• 제목/요약/키워드: annulus

검색결과 487건 처리시간 0.039초

Slim hole 경사 환형관내 고-액 혼합유동 특성에 관한 연구 (Solid-liquid mixture flow characteristics in an inclined slim hole annulus)

  • 서병택;한상목;우남섭;김영주;황영규
    • 대한설비공학회:학술대회논문집
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    • 대한설비공학회 2008년도 하계학술발표대회 논문집
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    • pp.1315-1320
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    • 2008
  • An experimental study was carried out to study the solid-liquid mixture upward flow in a vertical and inclined annulus with rotating inner cylinder. Lift forces acting on a fluidized particle plays a central role in many importance applications, such as the removal of drill cuttings in horizontal drill holes, sand transport in fractured reservoirs, sediment transport and cleaning of particles from surfaces, etc. Field measurements have revealed that the pressure drop over a borehole during drilling of a slim oil well or a well with a long reach can depend significantly on the rotation speed of the drill pipe. An accurate prediction of the annular frictional pressure drop is therefore important for conditions where the annular clearance is small. Effect of annulus inclination and drill pipe rotation on the carrying capacity of drilling fluid, particle rising velocity, and pressure drop in the slim hole annulus have been measured for fully developed flows of water and of aqueous solutions.

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Experimental Investigation on Critical Heat Flux in Bilaterally Heated Annulus with equal heat flux on both sides

  • Miao Gui;Junliang Guo;Huanjun Kong;Pan Wu;Jianqiang Shan;Yujiao Peng
    • Nuclear Engineering and Technology
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    • 제55권9호
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    • pp.3313-3319
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    • 2023
  • A phenomenological study on CHF in a bilaterally heated annulus with equal heat flux on both sides was experimentally performed. The working fluid of the present test was R-134a. Variation characteristics of CHF and transition of CHF occurrence location were investigated under different pressure, mass flux and quality conditions. With the increase of critical thermodynamic quality, it was found that CHF first occurred on the outer surface of the annulus, then simultaneously occurred on both sides, and finally occurred on the inner surface at relatively high critical quality. After the CHF location transitioned to the inner rod, the sharp fall of CHF in the limiting critical quality region was observed. The critical quality corresponding to the CHF location transition decreased with the increase of mass flux and pressure. Besides, CHF in tube, internally heated, externally heated and bilaterally heated annuli were compared under the same hydraulic diameter conditions. The present study is conducive to improving the understanding of complicated CHF mechanism in bilaterally heated annulus, enriching the experimental database, and providing evidence for developing accurate CHF mechanism model for annuli.

뉴튼 및 비뉴튼 유체의 헬리컬 유동에 관한 연구 (Helical flow of Newtonian and non-Newtonian fluid in an nnulus)

  • 우남섭;서병택;배경수;황영규
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2004년도 추계학술대회
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    • pp.1634-1639
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    • 2004
  • The present study concerns a experimental study of fully developed laminar flow of a Newtonian and non-Newtonian fluid through a concentric annulus with a combined bulk axial flow and inner cylinder rotation for the various radius ratio. This study shows the fundamental difference between Newtonian and non-Newtonian fluid flow in an annulus for various radius ratio.

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POSITIVE RADIAL SOLUTIONS OF $DELTA U + LAMBDA F(U) 0$ ON ANNULUS

  • Bae, Soo-Hyun;Park, Sang-Don;Pahk, Dae-Hyeon
    • 대한수학회지
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    • 제33권2호
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    • pp.381-386
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    • 1996
  • We consider the behavior of positive radial solutions (or, briefly, pp.r.s.) of the equation $$ (1.1) ^\Delta u + \lambda f(u) = 0 in\Omega, _u = 0 on \partial\Omega, $$ where $\Omega = {x \in R^n$\mid$A < $\mid$x$\mid$ < B}$ is an annulus in $R^n, n \geq 2, \lambda > 0 and f \geq 0$ is superlinear in u and satisfies f(0) = 0.

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Ebstein 기형에 인공판윤을 이용한 금속형 St. Jude Medical 인공판막 대치술 (Ebstein`s anomaly ; St. Jude Medical valve replacement using partial artificial annulus formation - A Case Report -)

  • 이종국;조재민
    • Journal of Chest Surgery
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    • 제25권8호
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    • pp.826-831
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    • 1992
  • Ebstein`s anomaly is characterized by a downward displacement of a malformed tricuspid valve, The ideal surgical management of Ebstein`s anomaly is not yet established. Recently we experience one case of Ebstein`s anomaly, which was treated sussessfully by partial artificial annulus formation, and tricuspid valve replacement with St. Jude Medical valve. We have achieved excellent results with mechanical valve replacement and partial artificial annulus formation using wessex pericardial patch. On follow up for 4 years, the patient is well and in functional class I.

