Simulation Of Borehole Heat Exchanger For A Ground-coupled Heat Pump

Ground-coupled heat pump, energy-saving and environment-friendly, is atopic of discussion in international refrigeration industry. Establishing a reasonablenumerical model of borehole heat exchanger is not only significant but alsocomplicated for the purpose of promoting the application of ground-coupled heatpump. The operation of borehole heat exchanger in the ground is a long timeunsteady-state process which occurred in a three-dimensional space. It can not besimulated accurately by two-dimensional or equivalent models which are usedcurrently.A numerical model of single U-tube borehole heat exchanger forground-coupled heat pump was constructed based on energy balances and law ofconservation of mass. First, energy transferred between the fluid and the tube walland heat conduction in the ground was simulated, the temperature of fluid in outletof borehole heat exchanger and variation of ground temperature around theborehole were investigated; Second, the affection of soil thermal properties, depthof borehole, diameter of borehole, backfill and pipe on the performance ofborehole heat exchanger were investigated; Third, the operation model of boreholeheat exchanger and heat balance between summer and winter were discussed. Aseries of directions for the design and operation of borehole heat exchanger werepresented.A numerical model of double U-tube borehole heat exchanger forground-coupled heat pump was also constructed based on energy balances and lawof conservation of mass. The performance between single U-tube and double U-tube borehole heat exchanger was compared. It can be concluded that the doubleU-tube borehole heat exchanger offered a better performance than single U-tubeborehole heat exchanger.