The Climate chamber system is an essential facility for aerodynamic performance development of commercial vehicles to investigate air flow field characteristics in different climatic conditions. In particular, the analysis of airflow fields within the chamber system is an essential consideration for optimal design. In this study, the pressure characteristics and velocity uniformity in the test section area were predicted with blower impeller rotational speed using CFD. The velocity uniformity is affected by the distance from the blower nozzle outlet, reaching up to 72.7% at 695 RPM. The pressure differential between 300 RPM and 740 RPM shows an approximate difference of 2651 Pa, with a high-pressure distribution observed along the right side wall of the blower. These results are expected to be used as design data applicable for improving the performance of environmental chamber systems.

The change in the performance of the range hood according to the pressure change was investigated through a comparative experiment, and the conclusion is as follows. KS C 9304: In 2020, static pressure was applied at 100 Pa according to the fan standard, and the test was conducted by varying the outlet diameter and power consumption. In the case of Motor power 55W, the air volume value was 184.6 when the outlet diameter was 125mm. As a result of the test, if the power consumption is 52.0W, the diameter of the outlet is 125mm, and the power consumption is 60.8W, and the diameter of the outlet is 100mm, it meets 160 or more and less than 200 (constant pressure 100Pa).

In this study, a graphite block is fabricated using artificial graphite processing byproduct and phenolic resin as raw materials. Mechanical and electrical property changes are confirmed due to the preforming method. After fabricating preforms at 50, 100, and 150 MPa, CIP molding at 150 MPa is followed by heat treatment to prepare a graphite block. 150UP-CIP shows a 12.9% reduction in porosity compared with the 150 MPa preform. As the porosity is decreased, the bulk density, flexural strength, and shore hardness are increased by 14.9%, 102.4%, and 13.7%, respectively; and the deviation of density and electrical resistivity are decreased by 51.9% and 34.1%, respectively. Therefore, as the preforming pressure increases, the porosity decreases, and the electrical and mechanical properties improve.

국내에서는 ‘태양광 발전 사업‘을 지원하여 태양광 발전소를 늘려나가고 있다. 태양광 발전기는 옥외에 있어 바람에 직접적 으로 노출되어있기 때문에 태풍과 같은 강풍에 큰 영향을 받게 된다. 최근 태풍의 강도와 빈도가 증가하면서 이에 따른 피해가 증가하 고 있다. 태양광 발전기는 유지 관리 및 보수 작업의 용이성 때문에 동서방향으로 배치한 태양광 어레이들 좌우 사이에 이격거리를 두 고 설치된다. 따라서 본 연구에서는 동서방향 이격거리를 변수로 특정하여 태양광 어레이에 작용하는 풍압분포와 피크순압력계수를 산출하였다. 이를 위해 이격거리를 0.3m, 0.5m, 1.0m로 선정하여 풍압실험을 진행하였다. 모든 변수에서 어레이의 양측 상부 모서리에 서는 상방향, 하부 모서리에서는 하방향의 피크순압력계수가 지배적이었다. 어레이 내단부에서는 상방향과 하방향의 피크순압력계수 가 이격거리 0.3m일 때 가장 크게 나왔으나, 외단부보다 전체적으로는 값이 작았다. 어레이 좌우 이격거리에 대한 내단부에서의 수속 효과보다 외단부에서 생긴 와로 인한 피크순압력계수가 크게 나타났기 때문에 외단부에 대한 안전성을 더 고려해야 할 것으로 판단된다.

In this study, the effects of fuel injection pressure changed from 45 to 65 MPa on combustion and emission characteristics were investigated in a common rail direct injection (CRDI) diesel engine fueled with diesel and palm oil biodiesel blends. The engine speed and engine load were controlled at constant 1700rpm and 100Nm, respectively. The tested fuel were PBD20 (20 vol.% palm oil biodiesel blended with 80 vol.% diesel fuel). The main and pilot injection timing was fixed at 3.5°CA BTDC and 27°CA BTDC (before top dead center), respectively. The experimental results show that the combustion pressure and heat release rate increased. In addition, the indicated mean effective pressure (IMEP) and maximum combustion pressure increased with an increase of the fuel injection pressure. Hydrocarbon (HC), smoke opacity and carbon monoxide (CO) decreased, but oxides of nitrogen (NOx) emissions increased as fuel injection pressure increased.

