• 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.

• 한국지열·수열에너지학회논문집
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• 제13권4호
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• pp.1-7
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• 2017

The energy slab is a ground coupled heat exchanger equipped in building slab structures, which represents a layout similar to the horizontal ground heat exchanger (GHEX). The energy slab is installed as one component of the floor slab layers in order to utilize the underground structure as a hybrid energy structure. However, as the energy slab is horizontally arranged, its thermal performance is inevitably less than the conventional vertical GHEXs. Therefore, stainless steel (STS) pipes are alternatively considered as a heat exchanger instead of high density polyethylene (HDPE) pipes in order to enhance thermal performance of GHEXs. Moreover, not only a floor slab but also a wall slab can be utilized as a heat-exchangeable energy slab in order to maximize the use of underground space effectively. In this paper, four field-scale energy slabs were constructed in a test bed, which consist of the STS and HDPE pipe, and a series of thermal response tests (TRTs) was conducted to evaluate relative heat exchange efficiency per unit pipe length according to the pipe material and the configuration of energy slabs. The energy slab equipped with the STS pipe shows higher thermal performance than the energy slab with the HDPE pipe. In addition, thermal performance of the wall-type energy slab is almost equivalent to the floor-type energy slab.

• 대한기계학회논문집 C: 기술과 교육
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• 제4권1호
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• pp.43-47
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• 2016

지열 히트펌프 시스템은 환경 친화적이고 에너지 절감 시스템으로 알려져 있다. 특히 지중 열교환기는 초기투자비와 시스템 성능을 결정하는 매우 중요한 요소다. 수직형 지열 시스템 설계를 위해서는 현장 열응답 테스트를 통해 지중 유효 열저항을 고려해야 한다. 본 연구에서는 지열이용검토서를 통해 접수된 전국의 지중 열전도도를 지역별로 분석하였다. 전국 평균 지중 열전도도는 2.56 W/mK로 분석되었다. 지중 열전도도가 가장 높은 지역은 서울로 평균 2.68 W/mK이고, 가장 낮은 지역은 부산으로 2.28 W/mK다. 또한 해안을 접하고 있는 지역의 열전도도는 전국 평균에 비해 약 30% 낮다.

• 한국태양에너지학회 논문집
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• 제35권1호
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• pp.81-87
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• 2015

Recently, in order to prevent increasing energy usages in the international community, many countries have attempted to develop the innovative renewable energy systems. Among the renewable energy systems, Ground source heat pump(GSHP) system which supply the heating, cooling and hot water in the building has been attracted by its stability of heat production and high efficiency. However, the initial drilling costs become very expensive and the construction period takes longer the other systems, because GSHP system needs more than 100 m depth drilling. In this study, in order to reduce initial costs of the GSHP, the building integrated geothermal system using the horizontal heat exchanger was developed. The heating and cooling load in the standard housing model was calculated by a simulation and the system design capacity in the high-rise apartment was decided by the total load. Based on the system design capacity, the high-rise apartments were applied to a BIGS and vertical GSHP system and there are analyzed about initial costs. In the result, the initial cost of BIGS could reduce 24% of the initial cost of the vertical GSHP system.

• International Journal of Air-Conditioning and Refrigeration
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• 제16권4호
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• pp.109-116
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• 2008

Ground temperature restoration characteristics are the crucial factors to evaluate whether a ground source heat pump system can keep long time steady operation. They are mainly dependent on soil thermal properties, layout of pile group, operation/shutoff ratio, cooling/heating load, thermal imbalance ratio and so on. On the one hand, several types of vertical pile foundation heat exchangers are intercompared to determine the most efficient one by performance test and numerical method. On the other hand, according to the layout of pile group of a practical engineering and running conditions of a GSHP system in Shanghai, the temperature distribution during a period of five years is numerically studied. The numerical results are analyzed and are used to provide some guidance for the design of large-scale GSHP system.

• 한국산학기술학회논문지
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• 제19권10호
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• pp.128-135
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• 2018

