• Title/Summary/Keyword: borehole heat exchanger

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Regional Distribution of Ground Thermal Conductivity for Vertical Closed Type Ground Heat Exchanger Design (수직 밀폐형 지중열교환기 설계를 위한 지중 열전도도의 지역별 분포)

  • Jung, Kye-Hoon;Sohn, Byong-Hu;Lim, Hyo-Jae
    • Proceedings of the SAREK Conference
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    • 2007.11a
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    • pp.423-428
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    • 2007
  • This study was performed to construct a geothermal data base about thermal conductivity of ground heat exchanger and thermal properties of grouting material which used to refill the borehole. We have acquired geothermal data sets from 39 sites over wide area of South Korea except to Jeju island. From data analysis, the range of thermal conductivity is 1.5$\sim$4.0 W/mK. It means that thermal conductivity varies with grouting material as well as regional geology and ground water system.

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A Study of Borehole Thermal Behavior with 1-Dimensional Model;Field Test Analysis included (1차원 모델에 의한 보어홀 열거동 해석 및 현지측정)

  • Kim, Dae-Ki;Woo, Joung-Son;Ro, Jeong-Geun;Lee, Se-Kyoun
    • 한국신재생에너지학회:학술대회논문집
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    • 2007.11a
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    • pp.550-554
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    • 2007
  • A one-dimensional heat transfer model coupled with parameter estimation is developed in this study to predict the effective thermal conductivities of soil formation and borehole resistances from in situ field test data. In this application a new method of using initial ignoring time(IIT) obtained from error estimation is tried and turned out to be successful in determining soil thermal conductivities. The validity of this model is accomplished through comparison of the predicted temperature profiles of the model with the data from laboratory scale experimental setting. Eleven test boreholes were constructed in Ochang, Chungcheong Buk Do, and thermal response test was carried out with each borehole. The results of the in situ tests were analyzed with our 1-D numerical model and compared with the results of line source method. The comparison shows that the thermal properties from line source method is a little lower (${\sim}95%$)than those from numerical method. The reason of such result seems to be the lower thermal conductivity of grout material, which is not counted in line source method.

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A Study on the Estimation of Soil Formation Thermal Conductivities and Borehole Resistances with One-Dimensional Numerical Model and In-Situ Field Tests (1차원 수치모델과 현지측정에 의한 지중열전도율 및 보어홀 전열저항 해석에 관한 연구)

  • Lee Se-Kyoun;Woo Joung-Son;Ro Jeong-Geun;Kim Dae-Ki
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.18 no.10
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    • pp.783-790
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    • 2006
  • A one-dimensional numerical model coupled with parameter estimation is used to predict the effective thermal conductivities of soil formations and borehole resistances from in situ field test data. In this application a new method of using initial ignoring time (IIT) obtained from error estimation is tried and turned out to be successful in determining soil thermal conductivities. This method is used for single-U and double-U borehole system. The results of this method are compared and agreed well with those of existing software (GPM) in the analysis of single-U borehole data. In the analysis of double-U borehole data this method seems to be better in predicting soil and borehole properties.

The Comparison of the EWT&LWT between Field Measurement and CFD of Vertical-type Geothermal Heat Exchanger (수직형 지열교환기의 입.출구온도에 대한 실측과 CFD 결과 비교)

  • Woo, Sang-Woo;Kim, Joong-Hun;Shin, Seung-Ho;Hwang, Kwang-Il
    • Journal of the Korean Society for Geothermal and Hydrothermal Energy
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    • v.3 no.1
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    • pp.11-16
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    • 2007
  • The purpose of this study is to use the CFD(Computational Fluid Dynamics) method for the ground source heat pump(GSHP) system with vertical U-tube ground heat exchangers. In order to predict LWT(leaving water temperature) in the length of time, This simulation is used by utilizing FLUENT which is commercial CFD code. It was performed by based on four boreholes in the field. Comparing with the results of CFD and field measurement for LWT, the results of CFD was presented very good agreement with 1.0% average difference.

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Case study on construction and economic analysis of geothermal heat pump system (지열 시공 사례 및 동절기 경제성 분석)

  • Park, Chen-Kwan;Shin, Yang-Han;Woo, Ju-Sik;Jeong, Hyo-Min;Chung, Han-Shik
    • Journal of the Korean Society for Geothermal and Hydrothermal Energy
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    • v.7 no.1
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    • pp.17-22
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    • 2011
  • Renewable energy is growing based on low-carbon green energy government policies. According to this policy, geothermal energy is highly efficient and environmental friendly energy which is being recently expanded. However, construction companies are generated disorderly but their ability has not been verified due to the poor geothermal facility which was reported in the media. In the this paper introduce on Busan region's largest geothermal facility, it was confirmed that thermal efficiency of the underground is close to heat exchanger performance. Therefore the study improving the efficiency of underground heat exchange found progressed. The results showed voids between borehole and ground heat exchanger should not be raised. And then geothermal facilities were installed very successfully through the principle grouting operation. As compared to the energy consumption on the basis of operating results energy usage was less than any other heat sources.

