Heat transfer performance of deep borehole heat exchanger with different operation modes

Shuai Huang, Ke Zhu, Jiankai Dong, Ji Li, Weizheng Kong, Yiqiang Jiang and Zhaohong Fang

Renewable Energy, 2022, vol. 193, issue C, 645-656

Abstract: The deep borehole heat exchanger (DBHE) is an essential component of medium-depth geothermal heat pump systems (MD-GHPs). Compared with the conventional borehole heat exchanger, the DBHE has the advantages of minimal land area need, good seasonal heat storage performance and high efficiency in winter. However, most current DBHE research is focused on a single operation mode, and few studies on multiple operation modes. In this study, a DBHE heat transfer model is developed and its governing equations are discretized using the Finite Difference Method (FDM). The model is then validated using measured data from a real-world engineering project. This is followed by an analysis of the outlet water temperature, heat loss rate, maximum heat affected radius, and rock and soil heat recovery characteristics of DBHE with a variety of run-stop ratios (i.e., the ratio of the running time to the intermission time in a day). The following are the key findings: thermal recovery of rock and soil, as well as DBHE operation stability, are negatively correlated with the run-stop ratio, but DBHE heat loss rate is positively correlated with the run-stop ratio; when the run-stop ratio is 24:0 after 15 years of operation, the heat affected radius of DBHE on the surrounding rock and soil is 91.36 m; the other three run-stop ratios (i.e., 16:8,12:12 and 8:16) maybe reduced by 9.07%, 17.34% and 24.86%, respectively. The results of this study have implications for the design of DBHE with different operation modes.

Keywords: Geothermal energy; Deep borehole heat exchanger; Heat transfer model; Run-stop ratio (search for similar items in EconPapers)
Date: 2022
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Citations: View citations in EconPapers (9)

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Persistent link: https://EconPapers.repec.org/RePEc:eee:renene:v:193:y:2022:i:c:p:645-656

DOI: 10.1016/j.renene.2022.05.055

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