• Title/Summary/Keyword: Interfacial condensation heat transfer

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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.

Condensation Heat Transfer Coefficient in Horizontal Stratified Cocurrent Flow of Steam and Cold Water (물-증기 동방향 성층이상 유동에서의 응축 열전달 계수)

  • 김효정
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.10 no.5
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    • pp.618-624
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    • 1986
  • Some studies on direct-contact condensation in cocurrent stratified flow of steam and subcooled water were reviewed. Several approaches have been performed to develop the condensation heat transfer coefficient relationshipo. The local Nusselt number is correlated in terms of the local water Reynolds and Prandtl numbers as well as the steam Froude number. In addition, a turbulence-centered model, developed principally for gas absorption in several geometries, is modified by using calculated interfacial paramters for the turbulent velocity and length scales. These approaches result in a fairly good agreement with the data, whereas, the turbulence-centered model is here rexcommened since it is based on the turbulent properties which may be closely related to the condensation phenemena.

An Improved Heat Transfer Prediction Model for Turbulent Falling Liquid Films with or Without Interfacial Shear (계면 전단응력이 있을 때와 없을 때 하강하는 난류액막에 대한 개선된 열전달 예측 모델)

  • Park, Seok-Jeong;Chun, Moon-Hyun
    • Nuclear Engineering and Technology
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    • v.27 no.2
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    • pp.189-202
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    • 1995
  • An improved method is presented for the prediction of heat transfer coefficients in turbulent fall-ing liquid films with or without interfacial shear for both heating or condensation. A modified Mudawwar and El-Masri's semi-empirical turbulence model, particularly to extend its use for the turbulent falling film with high interfacial shear, is used to replace the eddy viscosity model incorporated in the unified approach unposed by Yih and Liu. The liquid film thickness and asymptotic heat transfer coefficients against the film Reynolds number for wide range of interfacial shear predicted by both present and existing methods are compared with experimental data. The results show that in general, predictions of the modified model agee more closely with experimental data than that of existing models.

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Velocity and Temperature Profiles of Steam-Air Mixture on the Film Condensation (막응축 열전달에서 공기-수증기 혼합기체의 속도 및 온도분포)

  • 강희찬;김무환
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.10
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    • pp.2675-2685
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    • 1994
  • A study has been conducted to provide the experimental information for the velocity and temperature profiles of steam-air mixutre and to investigate their roles on the film condensation with wavy interface. Saturated gas mixture of steam-air was made to flow through the nearly horizontal$(4.1^{\circ})$ square duct of 0.1m width and 1.56m length at atmospheric pressure, and was condensated on the bottom cold plate. The air mass fraction in the gas mixture was changed from zero(W =0, pure steam) to one(W =1, pure air), and the bulk velocity was varied from 2 to 4 m/s. Water film was injected concurrently to investigate the effect of wavy interface on the condensation. The velocity and temperature profiles were measured by LDA system and thermocouples along the three parameters ; air mass fraction, mixture velocity and film flow rate. The profiles moved toward the interface with increasing steam mass fraction, mixture velocity and film flow rate. The Prandtl and Schmidt numbers were near one in the present experimental range, however there was no complete similarity between the velocity and temperature profiles of gas mixture. And the heat transfer characteristics and interfacial structure were coupled with each other.

Study on Fluid Flow and Heat Transfer Characteristics in a Flat Heat Pipe (평판형 히트 파이프 내의 유체 유동 및 열전달 특성에 관한 연구)

  • Do, Kyu-Hyung;Kim, Sung Jin
    • Proceedings of the KSME Conference
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    • 2007.05b
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    • pp.2113-2118
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    • 2007
  • In this study, a mathematical model for a thermal analysis of a flat heat pipe with a grooved wick structure is presented. The effects of the liquid-vapor interfacial shear stress, the contact angle, and the amount of liquid charge have been included in the proposed model. In particular, the axial variations of the wall temperature and the evaporation/condensation rates are considered by solving the one-dimensional conduction and the augmented Young-Laplace equations, respectively. In order to verify the model, the results obtained from the model are compared to existing experimental data.

