Journal of the Korean Geotechnical Society (한국지반공학회논문집)

Korean Geotechnical Society (한국지반공학회)
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Evaluation of Borehole Thermal Resistance in Ground Heat Exchanger

지중 열교환기의 보어홀 열저항 산정에 관한 연구

  • Yoon, Seok (Graduate Student, Dept. of Civil and Environmental Eng., KAIST) ;
  • Lee, Seung-Rae (Graduate Student, Dept. of Civil and Environmental Eng., KAIST) ;
  • Kang, Han-Byul (Graduate Student, Dept. of Civil and Environmental Eng., KAIST) ;
  • Go, Gyu-Hyun (Graduate Student, Dept. of Civil and Environmental Eng., KAIST) ;
  • Kim, Min-Jun (Graduate Student, Dept. of Civil and Environmental Eng., KAIST) ;
  • Shin, Ho-Sung (Dept. of Civil and Environmental Eng., Univ. of Ulsan)
  • Received : 2013.08.17
  • Accepted : 2013.10.04
  • Published : 2013.10.31
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Abstract

The use of geothermal energy has been increased for economic and environmental friendly utilization. Ground thermal conductivity and borehole thermal resistance are very important parameters in the design of geothermal heat pump system. This paper presents an experimental study of heat exchange rate of U and W type ground heat exchangers (GHEs) measured by thermal performance tests (TPTs). U and W type GHEs were installed in a partially saturated dredged soil deposit, and TPTs were conducted to evaluate heat exchange rates under 100-hr continuous operation condition. The heat exchange rates were also calculated by analytical models to estimate borehole thermal resistances and were compared with experimental results. It comes out that multi-pole and equivalent diameter (EQD) models resulted in more accurate agreement than shape factor (SF) model which is currently more often used.

최근 들어 경제적이고 친환경적인 에너지 활용을 위하여 지열에너지 필요성이 증대되고 있다. 지반의 열전도도(ground thermal conductivity)와 보어홀 열저항(borehole thermal resistance)은 지열 히트펌프 시스템(geothermal heat pump system)의 설계 과정에서 매우 중요한 변수이다. 본 논문에서는 일반 수직밀폐형에서의 U, W 타입의 지중 열교환기(ground heat exchanger)를 매립지 지반에 설치한 후 100시간 연속 운전 조건으로 현장 열성능 실험(thermal performance test)을 수행하였다. 또한 보어홀 열저항 산정 모델들을 이용하여 열효율을 산정한 후 이를 실험값과 비교하였다. 실험 결과 기존에 주로 적용되고 있는 shape factor(SF) 모델보다 multi-pole과 equivalent diameter(EQD) 모델이 계측값과 잘 일치하였다.

Keywords

References

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