화석연료의 사용은 대기가 오염되어 지구온난화와 이상기후 등의 문제를 야기하고 있다. 우리나라는 탄소 배출량을 줄이기 위하여 신재생에너지 개발에 관심이 집중되었고, 신재생에너지에 관한 정책 중 ‘그린 홈 100만호 보급사업’을 통해 일반 주택에 태양 광 발전기 보급이 확대되었다. 태양광 발전기는 외부에 노출되어 있어 직접적으로 태풍과 같은 강풍에 영향을 받게 된다. 따라서 보급 이 확대된 만큼 피해사례도 증가하고 있다. 본 연구에서는 태양광 발전기의 안전한 내풍설계를 위하여 주택설치 용량에 부합하는 태양광 발전기 형태를 특정하여 풍동실험을 진행하였다. 태양광 발전기의 모듈을 동일 면적의 정사각형(3 by 5 어레이), 직사각형(5 by 3 어레이)으로 배열하고 설치 각도를 30°, 35°, 40°로 하여 변수에 따른 풍압분포와 피크순압력계수를 산출하였다. 전체적으로 설치 각도가 증가할수록 값은 줄어들었으며 어레이 상부 모서리에서 상방향, 하부 모서리에서 하방향의 피크순압력계수가 지배적이었다. 또한 대체로 정사각형(3 by 5 어레이)보다 직사각형(5 by 3 어레이)의 배열이 바람에 더 불리한 것으로 나타났다.

본 연구에서는 CH4/CO2 혼합가스에서 CO2 분리를 위해 세라믹 중공사 접촉막 모듈(HFMC)을 이용하여 실험을 수행하였다. 고 내구성의 HFMC를 제작하기 위해, 고강도의 중공사막을 제조하여 평가하였다. 제조한 중공사막을 이용하여 HFMC를 제작하였고, 실험은 CH4/CO2 혼합 기체(30% CO2, CH4 balance)와 monoethanolamine (MEA)를 사용하였다. HFMC 운전 중 기체와 흡수제의 압력이 CO2 제거 효율에 어떠한 영향을 주는지 평가하였다. CO2 제거 효율은 기체압력이 증가함에 따라 같이 상승하였으며, CO2 흡수 flux 또한 액체유량과 함께 증가하는 추세를 보였다. 또한 CO2 흡수율이 40% 이하일 때 는 흡수제가 아래쪽에서 들어가는 향류형태인 LTS-1이 흡수제가 위쪽에서 들어가는 향류형태인 LTS-2보다 CO2 제거 성능 이 높았으며, 흡수율이 40% 이상일 때는 LTS-2가 LTS-1보다 성능이 높았다.

Amorphous In-Ga-Zn-O (a-IGZO) thin film transistors, because of their relatively low mobility, have limits in attempts to fulfill high-end specifications for display backplanes. In-Zn-O (IZO) is a promising semiconductor material for high mobility device applications with excellent transparency to visible light region and low temperature process capability. In this paper, the effects of working pressure on the physical and electrical properties of IZO films and thin film transistors are investigated. The working pressure is modulated from 2 mTorr to 5 mTorr, whereas the other process conditions are fixed. As the working pressure increases, the extracted optical band gap of IZO films gradually decreases. Absorption coefficient spectra indicate that subgap states increase at high working pressure. Furthermore, IZO film fabricated at low working pressure shows smoother surface morphology. As a result, IZO thin film transistors with optimum conditions exhibit excellent switching characteristics with high mobility (≥ 30cm2/Vs) and large on/off ratio.

In this study, the flat glass and adsorption pad were modeled using SolidWorks Simulation, to understand the deformation characteristics of the vertical flat glass by the adsorption pressure during vertical transport of LCD. The horizontal and vertical displacements and equivalent stresses of the flat glass were investigated by the structural analysis. From the displacement and stress visualization according to the adsorption pressure, the higher the adsorption pressure, the larger the glass surface protruded. The horizontal deformation of flat glass increased with increasing thickness and the vertical deformation increased with decreasing thickness. In addition, the maximum equivalent stress applied to the flat glass increased significantly as the adsorption pressure increased and the thickness decreased. As a result of the structural analysis, the thinner the thickness of the plate glass, the greater the effect on the adsorption pressure. Especially, the effect of the adsorption pressure was clearly observed at the thickness of 0.5mm.

