• 설비공학논문집
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• 제19권7호
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• pp.512-520
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• 2007

The design of a ground-source heat pump system includes specifications for a ground loop heat exchanger where the heat transfer rate depends on the effective thermal conductivity of the ground and the effective thermal resistance of the borehole. To evaluate these heat transfer properties, in-situ thermal response tests on four vertical test boreholes with different grouting materials were conducted by adding a monitored amount of heat to circulating water. The line-source method is applied to the temperature rise in an in-situ test and extended to also give an estimate of borehole effective thermal resistance. The effect of increasing thermal conductivity of the grouting materials from 0.818 to $1.104W/m^{\circ}C$ resulted in overall increases in effective thermal conductivity by 15.8 to 56.3% and reductions in effective thermal resistance by 13.0 to 31.1%.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.579-582
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• 2009

The thermal conductivity and viscosity(or workability) of graphite-added bentonite grouts and cementitious grouts have been evaluated and compared to determine the suitability of these materials for backfilling vertical boreholes of ground heat exchangers. Seven bentonite grouts from different product sources and a portland cement grout with various mixture ratios were considered in this paper. As a new additive for grout, we choose graphite which has high thermal conductivity. The bentonite grouts indicate that the thermal conductivity and viscosity increase with the content of bentonite or with an addition of Graphite compared with that of silica sand. In case of cementitious grout also increase the thermal conductivity and decrease the workability dramatically though an addition of Graphite. Therefore, we cautiously select the amount of graphite and mixture ratio of bentonite and cement considering not only thermal conductivity but also viscosity for the optimum condition of backfilling material.

• 설비공학논문집
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• 제28권3호
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• pp.103-109
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• 2016

The purpose of this study is to perform comparative economic evaluation for the systems of ground source heat pump (GSHP) and district heating and cooling (DHC) by focusing on the analysis of operation case of GSHP. The adapted research object is a public office building located in Seoul. The capacity of ground source pump is about 3,900 kW. Ground heat exchanger is closed loop type. The analysis period for life cycle cost is 30 years. Economic evaluation is assessed from the viewpoints of the following four parts: initial cost, energy cost, maintenance and replacement cost, and environment cost. The total life cycle cost of GSHP is approximately 8,447 million won. The cost of the DHC System is approximately 3,793 million won. The cost of the DHC is approximately 46% lower than GSHP system under the condition of current rate for GSHP and DHC.

• 한국태양에너지학회 논문집
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• 제31권4호
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• pp.80-86
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• 2011

Investigation of the effective soil thermal conductivity(k) is the first step in designing the ground loop heat exchanger(borehole) of a geothermal heat pump system. Another important factor is the borehole thermal resistance($R_b$). Thermal response tests offer a good method to determine the ground thermal properties for the total heat transport in the ground. This is done by supplying a constant heat power into a borehole heat exchanger. There are two methods to supply a constant heat power. One is to employ the electricity provided by Korea Electric Power Corporation(KEPCO). The other is to use electricity generated by a generator. In this study, the power supply regulation was found to reduce when the electricity generated by the generator was used. This is because the generator evaluated with the power supply characteristically reduces the power supply regulation between an overload and a complex using. But it sometimes occurs a power supply regulation in In-situ thermal response test. In this case getting of k,$R_b$ requires delay times and restored normal state. However, the effect of the delay times and restored normal state on the soil thermal conductivity and borehole thermal resistance is very small. Therefore it is possible to use a generally accepted delay times and restored normal state in the analysis. In this work, it is also shown that an acceptable range of ${\Delta}k$, ${\Delta}R_b$ for normal state and regulation state might be approximately 0.01-0.16W/m k, and -0.004-0.007m K/W, respectively. Thus, restored normal state of power supply regulation is valuable to recommend.

