• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.12
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• pp.1007-1017
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• 2003

An experimental study on the air-side pressure drop and heat transfer coefficient of slit fin-tube heat exchanger has been carried out. The data reduction methodology for air-side heat transfer coefficients in the literature is not based on a consistent approach. This paper focuses on new method of data reduction to obtain the air-side performance of fin-tube heat exchanger using R22 and recommends standard procedures for dry and wet surface heat transfer estimation in fin-tube heat exchanger having refrigerant on the tube-side. Results are presented as plots of friction f-factor and Colburn j -factor against Reynolds number based on the fin collar outside diameter and compared with previous studies. The data covers a range of refrigerant mass fluxes of 150∼250 kg/$m^2$s with air flows at velocity ranges from 0.3 m/s to 0.8 m/s.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.5
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• pp.490-498
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• 2004

This paper measures the forced convective heat transfer from heated cylinder to air flow in a rectangular duct at Re$_{D}$ =2,337, 4,589, 6,621 and 7,944 through experiments. And the heat transfer is computed by 3-D numerical computation in which various turbulent models are applied. It is shown through the comparison of experimental and computed data that numerical computation with standard k-$\varepsilon$ model predicts the experimental data most accurately. Furthermore, the correlation from the computed heat transfer is almost similar to that from the experiment when Re$_{D}$ is greater than 4,589. In addition, the correlation of McAdams is the closest to that from experimental data among various correlations from literature in the range of Reynolds number.ber.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.10
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• pp.936-941
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• 2000

Advanced space transportation systems, such as the National Aerospace Plane or an Orbital Transfer Vehicle, have atmospheric maneuvering capabilities. For such vehicles the use of aeroassisted orbital transfer from a high Earth orbit to a low Earth orbit, with unpowered flight in the atmosphere, has the potential for significant fuel savings compared to exoatmospheric Hohmann transfer. However, to exploit the fuel savings that can be achieved by using the Earths atmosphere to reduce the vehicles energy, a guidance law is required, and it must be able to handle large unpredictable fluctuations in atmospheric density, on the order of ${\pm}$50% relative to the 1962 US Standard Atmosphere. In this paper aeroassisted orbital transfer is considered as a differential game, with Nature controlling the atmosphere density to yield a worst case (min-max fuel required) atmosphere, from which the guaranteed playable set boundary are achieved. Inside the playable set, it is guaranteed that the vehicle achieves the optimal atmospheric exit condition for the minimum fuel consumption regardless of the atmospheric density variations.

• 한국전산유체공학회:학술대회논문집
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• 2003.10a
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• pp.237-239
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• 2003

The present study investigates on design optimization of rib-roughened two-dimensional channel to enhance turbulent heat transfer. Response surface method with Reynolds-averaged Navier-Stokes analysis is used as an optimization technique. Standard $k-{\varepsilon}$model with wall functions is adopted as a turbulence closure. The objective function is defined as a linear combination of heat transfer and friction drag coefficients with weighting factor. Computational results for overall heat transfer rate show good agreements with experimental data. Four design variables are optimized for weighting factor of 0.02.

• 한국가시화정보학회:학술대회논문집
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• 2004.11a
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• pp.30-33
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• 2004

In order to analyze the heat transfer phenomena in the plasma flames, a mathematical model describing heat and fluid How in an electric arc has been developed and used to predict heat transfer from the arc to the steel bath in a DC Electric Arc Furnace. The arc model takes the separate contributions to the heat transfer from each involved mechanism into account, i.e. radiation, convection and energy transported by electrons. The finite volume method and a SIMPLE algorithm are used for solving the governing MHD equations, i.e., conservation equations of mass, momentum, and energy together with the equations describing a standard $k-\varepsilon$ model for turbulence. The model predicts heat transfer for different currents and arc lengths. Finally these calculation results can be used as a useful insight into plasma phenomena of the industrial-scale electric arc furnace. from these results, it can be concluded that higher arc current and longer arc length give high heat transfer.

