In this paper, numerical simulations were conducted to secure both flow distribution and uniform flow discharge through a wall mount type air sterilizer. In order to increase the reliability of the simulation results where there is no well-known validation case for air sterilizer, mesh sensitivity study was performed under the constraint that y+ set to one for k-w SST turbulent modeling for both the air sterilizer and the fan. The installation of various guides and structures was reviewed in the point of flow distribution and pressure drop inside the sterilizer, and the exhaust pressure conditions were predicted to secure uniform flow discharge at outlets. This study has been done based on the computational analysis during the development stage of the air sterilizer, and the results will be verified through physical testing after production of prototype.

In this study, two ventilation holes were considered to prevent condensation in the circular column supporting the provision crane on a training ship(Saenuri) for Mokpo National Maritime University. The ventilation holes could be understood as the most simple and inexpensive way to prevent condensation because it was formed only by drilling. If sufficient ventilation is provided, the insulation and corrosion of an electric motor can be improved, and a comfortable state can be ensured in the circular column. The circular column had an electric motor for driving the provision crane so that the basic principle was to utilize the kinetic energy for the flow field from a cooling fan in the circular column. The ventilation holes attenuated the low-velocity area in the circular column and contributed to internal flow circulation with updrafts. The results were discussed through numerical analysis based on computational fluid dynamics.

The objectives of this study were to develop the optimal structures of recirculating aquaculture tank for improving the removal efficiency of solid materials and maintaining water quality conditions. Flow analysis was performed using the CFD (computational fluid dynamics) method to understand the hydrodynamic characteristics of the circular tank according to the angle of inclination in the tank bottom (0°, 1.5° and 3°), circulating water inflow method (underwater, horizontal nozzle, vertical nozzle and combination nozzle) and the number of inlets. As the angle in tank bottom increased, the vortex inside the tank decreased, resulting in a constant flow. In the case of the vertical nozzle type, the eddy flow in the tank was greatly improved. The vertical nozzle type showed excellent flow such as constant flow velocity distribution and uniform streamline. The combination nozzle type also showed an internal spiral flow, but the vortex reduction effect was less than the vertical nozzle type. As the number of inlets in the tank increased, problems such as speed reduction were compensated, resulting in uniform fluid flow.

In this study, the flow by impingement at water dust collector with movable nozzle was analyzed by computational fluid technique. The velocity and vorticity of the dust collector were compared by positioning the nozzle to up and down. Also, the mean velocity were compared through three specific locations that were the diffuser inlet, movable nozzle surface and dust collector outlet. It can be checked that the vorticity and velocity magnitude are verified by the fluid solver of Fluent. As the result of this study, the movable nozzle located at 4cm down from initial position of the nozzle shows the great characteristics of vorticity and velocity distribution for dust collection.

In this study, numerical analysis was carried out to develop low-noise axial fans, which are often used for ventilation in houses. A commercial program and the turbulence models are used for the analysis of internal fan. Proudman acoustic power model and the Curle surface acoustic power model were used for analysis. As a result, the distribution of flow velocity and pressure around the blade and guide of the fan was high, and low in the center of the fan. Noise from the inner wall of the fan case and the blade surface was the highest at the body and vane connections of the blade, and low at the center of the vane and the center of the body.

In this study, the uniformity of the horizontal velocity and the temperature of each zone were investigated by computerized analysis method to divide the drying room into three multi - rooms to ensure the uniformity of flow inside the forced convection hot air dryer. The internal structure of the drying room of the dryer was modeled using Solidworks. In order to control the flow of hot air circulating in the drying chamber, the possibility of controlling the horizontal flow inside the drying room was verified by using a perforated plate, a guide vane, and a vertical plate. From the results of the flow visualization in the drying room, it was understood that the internal flows of the dryer models 1, 2 and 3 change from ununiform flow to uniform flow. From the analysis of velocity and temperature fluctuation, the results of the analysis of the dryer model 3 satisfied the design conditions.

본 연구에서는 DVR 내부 공기유동을 직접 제어하여 CPU의 온도를 낮추기 위한 유동제어 구조물을 제안하였다. 제안된 구조물은 세 개의 얇은 판의 형태로 구성되었으며, DVR 내부의 공기 유동을 포괄적으로 제어하여 CPU의 효율적인 방열을 유도하고자 하였다. DOE와 RSM을 이용한 매개변수 연구기법을 통해 유동제어 구조물의 형상을 최적화하였으며, 해석에는 유한체적방법을 이용한 유체역학 분석 패키지인 FlowVision을 사용하였다. 실제 DVR 기기에서의 실험을 통해 해석 결과를 검증한 결과 CPU의 온도가 16.1℃ 낮아짐을 확인하였다

The non-reacting flow field and the movement of sand particles inside a 30MW circulating fluidized bed combustor is numerically simulated via the finite volume method. The primary air is supplied through 23x23 array of nozzles located on the bottom and the secondary air is supplied through 12 inlet pipes located on the side walls. The steady state velocity field shows that a very complex flow pattern is formed in the lower part of the combustor. As the gas moves upward, the velocity magnitude decreases and the gas exits the combustor after hitting the top wall. To investigate the behavior of sand particles with different diameters, a particle tracking calculation is performed by introducing sand particles continuously at the z=3 m plane. For the given air flow rate condition, sand particles smaller than 0.3 mm show a complex movement pattern near the secondary air inlet and then rise toward the outlet.

