• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.707-712
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• 2006

Knowing the ground thermal conductivity is very importnat in designing ground heat exchangers. Knowledge of the ground soil and rock composition information dose not guarantee the prediction of accurate thermal information. In Situ testing of ground heat exchangers is becoming popular. However, in situ testing are performed at construction sites in real life. Adequate data collection and analysis are not easy mainly due to poor power quality. Power fluctuation also causes the fluctuation of received data. The power quality must be maintained during the entire in situ testing processes. To accurately analyse the test data, the understanding of the response of the power fluctuation is essential. Testing under the power quality varied by tester is very difficult. Analyzing power variation by numerical simulation is a realistic option. By varying power in a sinosuidal manner, its effects on predicting thermal conductivity from thermal response plots made from the test data are examined.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.263-268
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• 2010

Thermal characterization of geomaterials has significant implication on the geothermal energy, disposal of nuclear wastes, geological sequestration of carbon dioxides and recovery of hydrocarbon resources. Heat transfer in multiphase materials is dominated by the thermal conductivity of consisting components, porosity, degree of saturation and overburden pressure, which have been investigated by the empirical correlation at macro-scale. The thermal measurement by Transient Plane Source (TPS) and associated algorithm for interpretation of thermal behavior in geomaterials corroborate the robustness of sensing techniques. The method simultaneously provides thermal conductivity, diffusivity and volumetric heat capacity. The newly introduced thermal network model enables estimating thermal conductivity of geomaterials subjected to the effective stress, which has not been evaluated using previous thermal models. The proposed methods shows the applicability of reliability of TPS technique and thermal network model.

• Tunnel and Underground Space
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• v.5 no.4
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• pp.323-335
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• 1995

지열에너지 개발의 기본적 개념은 지하 심부의 고온건조암체에 시추공을 이용한 수압파쇄를 실시하여 고온건조암체내에 인공파쇄대를 형성함으로써 유체의 유동회로를 구축하여 지열에너지의 회수를 도모하는 것이다. 본 논문에서는 수압파쇄균열의 발전방향 조절문제와 관련하여, 초고압수 절삭장치를 이용, 수압파쇄공 내에 인공슬롯을 형성하여 수압파쇄를 실시함으로써 균열의 발전방향을 조사하였으며, 수압파쇄에 의한 파쇄대내로의 유체순환실험을 통해 지열수의 유동특성을 규명하였다. 이를 위해 모델에 종균열과 횡균열을 형성시키고 균열내에 주입되는 물의 주입률, 정상류압력, 흐름저항을 조사하고, 이 결과를 이용하여 전산모델링을 수행하였다. 인공절리면에 대한 투수시험에서는 10$0^{\circ}C$까지의 온도변화에 따라 투수계수가 증가하였으며, 봉압 증가에 따라 증가율이 현저히 감소하였다.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.583-587
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• 2009

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.

• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.36-39
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• 2006

To evaluate the effect of groundwater flow on the outlet temperature of a geothermal heat pump, 3 dimensional numerical simulations are performed considering both groundwater flow and pipe flow in the U-tube using TOUGHS, The present study involved the following 4 simulation cases (1) no groundwater flow, (2) slow groundwater flow (hydraulic conductivity: $1.0{\times}10^{-9}m/s)$, (3) fast groundwater flow (hydraulic conductivity, $1.0{\times}10^{-7}m/s$), and (4) groundwater flow varying with the depth (hydraulic conductivity: $1.0{\times}10^{-7}-1.0{\times}10^{-10}m/s$). The effect of groundwater flow on the outlet temperature is significant where hydraulic conductivity of aquifer is $1.0{\times}10^{-7}m/s$. Where hydraulic conductivity of aquifer is $1.0{\times}10^{-10}m/s$, however, that effect is negligible.

