• 한국산업융합학회 논문집
• /
• 제22권2호
• /
• pp.173-181
• /
• 2019

This study was carried out numerically to investigate the flow characteristics in the Venturi tube with $90^{\circ}$ T-branch tube and the inflow of condensed water into the Venturi tube from the branch tube. In this study, the diameter of the branch tube(1, 2, 3mm) and the neck diameter of the Venturi tube(0.3, 0.9, 1.5mm) were varied. The flow rate of the water at the Venturi tube inlet is 80cc/min and the water temperature is 288K. The condensed water temperature at the branch tube inlet is 355K. It was found that the velocity and pressure of the fluid near the branch point in the Venturi tube were more dependent on the diameter of the Venturi tube than the diameter of the branch tube. The temperature of the mixed water at the exit of the Venturi tube was the highest when the Venturi tube's neck diameter is 0.9mm and the branch tube diameter is 2mm. This means that the condensed water is flowing well through the branch tube.

• 말소리와 음성과학
• /
• 제15권2호
• /
• pp.31-40
• /
• 2023

목적: 물 속에서 튜브 발성은 semi-occluded vocal tract(SOVT) 연습 중 하나로 환자가 튜브를 물 속에 잠기게 하여 거품을 내면서 발성을 하는 것으로 음성 훈련에 널리 사용되어 왔다. 본 연구는 과기능성 음성장애 환자를 대상으로 물저항발성 동안 튜브 직경과 튜브를 담그는 물 깊이가 물거품 높이와 최대발성지속시간(maximum phonation time, MPT)에 미치는 영향을 조사하는 것을 목적으로 한다. 방법: 과기능성 음성장애 환자 17명에게 튜브 직경(5, 7, 10 mm), 튜브를 담그는 물 깊이(4, 7, 10 cm)에 따라 지속적인 /u/발성을 하면서 거품을 내도록 하였다. 물거품 높이 및 MPT 기록을 위해 수위 센서를 이용한 물저항발성 바이오피드백 시스템을 사용하였다. 결과: 물거품 높이는 튜브 직경에 의해 유의하게 변화한 반면 MPT는 튜브 직경과 깊이에 따라 유의하게 변화하였다. 직경이 더 넓을수록 주어진 깊이에 대해 유의하게 낮은 물거품 높이를 나타냈지만, 상대적으로 일관된 버블 높이가 유지되었다. 물의 깊이에 따라 주어진 튜브 직경에서 물거품 높이는 유의한 차이가 없었으나, 물의 깊이에 따라 MPT는 유의하게 감소하였고 튜브가 넓을수록 MPT가 유의하게 감소하였다. 결론: 수위 센서 방식의 물저항 바이오피드백 시스템은 튜브 직경 및 수심에 따른 기포 특성 및 성대 진동에 대해 유용한 정보를 제공하였다. 또한, 수위센서를 이용한 물저항발성 바이오시스템은 과기능적 음성장애가 있는 환자의 물저항 발성 중 호흡 지지를 모니터링하는 데 유용하게 사용될 수 있다.

• 한국압력기기공학회 논문집
• /
• 제8권2호
• /
• pp.33-41
• /
• 2012

The component cooling water heat exchangers are critical components in a nuclear power plant. As the operation years of the heat exchanger go by, the maintenance costs required for continuous operation also increase. Most heat exchangers have carbon steel shells, tube support plates and flow baffles. The titanium tube is susceptible to flow induced vibration. The damage on carbon steel tube support rod and titanium tube around cooling water entrance area is inevitable. Therefore, analysis of internal flow around the component cooling water entrance and tube channel is a good opportunity to seek for failure prevention practice and maintenance method. The numerical study was carried out by FLUENT code to find out the causes of tube failure and its location.

• International Journal of Air-Conditioning and Refrigeration
• /
• 제9권3호
• /
• pp.57-62
• /
• 2001

Falling film heat transfer analyses with aqueous lithium bromide solution were performed to investigate the transfer characteristics of the copper tubes. Finned (knurled) tube and a smooth tube were selected as test specimens. Averaged generation fluxes of water and the heat flux were obtained. As the film flow rate of the solution increased, the generation fluxes of water decreased for both tubes due to the fact that the heat transfer resistance increased with the film thickness. The effect of the enlarged surface area at the knurled tube was supposed to be dominant at a small flow rate. The generation fluxes of water increased with the increasing degree of tube wall superheat. Nucleate boiling is supposed to occur at a wall superheat of 20K for a smooth tube, and at 10K for a knurled tube. The increased performance of the knurled tube was supposed to mainly come from the effect of the increased heating surface area.

