| In recent years,in order to solve the problem of energy waste and environmental pollution caused by winter heating in northern China,the state has vigorously promoted the reform of clean energy,and the air source heat pump is widely used in building heating with its advantages of high efficiency and energy saving and clean and pollution-free.Single screw compressor has the advantages of simple structure,force balance,single-stage pressure ratio,high volumetric efficiency,low noise,etc.,which is very suitable for air source heat pumps,in order to promote the application of single screw compressor air source heat pump.Therefore,this thesis conducts heating experiments and numerical calculation studies on single screw compressor air source heat pumps in cold areas,which is of great significance for China’s energy structure reform and green sustainable development.Firstly,through the analysis of meteorological parameters in Zhangjiakou area,the heat load of the photovoltaic power station complex building was calculated,and the single screw compressor air source heat pump heating system was designed and built.The test results of the heat pump system show that the minimum ambient temperature in Zhangjiakou area is-10.9°C,the maximum outlet water temperature of the heat pump can reach 51.6°C,the average temperature difference between supply and return water is 2°C,and the indoor temperature can reach 22°C,which can meet the heat load demand of building heating,and the average COP of the heat pump unit during the test period is 1.83.Among them,the suction pressure of the single screw compressor varies from 0.15 to 0.32 MPa,and the exhaust pressure can reach up to 1.99 MPa,and when the exhaust temperature exceeds 100°C,the compressor will be sprayed and cooled.Heat pumps defrost on average once an hour,with an average defrosting volume of 4MJ per defrost.Secondly,in order to analyze the energy consumption and economic performance of the single screw compressor air source heat pump heating system in the whole heating season,the mathematical model of the components of the single screw compressor air source heat pump heating system is established,and based on the prototype of the heating system,a single screw compressor air source heat pump heating system model is established on the TRNSYS simulation platform,and the simulation value of the system is obtained through numerical calculation through the model,and then the experimental value and simulation value during the test period are compared.After comparison,the relative error of the water supply temperature is 3.4%,the relative error of the return water temperature is 4.3%,and the relative deviation range between the heat of the corresponding heat pump and the input power is 0.3%～9.7%and 0.6%～14%,respectively.The error between the system simulation result and the actual measurement result is relatively small,which verifies the reliability of the calculation model of the single screw compressor air source heat pump heating system.Subsequently,in view of the problem that the measured heat load at the end of the heating system is small,resulting in frequent start and stop of the heat pump and the high temperature requirements of the radiator at the end of the heating,on the basis of the above heating model,the building heat load is increased and the end heating mode is changed,and then the single screw compressor air source heat pump floor radiant heating system,the fan coil heating system and the floor radiant heating system without buffer water tank are established on the TRNSYS simulation platform,and the working characteristics of the three heating systems are studied and compared.The results show that the total energy consumption and heat loss of the floor radiant heating system are lower than those of the fan coil heating system,and the number of heat pump starts and stops in the floor radiant heating system is much lower than that of the fan coil heating system.The energy consumption of the floor radiant heating system without buffer water tank is the lowest,the cumulative heat supply of the heating system is 266207.7k Wh,the total electricity consumption is 110684 k Wh,the average indoor temperature is 20.06°C,and the energy efficiency ratio of the floor radiant heating system with the buffer water tank is increased from 2.19 to 2.41.On this basis,for the radiant floor heating system without buffer water tank,the optimal operation scheme is proposed based on energy consumption and thermal incompatibility of the room.The optimal control scheme is optimized to set the return water temperature to 35°C-40°C and the ambient temperature below-20°C to start the second heat pump.The total energy consumption of the operating scheme system is 104970k Wh,which can save 5714k Wh compared with before optimization,and the average energy efficiency ratio of the system is 2.49,which is 3.3%higher than before optimization.Finally,in order to improve the operating efficiency of the single screw compressor air source heat pump heating system in the cold area of Zhangjiakou,a single screw compressor air source heat pump combined with solar photovoltaic solar thermal(PVT)composite heating system was established on the TRNSYS platform.Through the model of the composite heating system,the comprehensive energy efficiency ratio of the system in the initial,medium and final stages of the typical day is calculated to be 5.4,2.43 and 30.9,and the solar energy guarantee rate is 47.6%,13.6%and 100%,respectively.The average energy efficiency ratio of the heating system is3.8,and the average solar guarantee rate is 39.5%.The optimal design parameters are obtained based on the lowest annual cost value:PVT collector area is 556m~2,installation inclination angle is 60.5°,and hot water storage tank volume is 10m~3.The total electricity consumption of the optimal scheme of the composite heating system is reduced by 5.02%compared with the design scheme,the total energy efficiency ratio is increased by 4.47%,and the operating cost is reduced by 41.23%.Compared with the use of only unbuffered water tank single screw compressor air source heat pump floor radiant heating system,the static recovery period of the composite heating system is 4.72 years,and the cost savings can be 676,600 yuan in the whole life cycle. |
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