• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.1
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• pp.73-79
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• 2011

A portion of oil for lubrication of compressor flows together with refrigerant in the refrigeration system. If the oil discharge from a compressor is increased in the refrigeration system, not only pressure drop is increased in other components, such as evaporator and gas cooler, but also heat transfer coefficient in the heat exchangers is decreased. Oil discharge rate from a compressor may strongly depend on operating conditions of a compressor. In this study, one stage single rotary compressor is employed for measuring oil circulation ratio(OCR). Carbon dioxide and PAG oil are used as refrigerant and lubricant. Using a U-tube densimeter, mixture density is measured. Oil circulation ratio(OCR) can be estimated by measured mixture density. The results obtained indicate that the oil circulation ratio(OCR) is increased as the suction temperature or compressor operating frequency is increased. Oil circulation ratio(OCR) correlation of the compressor is also suggested.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1628-1630
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• 2002

In this paper, we measured 3-dimensional temporal behavior of the light emitted from discharge cell of plasma display panel(PDP) as a function of the pressure using the scanned point detecting system. The detected light signal through the PM tube is sent on the oscilloscope and oscilloscope which is connected to PC with GPIB. The whole system is controlled by a PC. From the temporal behavior results, we could analyze the discharge behavior of panel with Ne-Xe(4%) mixing gas and 300torr, 400torr, 500torr pressure. The top view of panel shows that the discharge moves from inner edge of cathode electrode to outer cathode electrode forming arc type. At the 300torr, initial emission time is very fast. The side view of panel shows that the light is detected up to $150{\mu}m$ height of barrier rib. In the panel of 300torr, emission distribution is wider than the others.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.5
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• pp.619-629
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• 1998

An experimental work was conducted to investigate a feasibility of simultaneous measurement of gas-liquid two-phase flowrates with double orifice plates using air and water. The tests were carried out under the atmospheric pressure and at the ambient temperature using two different tube sizes. Qualities of an air-water flow in the present study have values less than 0.1 and thus the mixed flow showed bubbly, plug, slug flow regimes. The probability density function (PDF) and the power spectral density function (PSDF) of the instantaneous pressure drop traces for the flow regimes were obtained. It is found that some distinctive features exist in the distribution of these functions, depending upon the two-phase flow pattern. The time-averaged value of the instantaneous pressure drop increases with increasing gas and liquid flowrates, showing a single-valued function for the total mass flowrate and the quality. It is also found that the two-phase discharge coefficient exhibits a consistent trend for variation of dimensionless parameters such as the superficial velocity ratio and the gas Reynolds number. The results indicate that simultaneous measurement of two-phase flowrate may be possible based upon a statistical analysis of the instantaneous pressure drop curves monitored using double orifice plates.

• Journal of the Korean Chemical Society
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• v.48 no.4
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• pp.351-357
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• 2004

We have investigated the intensity of Cu 510.6 nm emission line in see-through hollow cathode glow discharge (st-HCGD) for the development of medical Cu vapor laser. In order to acquire the stable plasma in st-HCGD cell at high current, several factors such as current, the length and the inner diameter of cathode tube, the shape of the tube, and the range of the sputtering range were tested. An optimum condition in our st-HCGD cell was obtained at 600 V, 700 mA, 2.3 Torr of Ar gas (100 SCCM), and 40 mm of tube with 4-11-4 mm type cathode design. Also, it was indirectly observed that temperature in the cell could reach more than $1,000{\circ}C$ since Cu cathode was melt at the current more than 700 mA (melting point of Cu, $1084{\circ}C$).

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.550-551
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• 2013

