• Title/Summary/Keyword: 막응축

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수직한 벽면에서 혼합증기(수증기/공기)의 막응축 열전달

  • 박수기;김무환;유건중
    • Proceedings of the Korean Nuclear Society Conference
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    • pp.217-223
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    • 1996
  • 혼합증기(수증기/공기)의 막응축 열전달 계수를 수직한 벽면에서 측정하고 상관식을 개발하였다. 열전달 상관식은 액막측과 증기측으로 구분하여 만들었고, 액막측 전열계수의 상관식은 액막의 Reynolds수와 Prandtl수의 함수로 나타냈으며, 증기측 전열계수의 상관식은 증기의 Reynolds수, Prandtl수, Schmidt수 및 공기의 질량분율, 액막 Reynolds수의 함수로 제안하였다. 응축 액막의 두께와 확산층의 순간온도 측정결과로부터 액막의 파형 계면이 확산층에서의 열 및 물질전달에 큰 영향을 끼치고 있음을 확인하였고, 증기측 전열계수의 상관식에 포함된 액막 Reynolds수가 파형 계면의 영향을 반영하고 있다.

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Filmwise Condensation of Freon Vapor Including Air on a Horizontal Tube (공기를 함유한 프레온 증기의 수평관 외부에서의 막응축)

  • Kim, K.H.;Ko, H.J.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.7 no.1
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    • pp.20-29
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    • 1995
  • A theoretical model for film condensation of a vapor including a relatively lighter noncondensable gas on a horizontal tube has been formulated on the basis of the conservation laws and other fundamental physical principles. The model is applied to the prediction of the condensation heat transfer characteristics for the Freon vapor in the presence of air on a horizontal tube. Calculated results for the mean heat transfer coefficient, which is shown to depend strongly on the bulk concentration of air, are in good agreement with the available experimental results for a range of operating conditions. The distributions of physical quantities along the surface of tube are also calculated, such as the boundary layer thickness and local heat transfer coefficient. The present model is readily reduced to the Nusselt model as the bulk concentration of air decreases to zero. Therefore, the transition from the condensation of pure vapor to that of vapor-air mixture occurs continuously not abruptly.

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Comparative Analysis of Models for Free Convective Film Condensation on an Isothermal Vertical Wall (등온 수직벽의 자연대류 막응축 모델에 관한 비교분석)

  • Sung, Hyun-Chan;Kim, Kyoung-Hoon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.24 no.10
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    • pp.1380-1387
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    • 2000
  • The existing theoretical models for steady two-dimensional free convective laminar film condensation of pure saturated or superheated vapor under atmospheric pressure on isothermal vertical wall have been reviewed. To investigate the effects such as inertia, thermal convective and liquid-vapor interface shear stress, the models of constant or variable properties in liquid film for condensation of saturated vapor are compared in detail with Nusselt model. Also, for condensation of superheated vapor, the effects of superheated temperature and variable properties in liquid and vapor layers are examined and then a new correlation is proposed to predict the heat transfer. The results are in good agreement with the Shang's correlation within 2% errors.

Comparative Analysis of Models for Free Convective Film Condensation on an Isothermal Vertical Wall (등온 수직벽의 자연대류 막응축 모델에 관한 비교분석)

  • Sung, Hyun-Chan;Kim, Kyoung-Hoon
    • Proceedings of the KSME Conference
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    • pp.31-36
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    • 2000
  • The existing theoretical models for steady two-dimensional free convective laminar film condensation or pure saturated or superheated vapor under atmospheric pressure on isotheraml vertical wall have been reviewed. To investigate the effects of inertia, thermal convective and liquid-vapor interface shear stress, the models of constant or variable properties in liquid film for condensation of saturated vapor are compared in detail with Nusselt model. Also, for condensation of superheated vapor the effects of superheated temperature and variable properties in liquid and vapor layer are examined and then new correlation is proposed to predict the heat transfer. The results are in good agreement with the Shang's correlation within 2% errors.

