• Title/Summary/Keyword: Ground-loop heat exchanger

Search Result 74, Processing Time 0.026 seconds

Numerical Analysis on the Heat Transfer Characteristics of HDPE Pipe with the Variation of Geometries for Ground Loop Heat Exchangers (지중열교환기의 고밀도폴리에틸렌 배관 형상에 따른 열전달 성능 특성에 대한 수치해석적 연구)

  • Mensah, Kwesi;Choi, Jong Min
    • Journal of the Korean Society for Geothermal and Hydrothermal Energy
    • /
    • v.12 no.4
    • /
    • pp.33-39
    • /
    • 2016
  • A ground source heat pump (GSHP) system is recommended as a heating and cooling system to solve the pending energy problem in the field of air conditioning, because it has the highest efficiency. However, higher initial construction cost works as a barrier to the promotion and dissemination of GSHP system. In this study, numerical analysis on the characteristics of high density polyethylene (HDPE) pipe with spiral inside was executed. The heat transfer and flow characteristics of it were compared with those of a conventional smooth HDPE pipe. The heat transfer coefficient and pressure drop of the spiral HDPE pipe were higher than those of the smooth HDPE pipes at the same fluid flow rate. By decreasing the flow rate, the spiral HDPE pipe represented similar values of heat transfer coefficient and pressure drop to the smooth HDPE pipe. The lower flow rate of the spiral HDPE pipe comparing with it of the smooth HDPE pipe is estimated to reduce the length of the ground loop heat exchanger.

Analysis of thermal stress and heat transfer due to circulating fluid in ground heat exchanger (지중 열교환기의 순환수에 의한 열응력 및 열전달 거동 분석)

  • Gil, Hu-Jeong;Lee, Kang-Ja;Lee, Chul-Ho;Choi, Hang-Seok;Choi, Hyo-Bum
    • Proceedings of the Korean Geotechical Society Conference
    • /
    • 2009.09a
    • /
    • pp.385-395
    • /
    • 2009
  • In this study, a series of numerical analysis has been accomplished on the thermal performance and sectional efficiency of a closed-loop vertical ground heat exchanger (U-loop) in a geothermal heat pump system (GHP) considering the circulating fluid, pipe, grout and soil formation. A finite element analysis program, ABAQUS, was employed to evaluate the temperature distribution on the cross section of the U-loop system involving HDPE pipe/grout/formation and to compare sectional efficiency between the conventional U-loop and a new latticed HDPE pipe system. Especially, the latticed pipe is equipped with a thermal insulation zone in order to reduce thermal interference between the inflow pipe and the outflow pipe. Also, a thermal stress analysis was performed with the aid of ABAQUS. 3-D finite volume analysis program, FLUENT, was adapted to analyze a coupled system between fluid circulation in the pipe and heat transfer and simulate an operating process of the closed-loop vertical ground heat exchanger. In this analysis, the effect of the thermal properties of grout, rate of circulation pump, distance between the inflow pipe and the outflow pipe, and the effectiveness of the latticed HDPE pipe system are taken into account.

  • PDF

Heat Transfer Performance of Pond Loop type Heat Exchanger for Ground Source Heat Pump using Extruding Ground Water(2) (유출지하수 열원 지열히트펌프용 Pond Loop형 열교환기의 열전달 성능(2))

  • Park, Geun-Woo;Lee, Eung-Youl
    • 한국신재생에너지학회:학술대회논문집
    • /
    • 2006.11a
    • /
    • pp.15-19
    • /
    • 2006
  • 유출지하수나 지표수를 열원으로 하는 지열히트펌프의 Pond Loop형 열교환기를 개발하기 위하여 미국에서 상용화된 Slim-Jim 열교환기와 본 연구에서 자체설계, 제작한 Pond-loop type의 열교환기를 유동이 없는 유출수조 내에서 수조온도가 변화함에 따라 일정한 열교환기 입구온도를 유지하면서 열전달량의 변화를 측정하였다. 그 결과 유출수를 Heat Source로 사용하는 경우 Slim-Jim에서는 $8,000{\sim}11,000 kcal/hr$의 열량이 전달되었고, 자체 제작한 열교환기에서는 $11,000{\sim}16,000kcal/hr$의 열량이 전달되었다. 유출수를 Heat Sink로 사용할 경우 Slim-Jim에서는 $2,500{\sim}7,000 kcal/h$의 열량이 전달되었고, 자체제작한 열교환기의 경우, $6,800{\sim}14,00 kcal/hr$의 열량이 전달되었다. 측정된 열전달량을 바탕으로 총괄열전달계수를 구한 결과 Slim-Jim 열교환기의 경우 $210{\sim}340 kcal/hr\;m^2{\circ}C$, 자체개발한 열교환기의 경우 $350{\sim}590 kcal/hr\;m^2{\circ}C$로 나타나 자체 개발한 열교환기의 열전달 성능이 비교적 우수함을 입증하였다.

