Structure and Control Optimization of the Buried Pipe Group Heat Exchanger With Vertical Inlet and Flat Outlet

Abstract

ObjectivesIn order to improve the utilization efficiency of shallow geothermal energy, it is urgent to optimize the structure and control of ground heat exchanger, which affects the performance of ground source heat pump system.MethodsA model of the buried pipe group heat exchanger with vertical inlet and flat outlet was established. Based on heat exchange system performance, the optimal structure and operation control mode were explored.ResultsThe heat transfer per unit area increases with the decreasing of transverse longitudinal ratio of the pipe group arrangement. The effect is small when the transverse longitudinal ratio exceeds 0.15. The smaller the heat exchanger spacing is, the higher the soil utilization rate is, but the greater the thermal short-circuit loss is. Compared with the double-row single-outlet type, the heat exchange per linear meter of the double-row double-outlet type buried pipe is increased by more than 7%. The fork arrangement is better when the load is larger. The average outlet temperature of optimization structure in the whole summer is decreased by 2.28 ℃, and the soil temperature around the heat exchanger is decreased by more than 1℃. In the actual operation process, the control mode of the flow rate changing with load should be given priority.ConclusionsThe research results can provide a theoretical basis for the design and manufacture of ground source heat pump heat exchanger.

Keywords

• ground source heat pump
• underground pipe group
• heat exchanger
• thermal short circuit
• control mode