• International Journal of Precision Engineering and Manufacturing
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• v.7 no.2
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• pp.56-59
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• 2006

A vibrational model of powder transfer equipment based on the lumped parameter method was developed, in which the operating motion consists of surging, bouncing, and pitching. After decoupling the equation of motion, the vibrational excitation source of the pitching motion was removed. So the designers are able to plan the optimum design to adjust the motion trajectory of the powder transfer equipment. That is, a procedure to adjust the motion trajectory of powder transfer equipment by changing design specifications such as the installation position, the direction of the motor, the driving speed, the mass unbalance, the stiffness coefficient, and the installation position of the support spring, is presented in this paper. The powder transfer equipment manufactured according to the results of this study did not suffer fatigue destruction, since the maximum stress on the basket structure was sufficiently small.

• Journal of the Korean Society of Safety
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• v.15 no.1
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• pp.19-27
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• 2000

This paper numerically deals with combined heat transfer in a enclosure with a block. The block affected by hot wall is located centrally in the enclosure with a radiating gray gas. The discrete ordinate method(DOM) was used for solving the radiative transfer equation. Both laminar and turbulent cases were investigated for various Rayleigh number and standard k-$\varepsilon$ model was adopted to turbulent case. The effects of optical thickness, wall emissivity and fluid-solid thermal conductivity ratio are investigated on the flow and temperature fields. This study shows that as the wall emissivity decreases, the temperature distribution gradually becomes uniform and the heat transfer is reduced in enclosure. It is expected that this study can help to design the energy system related to the combined heat transfer and operate it safely.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.8
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• pp.1251-1257
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• 2004

In order to analyze the heat transfer phenomena in the plasma flames, a mathematical model describing heat and fluid flow in an electric arc has been developed and used to predict heat transfer from the arc to the steel bath in a DC Electric Arc Furnace. The arc model takes the separate contributions to the heat transfer from each involved mechanism onto account, that is radiation, convection and energy transported by electrons. The finite volume method and a SIMPLE algorithm are used for solving the governing MHD equations, that are conservation equations of mass, momentum and energy together with the equations describing a standard k-${\varepsilon}$ model for turbulence. The model predicts heat transfer for different currents and arc lengths. Finally these calculation results can be used as a useful insight into plasma phenomena of the industrial-scale electric arc furnace. From these results, it can be concluded that higher arc current and longer arc length give high heat transfer

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.3
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• pp.220-229
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• 2003

An experimental study on the air-side pressure drop and heat transfer coefficient of slit fin-tube heat exchanger has been carried out. The data reduction methodology for air-side heat transfer coefficients in the literature is not based on a consistent approach. This paper focuses on new method of data reduction to obtain the air-side performance of fin-tube heat exchanger using R22 and recommends standard procedures for dry surface heat transfer estimation in fin-tube heat exchanger having refrigerant on the tube-side. Results are presented as plots of friction f-factor and Colburn j -factor against Reynolds number based on the fin collar outside diameter and compared with previous studies. The data covers a range of refrigerant mass fluxes of 150~250 kg/$m^2$s with air flows at velocity ranges from 0.6 m/s to 1.6 m/s.

• Korean Journal of Computational Design and Engineering
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• v.9 no.1
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• pp.19-26
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• 2004

It is not possible to exchange parametric information of CAD models based on the current version of STEP (Standard for the Exchange of Product model data). The designer intents are lost during the transfer of CAD models. To resolve this problem, the macro-parametric approach had been proposed. To enable this approach, a set of standard modeling commands has been defined. Errors or missing elements of the standard modeling commands can be discovered by implementing macro-parametric translators. But there is a limit to discover problems only by using translators. This paper proposes a method to verify the standard modeling commands by implementing a geometric modeler. First, each argument of a modeling command is verified. Second, the set of the standard modeling commands is applied to geometric modeling of commercially available product parts. For the geometric modeling, nine test models have been selected.