  • PDF

The Characteristics of Thermal Diffusion With the Vertical-Closed Loop Type Geothermal Heat Exchanger (수직밀폐형 지중열교환기의 온도분포 특성)

  • Sun, Jong-Cheol;Kim, Byung-Chul;Koh, Young-Ha
    • Journal of the Korean Solar Energy Society
    • /
    • v.33 no.1
    • /
    • pp.57-65
    • /
    • 2013
  • The temperatures with the ground depth, the positions of circulation water in ground heat exchanger were measured and thermal diffusion characteristics with the distances of the direction normal to the borehole was analysed. The deeper the depth of ground, the less the influences of outdoor temperature, but below 10m of ground, there was no influences of ground temperature. When the depth of trench pipe was below the depth of 2m, there was no influence. In the ground of 10m when the distances between the pipe and the other places were above 0.5m, the variations of temperature were less than $1.6^{\circ}C$ and above 2.5m they were less than $0.1^{\circ}C$. When the distances of bore hole were above 5m, there were no. influences of the nearest ground heat exchanger.

Application textile-type geothermal heat exchanger for tunnel (텍스타일형 지중열교환기의 터널에서의 적용)

  • Lee, Chul-Ho;Lee, Kang-Ja;Gil, Hu-Jeong;Jeoung, Jae-Hyeung;Choi, Hang-Seok
    • 한국신재생에너지학회:학술대회논문집
    • /
    • 2009.06a
    • /
    • pp.604-607
    • /
    • 2009
  • The geothermal energy have been developed as the pro-environmental and the substantial long-term energy. Recently energy foundations and other thermo-active ground structures have been developed to enhance the use of geothermal energy. In this research, a tunnel wall is focused as a source of geothermal energy. If the tunnel wall can be used for geothermal source, it can provide relatively lower cost because it is not necessary to make a deep borehole like in case of closed-loop vertical ground heat exchanger. For analyzing efficiency of heat exchanger in tunnel, laboratory tests and the numerical analyses are performed.

  • PDF

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
    • /
    • 2007.11a
    • /
    • pp.423-428
    • /
    • 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.

  • PDF

Development of an Electric Circuit Transient Analogy Model in a Vertical Closed Loop Ground Heat Exchanger (수직밀폐형 지중열교환기의 회로 과도해석 상사모델 개발)

  • Kim, Won-Uk;Park, Hong-Hee;Kim, Yong-Chan
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.24 no.4
    • /
    • pp.306-314
    • /
    • 2012
  • Several numerical or analytical models have been proposed to analyze the thermal response of vertical ground heat exchangers (GHEX). However, most models are valid only after several hours of operation since they neglect the heat capacity of the borehole. Recently, the short time response of the GHEX became important in system simulation to improve efficiency. In this paper, a simple new method to evaluate the short time response of the GHEX by using an analogy model of electric circuit transient analysis was presented. The new transient heat exchanger model adopting the concept of thermal capacitance of the borehole as well as the steady-state thermal resistance showed the transient thermal resistance of the borehole. The model was validated by in-situ thermal response test and then compared with the DST model of the TRNSYS program.

