All Issue

2013 Vol.29, Issue 10 Preview Page
Evaluation of Borehole Thermal Resistance in Ground Heat Exchanger

지중 열교환기의 보어홀 열저항 산정에 관한 연구

Seok Yoon1
,
Seung-Rae Lee2
,
Han-Byul Kang3
,
Gyu-Hyun Go4
,
Min-Jun Kim3
,
Ho-Sung Shin5
윤 석1
,
이 승래2
,
강 한별3
,
고 규현4
,
김 민준3
,
신 호성5
1Graduate Student, Dept. of Civil and Environmental Eng., KAIST
2Prof., Dept. of Civil and Environmental Eng., KAIST
3Graduate Student, Dept. of Civil and Environmental Eng., KAIST
4Graduate Student, Dept. of Civil and Environmental Eng., KAIST
5Assistant Prof., Dept of Civil and Environmental Eng., Univ. of Ulsan
1KAIST 건설및환경공학과 박사과정
2KAIST 건설및환경공학과 교수
3KAIST 건설및환경공학과 석사과정
4KAIST 건설및환경공학과 박사과정
5울산대학교 건설환경공학부 조교수
교신저자. Corresponding Author. 
31 October 2013. pp. 49-56
PDF XML Citation
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.

Keywords
Ground heat exchanger
Heat exchange rate
Borehole thermal resistance
Multi-pole model

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.

References
1
1.Bennet, J., Claesson, J., and Hellstrom, G. (1987), “multi-pole method to compute the conductive heat flows to and between pipes in a composite cylinder”, Notes on Heat Transfer, 1987:3, Lund University, Lund, Sweden.
2
2.Brandl, H. (2006), “Energy foundations and other thermo-active ground structures”, Geotechnique, Vol.56, No.2, pp.81-122.
3
3.Carslaw, H. and Jaeger, J. (1947), “Conduction of Heat in Solids”, Oxford, Claremore Press.
4
4.Gaia Geothermal. Ground Loop Design Software, GLD2012.
5
5.Ground Source Heat Pump System Designer, GshpCalc Version 5.0, Energy information Services.
6
6.Gu. Y. and O’Neal, D.L. (1998), “Development of an Equivalent Diameter Expression for Vertical U-Tubes Used in Ground-Coupled Heat Pumps”, ASHRAE Transactions, Vol.104, pp.347-355.
7
7.Incropera, F.P. and Burkhard., S. (1996), Fundamentals of heat and mass transfer, (4th Edition), John Wiley and Sons.
8
8.Jun, L., Xu, Z., Jun, G., and Jie, Y. (2009), “Evaluation of heat exchange rate of GHE in goethermal heat pump systems”, Renewable energy, Vol.34, pp.2898-2904.
9
9.Min, H. S., Yun, T. S., and Jeong, S. S. (2011), “Effect of group spacing of energy piles on thermal analysis”, Journal of the Korean Geotechnical Society, Vol.27, No.8, pp.39-50.
10
10.Min, S., Lee, C., Park, M., Koh, H., and Choi, H. (2010), “Numerical study of heat transfer efficiency, performance and mechanical behavior induced by thermal stress of energy pile”, Transaction of the Korea Society of Geothermal Energy Engineers, Vol.6, No.2, pp.9-13.    
11
11.Park, H. K., Lee, S. R., Yoon, S., and Choi, J. C. (2013), “Evaluation of thermal response and performance of PHC energy pile: Field experiments and numerical simulation”, Applied Energy, Vol.103, pp.12-24.
12
12.Remund, C.P. (1999), “Borehole thermal resistance: laboratory and field studies”, ASHARE CH-99-2-1.
13
13.Sohn, B. H., Shin., H. J., and Park, S. K. (2005), “Evaluation of effective thermal conductivity and thermal resistance in ground heat exchanger boreholes”, Korean Journal of Air-Conditioning and Refrigeration Engineering, Vol.17, No.8, pp.695-703.
14
14.Yoon, S., Lee, S. R., Park, H., and Park, S. (2012), “Thermal conductivity estimation of soils using coil shaped ground heat exchanger”, Journal of Korean Society of Civil Engineers, Vol.32, No.5C, pp.177-183.
Information
  • Publisher :The Korean Geotechnical Society
  • Publisher(Ko) :한국지반공학회
  • Journal Title :Journal of the Korean Geotechnical Society
  • Journal Title(Ko) :한국지반공학회 논문집
  • Volume : 29
  • No :10
  • Pages :49-56
  • Received Date : 2013-08-17
  • Revised Date : 2013-09-23
  • Accepted Date : 2013-10-04
  • DOI :https://doi.org/10.7843/kgs.2013.29.10.49
Journal Informaiton Journal of the Korean Geotechnical Society Journal of the Korean Geotechnical Society
Archives
: Vol.23~28 (2007~2012)
  • NRF
  • KOFST
  • KISTI Current Status
  • KISTI Cited-by
  • crosscheck
  • orcid
  • open access
  • ccl
Journal Informaiton Journal Informaiton - close