• 자원환경지질
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• 제38권6호
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• pp.717-729
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• 2005

일반적으로 대규모 건물의 피크 냉방 부하는 난방부하보다 크다. 북위도의 한냉한 지역에 소재한 대규모건물의 냉난방 설비는 건물 내부에서 생성되는 발열량과 태양으로부터 획득되는 열량에 따라 좌우된다. 최대 냉방부하에 적합하도록 냉난방설비와 지중루프를 설치하는데 소요되는 비용은 일반적으로 초기투자비가 적게 드는 전통적인 HVAC시스템에 비해 다소 고가이다. 빙축열조(Thermal ice storage, TES)시스템은 과거 수년동안 일반 HVAC에서 냉동기의 용량을 축소시키거나 최대 전력부하 시간대를 바꾸기 위해 사용되어온 기술이다. 일반적으로 건물 난방을 위해서는 보일러와 같은 전통적인 난방설비를 이용하고 그 다음날의 건물냉방을 위해서는 전력료가 저렴한 야간에 빙축을 시키는 빙축열기법을 이용한다. 얼음에서 추출한 잠열 에너지의 장점을 이용하기 위해 설계된 분배시스템(distribution system)과 열원과 열배출원(열침, sink)대신에 지중열 교환기(지중루프)를 이용하면 많은 장점이 있다. 공간 난방과 급탕을 공급하기위한 분리형 설비를 별도로 사용하지 않아도 된다. 공간난방용으로 소요되는 설비용량을 축소시킬 수 있으며-소요 지중열 교환기의 규격과 비용을 절감시킴은 물론 지열 HVAC시스템의 효율을 배가 시킬 수 있으며 온실가스 배출량을 대폭 감축시킬 수 있다. 또한 TES를 적용하면 대규모 건물의 냉난방부하와 열펌프의 용량을 $40\~60\%$ 정도 감축시킬 수 있으며 설비대수와 기계실 공간을 줄일 수 있다. 뿐만아니라 피크 냉난방부하를 토대로 설계한 지원 열펌프 시스템(Ground source heat pump system)의 지중루프를 $1/4\~1/3$가지 줄일 수 있어 도심지역에서 지중루프를 설치할 때 장애요인인 지중루프 설치공간문제와 지중암석의 열적특성문제를 동시에 해결할 수 있다.문이며, 따라서 $^{137}Cs$의 분포는 광물분포 보다는 TOC의 함량에 더 큰 영향을 받고 있음을 보여준다.과 위기 고조 단계, 그리고 갈등 해소 단계등 모든 시기에서 두 신문의 주요 행위자 구성에 있어서 차이가 나타났다. 다시 말해, 조선일보는 기본적으로 총파업을 둘러싼 문제의 구성과 발전, 해소 과정에서 정당이나 대통령, 야당 지도자 등과 같은 정치관련 행위자를 강조하고 있었다. 반면에, 한겨레는 대체로 로든 사건진행 단계에서 노동 관련 단체들과 시민단체의 역동적인 연대와 활동에 초점을 맞추고 있는 것으로 나타났다.술 후 24시간에 599.4$\pm$145.6, 678.8 $\pm$256.4였다(t-test, p < 0.05). 동종 수혈은 RAP군에서 34명 중 7명에서(20.6$\%$), 대조군에서는 46명중 16명에서(34.8$\%$) 시행되어, RAP군에서 유의하게 빈도가 낮았다(Chi-square test, p < 0.05). 결론: 역행성 자가 충전법은 심폐바이패스의 충전에 의한 혈액희석을 최소화함으로서, 개심술 후 출혈과 동종수혈을 또한 줄이는 데 효과적인 방법이 될 수 있다고 생각된다.타내지 않았다.성 교사, 가정 전공 교사가 그렇지 않은 교사보다 해석적, 해방적 행동목표를 더 중요하게 인식하고 있었다. 특히 가정교육 철학을 배운 경험이 있는 교사가 그렇지 않은 교사보다 해방적 행동체계 목표를 중요시하는 것으로 나타났다. 이 연구 결과는, 실천 비판적인 가정 교과의 본질을 구현하기 위해서는 주생활 영역의 교육과정에 기술적, 해석적, 해방적 행동에 대한 목표들을 고루 포함하여야 하며 특히 교사들이 중요하게 인식하는 해방적 행동에 대한 목표를 강조하여 적용할 필요가 있음을 시사하고 있다.교하여 유의한 차이가 관찰되지 않았다. 또한

• 한국태양에너지학회 논문집
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• 제32권5호
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• pp.68-74
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• 2012

Investigation of the effective soil thermal conductivity($k$) is the first step in designing the ground loop heat exchanger(borehole) of a geothermal heat pump system. Another important factor is the borehole thermal resistance($R_b$). Thermal response tests offer a good method to determine the ground thermal properties for the total heat transport in the ground. The first step is measured for initial soil temperature. This is done by supplying a only pump power into a borehole heat exchanger. They need to supply into water unload heat power more than 30 minutes. In this study, the initial soil temperature was found to analysis $14.1{\sim}16.0^{\circ}C$,the ratio was 68.7% represented. In this case of $k$, was 2.1~3.0 $W/m{\cdot}k$, $R_b$ was 0.11~0.20 $m{\cdot}K/W$. In this work, it is also shown that the distribution of a soil thermal conductivity and borehole thermal resistance were on the influence of initial soil temperature. And soil thermal conductivity was related with factors of equation by linear least square method, borehole thermal resistance was on the influence of composite factors.

