Field Test and Numerical Simulation on Heat Transfer Performance of Coaxial Borehole Heat Exchanger

Peng Li, Peng Guan, Jun Zheng, Bin Dou, Hong Tian, Xinsheng Duan and Hejuan Liu
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Peng Li: Faculty of Engineering, China University of Geosciences, Wuhan 430074, China
Peng Guan: Faculty of Engineering, China University of Geosciences, Wuhan 430074, China
Jun Zheng: Faculty of Engineering, China University of Geosciences, Wuhan 430074, China
Bin Dou: Faculty of Engineering, China University of Geosciences, Wuhan 430074, China
Hong Tian: Faculty of Engineering, China University of Geosciences, Wuhan 430074, China
Xinsheng Duan: Faculty of Engineering, China University of Geosciences, Wuhan 430074, China
Hejuan Liu: Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan 430071, China

Energies, 2020, vol. 13, issue 20, 1-19

Abstract: Ground thermal properties are the design basis of ground source heat pumps (GSHP). However, effective ground thermal properties cannot be obtained through the traditional thermal response test (TRT) method when it is used in the coaxial borehole heat exchanger (CBHE). In this paper, an improved TRT (ITRT) method for CBHE is proposed, and the field ITRT, based on the actual project, is carried out. The high accuracy of the new method is verified by laboratory experiments. Based on the results of the ITRT and laboratory experiment, the 3D numerical model for CBHE is established, in which the flow directions, sensitivity analysis of heat transfer characteristics, and optimization of circulation flow rate are studied, respectively. The results show that CBHE should adopt the anulus-in direction under the cooling condition, and the center-in direction under the heating condition. The influence of inlet temperature and flow rate on heat transfer rate is more significant than that of the backfill grout material, thermal conductivity of the inner pipe, and borehole depth. The circulating flow rate of CBHE between 0.3 m/s and 0.4 m/s can lead to better performance for the system.

Keywords: ground source heat pumps; coaxial borehole heat exchangers; improved thermal response test; sensitivity analysis (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: 2020
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (7)

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