• The Transactions of the Korean Institute of Electrical Engineers P
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• v.62 no.1
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• pp.6-11
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• 2013

In this paper, the temperature characteristics of mold transformer for the distribution power system have been analyzed by using computational fluid dynamics(CFD). The model has been modeled by coil, cores, insulating materials and frames about 3MVA grade mold transformer and analyzed the temperature distribution of the structure with a heat fluid. The fluid, which is incompressible ideal gas, is analyzed as a turbulent flow phenomenon on the assumption that it is natural cooling of transformer cooling system. Through this study, by examining the temperature distribution and hot-spot of the structure field of the mold transformer, cooling design and temperature distribution information, which are demanded for designing are estimated.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.2017-2022
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• 2004

There are multistage preheaters in the power generation plan to improve the thermal efficiency of the plant and to prevent the components from the thermal shock. The energy source of these heaters comes from the extracted two phase fluid of working system. These two-phase fluid can cause the so-called Flow Accelerated Corrosion(FAC) in the extracting piping and the bubble plate of the heater for example, in case of point Beach Nuclear Power Plant and in the Wolsung Nuclear Power Plant. The FAC is due to the mass transport of the thin oxide layer by the convection. FAC is dependent on many parameters such as the operation temperature, void fraction, the fluid velocity and pH of fluid and so on. Therefore, in this paper velocity was calculated by FLUENT code in order to find out the root cause of the wall thinning of the feedwater heaters. It also includeed in the fluid mixing analysis model are around the number 5A feedwater heater shell including the extraction pipeline. To identify the relation between the local velocities and wall thinning, the local velocities according to the analysis results were compared with distribution of the shell wall thicknes by ultrasonic test.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.474-478
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• 2008

It has been shown that a nanofluid consisting of nanoparticles dispersed in base fluid has much higher effective thermal conductivity than pure fluid. In this study, four kinds of nanofluids such as multiwalled carbon nanotube (MWCNT) in water, CuO in water, SiO2in water, and CuO in ethylene glycol, are produced. Their thermal conductivities are measured by a transient hot-wire method. The thermal conductivity of water-based MWCNT nanofluid is shown to be increased by up to 11.3% at a volume fraction of 0.01. The measured thermal conductivities of MWCNT nanofluids are higher than those calculated with Hamilton-Crosser's model due to neglecting solid-liquid interaction at the interface. The results show that the thermal conductivity enhancement of nanofluids depends on the thermal conductivities of both particles and the base fluid. Stability of nanofluids is estimated by UV-vis spectrum analysis. Stability of nanofluid depends on the type of base fluid and the suspended particles. Also it can be improved in addition of a surfactant.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.12
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• pp.1627-1633
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• 2011

Injection molds are generally fabricated by assembling a number of plates in which the core and cavity components are assembled. This assembled structure has a number of contact interfaces where the heat transfer characteristics are affected by thermal contact resistance. In previous studies, numerical approaches were investigated to predict the effect of thermal contact resistance on the temperature distribution of injection molds. In this study, thermal-fluid coupled numerical analyses are performed to take into account the thermal contact effect on the numerical evaluation of the mold filling characteristics. Comparisons with experimental results show that the proposed coupled analysis provides more reliable results than the conventional analyses in predicting the mold filling characteristics by taking into account the effect of thermal contact resistance inside the injection mold assembly.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.385-395
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• 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.

• International Journal of Fluid Machinery and Systems
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• v.2 no.1
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• pp.55-60
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• 2009

The present study investigated temperature and thermal stress distributions in a film cooling system with normal injection cooling flow. 3D-numerical simulations using the FEM commercial code ANSYS were conducted to calculate distributions of temperature and thermal stresses. In the simulations, the surface boundary conditions used the surface heat transfer coefficients and adiabatic wall temperature which were converted from the Sherwood numbers and impermeable wall effectiveness obtained from previous mass transfer experiments. As a result, the temperature gradients, in contrast to the adiabatic wall temperature, were generated by conduction between the hot and cold regions in the film cooling system. The gradient magnitudes were about 10~20K in the y-axis (spanwise) direction and about 50~60K in the x-axis (streamwise) direction. The high thermal stresses resulting from this temperature distribution appeared in the side regions of holes. These locations were similar to those of thermal cracks in actual gas turbines. Thus, this thermal analysis can apply to a thermal design of film cooling holes to prevent or reduce thermal stresses.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.6 no.4
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• pp.81-85
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• 2007

A safety valve is used for protecting the pressure vessel and facilities by discharging the operating fluid into the valve from the accident when the pressure is over the designated value. The fluid is sulfurous acid and nitric acid. etc. in the semi-conductor assembly line. Thus the valve elements material must be acid resistance. Teflon, which is used generally as inner parts of a valve, tends to easily sticks to sliding surface by thermal expansion under high temperature. Some studies are performed to change teflon to another material and shape to have a better fluidity under the condition. The analysis of the thermal expansion is conducted by commercial FEM software to improve the problems. Boundary conditions were temperature and load in this study. From the analysis, the thermal expansion of stainless steel is verified to be lower than that of teflon under high temperature. Thus coupled teflon/stainless steel-made valve is applied to assembly line without danger due to thermal expansion.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.15 no.2
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• pp.38-43
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• 2006

A turbine blade operates under high temperature, high pressure, and the loads have the characteristics that the amplitudes change. Therefore, it is important to perform a stress analysis considering thermal and pressure loads. The purpose of this study is to investigate the effects of these loads on gas turbine blade through thermal stress analysis. The analysis results shows that pressure in gas fluid flow around blade is high in leading edge part, Gas temperature is connections with pressure of flow around blade. The distribution of stress from blade is appearing as is different at suction side and pressure side.

• Journal of the Korea Institute of Military Science and Technology
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• v.15 no.2
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• pp.130-137
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• 2012

In this paper, a post-analysis of cooling system for infrared(IR) window was performed based on heating experiment of IR window system. We applied the same experimental conditions to analysis, and then validated the analysis technique by comparing numerical and experimental results. For an analysis software, we used a professional heat/fluid analysis program and the numerical and experimental results were in fairly good agreement. We investigated the effect of thermal transfer between the frame and IR window and also a cooling efficiency between fluid and structure in order to determine the proper parameters for the analysis. In this study, 100 % thermal transfer between the frame and IR window and 30 % cooling efficiency between fluid and structure have been proposed, which can be used in the future conceptual design and analysis of similar IR windows.

• Nuclear Engineering and Technology
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• v.53 no.5
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• pp.1540-1555
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• 2021

The plate-type fuel assembly adopted in nuclear research reactor suffers from complicated effect induced by non-uniform irradiation, which might affect its stress conditions, mechanical behavior and thermal-hydraulic performance. A reliable numerical method is of great importance to reveal the complex evolution of mechanical deformation, flow redistribution and temperature field for the plate-type fuel assembly under non-uniform irradiation. This paper is the first part of a two-part study developing the numerical methodology for the thermal-fluid-structure coupling behaviors of plate-type fuel assembly under irradiation. In this paper, the thermal-fluid-structure coupling methodology has been developed for plate-type fuel assembly under non-uniform irradiation condition by exchanging thermal-hydraulic and mechanical deformation parameters between Finite Element Model (FEM) software and Computational Fluid Dynamic (CFD) software with Mesh-based parallel Code Coupling Interface (MpCCI), which has been validated with experimental results. Based on the established methodology, the effects of non-uniform irradiation and fluid were discussed, which demonstrated that the maximum mechanical deformation with irradiation was dozens of times larger than that without irradiation and the hydraulic load on fuel plates due to differential pressure played a dominant role in the mechanical deformation.