Experimental study on thermal resistance of vertical ground heat exchangers

Hiroaki Okubo, Hikari Fujii, Ryuichi Itoi

Research output: Chapter in Book/Report/Conference proceedingConference contribution

4 Citations (Scopus)


Thermal resistance values in ground heat exchangers (GHEs) were evaluated using the results of six thermal response tests (TRTs) with two methods. In the first method, Kelvin's line source theory is applied on the temperature performance in TRT results. In the second method, the thermal resistance is calculated on the basis of well completion information. Thermal resistance values estimated from the two methods showed good agreements. Then, the thermal resistances of various well completion types were compared, using the second method. Thermal resistance increased in the order of co-axial GHE, double U-tubes, and single U-tube. As grouting materials, silica sand was the most effective in reducing thermal resistance. The evaluation result also showed that a borehole without grouting could minimize thermal resistance, when natural convection exists in the GHE.

Original languageEnglish
Title of host publicationGeothermal Resources Council Transactions - GRC 2006 Annual Meeting
Subtitle of host publicationGeothermal Resources-Securing Our Energy Future
Number of pages6
Publication statusPublished - 2006
EventGRC 2006 Annual Meeting: Geothermal Resources-Securing Our Energy Future - San Diego, CA, United States
Duration: Sept 10 2006Sept 13 2006

Publication series

NameTransactions - Geothermal Resources Council
Volume30 II
ISSN (Print)0193-5933


OtherGRC 2006 Annual Meeting: Geothermal Resources-Securing Our Energy Future
Country/TerritoryUnited States
CitySan Diego, CA

All Science Journal Classification (ASJC) codes

  • Renewable Energy, Sustainability and the Environment
  • Energy Engineering and Power Technology
  • Geophysics


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