현재 지열 열펌프 시스템에 수직밀폐형 지중열교환기가 가장 많이 적용되고 있으며, 수직밀폐형 지중열교환기의 성능에 영향을 미치는 주요 인자로는 지중 열전도율(k)과 보어홀 전열저항($R_b$)이 있다. 본 연구에서는 현장에서 측정된 열응답시험 데이터를 이용하여 보어홀 전열저항을 계산하였으며 지중열교환기 개별 설계인자들(순환수유량, 파이프 수, 그라우팅재)이 보어홀 전열저항에 미치는 영향을 분석하였다. 또한 도출된 그라우팅 열저항은 문헌에 제시된 다양한 상관식과 비교 분석하였다. 시험데이터를 통해 본 시험에서의 지중열교환기 보어홀 전열저항은 0.1303 W/m.K로 나타났으며, 보어홀 전열저항에서 그라우트 열저항이 66.6 %, 파이프 열저항이 31.5 %, 순환수 대류열저항이 1.9 %를 차지하여 그라우트가 보어홀 열전달에 가장 큰 영향을 미치는 인자임을 확인하였다. 또한 각 설계인자의 설계변수가 보어홀 전열저항에 미치는 영향을 분석한 결과 실리카샌드를 혼합하여 그라우트 열전도율를 높이는 방법이 파이프 수 증가나 순환수 유량증가보다 열전달 증진에 더 효과적임을 알 수 있었다.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 동계학술발표대회 논문집
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• pp.39-44
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• 2008

The heat exchange between the Borehole Heat Exchanger(BHE) and the surrounding ground depends directly on ground thermal conductivity k at the certain site. The k is thus a key parameter in designing BHE and coupled geothermal heat pump systems. Currently, although a thermal hydraulic response test(TRT) is mostly used in practice, the thermal hydraulic TRT needs additional power and is generally time-consuming. A new, simple wireless P/T probe for a hi-speed k determination was introduced in this paper. This technique using a wireless P/T probe is less time-consuming and requires no external source of energy for measurement and predicts local thermal properties by measuring soil temperatures along the depth. Measured temperature data along the depth was analyzed. In order to verify the new technique for the determination of ground thermal conductivity, ground thermal conductivity k that calculated from the measured temperature data using a wireless P/T probe was compared with one obtained from conventional hydraulic TRT. When comparing the average k of two methods, the relative error was approximately 10%. As a result, the electronic TRT can replace the conventional hydraulic TRT method after carrying out the additional research on a lot of sites.

• 설비공학논문집
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• 제19권5호
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• pp.372-378
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• 2007

GHX (Geothermal Heat Exchanger) design which determines the performance and initial cost is the most important factor in ground source heat pump system. Performance of GHX is strongly dependent on the thermal resistance of soil, grout and pipe. In general, GHX design is based on the static simulation program. In this study, dynamic simulation has been peformed to analyze the variation of system performance for various GHX parameters. Line-source theory has been applied to calculate the variation of ground temperature. The averaged weather data measured during a 10-year period $(1991\sim2000)$ in Seoul is used to calculate cooling and heating loads of a building with a floor area of $100m^2$. The simulation results indicate that thermal properties of borehole play significant effect on the overall performance. Change of grout thermal conductivity from 0.4 to $3.0W/(m^{\circ}C)$ increases COP of heating by 9.4% and cooling by 17%. Change of soil thermal conductivity from 1.5 to $4.0W/(m^{\circ}C)$ increases COP of heating by 13.3% and cooling by 4.4%. Change of GHX(length from 100 to 200 m increases COP of heating by 10.6% and cooling by 10.2%. To study long term performance, dynamic simulation has been conducted for a 20-year period and the result showed that soil temperature decreases by $1^{\circ}C$, heating COP decreases by 2.7% and cooling COP decreases by 1.4%.

• 설비공학논문집
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• 제17권4호
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• pp.364-369
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• 2005

An experimental study was conducted on the thermal conductivity of various grouting materials for geothermal heat exchanger which is used as a heat sink or source in the heat pump system. The grouting of the vertical heat exchanger is important for environmental and heat transfer reasons and is generally accomplished by the placement of a low permeability material into the annular space between the borehole wall and the pipes suspended in the borehole. In this study, a lab scale test apparatus was made and measured the thermal conductivity of four grouting materials. As a result, the temperature rising tendency was similar among them, but the increasing rate was different. Thus the thermal conductivity showed a maximum difference of $27\%$ among grouting materials.

• 에너지공학
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• 제15권3호
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• pp.160-165
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• 2006

지열원 히트펌프 시스템은 난방과 냉방부분에서 두드러진 관심을 보이고 있다. 국내에 설치된 지열원 히트펌프 시스템의 대부분은 수직형 방식으로 연구대상 또한 수직형이 주류이다. 본 연구에서는 수평형 지열원 시스템을 시설하우스에 설치하여 성능을 조사하였다. 연구결과, 히트펌프만 고려한 난방성능계수는 3.64이고 지열순환펌프를 포함한 성능계수는 3.31로 나타났다. 응축기 제거열에 대한 순환펌프의 동력은 28.0 W/kW이고, 열교환기길이는 53.3m/kW였다. 지중으로부터의 평균채열량은 14.58 W/m이고, 응축열에 대한 열교환기가 매립된 트렌치길이는 27.7m/kW였다.