• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.4
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• pp.87-93
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• 2016

In a Direct Connect(DC) mode altitude engine test, a labyrinth seal is set up between an air intake duct and an engine. The labyrinth seal plays a key role in mechanically isolating them, which contributes to the accurate measurement of thrust and the other component forces. However, when high vertical temperature gradient is generated in the supplied air in the duct, the isolation breaks down. In this paper, a labyrinth seal control device is designed and installed in an effort to eliminate the issue. Test result shows the device successfully gets rid of the contact problem even when high vertical temperature gradient is produced.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.6
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• pp.1330-1338
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• 1989

본 연구에서는 직각밀폐용기의 수평경계면이 단열인 경우뿐만 아니라 등온 조건을 갖는 경우에 대해 실험적으로 연구하여 경계조건의 변화가 직각밀폐용기내 흐름 및 열전달에 미치는 영향, 특히 등온조건을 갖는 경우 수직 온도차에 따르는 안정온도 구배효과로 예상되는 흐름의 억제, 지연효과를 작종 물리적 변수들의 영향과 함께 세밀히 조사하였다.

• Journal of the Korean Society of Propulsion Engineers
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• v.15 no.4
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• pp.65-72
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• 2011

Numerical simulation has been performed to investigate the bubbly flow in the liquid with vertical temperature gradient. The objective of this study is to establish an accurate numerical prediction program of gas-liquid two-phase flows in a vertical temperature gradient condition, whose mathematical model is formulated by the Eulerian-Lagrangian model. The present numerical results reveal the temperature mixing mechanism and the fluid dynamical characteristics induced by the bubbly flow in the liquid with stratified temperature. The effects of bubble radius, void fraction, and gas flow rate on bubble-driven convective flow are considered, too.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.6
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• pp.585-589
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• 1999

In order to grow $Bi_4Ge_3O_{12}$ crystals by the Czochralski method equipped with the auto-diameter control system, we used the resistance heater of our own design. We measure the temperature gradients under-arious thermal configurations. The relation between the critical rotation rate corresponding to the flat interface and the temperature gadient was investigated, and the importance of the axial temperature gradient was pointed out. The results from this work were compared with those obtained by other authors when RF heating was used. The optimal conditions for the crystal growth were determined as follows; under $O_2$ atmosphere with the pulling rate fixed at 2 mm/hr, rotation rate changed from 30 to 23 rpm as the crystal growth proceeded, radial and axial temperature gradients were 50 and $40^{\circ}C$/cm near melts respectively, and the composition was chemically stoichiometric.

• International Journal of Highway Engineering
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• v.12 no.4
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• pp.157-164
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• 2010

This research was conducted to analyze the behavior of Single-PTAS (Single Post-Tensioned Approach Slab) under tensioning and environmental loads by performing field tests when the demonstration Single-PTAS was being constructed. The temperature measurement sensors were installed at different depths, and the displacements in the approach slab under environmental loads and tensioning were measured using displacement transducers. As an experimental result, an abrupt change in the longitudinal displacement due to tensioning was not observed. The daily temperature change in the approach slab was negligible where the depth is over about 35cm. The temperature gradient in the approach slab adjacent to bridge was smaller than that adjacent to pavement. The patterns and magnitudes of vertical displacements were directly related to the temperature gradient at the measuring location. The behavior of Single-PTAS was very similar to that of concrete pavement. Therefore, a new design methodology for approach slabs is needed to include the pavement concept and to overcome drawback of current design procedures based on the simple beam concept.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.5
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• pp.1150-1157
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• 1988

Two-dimensional turbulent plane jet which is under the pressure gradient in the transverse direction is studied numerically. Full Navier-Stokes equations are used to correctly account for the pressure variation in the transverse direction. Using the standard k-.epsilon. turbulence model as a closure relationship, a time marching procedure gives the velocity field. The temperature fields are obtained for two different cases : (1) Hot jet is issued into the cold still air, and (2) Hot jet is issued into the surrounding across which exists a temperature difference. The velocity and temperature fields along with other flow and heat-transfer characteristics for two different pressure gradients are presented. A simple formula that relates the jet trajectory to the pressure gradient is also proposed. The mass flux in the longitudinal direction and the jet halfwidth seem insensitive to the pressure gradient. However, the pressure gradient increases the heat flux in the longitudinal direction as well as in the transverse direction.

• Journal of Power System Engineering
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• v.16 no.3
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• pp.37-43
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• 2012

감온액정을 추적입자로 사용한 PIV(Particle Image Velocimetry)법이 온도장을 정량적으로 가시화하기 위하여 사용되었다. 이 방법은 전체 유동장과 온도장을 동시에 계측할 수 있는 방법이지만, 온도장의 온도는 온도에 따라 변화되는 액정의 색을 정량적 온도 값으로 변환시켜야한다. 따라서 본 연구에서는 감온액정에 의한 온도장의 광학적 정보를 정량적 온도로 변환시키는 신경회로망 보정기법을 개발하여 그 타당성을 검토한 후, 수직온도구배를 가진 액체의 기포에 의한 대류유동에 적용하여 기포에 의한 온도혼합과정을 정량적으로 가시화하고자 한다.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.18 no.1
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• pp.47-53
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• 1982

An analysis of convection, in a fully developed laminar steady flow through the vertical square duct under the condition of variational symmetric heat flux, is considered. Finite element solution algorithm by Galerkin's method with triangular elements and linear interpolation polynominals for the temperature and velocity profiles are derived for the vertical square duct. The comparison of temperature distribution due to variational symmetric heat flux in the duct were made with available the other data when the condition of peripheral heat flux were uniform and zero. Numerical values for the dimensionless temperatures and Nusselt numbers at selected Rayleigh numbers and pressure gradient parameters were obtained at a few nodal points for the vertical square ducts and effects of corner in the duct were investigated.

• Journal of Aerospace System Engineering
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• v.16 no.5
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• pp.57-61
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• 2022

The various GaAs panel are applied widening for aircraft and aerospace structures. This study presented technology for the growth of large-diameter GaAs ingots greater than 4 inches through numerical analysis using temperature control technology. In this work, proposes manufacturing technology adapted to various temperature and environmental changes through temperature simulation. With the development of ingot technology, the possibility of future application increased by obtaining expected results with minor deviation.

• International Journal of Highway Engineering
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• v.10 no.4
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• pp.171-180
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• 2008

This study was conducted to analyze the curling behavior of concrete slabs on grade under temperature loading through the laboratory tests and to investigate the effects of the support conditions of underlying layers on the curling behavior of the slab on grade systems. For the laboratory tests, the concrete slabs were fabricated and the temperature measurement sensors were installed. The temperature loading was applied intentionally and the time histories of the vertical displacements of the slab at several different positions were measured. One-layered underlying layers were made using different materials and different thicknesses. Two-layered underlying layers were also made to have the same composite stiffness each other, but the material of the upper layer was designed to be different The experimental analysis results showed that the trend of the displacement time histories of the slab was basically the same as that of the temperature gradient time histories. The characteristics of the curling behavior of the slab were analyzed by separating the regions of curling up and curling down. The difference in the vertical displacements at the center and comer decreased as the stiffness of the underlying layer became larger, and the upper layer's material of the underlying layers affected the curling behavior of the slab.