• 설비공학논문집
• /
• 제18권1호
• /
• pp.55-65
• /
• 2006

The air and water flow distribution are experimentally studied for a round header - flat tube geometry simulating a parallel flow heat exchanger. The number of branch flat tube is thirty. The effects of tube outlet direction, tube protrusion depth as well as mass flux, and quality are investigated. The flow at the header inlet is identified as annular. For the downward flow configuration, the water flow distribution is significantly affected by the tube protrusion depth. For flush-mounted configuration, most of the water flows through frontal part of the header. As the protrusion depth increases, more water is forced to the rear part of the header. The effect of mass flux or quality is qualitatively the same as that of the protrusion depth. Increase of the mass flux or quality forces the water to rear part of the header. For the upward flow configuration, however, most of the water flows through rear part of the header. The protrusion depth, mass flux, or quality does not significantly alter the flow pattern. Possible explanations are provided based on the flow visualization results. Negligible difference on the water flow distribution was observed between the parallel and the reverse flow configuration.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2010년 춘계학술대회논문집
• /
• pp.365-367
• /
• 2010

In this paper, we presented the exact Riemann solver for the air-water two-phase shock tube problems where the strength of the propagated sock wave is moderately weak. The shock tube has a diaphragm in the middle which separates water medium in the left and air medium in the right. By rupturing the diaphragm, various waves such as rarefaction wave, shock wave and contact discontinuity are propagated into water and air. Both fluids are treated as compressible, with the linearized equations of state. We used the isentropic relations for the air and water assuming a weak shock wave. We solved the shock tube problem considering a high pressure in the water and a low pressure in the air. The numerical results cleary showed a left-traveling rarefaction wave in the water, a right-traveling shock wave in the air, and the right-traveling material interface.

• Corrosion Science and Technology
• /
• 제9권5호
• /
• pp.216-222
• /
• 2010

Most of the thirteen substations in operation in the metropolitan area were installed around the year 2000, and since water cooling methods are used to directly withdraw heat from transformer oils, a stable supply of electric power is required through optimal maintenance of facilities. The water cooling tower installed outdoors, which uses the water supply as sprinkler water, experiences the most problems. Since more than 90% of the cooling water is reused, the dissolved composition in the water becomes concentrated due to long operating hours, and impurities dissolve in the water due to air flowing in from the outside, forming hard scales on the outer surface of the cooling tube, and in extreme cases, reacting with the tube material composition, leading to corrosion. As a result, not only is cooling efficiency lowered, but in extreme cases the cooling tube must be replaced. In this study, the characteristics and composition of the scales formed on the cooling tube were analyzed and corrosion characteristics of material types were identified in order to find an efficient maintenance method for cooling tubes. In addition, the degree of dissolution of various chemicals were investigated during the removal of scales that have been formed.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2003년도 추계학술대회
• /
• pp.934-938
• /
• 2003

Flow analyses using FLUENT 5.4 code were performed to validate the application of the local bidirectional flow tube in case of water and air flow. In this study, sensitivity studies have been performed to optimize the design features of the bi-directional flow tube which can be applied for the various experimental conditions. 2-dimensional axisymmetric steady state flow analyses have been performed. By calculating the differential pressure at both the front and the rear hole of the flow tube, K values were evaluated. The K values show good linearity regardless of the tube sizes and the Re numbers in both water and air flow. And system pressure and water subcooling didn’'t affect the K values. Under the elevated pressure of 80bar with 80K water subcooling, the K value indicates a similar trend with the case of 2bar with 80K water subcooling.

• 복합신소재구조학회 논문집
• /
• 제6권3호
• /
• pp.86-94
• /
• 2015

A series of injection and drainage test were conducted on an circular acrylic tube to investigate the pressure generated by the accumulated fill materials inside a circular acrylic tube structure. The acrylic tube was filled by means of gravity filling with a slurry material having an average water content of 700%. The water head during the filling process was 1.8m and the bottom pressure during initial filling was 20.18kPa. The recorded stress at the sides of the acrylic tube was 17.89kPa during the filling process and was reduced to 13.58kPa during the leaving process. Continuous drainage of the acrylic tube has greatly influenced the stresses around the tube structure. As the water is gradually allowed to overflow, the generated pressure at the topmost pressure sensor of the tube was reduced further to 2.17kPa. Eventually, the initially liquid state slurry material transforms into plastic state after water has dissipated and substantial soil particles are deposited in the acrylic tube. The final water content of the deposited silt inside the acrylic tube after the test was 42%. It was found that the state of stresses(geo-static earth pressures) in the acrylic tube was anisotropic rather than isotropic.

• Tribology and Lubricants
• /
• 제24권6호
• /
• pp.362-367
• /
• 2008

Tubes in nuclear steam generators are held up by supports because the tubes are long and slender. Fluid flows of high-pressure and high-temperature in the tubes cause oscillating motions between tubes and supports. This is called as FIV (flow induced vibration), which causes fretting wear in contact parts of tube-support. The fretting wear of tube-support can threaten the safety of nuclear power plant. The tube and support materials were Inconel 690 and STS 409. The wear tests were conducted in various environments, which are in water without flow, in flowing water and in flowing water with air. The results showed that the flow of water influenced on the wear-life of tube. The wear-life of tube decreased in water flow as compared with wear-life in stationary water.