Large-area RF-driven ion source is being developed at Germany for the heating and current drive of ITER plasmas. Negative hydrogen (deuterium) ion sources are major components of neutral beam injection systems in future large-scale fusion experiments such as ITER and DEMO. RF ion sources for the production of positive hydrogen ions have been successfully developed at IPP (Max-Planck- Institute for Plasma Physics, Garching) for ASDEX-U and W7-AS neutral beam injection (NBI) systems. In recent, the first NBI system (NBI-1) has been developed successfully for the KSTAR. The first and second long-pulse ion sources (LPIS-1 and LPIS-2) of NBI-1 system consist of a magnetic bucket plasma generator with multi-pole cusp fields, filament heating structure, and a set of tetrode accelerators with circular apertures. There is a development plan of large-area RF ion source at KAERI to extract the positive ions, which can be used for the second NBI (NBI-2) system of KSTAR, and to extract the negative ions for future fusion devices such as ITER and K-DEMO. The large-area RF ion source consists of a driver region, including a helical antenna (6-turn copper tube with an outer diameter of 6 mm) and a discharge chamber (ceramic and/or quartz tubes with an inner diameter of 200 mm, a height of 150 mm, and a thickness of 8 mm), and an expansion region (magnetic bucket of prototype LPIS in the KAERI). RF power can be transferred up to 10 kW with a fixed frequency of 2 MHz through a matching circuit (auto- and manual-matching apparatus). Argon gas is commonly injected to the initial ignition of RF plasma discharge, and then hydrogen gas instead of argon gas is finally injected for the RF plasma sustainment. The uniformities of plasma density and electron temperature at the lowest area of expansion region (a distance of 300 mm from the driver region) are measured by using two electrostatic probes in the directions of short- and long-dimension of expansion region.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.4
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• pp.567-572
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• 2015

Discharge characteristics of linear microwave plasma were investigated by using fluid simulation of 2D axis-symmetry based on finite elements method. The microwave power was 2.45 GHz TEM mode and transmitted through linear antenna. Resistive power and pressure were considered simulation variables and argon was used for working gas. A decrease of electron density along the quartz tube was observed in low power condition but relatively uniform plasmas were generated in chamber by increasing the resistive power. The electron temperature was highly detected near the surface of quartz tube because the electron was heated only dielectric surface. The power transmission efficiency decreased and characteristics of surface plasma were observed in high electron density condition.

• Journal of the Korean Vacuum Society
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• v.17 no.6
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• pp.481-486
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• 2008

The different degrees of blackening were observed at the inner surface of borosilicate, soda-lime, and aluminosilicate glass tubes having different sodium (Na) contents. The sodium contents ($Na_2O$) within the borosilicate, soda-lime, and aluminosilicate glass tubes were found to be 4%, 14%, and 0.06%, respectively. The degree of blackening was shown to increase as the sodium content within the glass of the fluorescent lamp containing Ne+Ar+Hg gas mixture. Higher degree of blackening was observed from the inner surface of the glass tube coated with $Y_2O_3$. The blackening was found to be originated from the amalgam of $NaHg_2$ generated by the chemical reaction between the mercury ions within the discharge gas and sodium within the glass tube during operation.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.2065_2066
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• 2009

In this paper, we have developed high performance SPD(surge protective device) and evaluated the characteristics in comparison with typical SPD used in the inside and outside of the country. The new SPD was composed of MOV(metal oxide varistor), GDT(gas discharge tube) and impedance such as resistors, capacitors or varistors. To estimate operating the characteristic of the SPD which was developed, it was measured surge voltage caused by fault current or surge according to IEC 61000-4-5. As a result it was found that the power supply was cut off by high performance SPD when caused a short-circuit. In addition we could know that it could prevent ELB(earth leakage breaker)'s malfunction caused by surge.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.3
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• pp.328-333
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• 2009

In this paper, we have developed high performance SPD(surge protective device) and evaluated the characteristics in comparison with typical SPD used in the inside and outside of the country. The new SPD was composed of MOV(metal oxide varistor), GDT(gas discharge tube) and impedance such as resistors, capacitors or varistors. To estimate operating the characteristic of the SPD which was developed, it was measured surge voltage caused by fault current or surge according to IEC 61000-4-5. As a result it was found that the power supply was cut off by high performance SPD when caused a short-circuit. In addition we could know that it could prevent ELB(earth leakage breaker)'s malfunction caused by surge.

• 한국연소학회:학술대회논문집
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• 2004.06a
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• pp.242-247
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• 2004

An Experimental study was conducted on spray combustion using dual swirlers at different outlet angle; co-swirl and counter-swirl. To understand the characteristics of turbulent spray combustion of dual swirl flow (DSF), the axial helical annular vaned swirlers with various swirl ratios and combination of angle and direction were designed. and temperature measurements of a rapidly thermocouple insertion and measurements of soot volume fraction and microrstructure using thermophoretic sampling particle diagnostic (TSPD) as TEM were carried out. The NOx, $CO_2$, $O_2$, etc. was analyzed using emission gas analyzer. The results show that flame stability were maintained under very lean condition. for both co-swirl and counter-swirl case. And though Counter-swirl case kept the higher temperature region compared to co-swirl case, Counter-swirl combustion represented less NOx emission and soot formation than co-swirl case.