• 대한기계학회논문집B
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• 제27권6호
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• pp.781-788
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• 2003

In the present study, the heat and flow characteristics of a parallel-flow heat exchanger are numerically analyzed by using three-dimensional turbulent modeling. Heat transfer rate and pressure drop are evaluated using the concept of the efficiency index by varying the locations, the shapes and angles of inlet/outlet, and the protrusion height of flat tube. It is found that negative angle of the inlet improves the heat transfer rate and pressure drop. Results show that the locations of the inlet and outlet should be toward the right side and the left side to the reference model, respectively, in order to enhance the heat transfer rate and pressure drop. Increasing the height of the lower header causes pressure drop to decrease and yields the good flow characteristics. The lower protrusion height of flat tube shows the improvement of the heat transfer rate and pressure drop. The heat transfer rate is greatly affected by the parameters of outlet side such as the location and angle of the outlet. However, the pressure drop is influenced by the parameters of inlet side such as the location and angle of inlet and the height of the header.

• 한국추진공학회지
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• 제25권6호
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• pp.29-35
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• 2021

벨 마우스 흡입구는 압력 손실이 거의 발생하지 않으며 정확한 유량 계측이 가능하다는 장점이 있어 다양한 산업에서 적용되고 있다. 본 연구에서는 벨 마우스 흡입구의 벨 형태를 Long radius 형상으로 설계하였고 야외 환경에서 엔진 운용조건에 대해 흡입되는 공기의 압력강하가 발생되는 동시에 외부 물질에 의한 엔진 손상이 발생되지 않는 적합한 보호망의 격자 사이즈를 선정하였다. 보호망 설치로 인한 전압력 손실에 대해 전산 해석 및 실험 결과 획득한 두 가지 데이터 로부터 수정된 압력 강하 계수 방정식을 제시할 수 있었다.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.1226-1231
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• 2009

This paper presents operating characteristics of internal heat exchanger(IHX) for $CO_2$ geothermal heat pump in the heating mode. Mass flow rate of $CO_2$, inlet temperatures of $CO_2$ at high and low pressure side were selected as main effect factors by using fractional factorial DOE(Design of Experiments). And RSM(Response Surface Method) was used in optimization phase. The results show that heat transfer rate of IHX increases when either inlet temperature of low pressure side decreases or inlet temperature of high pressure side increases. Effectiveness of IHX increases with increasing of inlet temperature of either high pressure side or low pressure side. Finally, performance contour map was provided over the operation ranges of the main design factors.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2011년 춘계학술대회논문집
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• pp.218-224
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• 2011

A supersonic inlet at angle of attack has anti-symmetric pressure distribution, and it can make flow instability and structural problem. In this study, numerical analysis of three-dimensional inviscid flow was conducted under various throttle ratio and angle of attack conditions. Throttle ratio was defined as the ratio of the exit area to the smallest cross section area at inlet, and the ratio is controlled from 0 to 2.42. At various angle of attack, the characteristics of steady and unsteady flow around supersonic inlet is observed under different throttling ratios. From these results, pressure recovery curves and pressure history curves were plotted by post processing. Using pressure history data, FFT analysis is also carried out. Through these processes, it shows the tendency of pressure distribution anti-symmetricity and changing dominant frequency as increasing angle of attack.

• 융복합기술연구소 논문집
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• 제4권2호
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• pp.61-65
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• 2014

Pressure distribution around rotating impeller blades in centrifugal pump has been main issue for design of efficient and high performance automotive water pump. In addition, pressure losses of inlet water pipes should be considered to reduce additional pressure drop and design high performance engine cooling system. In this paper, pressure distribution inside water pump and pressure drop between inlet and outlet of water pump are investigated numerically to design plastic water pump for clean diesel engine application. And the inlet geometry of water pump was considered to analysis the effect of inlet water pipe geometry on pressure distribution around impeller blades and outlet pressure. The prediction results are compared with experimental data to validate and determine optimal operation condition without water pump cavitation. Major design parameters such as blade angle, volute geometry, system pressure, and coolant flow rate are considered to confirm applying possibility of plastic blades to the clean diesel engine.