• 전기의세계
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• v.23 no.2
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• pp.7-10
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• 1974

최근 신문, 잡지에 에너지문제에 관한 기사가 많이 기재됨은 내일의 에너지 위기에 대한 긴박감을 느끼기 때문이라고 생각된다. 지구상의 인구가 증가하는 한, 또 소득이 높아 에너지 소비가 증대하는 한, 현재의 화석연료(fossil fuel)를 주체로 하는 에너지원의 방향을 달리하여야 할 것이다. 왜냐하면 근시관적 경지에서는 석유매장량의 한계, 산유국에 대한 국제정세의 불안, 핵분열에 의한 방사능 폐기물, 온배수의 오염, 화석연료의 연소에 따르는 공해문제등이고, 원시관적입장에서는 자원의 고갈때문에 장래는 석유, 천연gas, 때로는 석탄까지도 오히려 인류의 의식주의 원료로 취급되어야 할 것이 아닌가 하는 생각이 든다. 따라서 현재의 에너지원을 대치할 수 있는 원자력, 태양에너지, 지열(geothermal)에너지 또는 핵융합반응에너지에 기대를 거는 비중이 날로 커지고 있다. 본문에서는 태양에너지(solar energy)원을 좌표로한 지구에너지 system에서 직접 혹은 간적적으로 우리 생활을 위한 에너지 변환을 할 수 있는 방법을 생각해 본다.

• Journal of Biosystems Engineering
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• v.22 no.4
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• pp.459-468
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• 1997

To optimize the design and operation of a soil- air heat exchanger system, the effects of variables characterizing system design and operation on the performance of the system were analyzed by a theoretical model which included the three-dimensional transient heat conduction equation. The solution of the theoretical model was acquired by a computer program that uses Finite Difference Methods and Gauss-Seidel iteration computation, in which the time discretization scheme was an implicit difference appoximation. The computer program was validated first by comparison of the results for different grid sizes. Air outlet temperature, energy gain, and heat exchange efficiency of the system were analyzed based upon the tube diameter, tube length, tube thickness, and tube thermal diffusivity.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.572-575
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• 2009

지층 내에 발달한 고투수성 단층은 유체, 에너지, 그리고 용질이 이동하는데 있어서 중요한 역할을 하는 지질구조이다. 따라서 고투수성 단층 주변부에서는 온천, 지열 이상대, 그리고 금속 광상 등이 형성될 가능성이 크다. 이 연구에서는 열-수리적 거동 모델링을 통하여 단층에 의한 온천 또는 지열 이상대의 형성 원인을 확인하였다. 단층의 구조에 따른 지하수 유동과 이에 따른 지층 내 열적 상태를 확인하기 위해서 단층 구조가 다른 3가지의 경우에 대해서 2차원 열-수리적 거동 정류 모델링을 수행하였다. 모델링 결과 단층 구조가 다른 3가지의 모든 경우에서 단층의 투수율이 커지면 단층대에서의 용출 온도가 초기 온도 보다 높아지는 경향을 확인 할 수 있고, 경우에 따라서 모암의 투수율 역시 용출온도에 영향을 미치는 것을 확인 하였다. 따라서 심부지열 개발을 위한 연구지역에 대해 보다 정확한 예측 모델링을 수행하기 위해서는 단층의 구조, 단층과 모암의 투수율, 그리고 수리지질학적 정보 등이 매우 중요하다고 할 수 있다.

• Journal of the Korean Society of Industry Convergence
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• v.18 no.4
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• pp.224-230
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• 2015

In this paper, it is presented a learning controller for repetitive walking control of biped walking robot. We propose the iterative learning control algorithm which can learn periodic nonlinear load change ocuured due to the walking period through the intelligent control, not calculating the complex dynamics of walking robot. The learning control scheme consists of a feedforward learning rule and linear feedback control input for stabilization of learning system. The feasibility of intelligent control to biped robotic motion is shown via dynamic simulation with 25-DOF biped walking robot.

• Journal of the Korean Society of Industry Convergence
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• v.18 no.4
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• pp.231-240
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• 2015

In this paper, it was presented to design and analyze the kinematics of grasping a rigid object by means of multi-degrees-of-freedom hand fingers. It is shown firstly that a set of kinematic equation describing dynamics system of the arm and object together with geometric constraint of tight area-contacts is formulated by Lagrange's equation. It has been presented secondly that the problems of controlling both the forces of pressing object and the rotation angle of the object under the geometric constraints are discussed. In this research, the control method for static stable grasping and enhancing dexterity in manipulating things is proposed. It is illustrated by computer simulation that the control system gives the performance improvement in the kinematic grasping of the hand fingers of robot.