Heat Transfer Performance of Pond loop type Heat Exchanger for Ground Source Heat Pump using Extruding Ground Wafer (유출지하수 열원 지열히트펌프용 Pond Loop형 열교환기의 열전달 성능)

  • Park Geun-Woo;Kim Jin-Sang;Lee Eung-Youl
    • New & Renewable Energy
    • /
    • v.2 no.2 s.6
    • /
    • pp.86-93
    • /
    • 2006
  • 유출지하수나 지표수를 열원으로 지열히트펌프의 지초자료로 활용하기 위하여 Pond Loop형 열교환기를 설계, 제작하여 유동이 없는 수조 내에서 수조의 온도가 변화함에 따라 일정한 열교환기 입구온도를 유지하면서 열전달량을 측정하였다. 그 결과 수조를 Heat Source로 사용하는 경우 $5,500{\sim}4,500kcal/h$의 열량이 전달되었고 수조를 Heat Sink로 사용할 경우 $5,200{\sim}3,500kcal/h$의 열량이 전달되었다. 또한 열교환기 관내 유속이 증가함에 따라 열전달량이 증가하는 경향성을 확인할 수 있었고 이는 동시에 열교환기 입출구의 차압을 증가시킴을 알 수 있었다. 열교환기의 설계단계에서 사용하였던 열전달관계식으로 구한 총괄열전달계수, U와 실험값을 통해 유추한 U값을 비교한 결과 실험에 의해 유추된 U값이 $24{\sim}27%$ 설계치보다 크게 나타났다. 본 연구를 통하여 유출지하수 뿐만 아니라 하수 및 하천수를 이용한 지열히트펌프의 기초자료를 확보할 수 있었다.

  • PDF

Study on physical characteristics of Graphite-added bentonite grout for backfilling closed-loop groud heat exchanger (수직 밀폐형 지중 열교환기용 뒤채움재로서 흑연(Graphite)을 첨가한 벤토나이트 그라우트재의 물리적 특성연구)

  • Lee, Kang-Ja;Gil, Hu-Jeong;Lee, Chul-Ho;Choi, Hang-Seok;Choi, Hyo-Pum
    • Proceedings of the Korean Geotechical Society Conference
    • /
    • 2009.03a
    • /
    • pp.179-187
    • /
    • 2009
  • Bentonite-based grouting has been popularly used to seal a borehole installed for a closed-loop vertical ground heat exchanger in a geothermal heat pump system (GHP) because of its high swelling potential and low hydraulic conductivity. The bentonite-based grout, however, has relatively lower thermal conductivity than that of ground formation. Accordingly, it is common to add some additives such as silica sand to the bentonite-based grout for enhancing thermal performance. In this study, graphite is adapted to substitute silica sand as an addictive because graphite has very high thermal conductivity. The effect of graphite on the thermal conductivity of bentonite-based grouts has been quantitatively evaluated for seven bentonite grouts from different product sources. In addition, comparisons of viscosity between applications of graphite and silica sand as additives has been carried out. In conclusion, using graphite has thermal conductivity about three times higher than that of silica sand.

  • PDF

Heat transfer analysis of closed-loop vertical ground heat exchangers using 3-D fluid flow and heat transfer numerical model (3차원 열유체 수치해석을 통한 현장 시공된 수직 밀폐형 지중열교환기의 열전달 거동 평가)

  • Park, Moon-Seo;Lee, Chul-Ho;Min, Sun-Hong;Kang, Shin-Hyung;Choi, Hang-Seok
    • Proceedings of the Korean Geotechical Society Conference
    • /
    • 2010.09a
    • /
    • pp.800-807
    • /
    • 2010
  • In this study, a series of numerical analyses has been performed in order to evaluate the performance of a full-scale closed-loop vertical ground heat exchanger constructed in Wonju. The circulation pipe HDPE, borehole and surrounding ground were modeled using FLUENT, a finite-volume method (FVM) program, for analyzing the heat transfer process of the system. Two user-defined functions (UDFs) accounting for the difference in the temperatures of the circulating inflow and outflow water and the change of the surrounding ground temperature with depth were adopted in the FLUENT model. The thermal properties of materials estimated in laboratory were used in the numerical analyses to compare the thermal efficiency of the cement grout with that of the bentonite grout used in the construction. The results of the simulation provide a verification of the in situ thermal response test data. The numerical model with the ground thermal conductivity of 4W/mK yielded the simulation result closer to the in-situ thermal response test than with the ground thermal conductivity of 3W/mK. From the results of the numerical analyses, the effective thermal conductivities of the cement and bentonite grouts were obtained to be 3.32W/mK and 2.99 W/mK, respectively.

  • PDF