• 대한기계학회논문집
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• 제17권8호
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• pp.2110-2121
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• 1993

A numerical investigation has been carried out for the flow characteristics after exchange of some filters from the original layer to the new low pressure loss layer with equal filtering efficiency. The solution domain includes upper plenum, filter layer, clean space, access panels, and lower plenum. The concept of the distributed pressure resistance was applied to describe the momentum loss in filter layer and access panels. The evolution of the flow field is simulated using the low Reynolds number k-.epsilon. over bar turbulent model and SIMPLE algorithm based on the finite volume method. As a result, after the exchange of filter layer the power requirement can be reduced by 8-9 percent. The results also demonstrate that the perpendicularity of the flow near access panels may become worse at new filter layer than origianl filter layer. But the situation can be recovered by adjusting the jopening ratio of access panels.

• 의료ㆍ복지 건축 : 한국의료복지건축학회 논문집
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• 제24권1호
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• pp.51-58
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• 2018

Purpose: In this study, through the comparison of the pressure fluctuation and air exchange volume in negative isolation room according to the type of the door and door opening/closing speeds, which is one of the main factors causing the cross contamination of the negative pressure isolation room, establishes standard operating procedures to prevent cross contamination in high risk infectious diseases and isolation room design. Methods: In this study, the air flow each of the room is analyzed using ANASYS CFX CODE for flow analysis. In addition, the grid configuration of the door is constructed by applying Immersed Solid Methods. Results: The pressure fluctuation due to the opening and closing of the hinged door was very large when the moment of the hinged door opened and closed. Especially, at the moment when the door is closed, a pressure reversal phenomenon occurs in which the pressure in the isolation room is larger than the pressure in the anteroom. On the other hand, the pressure fluctuation due to the opening and closing of the sliding door appeared only when the door was closed, but the pressure reversal phenomenon not occurred at the moment when the sliding door was closed, unlike the hinged door. As the opening and closing speed of the hinged door increases, the air exchange volume is increased. However, as the opening and closing speed of the sliding door is decreased, the air exchange volume is increased. Implications: According to the results of this study, it can be concluded that the pressure fluctuation due to the opening and closing of the hinged door is greater than the pressure fluctuation due to the opening and closing of the sliding door. In addition, it can be confirmed that the pressure reversal phenomenon, which may cause to reduce the containment effect in negative pressure isolation room, is caused by the closing of the hinged door. Therefore, it is recommended to install a sliding door to maintain a stable differential pressure in the negative isolation room. Also, as the opening and closing speed of the hinged door is slower and the opening and closing speed of the sliding door is faster, the possibility of cross contamination of the room can be reduced. It is therefore necessary to establish standard operating procedures for negative isolation room for door opening and closing speeds.

• Design & Manufacturing
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• 제13권2호
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• pp.49-53
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• 2019

The temperature distribution and lifetime of molds were predicted by computer simulation analysis with various spraying and blowing process of high pressure die casting. After varying the spraying angle and time, the mold temperature, heat exchange and mold life were predicted. As the spraying angle increases, the maximum temperature of the mold decreases, which is because the spraying area increases and the heat exchange with the mold increases. Heat exchange occurs more actively in the blowing process than in the spraying process. This is because the cooling is not performed due to the steam generation. When the spraying angle is 50 degree, the minimum life of the mold is analyzed 200 times. After adjusting the blowing time from 5s to 3s, the minimum lifetime of the mold has been increased almost twice.

• 동력기계공학회지
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• 제10권4호
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• pp.31-37
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• 2006

In this study, the ability for the function of double pipe inserted liquid pipe with small diameter in the gas pipe with large diameter for the circulating of liquid of high temperature and high pressure and low temperature and low pressure at the same time is presented. And in this double pipe, liquid pipe of high temperature and pressure is used to connect condenser and expansion valve and gas pipe of low temperature is used to connect evaporator and compressor. Also, when liquid refrigerant of high temperature and gas refrigerant of low temperature is circulated by reversed flow in the double pipe. The contribution of liquid gas heat exchange pipe is studied by comparison of the effect of heat transfer by temperature difference when liquid pipe and gas pipe is installed separately.

• Mass Spectrometry Letters
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• 제12권4호
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• pp.146-151
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• 2021

In this study, the hydrogen/deuterium (HDX) exchange mechanism of active hydrogen, nitrogen, and sulfur-containing polycyclic aromatic hydrocarbon (PAH) dissolved in toluene and deuterated methanol by atmospheric pressure photoionization (APPI) is investigated. The comparison of the data obtained using APPI suggests that aniline and benzene-1,2-dithiol contain two exchanging hydrogens. The APPI HDX that best explains the experimental findings was investigated with the use of quantum mechanical calculations. The HDX mechanism is composed of a two-step reaction: in the first step, analyte radical ion gets deuterated, and in the second step, the hydrogen transfer occurs from deuterated analyte to de-deuterated methanol to complete the exchange reaction. The suggested mechanism provides fundamentals for the HDX technique that is important for structural identification with mass spectrometry. This paper is dedicated to Professor Seung Koo Shin for his outstanding contributions in chemistry and mass spectrometry.