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Modal analysis of eccentric shells with fluid-filled annulus

  • Jhung, Myung Jo;Jeong, Kyeong Hoon;Hwang, Won Gul
    • Structural Engineering and Mechanics
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    • 제14권1호
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    • pp.1-20
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    • 2002
  • Investigated in this study are the modal characteristics of the eccentric cylindrical shells with fluid-filled annulus. Theoretical method is developed to find the natural frequencies of the shell using the finite Fourier expansion, and their results are compared with those of finite element method to verify the validation of the method developed. The effect of eccentricity on the modal characteristics of the shells is investigated using a finite element modeling.

수직 동심 환형관 내의 난류혼합대류 현상에 관한 직접수치모사 (Direct Numerical Simulation of Turbulent Mixed Convection in Heated Vertical Annulus)

  • 전용준;배중헌;유정열
    • 대한기계학회논문집B
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    • 제33권9호
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    • pp.674-681
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    • 2009
  • Turbulent mixed convection in heated vertical annulus is investigated using Direct Numerical Simulation (DNS) technique. The objective of this study is to find out the effect of buoyancy on turbulent mixed convection in heated vertical annulus. Downward and upward flows with bulk Reynolds number 8500, based on hydraulic diameter and mean velocity, have been simulated to investigate turbulent mixed convection by gradually increasing the effect of buoyancy. With increased heat flux, heat transfer coefficient first decreases and then increases in the upward flow due to the effect of buoyancy, but it gradually increases in downward flow. The mean velocity and temperature profiles can not be explained by the wall log laws due to the effect of buoyancy, too. All simulation results are in good quantitative agreement with existing numerical results and in good qualitative agreement with existing experimental results.

하부 유로단면적이 수직 환상공간 내부 풀비등열전달에 미치는 영향 (Effects of Bottom Inflow Area on Pool Boiling Heat Transfer in a Vertical Annulus)

  • 강명기;유주식
    • 대한기계학회논문집B
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    • 제31권7호
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    • pp.604-610
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    • 2007
  • To investigate effects of the inflow area on pool boiling heat transfer in a vertical annulus, the inflow area at its bottom has been changed from 0 to $1060.3mm^2$. For the test, a heated tube of 34 mm diameter and water at atmospheric pressure have been used. To elucidate effects of the inflow area on heat transfer results of the annulus are compared to the data of a single unrestricted tube. The change in the inflow area at the bottom of the annulus results in much variation in heat transfer coefficients. When the inflow area is $113.1mm^2$ the deterioration point of heat transfer coefficients gets moved up to the higher heat fluxes because of the convective flow at the bottom regions.

하나의 실린더가 회전하는 수평 환형 공간에서의 혼합 대류 (Mixed Convection in a Horizontal Annulus with a Rotating Cylinder)

  • 유주식;하대홍
    • 한국전산유체공학회지
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    • 제6권3호
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    • pp.1-9
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    • 2001
  • Mixed convection in a horizontal annulus is considered, and the effect of a forced flow on the natural convective flow is investigated. The inner cylinder is hotter than the outer cylinder, and the outer cylinder is rotating with constant angular velocity with its axis at the center of the annulus. The unsteady streamfunction-vorticity equation is solved with a finite difference method. For the fluid with Pr=0.7, there appear flows with two eddies, one eddy, or no eddy according the Rayleigh and Reynolds numbers. The rotation of the outer cylinder reduces the heat transfer rate at the wall of the annulus. The oscillatory multicellular flow of a low Prandtl number fluid with Pr=0.01 can be effectively suppressed by the forced flow.

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동시 회전하는 수평 실린더 내 환상공간에서의 혼합대류 (Mixed-Convection in an Annulus Between Co-Rotating Horizontal Cylinders)

  • 이관수;김양현;임광옥
    • 대한기계학회논문집B
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    • 제26권4호
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    • pp.622-628
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    • 2002
  • Numerical analysis has been carried out for two-dimensional steady and unsteady mixed convection in the annulus between co-rotating horizontal cylinders with a heated inner cylinder. The ratio of annulus gap($\sigma$) is taken from 1 to 10 and the order of mixed-convection parameter B(=Gr/(1+Re)$^2$) varies from 10$^4$to $10^0$. The flow patterns over this parameter range are steady multicellular, oscillatory multicellular or steady unicellular. The addition of co-rotating of both cylinders stabilizes the flow in the annulus and weakens the unsteadiness. Even in the large values of rotating parameter such as of $10^0$/($\sigma$=2) and 10$^2$($\sigma$=10), the flow pattern becomes asymptotic to the steady unicellular flow, like as in the rigid-body rotating flow.