• Title/Summary/Keyword: Flow Condensation

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The Effect of Nonequilibrium Condensation on Shock/Boundary Layer Interaction (비평형응축이 충격파와 경계층의 간섭에 미치는 영향)

  • Kim, H.D.;Lee, K.H.;Setoguchi, T.
    • Proceedings of the KSME Conference
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    • 2000.11b
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    • pp.544-549
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    • 2000
  • The effects of nonequilibrium condensation on the shock boundary layer interaction over a transonic bump model were investigated experimentally and numerically. An experiment was conducted using a supersonic indraft wind tunnel. A droplet growth equation was incorporated into two-dimensional Navier-Stokes equation systems. Computations were carried out using a third-order MUSCL type TVD finite-difference scheme with a second-order fractional time step. Computations compared with the experimental results. Nonequilibirum condensation suppressed the boundary layer separation and the pressure fluctuations due to the shock boundary layer interaction. Especially the nonequilibrium condensation was helpful to suppress the high frequency components of the pressure fluctuations.

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Measurement of Single Phase and Condensation Heat Transfer Coefficients of Ammonia in a Horizontal Tube (암모니아의 수평관내 단상 및 응축 열전달계수의 측정)

  • 백영진;장영수;김영일
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.12 no.6
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    • pp.561-569
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    • 2000
  • Single phase and condensation heat transfer characteristics of ammonia in a horizontal tube have been investigated experimentally The horizontal test section is composed of smooth SUS316 tube for refrigerant flow, surrounding annulus for water flow, and temperature and Pressure measuring sensors. For single phase test, subcooled ammonia mass flux was varied from 320 to 501 kg/mrs and temperature was varied from 18 to $47^{\circ}C$. For condensation test, mass flux and saturation temperature were varied from 86 to 128 kg/$m^2$s and 34 to $47^{\circ}C$, respectively. The equations of Gnielinski Soliman et al., Traviss et at., Cavallini and Zecchin, Shah, Chen et al., Tandon et al., and Chilli and Anand were compared with the experimental data. New correlations are proposed based on the experimental results and the absolute mean deviation of the experimental data becomes 1.0% for single phase test and 4.9% for condensation test.

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Approximate Solutions for Laminar Film Condensation on a Flat Plate (평판에서 층류 막응축의 근사해)

  • Lee, S.H.;Kweon, J.Y.;Lee, E.S.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.3 no.4
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    • pp.215-221
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    • 1991
  • Laminar film condensation of a saturated vapor in forced flow over a flat plate is analyzed by using integral method. Laminar condensate film is so thin that the inertia and thermal convection terms in liquid flow can be neglected. Approximate solutions for water are presented and well agreed with the similarity solutions over the wide range of physical parameter, Cp1(Ts-Tw)/Pr.hfg. For the strong condensation case, it is found that magnitude of the interfacial shear stress at the liquid-vapor interphase boundary is approximately equal to the momentum transferred by condensation, i.e., ${\tau}_i{\simeq}\dot{m}(U_O-U_i)$.

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Passive Control of the Condensation Shock Wave Using Bleed Slots

  • Kim, H.D.;Lee, K.H.;Setoguchi, T.
    • Proceedings of the KSME Conference
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    • 2001.06e
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    • pp.299-304
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    • 2001
  • The current study describes experimental and computational work on the passive control of the steady and unsteady condensation shock waves, which are generated in a transonic nozzle. The bleed slots are installed on the contoured wall of the transonic nozzle in order to control the magnitude of the condensation shock wave and its oscillations. For computations, a droplet growth equation is incorporated into the two-dimensional Navier-Stokes equation systems. Computations are carried out using a third-order MUSCL type TVD finite-difference scheme with a second-order tractional time step. Baldwin-Lomax turbulence model is employed to close the governing equations. An experiment using an indraft transonic wind tunnel is made to validate the computational results. The current computations represented well the experimental flows. From both the experimental and computational results it is found that the magnitude of the condensation shock wave in the bleed slotted nozzle is significantly reduced, compared with no passive control of solid wall. The oscillations of the condensation shock wave are successfully suppressed by a bleed slot system.

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Study of the Periodic Ludwieg Tube Flow with Heat Addition (가열을 수반하는 Ludwieg Tube 유동에 대한 연구)

  • Baek, S.C.;Kwon, S.B.;Kim, H.D.
    • Proceedings of the KSME Conference
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    • 2001.11b
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    • pp.450-455
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    • 2001
  • The time-dependent behavior of nonequilibrium condensation of moist air through the Ludwieg tube is investigated with a computational fluid dynamics(CFD) method. The two-dimensional, compressible, Navier-Stokes equations, fully coupled with the condensate droplet growth equations, are numerically solved by a third-order MUSCL type TVD finite-difference scheme, with a second-order fractional time step. Baldwin-Lomax turbulence model is employed to close the governing equations. The computational results are compared with the previous experiments using the Ludwieg tube with a downstream diaphragm. The results clearly show that for an initial relative humidity below 30% there is no periodic oscillation of the condensation shock wave, but for an initial relative humidity over 40% the periodic excursions of the condensation shock occurs in the Ludwieg tube, and the frequency increases with the initial relative humidity. It is also found that total pressure loss due to nonequilibrium condensation in the Ludwieg tube should not be ignored even for a very low initial relative humidity, and the periodic excursions of the condensation shock wave are responsible for the total pressure loss.

