• Journal of Welding and Joining
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• 제15권4호
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• pp.99-108
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• 1997

Analytical model for the temperature distribution and the cooling rate of weld in dual beam laser welding is presented for investigating the possibility of controling the cooling rate. The model is based on the solutions to the problem of heat flow due to the distributed and line heat sources for preheating and welding respectively in plates with finite thickness. The effects of beam power, beam distribution parameter, interbeam distance, and welding speed on the resulting temperature distribution and cooling rate are presented. The cooling rates of dual beam laser weld at the weld centerline under the investigated conditions are reduced to as one third of those of welds which were produced by single beam laser. And it appeared that the cooling rate of dual beam laser weld is strongly dependent on the process parameters of preheating laser beam power and welding speed.

• 설비공학논문집
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• 제12권9호
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• pp.802-809
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• 2000

This study numerically analyzes the thermal and flow characteristics inside the header in PFHE(parallel-flow heat exchanger) by employing a three-dimensional turbulence modeling. The following quantities are examined by varying the injection angle of the working fluid, the location of entrance and the shape of entrance: flow nonuniformity, heat transfer rate, and flow distribution in each passage. The result shows that the degree of significance among the parameters affecting the header part is in the order of the injection angle, the shape of entrance, and the location of entrance. The result also indicates that heat transfer rates compared to the reference model are increased by about 152% for the angle of injection of -$20^{\circ}C$, by about 127% for the shape of entrance with right and left long rectangular form, and by about 108% for the location of entrance located at the lowest Position.

• 한국환경과학회지
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• 제11권6호
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• pp.543-551
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• 2002

A Numerical simulation on the thermal flow performance was carried out to propose the incinerator type for the domestic refuses and to investigate the design factor and operating conditions. The SSTI(Standard Stoker Type Incinerator) proposed in this study was modified from the type with central f)ow. It has the characteristics of good mixing between refuse and hot combustion gas in primary combustion chamber and between unburned gas inflowing and secondary air jet in secondary chamber. By predictive results, the SSTI was no recirculation zone in secondary chamber so that mixing time was increased with high residence time. It has good characteristics of combustion and low emission. Parametric screening studies have been understood with phenomenon of combustion in incinerator.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1472-1475
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• 2004

Current processor power consumption has dramatically increased and already reached 115 Watts. Therefore, Heat sink design needs more high accuracy in 1U server. The target performance of heat sink is very dependent of fin geometry and it is also seriously affected by design conditions such as fan type, air duct shape and heatsink design parameters. The present paper investigates the behavior of heat sink performance under various conditions. The present work addresses pressurized type plane fin heat sinks having dimension of 40 mm by 40 mm by 56 mm fan.

• Journal of Welding and Joining
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• 제8권1호
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• pp.62-69
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• 1990

Being focused on the recent studies that the fatigue strength of resistance spot weldmentes can be improved by using ellipsoidal weld nuggets, the voltage and temperature distribution in resistance spot weldments were simulated for the various rectangular electrodes which had the different aspect ratio of the contact area. Because the electrode shape was not axi-symmetric, the solution domain for simulation should be three dimensional. A series of experiments were carred out to verify the analytically obtained temperature distribution in the weldment. From the calculational and experimental results, it could be revealed that the nugget took the form of ellipsoid, while both results showed a considerable discrepancy for the high aspect ratio.

• 한국주조공학회지
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• 제32권3호
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• pp.133-137
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• 2012

Chill vent has a zigzag venting path which allows residual air or gases to exhaust out very quickly from the die cavity. However molten metal sometimes comes out through the gas venting surfaces causing flash. Effect of designing factors of chill vent and processing variables in high pressure die casting on the performance of chill vent was investigated through a series of calculations by using a commercial code. The most influential factor was the thickness of chill vent, followed by inlet velocity, vent width and die temperature.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2012년도 제45회 KOSCO SYMPOSIUM 초록집
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• pp.147-148
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• 2012

The syngas produced from coal gasification is cooled down for gas cleaning by a syngas cooler that produces steam. Due to the presence of fly slag in the syngas, erosion, slagging and corrosion especially in the upper part of the syngas cooler may cause major operational problems. This study investigates the flow, heat transfer and particle behaviors in the syngas cooler of a 300MWe IGCC plant by using computational fluid dynamics. For various operational loads and geometry, the gas and particle flows directly impinged on the wall opposite to the syngas inlet, which may lead to erosion of the membrane wall. In the evaporate channels inside the syngas cololr, the particle flows were concentrated more on the outer channel where slagging becomes more serious. The heat transfer to the wall was mainly by convection which was larger on the side wall below the inlet level.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 춘계학술대회 논문집
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• pp.685-689
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• 2004

Numerical simulation is conducted to clarify the heat transfer and fluid flow characteristics of HVAC(Heating, Ventilating and Air-Conditioning) for double' deck train. The HVAC system is installed under the roof of carbody. In the lay-out of HVAC system, air duct must be installed to supply air to 1st and 2nd floor respectively. The standard k-$\epsilon$ and LES models for turbulence and SIMPLE algorithm for pressure equation hased on finite volume method are used to solve the physic a] HVAC model. To assure convergence, QUICK scheme for momentum equation and the 2nd order upwind scheme for turbulent equations arc used. From the results of simulation, the temperature and velocity magnitude are also distributed uniformly in the interior of double-deck passenger car.

• Journal of Welding and Joining
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• 제18권3호
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• pp.76-82
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• 2000

In this study, three-dimensional heat flow in laser beam welding for deep penetration was analyzed by using F.E.M common code, and then the results were compared with the experimental data. The models for analysis are full penetration welds and are made at three different laser powers (6, 9.9, 4.5 kW) with two different welding speeds (5.8mm/s, 5mm/s). The characteristics of thermal absorption by the workpiece during deep penetration laser welding can be represented by a combination of line heat source through the workpiece and distributed heat source at the top surface due to the plasma plume above the top surface. This gives an insight into the way in which the beam interacts with the material being welded. The analyses performed with the combined heat source models show comparatively good agreement between the experimental and calculated melt temperature isotherm, i.e, the fusion zone boundary. The results are used to explain the "nail head" appearance of fusion zone, which is quite common in laser beam welds.eam welds.

• 한국공작기계학회논문집
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• 제10권1호
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• pp.65-70
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• 2001

The hear transfer mechanism initiating the friction welding is examined and a transient three dimensional heat conduc-tion model for the welding of two dissimilar cylindrical metal bars is investigated. The cylindrical metal bars are made of materials made of A2024 and SM 45C. Numerical simulations of heat flow are performed using the finite volume method. Respectively. Commercial FLUENT code is used in the heat flow simulation and maximum temperature and distribution of temperature are calculated. Temperature of friction welded joining face is compared with the temperature distribution measured by experiment and numerical simulation. The maximum temperature of friction welded joining face is lower than melting point of A2024-T6 aluminum alloy using insert metal. The temperature distribution of friction welded join- ing face with insert metal is more uniform than that of without inset metal.