• 신재생에너지
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• 제3권4호
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• pp.31-37
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• 2007

Because of their low operating and maintaining costs, ground-source heat pump(GSHP) systems are an increasingly popular choice for providing heating, cooling and water heating to public and commercial buildings. Despite these advantages and the growing awareness, GSHP systems to residential sectors have not been adopted in Korea until recently. A feasibility study of a residential GSHP system was therefore conducted using the traditional life cycle cost(LCC) analysis within the current electricity price framework and potential scenarios of that framework. As a result, when the current residential electricity costs for running the GSHP system are applied, the GSHP system has weak competitiveness to conventional HV AC systems considered. However, when the operating costs are calculated in the modified price frameworks of electricity, the residential GSHP system has the lower LCC than the existing cooling and heating equipments. The calculation results also show that the residential GSHP system has lower annual prime energy consumption and total pollutant emissions than the alternative HVAC systems considered in this work.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 추계학술대회 논문집
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• pp.515-518
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• 2007

Because of their low operating and maintaining costs, ground-source heat pump(GSHP) systems are an increasingly popular choice for providing heating, cooling and water heating to public and commercial buildings. Despite these ad- vantages and the growing awareness, GSHP systems to residential sectors have not been adopted in Korea until recently. A feasibility study of a residential GSHP system was therefore conducted using the traditional life cycle cost(LCC) analysis within the current electricity price framework and potential scenarios of that framework. As a result, when the current residential electricity costs for running the GSHP system are applied, the GSHP system has weak competitiveness to conven- tional HVAC systems considered. However, when the operating costs are calculated in the modified price frameworks of electricity, the residential GSHP system has the lower LCC than the existing cooling and heating equipments. The calculation results also show that the residential GSHP system has lower annual prime energy consumption and total pollutant emissions than the alternative HVAC systems considered in this work.

• 한국지열·수열에너지학회논문집
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• 제10권2호
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• pp.13-18
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• 2014

This paper proposes an optimum pipe material (PVC vs. PE) design & selection for open loop ground heat exchangers. Heat exchange efficiency and/or workability, and the need for trench insulation were investigated by comparing EWT (cooling mode) of each system. CFD simulations for the PVC and PE pipe with the same inner diameter show similar EWT. This is because the PVC pipe has a small thickness but a low thermal conductivity as compared to the PE pipe, and thus these two properties tend to offset each other. However, a hypothetically insulated pipe led to a meaningful drop of EWT. This means pipe insulation is of importance in performance of ground heat exchangers. From analyzing climate data and system operation, it is not advantageous to insulate trench pipes due to construction difficulties and ground temperature characteristics that are seasonally varied.

• 한국지반신소재학회논문집
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• 제12권4호
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• pp.143-147
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• 2013

지열 에너지는 지구에 저장된 활용하기 쉬운 재생에너지 이며, 열교환 배관 시스템을 통해 수집될 수 있다. 본 연구에서는 터널 주변 라이닝에 지열 에너지를 포집할 수 있는 열교환 파이프 루프를 간편하게 설치할 수 있는 시스템을 개발하였다. 터널 세그먼트에 결합된 열 교환 파이프 루프 시스템은 수송 유체 순환을 통해, 지중 주변의 열을 인근 구조물 또는 지역의 냉난방 열원으로 사용할 수 있다. 터널 세그먼트에 통합 연결된 열 교환 파이프 루프 시스템을 에너지 라이닝 세그먼트(Energy Lining Segment)이라고 명하도록 하겠다. 유럽에서는 터널 라이닝에 열 교환 파이프 루프 시스템을 통합한 수차례의 사례가 있다. 본 연구에서는 에너지 라이닝 세그먼트에 대한 적용성 평가를 위해, 독일 사례와 유럽 도시에 적용된 사례를 조사해 보았다. 또한, 에너지 라이닝 세그먼트의 열 전도특성을 파악하기 위해, 전산유체해석(CFD)을 수행해 보았다.