Journal of the Korean Geotechnical Society (한국지반공학회논문집)

Korean Geotechnical Society (한국지반공학회)
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Evaluation of Conventional Prediction Models for Soil Thermal Conductivity to Design Horizontal Ground Heat Exchangers

수평형 지중열교환기 설계를 위한 토양 열전도도 예측 모델 평가

  • Sohn, Byonghu (Green Building Research Division, Korea Institute of Construction Technology) ;
  • Wi, Jihae (School of Civil, Environmental and Architectural Engrg., Korea Univ.) ;
  • Park, Sangwoo (School of Civil, Environmental and Architectural Engrg., Korea Univ.) ;
  • Lim, Jeehee (School of Civil Engrg., Purdue Univ.) ;
  • Choi, Hangseok (School of Civil, Environmental and Architectural Engrg., Korea Univ.)
  • 손병후 (한국건설기술연구원 그린빌딩연구실) ;
  • 위지혜 (고려대학교 건축사회환경공학부) ;
  • 박상우 (고려대학교 건축사회환경공학부) ;
  • 임지희 ((미)퍼튜대학교 토목공학과) ;
  • 최항석 (고려대학교 건축사회환경공학부)
  • Received : 2011.12.16
  • Accepted : 2012.12.15
  • Published : 2013.02.28
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Abstract

Among the various thermal properties, thermal conductivity of soils is one of the most important parameters to design a horizontal ground heat exchanger for ground-coupled heat pump systems. It is well known that the thermal conductivity of soil is strongly influenced by its density and water content because of its particulate structure. This paper evaluates some of the well-known prediction models for the thermal conductivity of particulate media such as soils along with the experimental results. The semi-theoretical models for two-component materials were found inappropriate to estimate the thermal conductivity of dry soils. It comes out that the model developed by Cote and Konrad provides the best overall prediction for unsaturated sands available in the literature. Also, a parametric analysis is conducted to investigate the effect of thermal conductivity, water content and soil type on the horizontal ground heat exchanger design. The results show that a design pipe length for the horizontal ground heat exchanger can be reduced with an increase in soil thermal conductivity. The current research concludes that the dimension of the horizontal ground heat exchanger can be reduced to a certain extent by backfilling materials with a higher thermal conductivity of solid particles.

지중 토양의 열 물리적 성질 중 열전도도(thermal conductivity)는 지열 히트펌프 시스템(ground-coupled heat pump systems)의 지중열교환기 설계 과정에서 매우 중요한 변수다. 토양의 열전도도는 3상 구조로 인해 함수비와 건조밀도의 영향을 많이 받는다. 본 논문에서는 수평형 지중열교환기의 트렌치 뒤채움재로 사용되는 9종류의 토양(모래-물혼합물)을 대상으로 열전도도 측정결과와 기존 상관식에 의한 계산결과를 비교하였다. 건조토인 경우, 2상 구조의 열전도도 예측모델인 준이론 모델에 의한 열전도도 계산 결과는 측정 결과와 큰 차이를 보였다. 불포화토인 경우, 기존 모델 중 Cote와 Konrad가 제시한 모델에 의한 계산 결과가 측정 결과와 가장 잘 일치하였다. 또한 토양의 열전도도와 함수비, 종류 등이 수평형 지중열교환기의 설계 길이에 미치는 영향을 고찰하였다. 뒤채움재로 사용되는 토양의 열전도도가 증가할수록 수평형 지중열 교환기의 설계 길이는 감소하였다.

Keywords

References

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