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파이프 순환수의 수치해석 모사를 통한 수직 밀폐형 지중열교환기 단면의 열전달 효율 평가
길후정(Gil, Hu-Jeong),이강자(Lee, Chul-Ho),이철호(Lee, Kang-Ja),최항석(Choi, Hang-Seok) 한국신재생에너지학회 2009 한국신재생에너지학회 학술대회논문집 Vol.2009 No.06
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 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 the thickness of HDPE pipe and grout thermal properties, 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.
흑연(Graphite) 첨가를 통한 수직 밀폐형 지중열교환기 뒤채움재의 열전도 특성 향상 연구
이강자(Lee, Kang-Ja),길후정(Gil, Hu-Jeong),이철호(Lee, Chul-Ho),최항석(Choi, Hang-Seok),최효범(Choi, Hyo-Pum) 한국신재생에너지학회 2009 한국신재생에너지학회 학술대회논문집 Vol.2009 No.06
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.
이철호(Lee, Chul-Ho),이강자(Lee, Kang-Ja),길후정(Gil, Hu-Jeong),정재형(Jeoung, Jae-Hyeung),최항석(Choi, Hang-Seok) 한국신재생에너지학회 2009 한국신재생에너지학회 학술대회논문집 Vol.2009 No.06
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.
Fluid loss 시험을 통한 벤토나이트 필터케익의 투수계수 평가
웽테바오 ( Nguyen The-bao ),이철호 ( Lee Chulho ),박문서 ( Park Moonseo ),길후정 ( Gil Hujeong ),최항석 ( Choi Hangseok ) 한국구조물진단유지관리공학회 2009 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.13 No.2
The mixture of bentonite powder and water is widely used in the construction of vertical cutoff walls to maintain the stability of excavation surfaces. The filter cake possesses a very low hydraulic conductivity compared to that of the cutoff wall. This paper presents the hydraulic conductivities of bentonite filter cakes of three types of bentonites measured by the modified fluid loss test under various pressure levels. Theory of filtration process was reviewed to explain the procedure in the experiment.
Fluid loss 시험을 통한 벤토나이트 필터케익의 투수계수 평가
웽테바오(Nguyen, The-Bao),이철호(Lee, Chulho),박문서(Park, Moonseo),길후정(Gil, Hujeong),최항석(Choi, Hangseok) 한국구조물진단유지관리학회 2009 한국구조물진단학회 학술발표회논문집 Vol.2009 No.2
The mixture of bentonite powder and water is widely used in the construction of vertical cutoff walls to maintain the stability of excavation surfaces. The filter cake possesses a very low hydraulic conductivity compared to that of the cutoff wall. This paper presents the hydraulic conductivities of bentonite filter cakes of three types of bentonites measured by the modified fluid loss test under various pressure levels. Theory of filtration process was reviewed to explain the procedure in the experiment.
수직 밀페형 지증 열교환기용 뒤채움재의 열전도 및 점도특성 연구
최항석(Choi, Hang-Seok),이철호(Lee, Chul-Ho),길후정(Gil, Hu-Jeong),최효범(Choi, Hyo-Pum),우상백(Woo, Sang-Baik) 한국신재생에너지학회 2007 한국신재생에너지학회 학술대회논문집 Vol.2007 No.11
In order to characterize the thermal conductivity and viscosity of grout materials used for backfilling ground heat exchangers, nine bentonite grouts and cement grouts being adapted in the United State have been considered in this study. The bentonite grouts indicate that the thermal conductivity and viscosity increase with the content of bentonite or filler (silica sand). In addition, material segregation can be observed when the viscosity of grout is relatively low. The saturated cement grouts appear to possess much higher thermal conductivity than the saturated bentonite grouts, and the reduction of thermal conductivity in the cement grouts after drying specimens is less than in case of the bentonite grouts. Maintaining the moisture content of grouts is a crucial factor in enhancing the efficiency of ground heat exchangers.