Thermal Properties of Granite for Installation of Underground Heat Exchanger (지중 열교환기 설계를 위한 화강암의 열물성 연구)

  • Kim, Jong-Chan;Lee, Young-Min;Koo, Min-Ho
    • 한국신재생에너지학회:학술대회논문집
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    • 2007.06a
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    • pp.456-459
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    • 2007
  • Thermal conductivities (TC) of 57 Jurassic muscovitic granite samples (KIGAM) and 149 porphyritic granite samples (Yeonki: BE-2, BE-3) were measured with LFA-447. Ranges of TC values are $2.429{\sim}3.878$ W/mK (KIGAM), $2.220{\sim}3.767$ W/mK (Yeonki, BE-2) and $2.019{\sim}3.990$ W/mK (Yeonki, BE-3); arithmetic means are 2.924 W/mK (KIGAM), 2.907 W/mK (Yeonki, BE-2), and 2.881 W/mK (Yeonki, BE-3), respectively. In this study, harmonic mean values were calculated to estimate the average value of TC. Harmonic mean values are 2.883 W/mK (KIGAM), 2.886 W/mK (Yeonki, BE-2), and 2.866 W/mK (Yeonki, BE-3), respectively. Heat extraction rates of a borehole heat exchanger strongly depend on TC values. Heat-extraction rates from re values are expected to be a little lower than 84 W/m in all sites. However, considering ground water flow, it is expected that actual heat extraction rate would be higher than the expected value.

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Preliminary Analysis on Design Parameters and Application Effects of Surface Water Heat Exchanger (SWHE) (지표수 열교환기 설계 변수와 적용 효과에 대한 선행 분석)

  • Sohn, Byonghu
    • Journal of the Korean Society for Geothermal and Hydrothermal Energy
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    • v.12 no.3
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    • pp.24-32
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    • 2016
  • Commercial buildings and institutions are generally cooling-dominated and therefore reject more heat to a borehole ground heat exchanger (BHE) than they extract over the annual cycle. Shallow ponds can provide a cost-effective means to balance the thermal loads to the ground and to reduce the length of BHE. This paper presents the analysis results of the impact of design parameters on the length of SWHE pipe and its application effect on geothermal heat pump (GHP) system using BHE. In order to analysis, we applied ${\varepsilon}-NTU$ method on designing the length of SWHE pipe. Analysis results show that the required pipe length of SWHE was decreased with the increase of approach temperature difference and with the decrease of pipe wall thickness. In addition, when the SWHE was applied to the GHP system, the temperature of BHE was more stable than that of standalone BHE system.

A Study on Performance of Seasonal Borehole Thermal Energy Storage System Using TRNSYS (TRNSYS를 이용한 Borehole 방식 태양열 계간축열 시스템의 성능에 관한 연구)

  • Park, Sang-Mi;Seo, Tae-Beom
    • Journal of the Korean Solar Energy Society
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    • v.38 no.5
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    • pp.37-47
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    • 2018
  • The heating performance of a solar thermal seasonal storage system applied to a glass greenhouse was analyzed numerically. For this study, the gardening 16th zucchini greenhouse of Jeollanam-do agricultural research & extension services was selected. And, the heating load of the glass greenhouse selected was 576 GJ. BTES (Borehole Thermal Energy Storage) was considered as a seasonal storage, which is relatively economical. The TRNSYS was used to predict and analyze the dynamic performance of the solar thermal system. Numerical simulation was performed by modeling the solar thermal seasonal storage system consisting of flat plate solar collector, BTES system, short-term storage tank, boiler, heat exchanger, pump, controller. As a result of the analysis, the energy of 928 GJ from the flat plate solar collector was stored into BTES system and 393 GJ of energy from BTES system was extracted during heating period, so that it was confirmed that the thermal efficiency of BTES system was 42% in 5th year. Also since the heat supplied from the auxiliary boiler was 87 GJ in 5th year, the total annual heating demand was confirmed to be mostly satisfied by the proposed system.

Study on the Optimum Design of Ground Source Heat Pumps (지열원 히트펌프 시스템의 최적 설계 기법 연구)

  • Choi, Jong Min
    • Journal of the Korean Society for Geothermal and Hydrothermal Energy
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    • v.14 no.4
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    • pp.35-42
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    • 2018
  • Among the various ground source heat pump systems, vertical-type heat pump systems have been distributed greatly. Most of the vertical-type ground source heat pump systems have been designed based on the Korean Ministry of Knowledge Economy Announcement in Korea. In this study, the design process of the vertical-type ground source heat pump system in the announcement was analyzed, and the effects of the design parameters on the ground loop heat exchanger were investigated. Borehole thermal conductivity was the highest dominant design parameter for ground loop heat exchangers. The borehole thermal conductivity was changed according to the pipe and grout thermal conductivity. For optimal design of the ground heat pump system, it is highly recommended that the design process in the announcement will be revised to adopt the various tubes and grout which have higher thermal conductivity. In addition, the certification standard for heat pump unit should be revised to develop the heat pump with a small flow rate.