• 설비공학논문집
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• 제27권9호
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• pp.468-474
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• 2015

When oil is used for cooking in detached or apartment houses, large amounts of oil-mist, smoke, and particulate substances are generated and dispersed into the indoor-air environment. These pollutants diffuse into the surroundings and spread their odor while rising fast at a high temperature due to the heat energy from the gas range. Although the exhaust gas is discharged from the exhaust hood, which is installed on the top of a gas range to remove the diffuse pollutants, the exhaust conditions can vary greatly because they depend on the shape of the exhaust hood and the discharge rate. In this paper, the air that is required for the gas-exhaustion process is supplied by an air curtain that surrounds the kitchen hood, and the pollutant-capturing efficiency varies depending on the angle of the discharge grills; the pollutant-capturing efficiency was studied using a numerical-analysis method. The results indicate that the pollutant-capturing efficiency is not significantly changed by a change of the discharge-grill angle at a low air-discharge rate; however, at a high air-discharge rate, the efficiency value increases with an increase of the discharge-grill angle, whereby the best value occurs at 30 degrees and the efficiency decreases above this angle. Below 30 degrees, the effect of the discharge rate on the capturing efficiency is more than that of the discharge-grill angle.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.746-752
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• 2000

A study on discharge characteristics of a rotating discharge hole is very important to enhance the performance of an induction motor which have external forced cooling system. The discharge characteristics of rotating discharge holes are influenced by rotating speed, length-to-diameter ratio, inlet shape of rotor holes, etc. An experimental study on the effect of chamfered inlet edge of rotor inlet part with various depth-to-diameter and inlet chamfered edge angle is conducted. Depth-to-diameter ratios range from 0 to 0.5 and inlet chamfered edge angle range from 0 to 60. As a result, there is an optimal design point of inlet chamfered edge depth. And the inlet edge angle far maximum discharge coefficient is influenced mainly by the rotating speed of discharge holes.

• 한국수자원학회논문집
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• 제37권10호
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• pp.881-888
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• 2004

본 연구에서는 지류와 본류의 합류부의 접근각도, 상류부 유량 및 본류와 지류의 유량비 변화에 따른 수리 모형실험을 통한 합류부의 수리학적 특성을 파악하였다. 합류부의 수리학적 특성은 합류점 부근의 유속과 관련된 최대유속의 크기 및 발생위치를 분석하였다. 합류점 부근의 최대유속은 접근각도가 증가함에 따라 점차 증가하며, 이는 유량 및 유량비가 증가하는 경우에도 동일한 경향을 나타낸다. 합류점 부근의 최대유속의 발생지점은 접근각도가 증가함에 따라 거리가 증대되는 것으로 나타났다. 또한, 유량이 증가하는 경우에도 거의 동일한 양상을 보여준다.

• 설비공학논문집
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• 제22권2호
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• pp.57-63
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• 2010

Air curtains are widely used for gates of shopping mall, warehouse, cold stores and refrigerated display cabinets. The purpose of the air curtain is to reduce the infiltration of outdoor air and heat loss from the air conditioning space to ambient air. The discharge angle of air curtain is very important as the sealing efficiency is affected by it. This paper presents a performance of single jet air curtain in heating space when the discharge angle of nozzle changes. A numerical simulation is used to study the influence of various parameters on the efficiency of the downward-blowing air curtain device which is installed inside of the wall above the door. The performance of the air curtain is evaluated by sealing efficiency which provides the assessment of the energy savings. A condition of discharge angle that has the highest sealing efficiency is proposed.

• International Journal of Aeronautical and Space Sciences
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• 제3권1호
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• pp.1-8
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• 2002

A numerical analysis was performed on the fluid flow in injector orifice of a liquid rocket engine. The present computational code was verified against the published data for turbulent flow in a pipe with a sudden expansion-contraction. Considered were the parameters for the flow analysis in an injector orifice: Reynolds number, ratio of mass flow rate of the injector orifice and inlet flow rate, and slant angle of the injector orifice. The discharge coefficient increased slightly as the Reynolds number increased. The slant angle of the injector changed critically the discharge coefficient. The discharge coefficient increased by 7% when the slant angle changed from $-30^{\circ}$ to $30^{\circ}$ The ratio of mass flow rate had relatively little impact on the discharge coefficient.

