Shallow geothermal energy is an important part of clean energy, and its development and utilization meet the needs of national and social development. The technology of ground source heat pump with borehole heat exchanger (BHE) is the main technology for developing shallow geothermal energy. BHE is the core part of ground source heat pump system (GSHP), and its heat transfer performance is affected by many factors. Because the distance between the two branches of the BHE is very small, there is a serious thermal short circuit phenomenon. In the construction process of BHE, the actual distance between two branches is unknown. And different spacing will lead to different degrees of thermal short circuit, which will affect the performance of BHE. Based on the thermal response test (TRT) of GSHP project, through the combination of field test and numerical simulation, a 3D numerical model is established to study the effect of thermal short circuit between two branches of BHE on its heat transfer performance. The results show that increasing the distance between the two branches can significantly improve the heat transfer performance of the BHE. The maximum distance of two branch pipes is 22.7% higher than that of the minimum distance. The linear relationship between heat exchange and branch distance in linear meter is presented. It is suggested that pipe clamps should be strictly used in the construction of buried pipes to ensure sufficient distance between the two branches.

borehole heat exchanger  /  thermal response test  /  thermal short circuit