• Journal of the Korean Society for Precision Engineering
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• v.26 no.8
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• pp.112-118
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• 2009

A pressure rise is generated while air bearing stages are moving in high vacuum environment. This study analyzed this pressure rise phenomenon theoretically and verified it experimentally using two different kinds of stages - linear and rotary air bearing stages. Results indicate that the pressure rise was caused by additional leakage resulting from stage velocity, along with adsorption and outgassing of gas molecules from the guide rail surface. Though tilting of the stage due to acceleration and deceleration reached several micrometers, it had a negligible effect on pressure rise because the tilting time was very short. Therefore, a rotary air bearing stage showed much less pressure rise than a linear stage because the rotary stage theoretically has nothing to do with the above causes. Additional leakage caused by stage velocity was inevitable if the stage had movements, but pressure rise caused by adsorption and outgassing could be suppressed by improving the surface quality to reduce real surface area, and by coating the guide rail surface with titanium nitride (TiN) which has less adhesion probability of gas molecules. The results also indicate that the pressure rise increased when the air bearing stage operated under high vacuum conditions.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.8
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• pp.102-106
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• 2012

This paper was carried out to survey fire hazard and improvement at the drain pump in air-conditioners. Based on the results of analysis, the proposal of electrical accidents prevention and a construction improvement are as follows. A power connection of the drain pump has two types, an electrical outlet type and direct connection type at control board of air-conditioner. The electrical outlet types need a bulletin sign or education as malfunction of the drain pump include an additional accidents, current leakage and overflowing with water on the floor from breaker trip by exterior cause and breaker off by mistake of worker. On the other hand, the direct connection types prevent a power interruption as exterior cause, but it has some trouble, cut of ground cable and without protection device. Usually it doesn't work by electrician when air-conditioner and the drain pump power work. Therefore an education or countermeasures are recommended for not electrician. Generally malfunction of the drain pump causes accumulated materials into the tank. Even though the accumulated materials lead to an overheating and burning as failure of detector occur an idling, periodic inspection of the air-conditioner filter and the drain pump tank prevent the trouble.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.8
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• pp.547-555
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• 2008

The effects of paper properties such as density, air permeability, water vapor transmission rate on the thermal performance of plate-type enthalpy exchanger were experimentally investigated. Papers having different properties were made from the same pulp by calendering or refining. Enthalpy exchanger samples were made from the papers, and were tested according to the standard test procedure (KS B 6879). Effective efficiencies were obtained, which accounted for the air leakage between supply and exhaust streams. Results showed that paper density affected the sensible heat transfer of the samples. Sensible heat transfer increased with density of the paper. It was also shown that effective efficiency of latent heat transfer was approximately the same independent of the samples, which suggests that papers made of the same pulp show similar water vapor transmission characteristics independent of the degree of calendering or refining. Best performance was obtained for the sample having highest paper density and moderate water vapor transmission ratio.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.414-418
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• 2008

The effects of paper properties such as density, air permeability, water vapor transmission rate on the thermal performance of plate-type enthalpy exchanger were experimentally investigated. Three enthalpy exchanger samples having different properties were made, and were tested according to the standard test procedure (KS B 6879). Effective efficiencies were defined, which accounted for the air leakage between supply and exhaust streams. Results showed that paper density affected the sensible heat transfer of the samples. Sensible heat transfer increased with density of the paper. It was also shown that water vapor transmission rate alone was not a proper indicator for the efficiency of latent heat transfer. Air permeability should also be considered for adequate evaluation of the latent heat transfer. Best performance was obtained for the sample having highest paper density and moderate water vapor transmission ratio.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.857-862
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• 2009

In this study, the numerical study has carried out to analyze the leakage in a steam turbine labyrinth seal. We modified tooth shape of the labyrinth seal and finds out difference of leakage in this study. Original model is straight labyrinth seal and its modified model is slant labyrinth seal. The numerical analyses are implemented on two models. The numerical results show that each leakage of tooth shape are found 0.4781 kg/s and 0.4485 kg/s, respectively. Slant labyrinth seal seals in a steam better than straight labyrinth seal. Since, actual clearance of the stream function in the slant model is smaller than the straight model.

