Thermal Performance of Deep Borehole Heat Exchangers (DBHEs) Installed in a Groundwater-Filled Hot Dry Rock (HDR) Well in Qinghai, China

Qixing Zhang, Feiyang Lu, Yong Huang, Liwei Tan, Jin Luo and Longcheng Duan ()
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Qixing Zhang: Hydro Geology and Engineering Geology and Environmental Geology Survey Institute of Qinghai Province, Xining 810008, China
Feiyang Lu: Faculty of Engineering, China University of Geosciences (Wuhan), Wuhan 430074, China
Yong Huang: Hydro Geology and Engineering Geology and Environmental Geology Survey Institute of Qinghai Province, Xining 810008, China
Liwei Tan: Hydro Geology and Engineering Geology and Environmental Geology Survey Institute of Qinghai Province, Xining 810008, China
Jin Luo: Faculty of Engineering, China University of Geosciences (Wuhan), Wuhan 430074, China
Longcheng Duan: Faculty of Engineering, China University of Geosciences (Wuhan), Wuhan 430074, China

Energies, 2025, vol. 18, issue 9, 1-14

Abstract: Deep borehole heat exchangers (DBHEs) have been widely used for extracting geothermal energy in China. However, the application of this technology in an open well with high temperature remains unknown. In this paper, the thermal performance of a DBHE installed in a groundwater-filled hot dry rock (HDR) well in the Gonghe Basin of Qinghai Province in China was investigated. A U-shaped pipe subjected to a hydraulic pressure of 30 MPa and a temperature of 180 °C was tested successfully. Severe heat loss was detected during the test, which might have been due to the pipe not being well-insulated. To better understand the performance of DBHEs, a numerical model was developed. The results indicate that the pipe’s thermal performance increased by 247% using insulation with a 15 mm layer thickness and a thermal conductivity of 0.042 W/m·K. Thermal performance was significantly improved by increasing the fluid flow rate and pipe diameter. Among the different pipe configurations, double U-shaped buried pipes can achieve the highest performance. The heat-specific rate can reach up to 341.33 W/m with a double U-shaped pipe with a diameter of 63 mm. The second highest rate can be achieved with a coaxial pipe, while single U-shaped pipes have the lowest one.

Keywords: thermal extraction performance; hot dry rock (HDR); heat transfer process; pipe configurations (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2025
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