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장창규,최창호,이철호,이장근 한국지반공학회 2013 한국지반공학회논문집 Vol.29 No.8
Soil freezing is a phenomenon arising due to temperature difference between atmosphere and ground, and physical properties of soils vary upon the phase change of soil void from liquid to solid (ice). A heat-transfer mechanism for this case can be explained by the conduction in soil layers and the convection on ground surface. Accordingly, the evaluation of proper thermal properties of soils and the convective condition of ground surface is an important task for understanding freezing phenomenon. To describe convection on ground surface, simplified coefficient methods can be applied to deal with various conditions, such as atmospheric temperature, surface vegetation conditions, and soil constituents. In this study, two methods such as n-factor and convection coefficient for the convective ground surface boundary were applied within a commercial numerical program (TEMP/W) for modeling soil freezing phenomenon. Furthermore, the numerical results were compared to laboratory testing results. In the series of the comparison results,the convection coefficient is more appropriate than n-factor method to model the convective boundary condition.
장창규,최창호,이장근,이철호 한국지반공학회 2014 한국지반공학회논문집 Vol.30 No.9
The ground in cold region consists of active and permafrost layers. The active layer at the unstable state may cause ground corrosion and uplift, when the temperature of frozen ground increases due to seasonal changes. The thermosyphon is one of the stabilization methods to maintain the ground stability in the frozen ground. The thermosyphon is a closed two-phase convection device that extracts heat from the ground and discharges it into the atmosphere. In this study, ground freezing experiment using a thermosyphon and simulated ground with the isolation material was conducted to evaluate the thermal performance of the thermosyphon. In order to consider the thermal performance of the thermosyphon, commercial numerical program (TEMP/W) was adopted. Likewise, the thermal performance of thermosyphon and thermal properties of ground were applied in the numerical model. In a series of comparisons with experiment results and numerical study, thermal performance of thermosyphon can be evaluated.
실내실험과 수치해석을 통한 열사이펀의 지반 열전달 성능에 관한 연구
장창규(Changkyu Jang),최창호(Changho Choi),이장근(Jangguen Lee),이철호(Chulho Lee) 한국지반신소재학회 2014 한국지반신소재학회 학술발표회 Vol.2014 No.4
The thermosyphon is a closed natural two-phase convection device that extracts heat from the ground and discharges it into atmosphere. It has a pressure vessel with a condenser section above the ground surface and an evaporator section installed within the frozen ground. Exchange of heat operates throughout the winter as long as the air temperature is colder than the ground. Because of stabilizing in frozen ground, the thermosyphon is gradually employed to structures such as pipeline and roadways. In This study, numerical study and experimental study were conducted to investigate the thermal performance of the thermosyphon which was subject to different temperatures. The experimental results were analyzed in terms of effective thermal conductance with operating temperature.
동결 모델링을 통한 주문진사의 열전달계수와 표면 대류 열전달계수 산정
장창규(Changkyu Jang),최창호(Changho Choi),이장근(Jangguen Lee),이철호(Chulho Lee) 한국지반신소재학회 2013 한국토목섬유학회 학술발표회 Vol.2013 No.11
Soil freezing phenomenon occurred mainly due to temperature difference between ground and air on the ground surface. A heat transfer mechanism of frozen ground is accounted for the conduction in soil particles and convection on the ground surface. In this study, convection coefficient were applied to model soil freezing phenomenon. In order to evaluate the convection coefficient, a commercial numerical program (TEMP/W) and laboratory test were conducted. In the series of the comparison, the convection coefficient on the ground surface was appropriately within 9 W/m²k
에너지 텍스타일에서 배수재에 의한 열교환기의 열성능 변화
이철호(Chulho Lee),장창규(Changkyu Jnag),박상우(Sangwoo Park),최항석(Hangseok, Choi) 한국지반신소재학회 2013 한국토목섬유학회 학술발표회 Vol.2013 No.11
To evaluate effects of the drainage layer in the energy textile, as a continuing study from preliminary research, the simulation for daily cooling and heating operation were performed. In this study, a long-term monitoring has been performed to evaluate the heat exchange rate of each constructed energy textile by simulating daily cooling and heating schedule. Using FLUENT, a 3D finite-volume-method program, a numerical model was carried out to simulate the field test for each energy textile with consideration of air temperature inside the tunnel and drainage layer. After verification of numerical model for field conditions, effect of drainage layer in energy textile was evaluated. From the CFD numerical analyses, average increasing of heat exchange is about 8% in this case due to the drainage layer in energy textile.