• Title/Summary/Keyword: Internal flow

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Flow and Internal Experiences of Korean High School Students in View of the Comparison between Public and Proprietary School (학교와 학원의 비교를 통해 본 청소년의 플로우 및 내적경험)

  • 김기옥;현은자;최인수;유현정
    • Journal of the Korean Home Economics Association
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    • v.42 no.4
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    • pp.127-142
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    • 2004
  • The Purpose of this study was to compare the school life of Korean high school students between Public and proprietary schools, especially focused on their internal experiences and flow. Internal experiences were composed of three dimensions: emotion, cognitive efficiency, and satisfaction. How was classified into four conditions: apathy, boredom, anxiety, and flow. The study results are: 1. Korean high school students felt more flow when they were in public school than in proprietary school,. In public school, they felt relatively more bored, and on the other hand, they were relatively more anxious in proprietary school. 2. Korean high school students felt more positive emotions when they were in public school than in proprietary school. 3. Korean high school students were more involved into study when they were in public school than in proprietary school. 4. Korean high school students were more satisfied when they were in public school than in proprietary school.

Internal Flow Measurement of Very Low Specific Speed Semi-Open Impeller by PIV (PIV를 이용한 극저비속도 세미오픈임펠러의 내부유동 계측)

  • Nishino Koichi;Lee Young-Ho;Choi Young-Do
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.29 no.7 s.238
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    • pp.773-783
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    • 2005
  • Internal flow measurement of very low specific-speed semi-open impellers has been carried out by PIV in order to understand better the internal flow patterns that are responsible fur the unique performance of these centrifugal pumps operating in the range of very low specific speed. Two types of impellers, one equipped with six radial blades (Impeller A) and the other with four conventional backward-swept blades (Impeller B), are tested in a centrifugal pump operating at a non-dimensional specific-speed of $n_s=0.24$. Complex flow patterns captured by PIV are discussed in conjunction with the overall pump performance measured separately. It is revealed that Impeller A achieves higher effective head than Impeller B even though the flow patterns in Impeller A are more complex, exhibiting secondary flows and reverse flows in the impeller passage. It is shown that both the localized strong outward flow at the pressure side of each blade outlet and the strong outward through-flow along the suction side of each blade are responsible for the better head performance of Impeller A.

Unsteady Internal Flow Analysis of a Cathode Air Blower Used for Fuel Cell System (연료전지용 캐소드 공기블로어의 비정상 내부유동장 연구)

  • Jang, Choon-Man;Lee, Jong-Sung
    • New & Renewable Energy
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    • v.8 no.3
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    • pp.6-13
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    • 2012
  • This paper describes unsteady internal flow characteristics of a cathode air blower, used for the 1 kW fuel cell system. The cathode air blower considered in the present study is a diaphragm type blower. To analyze the flow field inside the diaphragm cavity, compressible unsteady numerical simulation is performed. Moving mesh system is applied to the numerical analysis for describing the volume change of the diaphragm cavity in time. Throughout a numerical simulation by modeling the inlet and outlet valves in a diaphragm cavity, unsteady nature of an internal flow is successfully analyzed. Variations of mass flow rate, force and pressure on the lower moving plate of a diaphragm cavity are evaluated in time. The computed mass flow rate at the same pressure and rotating frequency of a motor has a maximum of 5 percent error with the experimental data. It is found that flow pattern at the suction process is more complex compared to that at the discharge process. Unsteady nature of internal flow in the cathode air blower is analyzed in detail.

