Journal of the Korean Society of Mineral and Energy Resources Engineers (한국자원공학회지)

The Korean Society of Mineral and Energy Resources Engineers (한국자원공학회)
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Investigation of Thermal and Hydraulic Characteristics for the Performance Analysis of a Borehole Heat Exchanger

지중 열교환기 효율 분석을 위한 지반내 열적.수리적 특성 조사

Sim, Byeong-Wan;Lee, Yeong-Min;Kim, Hyeong-Chan;Song, Yun-Ho
심병완;이영민;김형찬;송윤호

  • Published : 20060000
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Abstract

Several hydraulic and geothermal characteristic surveys are carried out in a site for the ground source heat pump system to estimate the long-term performance of a shallow geothermal utilization system. Estimated mean thermal conductivity from density, specific heat, and thermal diffusivity measurements of 61 core samples from a 300 m deep borehole is 2.98W/m-K. Estimated heat flow from the thermal gradient(20°C/km) and average thermal conductivity(2.98W/m-K) is 59.7mW/m2. The correlation between the fracture system and the hydraulic conductivity is analyzed because ground water flow can give influences at the efficiency of the heat pump system. We estimated in-situ thermal conductivity as 3.28W/m-K, 10 percent larger than the value from the sample, and heat exchange rate of a borehole in double U-tube system through a thermal response test. Based on the estimated thermal properties, the long-term performance of the borehole heat exchanger system can be evaluated by numerical simulations. In addition, heat pump operation method and optimal system design techniques can be developed.

천부 지열활용 시스템의 장기적인 효율을 추정하기 위하여 지중 열교환기를 설치한 부지에서 몇가지 수리 및 지열 특성 조사를 수행하였다. 본 연구에서는 300m 심도의 관측공에서 61개의 코아샘플을 채취한 후, 밀도, 비열, 열확산율을 측정하여 열전도도를 산출하였다. 그리고 열전도도 산술평균값(2.98W/m-K)과 지온경사(20°C/km)를 이용하여 지열류량(59.7mW/m2)을 산출하였으며, 또한 지하수의 유동 특성이 지중 열교환기 효율에 많은 영향을 미치기 때문에 균열시스템과 수리전도도간의 상관성을 추정하였다. 그리고 열응답 실험을 통하여 원위치 열전도도를 측정하여 코아 샘플의 열전도도보다 10% 높은 3.28W/m-k의 값을 얻었으며, 이를 통하여 시추공의 열교환율을 계산하였다. 조사된 연구지역 지반의 열적 수리적 특성들은 수치 시뮬레이션을 통하여 지열펌프 시스템의 활용 기술 및 최적 지중 열교환기 시스템 설계를 개발하거나 시스템의 장기적인 효율을 예측하는데 활용된다

Keywords

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