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Condensation Heat Transfer Characteristics of HCFC - 123 inside Horizontal Smooth Tube (HCFC-123의 수평 평활관내 응축 전열 특성에 관한 연구)

  • 권옥배;오후규;오종택;김성규
    • Journal of Advanced Marine Engineering and Technology
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    • v.17 no.3
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    • pp.24-32
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    • 1993
  • Experimental data on the heat transfer characteristics of HCFC-123 and CFC-11 during condensation in horizontal smooth tube are presented. The experimental apparatus consisted of a closed working fluid loop, coolant loop, and measuring system. The major components of the working fluid loop made of a refrigerant pump, boiler, superheater, refrigerant flow meter, receiver and test section. The tube-in-tube type test section was made of smooth tube which were constructed form 9.52 mm outer diameter of smooth copper tube with 50 mm outside diameter of PVC tube duct. The ranges of parameter, such as refrigerant mass velocity, coolant flow rate, and quality were 90-325kg/($m^2$.s), 60-360kg/h, 5-95% respectively. Data were obtained under steady state condition for annular flow. As a result of these, the condensation heat transfer coefficients for HCFC-123 were slightly lower than those of CFC-11 from 8% to 15% inside horizontal smooth tube. Furthermore, a new generalized correlation for the heat transfer coefficients of HCFC-123 and CFC-11 during condensation inside horizontal smooth tube is proposed.

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Experimental Study of Air-cooled Condensation in Slightly Inclined Circular Tube (경사진 원형관에서의 공냉응축에 관한 실험적 연구)

  • Kim, Dong Eok;Kwon, Tae-Soon;Park, Hyun-Sik
    • The KSFM Journal of Fluid Machinery
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    • v.19 no.4
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    • pp.29-34
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    • 2016
  • In this study, the experimental investigation of air-cooled condensation in slightly inclined circular tubes with and without fins has been conducted. In order to assess the effects of the essential parameters, variable air velocities and steam mass flow rates were given to the test section. The heat transfer performance of air-cooled condensation were dominantly affected by the air velocity, however, the increase of the steam mass flow rate gave relatively weaker effects to total heat transfer capability. And in the experimental cases with the finned tube, the total heat transfer rate of the finned tube was significantly larger than that of the flat tube. From those results, it can be confirmed that the most important parameter for air-cooled condensation heat transfer is the convective heat transfer characteristics of air. Therefore, for the well-designed long-term cooling passive safety system, the consideration of the optimal design of the fin geometry is needed, and the experimental and numerical validations of the heat transfer capability of the finned tube would be required.

Effects of Nonequilibrium Condensation on an Oblique Shock Wave in a Supersonic Nozzle of Constant Expansion Rate (팽창률이 일정한 초음속 노즐흐름에 있어서 비평형 응축이 경사충격파에 미치는 영향)

  • 강창수;권순범;김병지;홍종우
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.14 no.5
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    • pp.1311-1319
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    • 1990
  • For the purpose of preventing the flow undulation in the cascade of steam turbine, the blades are made into a constant expansion rate in static pressure. And the flow in those cascades is transonic or supersonic in the range of 0.7-2.0 in Mach number. As a consequence, an oblique shock wave, known as inner or outer edge shock wave, arises in the flow of cascades. Especially when the steam in cascades is in a state of high wetness, nonequilibrium condensation and condensation shock wave occur, and they give rise to an interference with oblique shock wave. In the present study the case of expansion of moist air through a supersonic nozzle of constant expansion rate, which behaves similar to that of wet steam, was adopted. The effect of nonequilibrium condensation on the oblique shock wave generated by placing the wedge into the supersonic part of the nozzle was investigated. Furthermore, the relationship between nonequilibrium condensation zone and incident point of the oblique shock wave, oblique shock wave angle, the variations of angles of incident and reflected shock waves due to the variation of initial stagnation supersaturation and the relationship between the height of Mach stem and initial stagnation supersaturation are discussed.

Photocatalytic Properties of TiO2 Nanopowder Synthesized by Chemical Vapor Condensation Process (화학기상응축 공정으로 제조한 TiO2 나노분말의 광촉매 특성)

  • 임성순;남희영;윤성희;이창우;유지훈;이재성
    • Journal of Powder Materials
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    • v.10 no.2
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    • pp.123-128
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    • 2003
  • $TiO_2$ nanopowder was synthesized by chemical vapor condensation (CVC) process and its photocatalytic property depending on microstructure was considered in terns of decomposition rate of organic compound. In order to control microstructure of $TiO_2$ nanopowder such as particle size and degree of agglomeration, precursor flow rate representing number concentration was changed as a process variable. In TEM observation, spherical $TiO_2$ nanoparticles with average size of 20 nm showed gradual increases in particle size and degree of agglomeration with increase of precursor flow rate. Also decomposition rate of organic compound increased with decreasing precursor flow rate. Thus, it was concluded that photocatalytic property was enhanced by targe surface area of disperse $TiO_2$ nanoparticles synthesized at lower precursor flow rate condition in CVC process.

Measurement of temperature profile using the infrared thermal camera in turbulent stratified liquid flow for estimation of condensation heat transfer coefficients

  • Choi, Sung-Won;No, Hee-Cheon
    • Proceedings of the Korean Nuclear Society Conference
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    • 1999.05a
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    • pp.107-107
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    • 1999
  • Direct-contact condensation experiments of atmospheric steam and steam/air mixture on subcooled water flowing co-currently in a rectangular channel are carried out uszng an infrared thermal camera system to develop a temperature measurement method. The inframetrics Model 760 Infrared Thermal Imaging Radiometer is used for the measurement of the temperature field of the water film for various flow conditions. The local heat transfer coefficient is calculated using the bulk temperature gradient along the (low direction. It is also found that the temperature profiles can be used to understand the interfacial condensation heat transfer characteristics according to the flow conditions such as noncondensable gas effects, inclination effect, and flow rates.

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