• 상하수도학회지
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• 제21권5호
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• pp.581-587
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• 2007

In order to suggest the methodology for improving the equality of flow distribution in a distribution channel, wet tests were carried out for pilot plant which was scaled down to 1/8 of full scale distribution channel being operated in domestic K_water treatment plant. The correlation between various hydraulic variables and their effects on the equality of flow distribution was evaluated through wet tests using pilot plant. From the results of wet tests, the longitudinal baffle with orifices was installed in the distribution channel, the equality of flow distribution was improved on the condition that the Froude number in pilot plant was similar with that in the full scale channel. Also, the opening ratio of the orifices on the longitudinal baffled did not have influence on the performance of the equality of flow distribution when the average flow velocity and Froud number were relatively low (Froude number ${\fallingdotseq} 0.01$). In the other hand, the performance of the equality of flow distribution was improved with increasing the opening ration of on the longitudinal baffle under conditions of relatively high average flow velocity and high Froud number(${\gtrsim}0.1$)

• Nuclear Engineering and Technology
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• 제54권2호
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• pp.546-553
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• 2022

Narrow rectangular channels are employed in nuclear research reactors that use plate-type nuclear fuels, high heat-flux compact heat exchangers, and high-performance micro-electronics cooling systems. Two-phase flow in narrow rectangular channels is important, and it needs to be better understood because it is considerably different than that in round tubes. In this study, mechanistic models were developed for the flow regime transition criteria for various flow regimes in co-current air-water two-phase flow for vertical downward flow inside a narrow rectangular channel. The newly developed criteria were compared to a flow regime map of downward air-water two-phase flow inside a narrow rectangular channel with a 2.35-mm gap width under ambient temperature and pressure conditions. Overall, the proposed model showed good agreement with the experimental data.

• International Journal of Vascular Biomedical Engineering
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• 제1권2호
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• pp.30-35
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• 2003

Flow characteristics of blood flow in a micro channel were investigated experimentally using a micro-PIV (Particle Image Velocimetry) velocity field measurement technique. The main objective of this study was to understand the real blood flow in micron-sized blood vessels. The Reynolds number based on the hydraulic diameter of micro-channel for deionized (DI) water was about Re=0.34. For each experimental condition, 100 instantaneous velocity fields were captured and ensemble-averaged to get the spatial distributions of mean velocity. In addition, the motion of RBC (Red Blood Cell) was visualized with a high-speed CCD camera. The captured flow images of nano-scale fluorescent tracer particles in DI water were clear and gave good velocity tracking-ability. However, there were substantial velocity variations in the central region of real blood flow in a micro-channel due to the presence of red blood cells.

• 한국전산유체공학회지
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• 제18권4호
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• pp.17-24
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• 2013

In this study, we consider the characteristics of channel flow in the presence of an infinite streamwise array of equispaced identical rotating circular cylinders. This flow configuration can be regarded as a model representing a micro channel or an internal heat exchanger with cylindrical vortex generators. A numerical parametric study has been carried out by varying Reynolds number based on the bulk mean velocity and the cylinder diameter, and the gap between the cylinders and the channel wall for some selected angular speeds. An immersed boundary method was employed to facilitate implementing the cylinders on a Cartesian grid system. No-slip condition is employed at all solid boundaries including the cylinders, and the flow is assumed to be periodic in the streamwise direction. The presence of the rotating circular cylinders arranged periodically in the streamwise direction causes a significant topological change of the flow, leading to increase of mean friction on the channel walls. More quantitative results as well as qualitative physical explanations are presented to justify the effectiveness of rotating cylinders to modify flow topology, which might be used to enhance heat transfer on the channel walls.

• 한국자동차공학회논문집
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• 제21권6호
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• pp.72-80
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• 2013

For the proper cooling of in-wheel motor, the cooling channel should have the characteristics which are low pressure drop and adequate cooling oil supply to motor part. In this study, the flow performance of cooling channel for in-wheel motor was evaluated and the shape of the channel was optimized. First, the pressure drop and flow distribution characteristics of the initial channel model were evaluated using numerical analysis. Also, by the result of analysis and design modification, 4 design parameters of the channel were selected. Second, using the Taguchi optimal method, the cooling channel was optimized. In the method, nine models with different levels of the design parameters were generated and the flow characteristics of each models was estimated. Base on the result, the main effect of the design parameters was founded and optimized model was obtained. For the optimized model, the pressure drop and oil flow rate were about 0.196 bar and 0.207 L/min, respectively. The pressure drop decreased by about 0.3 bar and the oil flow rate to the motor part increased by about 0.2 L/min compared to the initial model.

• 대한기계학회논문집B
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• 제31권12호
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• pp.1033-1041
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• 2007

This paper studied the characteristics of performance and temperature in a unit cell of a planar type SOFC under various conditions by employing computational fluid dynamics (CFD). In order to derive thermal stress distribution and performance characteristics, the 3-D model simulation for a single channel was performed in various conditions which include interconnect materials $(LaCrO_3/AISI430)$, gas flow direction (co-flow/counter-flow) and inlet temperature (923 K/1173 K). From these results of a single channel, the most effective conditions were applied to the unit stack with multi-channel and the temperature distribution is displayed. Considering both thermal stress and performance, the best combination is 923 K inlet temperature, counter-flow and interconnector of stainless steel. As the end results, flow, thermal and current density distributions were found in the model with multi-channel applied to the best combination and were concentrated in the middle of channels than in the edge.