• Nuclear Engineering and Technology
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• 제37권6호
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• pp.595-604
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• 2005

A new instrument, an average BDFT (Birectional Flow Tube), was proposed to measure the flow rate in single and two phase flows. Its working principle is similar to that of the Pilot tube, wherein the dynamic pressure is measured. In an average BDFT, the pressure measured at the front of the flow tube is equal to the total pressure, while that measured at the rear tube is slightly less than the static pressure of the flow field due to the suction effect downstream. The proposed instrument was tested in air/water vertical and horizontal test sections with an inner diameter of 0.08m. The tests were performed primarily in single phase water and air flow conditions to obtain the amplification factor(k) of the flow tube in the vertical and horizontal test sections. Tests were also performed in air/water vertical two phase flow conditions in which the flow regimes were bubbly, slug, and churn turbulent flows. In order to calculate the phasic mass flow rates from the measured differential pressure, the Chexal drift-flux correlation and a momentum exchange factor between the two phases were introduced. The test results show that the proposed instrument with a combination of the measured void fraction, Chexal drift-flux correlation, and Bosio & Malnes' momentum exchange model could predict the phasic mass flow rates within a $15\%$ error. A new momentum exchange model was also proposed from the present data and its implementation provides a $5\%$ improvement to the measured mass flow rate when compared to that with the Bosio & Malnes' model.

• 한국자기학회지
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• 제8권6호
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• pp.369-373
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• 1998

본 연구에서는 마그네트론 스퍼터링 법으로 제작한 Ni-Fe/NiO 이층 박에서, NiO 증착 중 Ar 압력에 따른 교환이 방성의 변화를 고찰하엿으며 이를 미세조작과 관련시켜 해석하고자 하였다. 낮은 Ar 압력에서 증착한 Ni-Fe/NiO 이층막은 우수한 교환이방성 특성을 나타내었으나 Ar 압력이 증가함에 따라 교환이방성은 급격하게 감소하였다. 낮은 Ar 압력에서 증착한 시편은 NiO와 Ni-Fe 계면에서 epitaxy 경향을 나타내었으며 그 계면은 평범하고 그 경계는 두렷하게 구분하였다. 그러나 높은 Ar 압력에서 증착한 시편은 NiO와 Ni-Fe의 경계가 뚜렷하게 구분되지 않고 그 계면 또한 평활하지 않았다. 한편 NiO의 조성은 Ar압력의 증가에 따라 산소의 조성이 점점 증가하였다.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2012년도 임시총회 및 하계학술연구발표회
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• pp.70-71
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• 2012

In summary, the BLS experiments was applied to investigate the magnetic properties of $Co_{40}Fe_{40}B_{20}$ thin films. We find that the exchange stiffness constant decrease with increasing Ar gas pressure.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.995-1000
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• 2001

Distributions of the parameters in proton exchange membrane fuel cell (PEMFC) has been analyzed numerically under steady-state and isothermal conditions. The distributions of the crucial parameters (e.g., temperature and pressure) in a PEMFC have a major impact on its safe and efficient operation. This paper predicts the performance of the model electrode plates by calculating the pressure and temperature distributions of working fluid. The calculated results of pressure and temperature at exit condition shows good agreement to experiments and gives details of flow pattern inside of electrode plates.

• Journal of Advanced Marine Engineering and Technology
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• 제25권3호
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• pp.581-587
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• 2001

Plate heat exchange(PHE) will be applied to the refrigeration and air conditioning systems as evaporators or condensers for their high efficiency and compactness. The purpose of this study is the analyze the characteristics of heat transfer and pressure drop of plate heat exchanger. Numerical work was conducted using the FLUENT code k-$\varepsilon$model. Also the dependence of heat transfer coefficient and friction factor on Reynolds number was investigated. As the Reynolds number increases, it is found that heat transfer coefficient also increases, but friction factor decreases. The study examines the internal flow, thermal distribution and the pressure distribution in the channel of plate heat exchanger. The results of CFD analysis compared with experimental data, and the difference of friction factor and Nusselt number in plate heat exchanger are 10% and 20%, respectively, Therefore the CFD analysis model is effective for the performance prediction of plate heat exchanger.