Thermo-Hydraulic Performance of U-Tube Borehole Heat Exchanger with Different Cross-Sections

Aizhao Zhou, Xianwen Huang, Wei Wang, Pengming Jiang and Xinwei Li
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Aizhao Zhou: School of Civil and Architecture Engineering, Jiangsu University of Science and Technology, Zhenjiang 212003, China
Xianwen Huang: School of Civil and Architecture Engineering, Jiangsu University of Science and Technology, Zhenjiang 212003, China
Wei Wang: School of Civil Engineering, Shaoxing University, Shaoxing 312000, China
Pengming Jiang: School of Civil and Architecture Engineering, Jiangsu University of Science and Technology, Zhenjiang 212003, China
Xinwei Li: School of Architecture and Civil Engineering, Anhui University of Science and Technology, Huainan 232000, China

Sustainability, 2021, vol. 13, issue 6, 1-20

Abstract: For reducing the initial GSHP investment, the heat transfer efficiency of the borehole heat exchange (BHE) system can be enhanced to reduce the number or depth of drilling. This paper proposes a novel and simple BHE design by changing the cross-sectional shape of the U-tube to increase the heat transfer efficiency of BHEs. Specifically, in this study, we (1) verified the reliability of the three-dimensional numerical model based on the thermal response test (TRT) and (2) compared the inlet and outlet temperatures of the different U-tubes at 48 h under the premise of constant leg distance and fluid area. Referent to the circular tube, the increases in the heat exchange efficiencies of the curved oval tube, flat oval tube, semicircle tube, and sector tube were 13.0%, 19.1%, 9.4%, and 14.8%, respectively. (3) The heat flux heterogeneity of the tubes on the inlet and outlet sides of the BHE, in decreasing order, is flat oval, semicircle, curved oval, sector, and circle shapes. (4) The temperature heterogeneity of the borehole wall in the BHE in decreasing order is circle, sector, curved oval, flat oval, and semicircle shapes. (5) Under the premise of maximum leg distance, referent to the heat resistance of the tube with a circle shape at 48 h, the heat exchange efficiency of the curved oval, flat oval, semicircle, and sector tubes increased 12.6%, 17.7%, 10.3%, and 7.8%, respectively. (6) We found that the adjustments of the leg distance and the tube shape affect the heat resistance by about 25% and 12%, respectively. (7) The flat-oval-shaped tube at the maximum leg distance was found to be the best tube design for BHEs.

Keywords: ground source heat pump; borehole heat exchange; single U-shape; tube shape; heat resistance (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2021
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (4)

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