• The KSFM Journal of Fluid Machinery
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• v.18 no.1
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• pp.44-50
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• 2015

Labyrinth seals are commonly used in various kinds of turbomachinery to reduce leakage flow. In the present 3D CFD analysis of see-through-type labyrinth air seal, the methodology of determining leakage and rotordynamic coefficients is suggested with the relative coordinate system for steady-state simulation. The leakage flow and rotordynamic forces predicted by using different solvers and turbulent models of FLUENT are compared with the results of the existing bulk-flow analysis code LABYSEAL.FOR and experiment. The present CFD result of direct stiffness(K) shows only improvement in prediction. The results of leakage and rotordynamic coefficients as well as computing time are sensitive against the used solver and turbulent model.

• Journal of Institute of Control, Robotics and Systems
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• v.11 no.7
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• pp.578-586
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• 2005

Air mattress is now used widely to prevent the pressure ulcer by reducing the localized pressure peaks. The pressure control method based on the anthrophometric model of an air-cell mattress developed in this study is presented. The air-cell mattress has 18 cylindrical air cells made of porous material allowing air leakage. Even though the air leakage can contribute to reducing the development of pressure ulcer by lowering the pressure peak, temperature and humidity, the air pressure changes with time and the desired air-cell pressure has to be determined as an optimal value for each user. To select the desired air-cell pressure, we first divide the parts of the body into four sections such as head, trunk, hip, and leg. Then, the pressure of each section grouped with air-cells is calculated from the weight of each part estimated from the individual height and body weight. Air supply system for the air-cell mattress is implemented by using four electronic solenoid valves and an air compressor, and it is driven by a real-time microcontroller. We experimented with five subjects of the contact pressure on skin. The experimental results show that the proposed air-cell mattress is effective for the prevention of the pressure ulcer.

• Journal of the Korean Institute of Gas
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• v.20 no.2
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• pp.10-15
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• 2016

This paper is to analyze and study the failure examples of refrigerant gas in automotive air conditioner. The first example, the air conditioner compressor continually operated that the refrigerant was leaked in air conditioner system. By lubrication shortage, the piston was partially sticked on cylinder of air conditioner compressor inner part. This was caused the phenomenon of engine operation trouble by load increasing with engine rpm variation during engine running. The second example, it sought the fact that the air conditioner refrigerant gas was leaked from air conditioner compressor to condenser high pressure pipe toward rear air conditioner checking with the lines of air conditioner. The third example, the refrigerant gas of air conditioner found that was leaked imperceptible from condenser inner by crack that was generated on the fins of air conditioner condenser. Therefore, the air conditioner system that maintain the air conditioner by decreasing the in-car temperature must meticulously manage to not leak the air conditioner refrigerant gas.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.3 no.2
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• pp.131-141
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• 1991

A method of optimum design of an axial rotary sensible heat exchanger for the heat recovery of exhaust gas from the air conditioning space was developed in consideration of economics of investment cost and profit according to the installation of heat exchangers. Leakage rate of exhaust gas was calculated and the correlation for the pressure drop due to leakage of exhaust gas was proposed. Heat transfer between the matrix and exhaust and intake gas was analysed to calculate the effectiveness of heat exchanger, which was used for the optimum design of rotary heat exchanger. The results show that optimum rotational speed increases as the length of rotor increases and there exists optimum NTU which maximizes the gain of total cost according to the installation of rotary heat exchanger.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.4
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• pp.165-170
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• 2016

Long-term performance of the enthalpy exchange element is a topic of current interest due to the concern of possible performance degradation over time. In this study, a 350 CMH enthalpy recovery ventilator equipped with an enthalpy exchange element was installed in an office room, and the performance has been traced over the past 5 years. The appearance, overall dimension, thermal performance, leakage ratio and anti-bacterial performance were checked annually. Results showed that the change in thermal performance (sensible, latent and enthalpy efficiency) was negligible with periodic cleaning with an air gun. However, the leakage ratio increased with time, measuring 7.3% after 5 years. Anti-bacterial test revealed that no bacteria were found during the test period. The largest change in the dimension occurred at the middle location of the element, although the change was less than 2% of the initial value.