Wind tunnel study on fluctuating internal pressure of open building induced by tangential flow

  • Chen, Sheng;Huang, Peng;Flay, Richard G.J.
    • Wind and Structures
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    • v.32 no.2
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    • pp.105-114
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    • 2021
  • This paper describes a wind tunnel test on a 1:25 scale model of TTU building with several adjustable openings in order to comprehensively study the characteristics of fluctuating internal pressures, especially the phenomenon of the increase in fluctuating internal pressures induced by tangential flow over building openings and the mechanism causing that. The effects of several factors, such as wind angle, turbulence intensity, opening location, opening size, opening shape and background porosity on the fluctuating internal pressures at oblique wind angles are also described. It has been found that there is a large increase in the fluctuating internal pressures at certain oblique wind angles (typically around 60° to 80°). These fluctuations are greater than those produced by the flow normal to the opening when the turbulence intensity is low. It is demonstrated that the internal pressure resonances induced by the external pressure fluctuations emanating from flapping shear layers on the sidewall downstream of the windward corner are responsible for the increase in the fluctuating internal pressures. Furthermore, the test results show that apart from the opening shape, all the other factors influence the fluctuating internal pressures and the internal pressure resonances at oblique wind angles to varying degrees.

Mass transfer in cross-flow dialyzer with internal recycle

  • Yeh, Ho-Ming;Chen, Chien-Yu
    • Membrane and Water Treatment
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    • v.4 no.4
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    • pp.251-263
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    • 2013
  • The internal reflux effect on dialysis through the retentate phase of a countercurrently cross-flow rectangular module is investigated. Theoretical analysis of mass transfer in cross-flow devices with or without recycling is analogous to heat transfer in cross-flow heat exchangers. In contrast to a device without reflux, considerable mass transfer is achievable if cross-flow dialyzers are operated with reflux, which provides an increase in fluid velocity, resulting in a reduction in mass-transfer resistance. It is concluded that reflux can enhance mass transfer, especially for large flow rate and feed-concentration operated under high reflux ratio.

Flow Characteristics of Floating Roof Tank with Varying the Number of Operation and Angle (믹서의 가동 수 및 각도 변화에 따른 유동형 지붕 탱크의 유동특성)

  • Kim, Noh-Hyeong
    • The KSFM Journal of Fluid Machinery
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    • v.18 no.3
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    • pp.20-25
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    • 2015
  • In this study, there are 6 mixers that are installed in a 600,000 barrel tank. We identified internal flow characteristics of floating roof tank with varying the number of operation from 4 to 6 because mixer is a variable that influence flow characteristics of the tank. And while varying an angle from Right $60^{\circ}$, Right $30^{\circ}$, Left $30^{\circ}$ to Left $60^{\circ}$, we identified internal flow characteristics of the tank. As a result, maximum velocity of flow was 0.02m/s stationarily when we changed the number of operation from 4 to 6. Maximum velocity of flow by change of an angle was from 0.42m/s to 0.47m/s. Therefore, we identified that these factors don't have a great influence on internal flow characteristics of a tank by investigating results with varying the number of operation and an angle.

Influence of guide vane shape on the performance and internal flow of a cross flow wind turbine

  • Son, Sung-Woo;Singh, Patrick Mark;Choi, Young-Do
    • Journal of Advanced Marine Engineering and Technology
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    • v.37 no.2
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    • pp.163-169
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    • 2013
  • In order to make the vertical-axis cross flow wind turbine commercially feasible, a guide vane is adopted and the effect of the guide vane shape is examined in order to improve the wind turbine performance. CFD analysis on the performance and internal flow of the turbine is carried out for the wind turbine model. The result shows that when the guide nozzle is installed, almost over two times of power coefficient are achieved in comparison with the case of no guide nozzle installation. The guide nozzle acts as a role of suppressing the flow resistance at the blade passage, which is found when the guide nozzle is installed. Moreover, in this study, two kinds of the guide vane with a straight type and a curved type are adopted and compared. The curved guide vane nozzle produces higher power coefficient in comparison with that of straight guide vane nozzle.

