• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.377-381
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• 2006

This paper describes experimental work to control supersonic jet noise using a mesh screen that is placed at the nozzle exit plane. The mesh screen is a wire-gauze screen that is made of long stainless wires with a very small diameter. The nozzle pressure ratio is varied to obtain the supersonic jets which are operated in a wide range of over-expanded to moderately under-expanded jets. In order to perturb mainly the initial jet shear layer, the hole is perforated in the central part of the mesh screen. The hole size is varied to investigate the noise control effectiveness of the mesh screen. A schlieren optical system is used to visualize the flow fields of supersonic jet with and without the mesh screen device. Acoustic measurement is performed to obtain the OASPL and noise spectra. The results obtained show that the present mesh screen device leads to a substantial suppression of jet screech tones. The hole size is an important factor in reducing the supersonic jet noise. For over-expanded jets, the noise control effectiveness of the mesh screen appears more significant, compared to correctly and under-expanded jets

• Journal of Energy Engineering
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• v.13 no.4
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• pp.267-274
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• 2004

Theoretical analysis for predicting the heat transport limitations of screen mesh wick and sintered wick heat pipes was performed. The heat pipe diameter was 8mm and water was used for working fluid. For the 250 mesh, each capillary pressures and heat transport limitations, thermal resistances were analyzed according to the operating temperatures, wick thicknesses and inclination angles, based on the effective capillary radius (r$\_$c/), porosity ($\varepsilon$) and permeability (K). The wick capillary limitation was increased as the operating temperature and the wick thickness were increased, and generally the sintered wick showed higher heat transport limitations than that of the screen wick. The thermal resistance of the screen wick was higher than that of the sintered wick and both thermal resistances were linearly increased as the wick thickness was increased.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.1
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• pp.274-284
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• 1991

Mean flows and Reynolds stresses through circular and elliptic wire-mesh screens in the wind tunnel are measured by using the hot-wire system, and flow structures are investigated. Flow in the core of the wake are nearly uniform and the shear layer is developed along the edge of the screen The turbulent kinetic energy in the core decreases at the fast rate. However turbulence components are not in local equilibrium in the shear layer. The shear layer of the circular screen develops outward according to the radial mean motion. On the other hand, 3-dimensional transverse mean motion was turned to the main mechanism for the elliptic shape of the wake to be circular at the downstream.

• Journal of Power System Engineering
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• v.15 no.3
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• pp.31-37
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• 2011

직조 금속 스크린 리브(rib) 이 바닥에 설치된 사각 덕트에서 열전달과 유체유동의 압력강하를 측정하기 위해 실험적 연구를 수행하였다. 시험부의 치수는 200 mm(W) ${\times}$ 40 mm(H) ${\times}$ 712 mm(L)이고 수력직경은 66.6 mm이다. 입구영역에는 1.72m 길이의 가열되지 않은 동일한 치수의 채널을 설치하였다. 메쉬가 다른 4가지의 직조금속 스크린 리브에 대해 측정하였다. 그리고 비교를 위해 일체형 리브에 대해서도 측정하였다. 국부 열전달 계수의 측정에는 스테인레스 강제 포일(foil) 히터와 T형 열전대률 이용하였다. 레이놀즈 수는 23,000에서 58,000의 범위이다. 덕트의 수력직경($D_h$)에 대한 직조 금속 리브의 높이(e)의 비($e/D_h$)는 0.075 이고 리브 간격(p)과 높이의 비(p/e)는 10이다. 실험 결과 메쉬가 없는 일체형 리입에서 가장 누셀트 수와 마찰계수가 컷다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.9
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• pp.685-692
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• 2018

Using Babinet's principle and generalized sheet transition conditions(GSTCs), an analysis method for metascreens is proposed. First, the relation of a complementary screen between a metafilm and metascreen with the same dimensions was confirmed using Babinet's principle. These properties were verified by comparing the reflection coefficient of the patch and the transmission coefficient of the mesh. The patch and mesh are the basic structures of metafilms and metascreens, respectively. Based on these findings, it is also confirmed that the reflection coefficient of the patch surface calculated by GSTCs has the same value as the transmission coefficient of the mesh surface. It is expected that the proposed analysis methods can be applied to the magnitude, phase, and polarization of electromagnetic waves in the various unit structures of a given metasurface.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1506-1511
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• 2003

