Heat transfer character of deep multi-borehole under different geothermal recovery period

Abstract

The deep-borehole coaxial heat exchanger (DBCHE) can utilize mid-deep geothermal energy steadily. However, most studies of DBCHE were based on a single well; with the growth of building heating area, the applications such as multi-borehole collaborative heating would increase. A 3D heat transfer model was established in this study to discuss the heat transfer character of multi-borehole and the geothermal recovery process of stratum. Analysed the outlet temperature of DBCHE under different borehole distance and the stratum temperature field with different geothermal recovery period. The results indicated that, the mutual thermal influence of two borehole depends on their distance, geothermal recovery speed was rapid at the beginning of recovery period but slow down over time gradually, and the geothermal recovery rate was decrease as the increase of depth.