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Geofluids
Volume 2017, Article ID 1285428, 11 pages
https://doi.org/10.1155/2017/1285428
Research Article

Thermal Performance Analyses of Multiborehole Ground Heat Exchangers

1School of Energy Resources, China University of Geosciences (Beijing), Beijing 100083, China
2Exploration Research Institute, Anhui Provincial Bureau of Coal Geology, Hefei, Anhui 230088, China
3University of Louisiana at Lafayette, Lafayette, LA 70504, USA
4Beijing Key Laboratory of Unconventional Natural Gas Geological Evaluation and Development Engineering, Beijing 100083, China

Correspondence should be addressed to Wanjing Luo; nc.ude.bguc@gnijnawoul

Received 30 June 2017; Revised 24 September 2017; Accepted 14 November 2017; Published 11 December 2017

Academic Editor: Paolo Fulignati

Copyright © 2017 Wanjing Luo et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Geothermal energy known as a clean, renewable energy resource is widely available and reliable. Ground heat exchangers (GHEs) can assist the development of geothermal energy by reducing the capital cost and greenhouse gas emission. In this paper, a novel semianalytical method was developed to study the thermal performance of multiborehole ground heat exchangers (GHEs) with arbitrary configurations. By assuming a uniform inlet fluid temperature (UIFT), instead of uniform heat flux (UHF), the effects of thermal interference and the thermal performance difference between different boreholes can be examined. Simulation results indicate that the monthly average outlet fluid temperatures of GHEs will increase gradually while the annual cooling load of the GHEs is greater than the annual heating load. Besides, two mechanisms, the thermal dissipation and the heat storage effect, will determine the heat transfer underground, which can be further divided into four stages. Moreover, some boreholes will be malfunctioned; that is, boreholes can absorb heat from ground when the GHEs are under the cooling mode. However, as indicated by further investigations, this malfunction can be avoided by increasing borehole spacing.