Journal of the Korean Geotechnical Society (한국지반공학회논문집)

Korean Geotechnical Society (한국지반공학회)
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Evaluation of Heat Exchange Rate in Horizontal Slinky and Coil Type Ground Heat Exchangers Considering Pitch Interval

피치 간격에 따른 수평 슬링키형과 코일형 지중 열교환기의 열효율 평가

  • Received : 2014.06.20
  • Accepted : 2014.07.22
  • Published : 2014.07.31
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Abstract

The need of geothermal energy is constantly increasing for economical and environmental utilization. Horizontal ground heat exchangers (GHEs) can reduce installation cost and increase efficiency. There are many kinds of GHEs, and it is known that slinky and spiral coil type GHEs show high thermal performance. Therefore, this paper presents experimental results of heat exchange rates in horizontal slinky and spiral coil type GHEs installed in a steel box whose size is $5m{\times}1m{\times}1m$. Dried Joomunjin standard sand was filled in a steel box, and thermal response tests (TRTs) were conducted for 30 hours to evaluate heat exchange rates by changing different pitch spaces of horizontal slinky and spiral coil type GHEs. As a result, spiral coil type GHE showed 30~40% higher heat exchange rates per pipe length than horizontal slinky type GHEs. Furthermore, long pitch interval (Pitch/Diameter=1) showed 200~250% higher heat exchange rates per pipe length than short pitch interval (Pitch/Diameter=0.2) in both spiral coil and horizontal slinky type GHEs, respectively.

최근 들어 경제적이고 친환경적인 에너지 활용을 위하여 지열에너지 필요성이 증대되고 있다. 수평형 지중 열교환기는 설치 비용이 저렴하여 비용 대비 효율면에서 우수하다. 수평형 지중 열교환기의 타입에는 여러 가지가 있으나 이 중 슬링키형과 코일형이 우수한 것으로 알려져 있다. 따라서 본 논문에서는 $5m{\times}1m{\times}1m$ 크기의 모형 토조내에 수평 슬링키형과 코일형 지중 열교환기를 각각 설치한 후 열교환율을 실험적으로 측정하였다. 모형 토조 내에는 건조 상태의 주문진 모래가 조성되었으며 수평 슬링키형과 코일형의 피치 간격에 따라 열교환율을 측정하기 위해 30시간 동안 연속으로 열응답 시험을 실시하였다. 실험 결과 코일형 지중 열교환기 이용시 수평 슬링키형 보다 약 30, 40% 정도의 높은 파이프 단위 길이당 열교환율을 보였다. 또한 수평 슬링키형과 코일형 이용시 피치 간격이 넓을 때(피치/직경 = 1)가 좁을 때(피치/직경 = 0.2)보다 약 200, 250% 정도의 높은 파이프 단위 길이당 열교환율을 나타냈다.

Keywords

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