Internal Flow of a Two-Bladed Helical Inducer at an Extremely Low Flow Rate

  • Watanabe, Satoshi;Inoue, Naoki;Ishizaka, Koichi;Furukawa, Akinori;Kim, Jun-Ho
    • International Journal of Fluid Machinery and Systems
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    • v.3 no.2
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    • pp.129-136
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    • 2010
  • The attachment of inducer upstream of main impeller is an effective method to improve the suction performance of turbopump. However, various types of cavitation instabilities are known to occur even at the designed flow rate as well as in the partial flow rate region. The cavitation surge occurring at partial flow rates is known to be strongly associated with the inlet back flow. In the present study, in order to understand the detailed structure of internal flow of inducer, we firstly carried out the experimental and numerical studies of non-cavitating flow, focusing on the flow field near the inlet throat section and inside the blade passage of a two bladed inducer at a partial flow rate. The steady flow simulation with cavitation model was also made to investigate the difference of flow field between in the cavitating and no-cavitating conditions.

Internal Flow Analysis on a Mixed Flow Pump for Developing Marine Mineral Resources (해양광물자원 개발을 위한 사류형펌프의 내부유동 해석)

  • Lee, J.W.;Choi, Y.D.;Lee, Y.H.;Yoon, C.H.;Park, J.M.
    • The KSFM Journal of Fluid Machinery
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    • v.13 no.5
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    • pp.11-16
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    • 2010
  • The development of lifting pumps that lift minerals to a mining vessel are one of the vital parts of the commercial mining process. The purpose of this study is to investigate internal flow and its effect on the performance of a mixed flow pump in order to improve the pump's performance. Numerical analysis was performed by commercial code of ANSYS CFX-11 based on flow rate and length of flexible hose. The rated rotational speed of the impeller is 1750rpm. For taking into account the turbulence, k-$\omega$ SST model was selected to guarantee more accurate prediction of flow separation. The simulated results are in good agreement with the experimental results and showed that its efficiency and the head of the pump are related mainly to the flow rate and the length of flexible hose. A lesser flow rate caused more secondary flow through the guide vane passage. The length of flexible hose and flow rate exert much more influence on the pump's performance than the shape of the flexible hose.

Free Flow in Internal Thoracic Artery and Internal Thoracic Artery-Radial Artery Composite Graft (속가슴동맥 편 및 속가슴동맥-노동맥 복합이식편의 자유혈류)

  • 고광표;이미경;류대웅;이삼윤;최종범
    • Journal of Chest Surgery
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    • v.37 no.10
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    • pp.839-844
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    • 2004
  • Background: The Y-composite graft of internal thoracic artery and radial artery is commonly used in coronary bypass surgery. The aim of this study is to look for a way to raise the free flow of the internal thoracic graft and to see flow dynamics of the Y-graft. Material and Method: In 15 patients undergoing coronary bypass surgery, free flow of the in-situ internal thoracic artery graft was measured using two different papaverine application methods; extraluminal papaverine spray in 7 patients and intraluminal papaverine injection in 8. In 18 other patients for whom the Y-graft was used, total free flow and flow changes from the two ends were measured. Result: The free flow of the in-situ internal thoracic artery graft almost doubled with internal papaverine injection than with external papaverine spray $(47.7\pm9.6$ mL/min $vs.100.8\pm26.3$ mL/min, p<0.001). Total flow of the Y-composite graft was significantly more than either flow of the internal thoracic artery end or radial artery graft end $(173.3\pm45.3$ mL/min vs. $121.1\pm34.3$ mL/min or $117.5\pm42.8$ mL/min). When both ends of the Y-composite graft were opened, free flows from the two ends were similar $(85.4\pm27.8$ mL/min vs: $87.9\pm42.4$ mL/min, p=0.772). The flow of one end of the Y-composite graft was increased significantly by clamping of the other-end than when both ends were opened. Conclusion: Intraluminal papaverine injection is very effective in raising free flow of the internal thoracic artery graft, and the free flow of the Y-composite graft of in-situ internal thoracic artery and free radial artery graft is more than that of the in-situ internal thoracic artery graft. The flow of one end flow of the Y-graft may be altered by the flow change of the other end.