Heat transfer and pressure drop of horizontal heat exchangers with different configurations and installations numerically characterized. Three different heat exchangers were used and shaped as linear, wavy, and horizontal slinky, respectively. Installation depth was set from 0.5m to 3.0m and pipe spacing was ranged from 0.3m to 2.1m. The results showed that heat transfer rate and pressure drop were increased with the increase in the installation depth and the pipe spacing. The horizontal slinky heat exchanger carried more heat compared to others due to the greater effective heat transfer surface area per installation area. In terms of a ratio of heat transfer rate to pressure drop indicating the system efficiency, the linear heat exchanger performed better than others. On the other hand, the horizontal slinky heat exchanger was the most effective with respect to a ratio of heat transfer rate to installation cost.

To understand the effect of high pressure on nitrogen oxides (NOx) formation in water added methane flames, opposed nonpremixed Water-methane/air (H2O-CH4/air) flames are numerically studied with high initial pressure. With GRI 3.0 detailed kinetic mechanism, NOx emissions are predicted for various strain rates. Due to high pressure, the chemical species are distributed in a narrow region, which means the thickness of the flame is thin. This can be clearly seen with high strain rate. Elevated pressure increases maximum temperature of flames which results in increased NOx emission. Even with elevated initial pressure, NOx emissions for H2O added methane flames are significantly decreased compare to pure methane flame. In addition, increased strain rate is also significant factor for decreasing NOx emission. With detailed rate of production analysis, in case of high pressure, it is confirmed that NO2 pathway is the most dominant reaction pathway than any other pathways.

점적기의 성능은 압력보상 기능에 따른 유량 균등성에 의해 좌우되고, 유량의 균등성은 점적기 내부 의 위치에 따른 공급압력이 일정할 때 이루어진다. 점적기의 압력보상은 탄성을 가진 연질의 실리콘과 미로가 동시에 결합된 경우에 가장 큰 효과를 나타낸다. 그러나 경질 미로만으로 구성된 점적기의 경우 에는 미로의 길이와 내부구조에 따라 유량이 크게 달라진다. 경질 미로만으로 구성된 점적기의 경우에는 연질의 실리콘을 동시에 결합한 점적기보다 공급 압력에 따른 유량의 오차가 훨씬 크게 나타나므로 간편한 반면에 성능에서는 불리한 조건을 가진다. 경질미로로 구성된 점적호스의 경우 공급 압력과 미로의 길이와 단면에 따른 최적 설계를 통하여 적절한 조건에서 폭넓게 사용할 수 있는 장점이 있으므로 이에 대한 연구는 점적기의 성능을 개선하는데 매우 중요한 역할을 한다. 그러나 이러한 분야의 연구는 거의 이루어지지 않은 실정이다. 따라서 본 연구에서는 경질미로로 구성된 점적호스의 성능평가를 구명 하기 위해 원형의 미로를 길이별로 8단계(#1~#8)로 나누어, 공급압력(0.5~3.0bar) 변화에 따른 출구유량을 실험적 방법과 이론적 해석(CFD)으로 구하였다.

In pressure retarded osmosis (PRO) process, thin film composite (TFC) type membranes which can withstand high operating pressure are required. In this study, glass fibers (GF) are used as additive for mechanical strength enhancement of the support layer of TFC membranes. The support layers were fabricated by a phase inversion method by using the casting solution of blended GF (two different size of milled GF) with polyethersulfone (PES). The fabricated support layers were characterized by FE-SEM, FT-IR, contact angle goniometer, and universal testing machine. Lab-scale ultrafiltration experiment was carried out to measure their performance. As a result, the support layer with milled GF showed higher mechanical strength and water flux than the pure PES support layer, and the support layer with smaller size GF showed higher performance.