The present study proposes a new structure for a flat plate heat pipe which could embody a thin thickness, any shapes and high heat density a unit area. It is on the structure for the formation of vapor passages and the support of the case of the flat plate heat pipe. A screen mesh is used as the one. To verify the validity of the one, the flat plate heat pipe of 1.08mm thickness was made with a layer of the screen mesh with 14 and 100 mesh number respectively and tested. Here the screen mesh with 14 mesh number plays a role of the vapor passage and the support of the case and the screen mesh with 100 mesh number functions as the wick structure. T he results show that the screen mesh excellently carries out the function of the vapor passage and the support of the case.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1-6
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• 2003

The purpose of the present study is to investigate the capillary heat transportation limitation in heat pipe according to the change of screen mesh wick porosity. Diameter of pipe was 6 mm, and mesh numbers are 100, 150, 200 and 250 and water was selected as a working fluid. According to the change of wick porosity and mesh number, the capillary pressure, pumping pressure, liquid friction coefficient in wick, vapor friction coefficient, and capillary heat transportation limitation are analyzed by theoretical design method of a heat pipe. As some results, the capillary heat transportation limitation in screen mesh wick heat pipe is largely affected by wick porosity and mesh number.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.11
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• pp.880-889
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• 2002

The purpose of the present study is to examine the factors affecting the heat transfer limitations of screen mesh heat pipe for electronic cooling by theoretical analysis. Diameter of pipe was 6 mm, and mesh numbers are 50, 100, 150, 200 and 250 and water was selected as a working fluid. According to the change of mesh number, wick layer, inclination and saturation temperature, capillary pressure, pumping pressure, liquid friction coefficient in wick, vapor friction coefficient, capillary limitation, entrainment limitation, sonic limitation and boiling limitation we analyzed by theoretical design method of a heat pipe. As some results, the capillary limitation in small diameter of heat pipe is largely affected by mesh number and wick layer.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3150-3155
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• 2007

This paper describes an experimental work to investigate the effect of mesh screen device on the jet structure and acoustic characteristics of over-expanded supersonic jet. The mesh screen device is placed into the supersonic jet stream. In order to perturb mainly the initial jet shear layer, the hole is perforated in the central part of the mesh screen. The diameter of the perforated hole and the location of mesh screen device are varied. A Schlieren optical system is used to visualize the flow fields of supersonic jet without and with the mesh screen device. Pitot pressure measurement is carried out to obtain the pressure distribution in the jet flow. Acoustic measurement also is performed to obtain the OASPL and noise spectra. The results obtained show that the jet structure and the jet noise control effectiveness is strongly dependent upon the diameter of the perforated hole and the location of the mesh screen device in the jet stream. Provided that the mesh screen device is placed at the location to perturb effectively the initial shear layer, the present control method is effective in suppressing the supersonic jet noise.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.7 s.238
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• pp.805-813
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• 2005

The thermal performance of a flat-strip heat pipe with inner grooves and the screen mesh cover was investigated experimentally. The heat pipes were made of 2024 aluminum alloy of which the dimensions were 30 (W) $\times$ 4 (T) $\times$ 150 (L) mm. The cross sectional dimensions of inner groove were 0.4$\times$0.9 mm and the space between grooves was 0.6 mm. To enhance the capillary force, foe screen meshes were attached to cover the grooved inner surface. In the grooved heat pipes without screen mesh cover, the maximum thermal load of 180 W (12 W/$cm^2$) was achieved for operating temperature below $130^{\circ}C$ at horizontal position. The heat pipes with screen mesh cover showed the thermal resistances less than one third of those without screen mesh cover, and showed less fluctuation in the thermal resistance values. Furthermore, the thermal performance of the former exhibited less dependence on the tilt angle and the fill charge ratio.