steam generator scheme was installed,and experiments were designed to measure the outlet steam temperature and steam volume of the high-temperature heat pump steam generator.The data showed that the steam temperature was rapidly increased to 150°C within 15 s,and the steam volume was 71.06 kg/h,which verified the technical feasibility of the air-source heat pump combined with the electromagnetic induction steam generator to generate high-temperature steam.