• 해양환경안전학회:학술대회논문집
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• 해양환경안전학회 2005년도 추계학술대회지
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• pp.159-163
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• 2005

채널 내부의 비정상 흐름을 규명하기 위하여 실제 사용 중인 판형 열교환기 모델을 대상으로 가시화 실험과 입자영상유속계(PIV)를 사용한 계측을 수행하였다. 실험은 기복을 가지고 있는 채널의 높이와 내부유동의 부분 평균속도벡터에 따른 7가지 종류의 레이놀즈수를 적용하였고, 순간속도벡터분포와 유동특성을 고찰하였다. 실험에서 삼각형상 그루브 채널은 하부 채널과 채널 흐름에 의해서 받고 있는 전단응력의 그루브 흐름과의 관계에서 복합적인 흐름의 형태로 나타났다. 삼각형상 그루브와 채널 사이의 경계인 전단혼합층은 채널에서 난류강도가 상승하는 주흐름에 영향을 미쳤다.

• 한국습지학회지
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• 제10권2호
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• pp.67-79
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• 2008

하천에서의 부정류 해석을 위해서 1차원 유한차분법(FDM)인 Abbott-Ionescu scheme과 2차원 유한체적법(FVM)인 근사의 Riemann solver(Osher scheme)에 대하여 살펴보았다. 두 모형은 직선 하도, 약간 굽어진 사행하도 및 사행하도에서의 흐름 문제들에 적용되었으며 결과의 비교는 균일한 직사각형 수로에 대하여 이루어졌다. 하천의 복잡한 형상의 표현하기 위해서는 이를 고려할 수 있는 유한체적법을 이용하였다. 유한차분법과 유한체적법 결과는 수위 및 유량 수문곡선에 대하여 매우 만족스러운 것으로 나타났다. 균일한 직선하도에 대해서는 1차원분석으로도 충분하다는 사실을 파악할 수 있었으며, 사행하도의 경우 흐름을 정확하게 모형화하기 위해서는 2차원 또는 3차원 모형을 사용하여야 할 것이다.

• 한국수자원학회논문집
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• 제41권8호
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• pp.773-784
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• 2008

본 연구는 노면배수시설에 이용될 수로 양단에 유출구를 가지며 유량이 연속적으로 증가하는 선형 배수로의 부등류 흐름의 해석 방법을 정립하기 위하여 수행되었다. 지배 방정식으로서 유한 차분 형태의 대수방정식을 사용하여 지배단면에서의 수심 값을 경계조건으로 Newton-Raphson 방법에 의하여 수면곡선을 계산하였다. 하류단에 유출구를 갖는 수로와 수로 양단에 유출구를 갖는 수로를 고려하고, 다양한 종단경사에 대하여 흐름 해석을 수행하였다. 단, 양단에 유출구를 갖는 수로의 경우 양단을 지배단면으로 만드는 임계 종단경사를 조사하여 이보다 작은 종단경사에 대한 흐름 해석을 수행하였으며, 임계경사는 지배단면의 위치와 종단경사의 관계로부터 결정하였다. 하류단에 하나의 유출구를 갖는 수로의 경우 수로 상에 존재하는 지배단면의 위치를 조사하여 그 지점을 기준으로 상류 및 하류 방향으로 수심을 계산한다. 반면 양단에 유출구를 갖는 수로의 경우 지배단면이 수로 양단이라면 분수계를 가정하여 분수계를 기점으로 구분되어지는 상류측 및 하류측 수로에 대한 흐름 해석을 수행하고, 상류단에서 분수계 방향으로 그리고 하류단에서 분수계 방향으로 계산된 분수계 지점의 두 수심이 동일할 때까지 흐름 계산을 반복한다. 흐름 계산 결과 양단에 유출구를 갖는 수로가 임계경사보다 큰 경사로 설치된 경우에는 하류단에 유출구를 갖는 수로의 흐름 거동과 유사지는 것으로 판단되었다. 노면배수시설 설계의 중요한 요소인 최대수심은 종단경사가 작을 때 등류 해석으로 계산된 값이 부등류 해석보다 크게 산정되었으며, 이는 종단경사가 작을 때 등류 해석을 기반으로 한설계가 과대설계가 되기 쉽다는 것을 의미한다.

• 한국유체기계학회 논문집
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• 제10권5호
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• pp.41-45
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• 2007

The effects of channel area on the performance of regenerative type fuel pump were numerically studied by commercial CFD code (ANSYS CFX-10). To examine the effects of channel area, the shapes of the side channel and blade were simplified. The channel area affected the flow characteristics of the internal recirculation flow between the side channel and the blade groove and also made a difference in the overall performance. These loss mechanism with circulation flow were adopted as a loss coefficient in the performance prediction program. The loss coefficient was newly derived from the results of calculations with different channel area, and compared with the experimental results in the reference paper and used to modify the performance prediction program. The circulation flow characteristics with different channel area, which is related with loss mechanism, were also discussed with the results of 3-dimensional flow calculations.