The refrigerant temperature of a compressor increases due to heat generated in the discharge chamber and the motor. The increase of the suction temperature raises the superheat resulting in EER reduction. Thus, accurate superheat prediction is needed for the design of an efficient compressor. In this paper, the unsteady flow analysis is performed using CFD to predict the superheat. The results show that the suction temperature increases by about 26 °C which agrees well with the experiments.

Abstract The increase of the superheat is one of several factors adversely affecting the efficiency of the refrigeration cycle. To this end, it is important to release the heat inside the compressor. Therefore, in this paper, we have increased the convective heat transfer coefficient inside the compressor by utilizing the vibration of the moving part of the compressor. The results show that reducing the gap between the shell and the moving part increases the flow velocity in the gap resulting in the increase of convective heat transfer coefficient.

본 연구는 원심펌프 내부 유동장 특성에 대한 시뮬레이션 및 시각화에 중점을 둔다. 3D 수치해석은 Reynolds Average Navier-stock 코드를 k-Ɛ 표준 2차방정식 난류 모델로 처리하여 수행하였다. 시뮬레이션은 흡입측, 임펠러, 토출측 영역에서 조도로 인한 마찰 손실과 임펠러 웨어링에서 체적 손실을 포함한다. 해석과 실험사이의 성능곡선 비교결과 최대 5 %의 작은 차이를 보이며 동일한 추세를 나타냈다. 최고 효율점에서 속도 벡터는 고르게 나타났지만 비 설계점에서는 현저한 변화가 나타났고, 텅 부근의 임펠러 유로토출부에서 강력한 재순환 영역이 나타났다. 비교적 일정한 압력분포가 텅 부근임에도 불구하고 임펠러 주위에 관찰되었다. 볼류트 내에서 기하학적으로 인해 형성된 나선형 와류가 이 영역에서 유동장이 상대적으로 난류이고 불안정하다는 것을 증명하였다.

본 연구에서는 볼텍스 세퍼레이터 내부의 밀폐된 영역 내에서 발생하는 회전에 의한 입자상 물질과 유체의 분리 특성 파악을 위하여 전산유체역학을 이용한 수치해석을 수행하였다. 볼텍스 세퍼레이터는 접선방향 운동량으로 인해 회전유동이 발생하여 원심력과 중력으로 인한 입자상 물질과 유체의 분리가 이루어지므로 비정상 상태의 복잡한 흐름을 갖는다. 본 연구에서는 유한체적법 기반의 3차원 점성 유동장의 비정상 해석을 수행하였으며 이상유동의 해석을 위하여 오일러-오일러 모델을 이용하였다. 효율적인 설계를 위하여 세 가지 형태의 볼텍스 세퍼레이터 내부 구조에 대한 분석을 수행하였으며, 입자상 체적비, 입자 직경의 변화에 따른 분리 효율을 비교하였다. 또한 전산해석을 통하여 얻어진 분리성능을 확인하였으며 실험을 통한 검증을 수행하였다.

Froude(Fr) 수의 상사성을 통해 문풀의 크기와 유동 속도를 결정할 경우 축척비에 따라 문풀 내부 유동에 대한 Reynolds(Re)수가 크게 달라진다. 즉 같은 Fr 수를 갖는다 할지라도 축척비에 따라 문풀 내부 유동 특성이 달라질 수 있음을 의미한다. 본 연구에서는 같은 Fr 수로 상사되었을 때 축척비가 문풀 내부 유동 특성에 미치는 영향을 분석하기 위해 2차원 수치 해석을 수행하였다. 문풀의 크기가 작을 때 문풀에 작용하는 힘은 매우 주기적인 특성을 보이는 반면 문풀의 크기가 커질수록 주기가 일정하지 않은 교란 특성을 보이기 때문에 과도 응답과 통계적 정상 상태의 응답을 구분하기 어려워진다. 주파수 특성에 있어서도 축척비의 제곱근에 반비례하여 나타나는 주파수 특성(f0.5 ~ 2f1 ~ 2f2.0)은 Fr 수의 상사성에 따른 유동 특성으로 볼 수 있으나, 문풀의 크기가 클 때 매우 낮은 주파수(f2.0=0.07)로 문풀 내부에서 매우 강한 와가 발생하는데 이는 축척비에 따른 영향이다.