Dexperimental And Optimization Of Enhanced Vapor Injection Air Sourceheat Pump System

With the popularization of the concept of environmental protection and energy saving,air source heat pump(ASHP)has been widely used in the "coal to electricity" project in North China.ASHP has some problems in the application,such as performance degradation at low temperature and high operating noise.Aiming at the above problems,based on the development of prototype,experiments on heating performance and noise characteristics of ASHP,relevant theoretical analysis and simulation optimization are carried out.Based on the thermodynamic cycle principle of enhanced vapor injection(EVI)with economizer,the thermodynamic calculation and prototype design of 25 HP EVI ASHP are completed.By adding an air supply loop,exhaust temperature is reduced,compression condition is improved,and refrigerant flow rate is increased.By adding an economizer,the enthalpy of refrigerant in main loop is reduced,and the heat capacity is significantly increased,so that the unit can meet the heating demand under the condition of low temperature in the north.A heating performance test platform is built for the prototype.The operating performance of the unit under different working conditions is tested by changing operating conditions.The results show that the heating capacity and COP of the system are significantly increased by EVI,and there is an optimal air injection valve opening(air injection volume)under each working condition,which leads to the highest energy efficiency of the systemA noise characteristic test platform is built for the prototype.The noise source of the unit was identified and the spectrum is analyzed,and the variation rule of noise under variable working conditions is studied.The results show that the noise spectrum has the characteristics of broadband and multi-peak.When the rotating noise frequency of fan is close to the excitation frequency of compressor,sound pressure level(SPL)will be amplified.With the increase of air injection valve opening and main circuit valve opening,the refrigerant pressure and flow rate in the pipeline will increase,and SPL will increase.Based on ANSYS,the finite element model of the prototype pipeline system is established,modal analysis and harmonic response analysis are carried out,and the design of pipeline damping,stiffness,length and direction are optimized,which reduces the vibration stress and amplitude.In addition,a new type of noise insulation cover based on the cabinet panel structure is proposed,and the sound field model of prototype is established based on RAYNOISE.The noise reduction effect of the noise insulation cover is 5.76 dB.Finally,based on the prototype,the heating system model of ASHP is established.Five typical cities of Beijing,Shijiazhuang,Taiyuan,Yinchuan and Shenyang are selected to simulate and analyze the operating characteristics of the heating system under the full working conditions.By comparing the fixed frequency unit and the frequency conversion unit through simulation,it is found that the frequency conversion operation has good energy saving and noise reduction effect.