Proceedings of the Korean Geotechical Society Conference (한국지반공학회:학술대회논문집)

Korean Geotechnical Society (한국지반공학회)
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Study on physical characteristics of Graphite-added bentonite grout for backfilling closed-loop groud heat exchanger

수직 밀폐형 지중 열교환기용 뒤채움재로서 흑연(Graphite)을 첨가한 벤토나이트 그라우트재의 물리적 특성연구

  • Lee, Kang-Ja (Dept. of Civil, Environmental and Architectural. Engineering, Korea University) ;
  • Gil, Hu-Jeong (Dept. of Civil, Environmental and Architectural. Engineering, Korea University) ;
  • Lee, Chul-Ho (Dept. of Civil, Environmental and Architectural. Engineering, Korea University) ;
  • Choi, Hang-Seok (Dept. of Civil, Environmental and Architectural. Engineering, Korea University) ;
  • Choi, Hyo-Pum (Research & Development Institute, Kunhwa Co.,Ltd.)
  • 이강자 (고려대학교 건축사회환경공학과) ;
  • 길후정 (고려대학교 건축사회환경공학과) ;
  • 이철호 (고려대학교 건축사회환경공학과) ;
  • 최항석 (고려대학교 건축사회환경공학과) ;
  • 최효범 ((주)건화 기술연구소)
  • Published : 2009.03.27
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Abstract

Bentonite-based grouting has been popularly used to seal a borehole installed for a closed-loop vertical ground heat exchanger in a geothermal heat pump system (GHP) because of its high swelling potential and low hydraulic conductivity. The bentonite-based grout, however, has relatively lower thermal conductivity than that of ground formation. Accordingly, it is common to add some additives such as silica sand to the bentonite-based grout for enhancing thermal performance. In this study, graphite is adapted to substitute silica sand as an addictive because graphite has very high thermal conductivity. The effect of graphite on the thermal conductivity of bentonite-based grouts has been quantitatively evaluated for seven bentonite grouts from different product sources. In addition, comparisons of viscosity between applications of graphite and silica sand as additives has been carried out. In conclusion, using graphite has thermal conductivity about three times higher than that of silica sand.

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