• 한국태양에너지학회 논문집
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• 제29권5호
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• pp.20-27
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• 2009

The effect of borehole thermal resistance on the borehole length is studied. In performing this work a new concept BLRR(borehole length reduction rate) is developed based on the line source model. The solution of line source model is shown to be valid through the comparison with the data of thermal response test. It is shown that BLRR is a function of soil thermal conductivity(k) and borehole thermal resistance($R_b$). The value of BLRR increases with increasing k, which means reducing $R_b$ is more effective when k is high. The reduction of borehole length with change of $R_b$ is easily estimated with BLRR. The validity of BLRR is also examined with EED analysis.

• 에너지공학
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• 제13권4호
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• pp.296-300
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• 2004

본 연구는 지열원 물 대 물(water to water)히트 펌프 시스템의 냉방 및 난방 운전시 성능 특성과 경제성 평가에 관한 것이다. 5개의 보어홀당 지중 100m의 깊이로 밀폐 수직형 지중 열교환기(closed-vertical ground source)가 설치된 냉난방 시스템이 적용된 건축물에 대하여 냉난방 운전성능을 평가하였으며, 연간 소비전력을 측정하여 실제 시스템의 경제성을 분석하였다. 또한, 순환수의 입구온도에 따른 시스템의 운전 성능을 분석한 결과 난방시에는 COP가 3.0에서 4.2로 증가한 반면, 냉방시에는 5.0에서 3.7로 감소하였다. 본 실험을 통해서,대상 건축물에 대한 지열 냉난방 시스템의 수명주기비용은 기존 냉난방 시스템(보일러+에어컨)에 비해서 68%까지 절감되었으며, 시스템의 경제성을 고려해 볼 때 기존 건축물에도 지열원 냉난방 시스템을 적용하는 것이 타당하다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.1638-1646
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• 2008

This paper presents a series of numerical simulations on the thermal performance and sectional efficiency of a closed-loop vertical ground heat exchanger (U-loop) equipped in a geothermal heat pump system (GHP). A 2-D finite element analysis, ANSYS, was employed to evaluate the temperature distribution on the borehole cross section involving HDPE pipe/grout/soil formation to compare the sectional efficiency between the conventional U-loop and a new latticed HDPE pipe system which is equipped with a thermally insulating latice in order to reduce thermal interference between the inflow and outflow pipes. In addition, a 3-D finite volume analysis (Fluent) was used to simulate the operating process of the closed-loop vertical ground heat exchanger by considering the effect of grout's thermal properties, rate of circulation pump, distance between the inflow and outflow pipes, and the effectiveness of the latticed HDPE pipe system. It was observed that the thermal interference between the two strands of U-loop is of importance in determining the efficiency of the ground heat exchanger, and thus it is highly recommendable to modify the cross section configuration of the conventional U-loop system by including a thermally insulating latice between the two strands.