Comparison of effective thermal conductivity in closed-loop vertical ground heat exchangers

Chulho Lee, Moonseo Park, Sunhong Min, Shin Hyung Kang, Byonghu Sohn, Hangseok Choi

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55 Citations (Scopus)


Performing a series of in-situ thermal response tests, the effective thermal conductivity of six vertical closed-loop ground heat exchangers was experimentally evaluated and compared to each other, which were constructed in a test bed in Wonju, South Korea. To compare thermal efficiency of the ground heat exchangers in field, the six boreholes were constructed with different construction conditions: i.e., different grouting materials (cement vs. bentonite), different shape of heat exchange pipe-sections (conventional U-loop type vs. new 3 pipe-type), and different additives (silica sand vs. graphite). One observation borehole was installed in the middle of the test site to measure a subsurface temperature change during performing the in-situ thermal response test. From the test results, it can be shown that cement grouting has a higher effective thermal conductivity than that of bentonite grouting, and graphite better performs over silica sand as a thermally enhancing addictive. In addition, a new 3 pipe-type heat exchanger yields less thermal interference between the inlet and outlet pipe than the conventional U-loop type heat exchanger, which results in superior thermal performance.

Original languageEnglish
Pages (from-to)3669-3676
Number of pages8
JournalApplied Thermal Engineering
Issue number17-18
Publication statusPublished - 2011 Dec

Bibliographical note

Funding Information:
The writers appreciate the financial support partially by grant No. 06 construction-core D04 from KICTEP, The Ministry of Land, Transport and Maritime Affairs and by National Research Foundation of Korea Grant funded by the Korean Government ( #2010-0011159 ).


  • Ground heat exchanger
  • In-situ thermal response test
  • Thermal conductivity
  • Thermal interference

ASJC Scopus subject areas

  • Energy Engineering and Power Technology
  • Industrial and Manufacturing Engineering


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