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Approximate Solution for Conjugate Heat Transfer of Laminar Film Condensation on a Flat Plate (평판의 층류 막응축에서 복합열전달에 대한 근사해)

  • Lee Euk-Soo
    • Journal of Advanced Marine Engineering and Technology
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    • v.29 no.5
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    • pp.509-518
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    • 2005
  • Liquid film thickness in laminar film condensation for flow over a flat plate generally is so thin that both fluid acceleration and thermal convection within the liquid film can be neglected. An integral solution method is proposed to solve the conjugate problems of laminar film condensation and heat conduction in a solid wall. It is found that approximate solutions of the governing equations involve four physical parameters to describe the conjugate heat transfer problem for laminar film condensation. It is shown that the effects of interfacial shear. mass transfer and local heat transfer are strongly dependent on the thermo-physical properties of the working fluids and the Jacob number.

A Study of Conjugate Laminar Film Condensation on a Flat Plate (수평평판에서 복합 층류 막응축에 대한 연구)

  • Lee Euk-Soo
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.17 no.4
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    • pp.303-311
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    • 2005
  • The problem of conjugate laminar film condensation of the pure saturated vapor in forced flow over a flat plate has been investigated as boundary layer solutions. A simple and efficient numerical method is proposed for its solution. The interfacial temperature is obtained as a root of 3rd order polynomial for laminar film condensation, and it is presented as a function of the conjugate parameter. The momentum and energy balance equations are reduced to a nonlinear system of ordinary differential equations with four parameters: the Prandtl number, Pr, Jacob number, $Ja^{\ast}$, defined by an overall temperature difference, a property ratio R and the conjugate parameter ${\zeta}$. The approximate solutions thus obtained reveal the effects of the conjugate parameter.

The Effect of Pressure on Laminar Film Condensation along a Horizontal Plate (수평평판의 층류 막응축에서 압력의 영향)

  • Lee, Euk-Soo;Lee, Sung-Hong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.32 no.12
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    • pp.945-953
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    • 2008
  • Laminar film condensation of saturated vapor in forced flow over a flat plate is analysed. The problem is formulated as exact boundary-layer solution and integral approximate solution. From numerical solutions of the governing equations, it is found that the energy transfer by convection and the effect of inertia term in the momentum equation in negligibly small for low pressure but quite important for high pressure. The condensate rate, liquid-vapor interfacial shear stress and local heat transfer are strongly dependent on the reduced pressure $P_r$ and the modified Jacob number Ja/Pr.

Conjugate Heat Transfer of Laminar Film Condensation Along a Horizontal Plate (강제대류 층류 막응축에서 복합열전달)

  • Lee Euk-Soo
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.30 no.3
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    • pp.238-245
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    • 2006
  • This paper proposes appropriate conjugate parameters and dimensionless temperatures to analysis the conjugate problem of heat conduction in solid wall coupled with laminar film condensation flow adjacent to horizontal flat plate. An efficient methods for some fluids are proposed for its solution. The momentum and energy balance equations are reduced to a nonlinear system of ordinary differential equations with four parameters: the Prandtl number, Pr, Modified Jacob number, $Ja^*/Pr$, defined by an overall temperature difference, a property ratio $\sqrt{\rho_l{\mu}_l/{\rho_v{\mu}_v}$ and the conjugate parameter $\zeta$. The obtained similarity solution reveals the effect of the conjugate parameter, and the results are compared with the simplified solution. The variations of the heat transfer rates as well as the interface temperature and frictions along the plate are shown explicitly.

The Effect of Heat Conduction resistance on Laminar Film Condensation along a Horizontal Plate (수평평판의 막응축에서 전도 열저항의 영향)

  • Lee, Euk-Soo
    • Proceedings of the Korean Society of Marine Engineers Conference
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    • pp.183-188
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    • 2005
  • The effect of heat conduction resistance on laminar film condensation of the pure saturated vapor in forced flow over a flat plate has been investigated as boundary layer solutions. A efficient numerical methods for water are proposed for its solution. The momentum and energy balance equations are reduced to a nonlinear system of ordinary differential equations with four parameters: the Prandtl number, Pr, Modified Jacob number, $Ja^{\ast}/Pr$, defined by an overall temperature difference, a property ratio $\sqrt{P_l{\mu}_l/P_v{\mu}_v}$ and the conjugate parameter ${\zeta}$. The similarity and simplified solutions obtained reveal the effects of the conjugate parameter.

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