HEAT TRANSFER CHARACTERISTICS ANALYSIS OF VERTICAL BURIED HEAT EXCHANGERS.

Heat transfer characteristics of buried closed-loop heat exchange tubes directly affect the efficiency of ground source heat pump systems. To improve the heat transfer efficiency of a geothermal system, a simulation model of a shallow buried closed-loop heat exchanger in Chengdu is established. The heat transfer characteristics of U-tube heat exchangers are investigated. The influence of tube diameter, flow velocity, tube configuration and well group distribution distance on the system heat transfer was studied. The results show that the highest heat transfer efficiency of the buried tube is at the bottom of the inlet section. The optimal heat transfer fluid velocity in the inlet is around 0.6 m/s, and the continuous operation time should not exceed 10 h. The efficiency of the W-shaped structure is increased by 4.8% than U-shaped, and the uniform distribution distance arrangement is the best. The overall heat transfer performance of the borehole heat exchanger is the highest when the distribution distance is 0.5-0.75 m. Those results can provide a basis for designing buried heat exchangers and optimizing geothermal systems. [ABSTRACT FROM AUTHOR]