• 대한환경공학회지
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• 제22권4호
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• pp.639-650
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• 2000

여과집진장치의 중요 문제점 중의 하나인 높은 압력손실을 해결하기 위해 하부유입식 원심 여과집진장치의 특성을 실험적으로 분석하는 것이 본 연구의 주목적으로, 실험은 원심 여과집진장치의 집진효율과 압력손실(특히, 여과포 압력손실) 특성을 일반 여과집진기와 비교 분석하기위해 유입유속, 유입농도 및 선회영역의 변화 등과 같은 다양한 파라메터들에 대해 수행하였다. 실험 결과, $1{\mu}m$ 이하의 서브마이크론 입자들에 대해서 접선유입식이 중앙유입식의 경우 보다 높은 집진효율을 보였으며, 총괄집진효율은 99% 이상을 나타내었다. 유입농도 $100mg/m^3$에서, 압력손실 감소율은 유입유속에 따라 large bag의 경우 15~38%인 반면, small bag의 경우 선회영역의 증가에 의해 30~48%이었다.

• 대한기계학회논문집
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• 제16권7호
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• pp.1408-1418
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• 1992

본 연구에서는 여러가지 흡기관 조건 및 밸브타이밍 변화에 대하여, 현재까지 연구에서 확인된 IVC에서 흡기포트압력 값의 체적효율에 대한 영향을 검토하고, 흡기 밸브가 열리는 동안 흡기 포트압력의 어느 부분 또는 지점이 엔진의 체적효율 변화를 설명해 줄 수가 있는지를 실험적으로 규명하고자 하였다.이 목적을 위해 각 흡입조 건에 대한 흡기포트압력 및 엔진 성능값을 측정.분석하여 서로의 연관성을 비교, 검토 하였다.

• 한국유체기계학회 논문집
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• 제13권1호
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• pp.35-41
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• 2010

Experimental study on the flow field inside the nozzle for radial turbine was performed. At design point, the pressure is high and the Mach number is low at the pressure side of the nozzle inlet semi-vaneless space as the flow turns through the nozzle vanes. As the flow accelerates through the nozzle passage to the throat the pressure level at the pressure and suction sides becomes similar. The flow continued accelerating from the throat to the inlet of turbine wheel and the pressure field became uniform in the circumferential direction in the vaneless space. In high expansion ratio condition, strong favorable pressure gradient band region occurred just after the throat in the semi-vaneless space in the circumferential direction and the pressure became uniform in the circumferential direction after this band. In low expansion ratio condition, core flow acceleration is dominant after the throat and this non-uniform pressure field reached to the inlet of turbine wheel.

• Tribology and Lubricants
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• 제38권5호
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• pp.213-221
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• 2022

This paper presents performance measurements of pressure drop and leakage flow rate of test flat seals with asymmetric inclined grooves. This study aims to reveal the influence of groove shapes, often machined in radial film riding-face seals, in forming a hydrodynamic wedge on leakage performance. A test facility was developed, and test seals were manufactured to study the effects of the inlet pressure level, ratio of inlet to outlet pressure, seal groove length, and seal groove height on the steady-state pressure drop and leakage performance. A series of tests were conducted, and the test data were compared to the predictions from a simple and efficient mathematical model using a one-dimensional Reynolds equation. The test results revealed that an increase in the inlet pressure increased the pressure drop through the test seals. The leakage flow rate increased significantly as the inlet pressure and ratio of the inlet to outlet pressure increased. The groove shape also affects seal performance. An increase in the groove length and height resulted in an evident increase in the leakage flow rate. The simple model predictions underestimated the leakage flow rates but showed good agreement with the trend in the measurements for all test operating conditions and changes in the groove shape.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제35회 추계학술대회논문집
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• pp.563-564
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• 2010

IRR의 부스팅 모드 시 흡입구에 발생하는 압력진동을 감쇄하기 위한 방안을 수치적으로 연구하였다. 축대칭 형태의 초음속 흡입구에 slit을 장착하여 유입되는 공기 유량을 줄여가며 흡입구 내부의 압력 진동을 조사하였다. 흡입되는 유량이 감소함에 따라 압력의 진폭은 감소하고 내부 압력의 최댓값 역시 감소하였으며, 주파수는 약간 증가하는 경향을 보였다. 흡입구의 slit을 이용하여 최적화된 압력 진폭과 주파수대를 얻어낼 수 있다면, 이 방안은 IRR의 부스팅 모드 및 천이 모드에서의 안정성을 높이는데 활용될 수 있을 것으로 판단된다.