• 산업기술연구
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• 제26권A호
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• pp.129-137
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• 2006

In this research, we made a one and two-dimensional analysis of numerical data collected from the bend curvature of a bended river section. According to the result from the numerical analysis, the inflow ＆ output angle caused a water level deviation which increased with an increase of the flood discharge. From the water level deviation of our two-dimensional numerical model, we obtained the maximum slope of 6,67% when the inflow and output angle was 105 degrees and the flood discharge was 500 CMS. As for the right side, the differences with the one-dimensional numerical model were reduced when the angle was more than $90^{\circ}$. As for the left side the differences were reduced when the angle was more than $105^{\circ}$. For a river with more than 90 degrees bend curvature, a hydraulic experiment would be more appropriate than a numerical analysis.

• 한국수자원학회논문집
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• 제37권8호
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• pp.623-630
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• 2004

본 논문에서는 수리모형 실험을 통하여 지류와 본류의 합류점의 접근각도, 본류의 유량 및 본류와 지류의 유량비 변화에 따른 합류부의 수리학적 특성을 파악하였다. 실험은 수로길이 450cm의 수로에서 실시하였으며, 본류와 지류의 수로폭은 각각 40cm와 32cm이었으며, 4조의 물탱크와 펌프가 설치되었다. 합류점 부근의 정체 구간의 길이는 접근각도가 증가함에 따라 증가되며, 본류의 유량과 지류와 본류와의 유량비가 증가되는 경우에도 이 경향은 동일하다. 그러나 동일한 합류점 접근각도와 유량비에 있어서 본류 유량 변화에 따른 합류점 부근의 정체구간 변화는 매우 적게 나타나고 있다. 또한 본류와 지류의 유량비가 증가할수록 유속의 정체 구간의 길이가 커져, 유사의 퇴적증가를 유도하는 주요원인이 된다. 합류점 부근의 가속유로는 접근각도가 작을수록 수로 내 중앙부에 한정되지만, 접근각도가 증가할수록 영향권이 증가된다.

• 한국유체기계학회 논문집
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• 제16권4호
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• pp.10-14
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• 2013

In this study, we have numerically investigated the hydraulic efficiency with various values of discharge angle($11^{\circ}$, $12^{\circ}$, $14^{\circ}$, $15^{\circ}$, $17^{\circ}$, $18^{\circ}$, $20^{\circ}$) in the Francis turbine of hydropower generation under 15MW with fixed values of head range of 151m and flow rate($10.97m^3/s$). We also conducted the numerical analysis with constant inlet angle in the Francis turbine using the commercial code, ANSYS CFX. Hydraulic characteristics for different values of the runner blade angle are investigated. The results showed that the change of discharge angles significantly influenced on the performance of the turbine hydraulic efficiency.

• 한국전기전자재료학회논문지
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• 제11권12호
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• pp.1055-1059
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• 1998

The correlation between the propagation of electrical tree and distributions of partial discharge(PD) pulses accompanying with electrical tree of bush type in low density polyethylene were discussed. We measured the growth of electrical tree by using optical microscope and PD data simultaneously. The PD data detected and analyzed were PD magnitude, repetition rate, average discharge power, average phase angle, and $\psi$-q-n distribution pattern. The average discharge power and repetition rate of PD had good linear relation with area of tree. Repetition rate and peak discharge magnitude and width of discharge phase angle increased with the tree.

• 한국수자원학회논문집
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• 제48권8호
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• pp.625-634
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• 2015

합류부에서의 지류의 합류각, 지류와 본류의 유량비에 추가하여, 본류 준설에 의한 하상고 불일치에 따른 다양한 양상의 분리구역의 특성을 CCHE2D 모형을 사용하여 분석하였다. 분리구역은 지류가 합류되어진 직후 단면에서의 유속이 0(영)인 경계로 정의하였다. 합류각 $30^{\circ}$ 이하에서는 분리구역이 형성되지 않았다. 유량비와 합류각 증가에 따른 분리구역의 크기는 일반적으로 증가하는 양상으로 나타났다. 준설 깊이비 증가에 따른 분리구역의 크기는 합류부 수용체의 증가에 기인한 지류에서의 상대적인 운동량의 감소로 인하여 감소되었다. 유량비와 합류각의 변화에 따른 분리구역의 수축지수를 규명하였고, 통수기능의 저하에 따른 배수영향을 확인하였다. 합류각, 유량비, 준설 깊이비에 따른 분리구역의 형상지수의 관계식을 제안하였다.