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KAIST-CIWH Computer Code and a Guide Chart to Avoid Condensation-Induced Water Hammer in Horizontal Pipes

  • Chun, Moon-Hyun;Yu, Seon-Oh
    • Nuclear Engineering and Technology
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    • v.32 no.6
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    • pp.618-635
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    • 2000
  • A total of 17 experimental data for the onset of slugging, which is assumed to be the precursor of the condensation-induced waterhammer (CIWH), have been obtained for various How rates of water Incorporating the most recent correlations of interfacial heat transfer and friction factor developed for a circular geometry and using an improved criterion of transition from stratified to a slug flow, two existing analytical models to predict lower and upper bounds for CIWH have been upgraded. Applicability of the present as well as existing CIWH models has been tested by comparison with two sets of CIWH data. The result of this comparison shows that the applicability of the present as well as existing models is reasonably good. Based on the present models for CIWH, a computer code entitled as“KAIST-CIWH”has been developed and sample guide charts to find CIWH free regions for a given combination of major flow parameters in a long horizontal pipe have been presented along with the results of parametric studies of major parameters (D, P, $T_{f,in}$, and L/D) on the critical inlet water flow rate($W_{f,in}_crit$ for both lower and upper bounds. In addition, two simple formulas for lower and upper bounds that can be used in an emergency for quick results have been presented.

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Absorption of Water Vapor into an Absorbing Binary Liquid Film Falling over a Horizontal Tube Bank (수평원관군상(水平圓管群上)의 이원흡수용액유동(二元吸收溶液流動)에 의(依)한 전달흡수특성(傳達吸收特性))

  • Kim, S.;Kim, Y.I.;Seo, S.C.;Hwang, D.K.
    • The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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    • v.17 no.5
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    • pp.583-589
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    • 1988
  • Condensation of water vapor into an absorbent liquid of LiBr-water solution falling over a bank of water cooled horizontal tubes was investigated theoretically. The governing conservation equation for a re-defined physical transport phenomena were solved numerically using a finite difference method. Raw parameters were used in this study, since reliable experimental data is required prior to a dimensionless parametric study. The average values of wall heat transfer coefficient and interfacial absorption rate were defined to see the system performance. Other parameters include tube diameter, streamwise coordinate (and number of tubes in row), mass flow rate, and the wall temperature. The effects of these quantities on the absorption processes and suggestions for a rational system design have been presented.

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Two-fluid modelling for poly-disperse bubbly flows in vertical pipes: Analysis of the impact of geometrical parameters and heat transfer

  • Andrea Allio ;Antonio Buffo ;Daniele Marchisio;Laura Savoldi
    • Nuclear Engineering and Technology
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    • v.55 no.3
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    • pp.1152-1166
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    • 2023
  • The bubbly flow of air or steam in subcooled water are investigated here in several test cases, characterized by different pipe sizes, bubble dimensions and flow rates, by means of CFD using a Eulerian-Eulerian approach. The performance of models that differ for the turbulence closure in the continuous phase, as well as for the description of the lift force on the dispersed phase, are compared in detail. When air is considered, the space of the experimental parameters leading to a reasonable performance for the selected models are identified and discussed, while the issues left in the modelling of the concurrent condensation are highlighted for the cases where steam is used.

Development of Three-dimensional Thermo-fluid Numerical Model for Steam Drum of a Basic Oxygen Furnace (순산소 전로의 증기드럼 내의 3차원 열 유동 해석모델 개발)

  • Jeong, Soo-Jin;Moon, Seong-Joon;Jang, Won-Joon;Kho, Suntak;Kwak, Hotaek
    • Korean Chemical Engineering Research
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    • v.54 no.4
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    • pp.479-486
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    • 2016
  • The efficient steam drum should be required to reduce carbon oxide emissions and heat recovery in oxygen converter hood system. However, steam generation is limited to the time of the oxygen blowing period, which is intermittent or cyclical in operation of steel-making process. Thus, steam drum should be optimized for an effective steam generation during the oxygen blowing portion of the converter cycle. In this study, a three-dimensional computational fluid dynamics (CFD) model has been developed to describe the impacts of changing various operating conditions and geometric shape on thermo-fluid characteristics and performance of the steam drum. This model encompasses not only fluid flow and heat transfer but also evaporation and condensation at the interfacial surface in the steam drum by using VOF (Volume of Fluid) method. To validate the prediction performance of this model, comparison of the steam flow rate between numerical and experimental result has been performed, resulting in the accuracy of the relative error by less than 3.2%.