Designe And Operation Research Of Vetical Borehole Ground Source Heat Pump Air Conditioning System

The ground-coupled heat pump system is paid wide attention to at home and abroad. However, the system performance is affected by multiple factors, which cause poor operation efficiency of the part of system that was put into used. The design parameters of ground-coupled heat pump air conditioning system were considered to explore heat transfer and operation performance based upon actual building. The influence of key factors to heat pump system was determined to provide reference of practical heat pump system design.Taking an office building in Changsha city as the research object, its all-year hourly dynamic load was simulated. On this basis, the software GLD2012 was used to design the vertical ground-coupled heat exchanger system. And running for a long time of the ground-coupled heat exchanger system were simulated to research influence rule of soil thermal conductivity, borehole spacing, drilling depth and backfill material thermal conductivity to the soil temperature field. Results showed that the increase of soil thermal conductivity, borehole spacing and drilling depth was contributed to alleviate soil temperature rise caused by unbalanced heat and cold. For the ground-coupled heat exchanger system, the value of 4~5 m was appropriate for borehole spacing and 70~100 m was suitable for drilling depth. Compared the four factors to soil temperature field around ground heat exchanger, borehole spacing and drilling depth are key factors to influence soil temperature rise around buried tube and the influence of the soil thermal physical properties and thermal conductivity of backfill material is smaller.Energy Plus simulation software was applied to establish the vertical ground-coupled heat pump air conditioning system model of the office building. And running for a long time of the ground-coupled heat pump air conditioning system were hourly simulated to research influence rule of the buried tubes and flow velocity of the fluid in the tube to inlet and outlet water temperature and unit power consumption of the ground-coupled heat exchanger. When the quantity of borehole keeps constant, the outlet water temperature of the ground-coupled heat exchanger decreased in summer and increased in winter with the increasing the drilling depth, which improved the performance of heat pump unit. The difference of inlet and outlet water temperature was decreased with the addition of water velocity in the tube, which reduced the performance of heat pump unit. And operation performance of the ground-coupled heat pump air conditioning system could be achieved with water velocity of 0.6m/s.