Performance Of Air Source Coupling Ground Source Integrated Heat Pump System

In recent years,the air quality in the east and north of China has deteriorated and climate problems have occurred frequently.One of the important factors is the unreasonable use of fossil fuels.There are four main ways to use fossil fuels:electricity,industry,transportation and heating.As far as heating is concerned,it will play a positive role in environmental governance to use clean energy as much as possible to meet the end load requirements.From the perspective of electric heating,electricity is a high-grade energy source,and the utilization rate of direct heating energy is extremely low.Equipment such as electric heat pumps should be used for heating as much as possible.According to low-level heat source sources,electric heat pumps can be divided into air source and ground source（including water and soil source）heat pumps.They have the advantages of energy saving,high efficiency,stability,and environmental protection.However,the following problems exist in the promotion process in the northern region:the air-source heat pump supply-demand relationship is not matched,and the frosting frequency in winter operation is high;ground-source heat pumps have high initial investment,large area of buried pipes,and difficult to balance the soil temperature in buried pipes.These are the inherent shortcomings of heat pump systems,and it is difficult to solve them well through system optimization.Therefore,multi-source combined heating has become one of the hot topics at present.Based on current research results,the combined form of air source and ground source heat pump is more promising.But the existing two-stage coupling system of air source and ground source is made up of two independent heat pump systems connected in parallel or in series relying on an intermediate water tank.The heat transfer loss caused by the introduction of an intermediate water loop is inevitable.At the same time,the system has the disadvantages of large volume,complex system operation,poor layout flexibility,and low energy saving.In view of the above drawbacks,a simpler and more efficient new type of enhanced vapor injection technology in air source coupling ground source heat pump system（ASCGSIHP coupled heat pump system）is designed and conducted the following research:（1）The ASCGSIHP system is designed and analyzed,and the system structure and refrigeration cycle process are analyzed.Through the air jet enthalpy compressor,the air-source heat exchanger and the ground-source heat exchanger refrigerant are effectively coupled.Coupling heat pump units adapted to different environmental temperatures in winter and summer.At the same time,the winter and summer operation process of the system was clarified,and the component thermodynamic analysis model and system thermodynamic analysis model were established.（2）For a case building in Taiyuan,based on the TRNSYS software platform,the ASCGSIHP module was established,and the ASCGSIHP simulation system was built..The existing equipment of the college laboratory was used to conduct an experimental study on the operating performance of the air source heat pump,and the data verification of the air source operating mode simulation results of the ASCGSIHP simulation system was verified based on the experimental data.After that,the existing ground source heat pump experimental data was used to verify the ground source operation mode of the ASCGSIHP simulation system.（3）Analyze the three operating modes of ASCGSIHP simulation system from the aspects of main component selection,parameter setting and simulation results.The simulation results were studied from the perspective of average soil temperature（air source operation mode does not include this item）,supply and return water temperature,performance coefficient.（4）Optimize the ratio of air source to ground source of the ASCGSIHP system based on the principle of having the best operating effect after comprehensive consideration of economy and energy saving.From the twenty-year time scale of the ASCGSIHP system’s life cycle,simulation analysis of 10 matching models was performed.The simulation results show that the air-side heat exchanger is coupled to the system air source only at the winter peak load,and it’s the optimal ratio of system air source to ground source.Based on the above results,the optimization results in the article are further analyzed from four aspects:applicability,energy saving,environmental protection,and economics.In terms of applicability,the ASCGSIHP system has a lower defrost frequency than air-source heat pumps in winter,and it is easier to achieve heat balance in buried pipes than ground-source heat pumps.It can better meet the heating needs in northern regions,and is better than the conventional air source heat pumps and conventional ground source heat pumps in applicability in northern regions;In terms of Energy saving,compared with air source heat pumps,the ASCGSIHP system improves CSPF by 26.2%in summer and HSPF by 12.3%in winter.In terms of environmental protection,after adopting the ASCGSIHP coupled heat pump system to replace large-scale regional boiler rooms,the CO₂ emission reduction during heating period is about 30667.5kg/a,the SO₂ emission reduction is about 248.3kg/a,and the dust is 124.2kg/a.The environmental protection benefits are significant;In terms of economy,ASCGSIHP system reduces the annual dynamic cost by 13.4%compared with air source heat pump and 2.1%compared with ground source heat pump,which has good economic benefits.