Turbulent film, condensation

Kinoshita, E, and Uehera, H., Turbulent Film Condensation of Binary Mixture on a Vertical Plate, ASME/JSME Thermal Engineering Conf., Vol. 2, pp367-373, 1995. 

Clements and Colver developed the modified Nusselt equation to correlate hydrocarbon and hydrocarbon mixtures in turbulent film condensation ... 

Figure 10-77. Turbulent film condensation of light hydrocarbons and their mixtures—up-flow, (used by permission Clements, L. D., and Colver, C. P. AlChE Heat Transfer Symposium V. 131, No. 69, 1973. American Institute of Chemical Engineers. All rights reserved.)...

Rosenow WM, Webber JH and Ling AT (1956) Effect of Velocity on Laminar and Turbulent Film Condensation, Trans ASME, 78 1645. 

WAVY AND TURBULENT FILM CONDENSATION ON A VERTICAL SURFACE... 

Consider laminar film condensation on a vertical plate when the vapor is flow ing parallel to the surface in a downward direction at velocity, V. Assume that a turbulent boundary layer is formed in the vapor along the outer surface of the laminar liquid film. Determine a criterion that will indicate when the effect of the shear stress at the outer edge of the condensed liquid film on the heat transfer rate is less than 59c. Assume that pv [Pg.602]

Develop an expression for the total condensate flow in a turbulent film in terms of the fluid properties, the temperature difference, and the dimensions of the plate. 

Nusselt s film condensation theory presumes a laminar film flow. As the amount of condensate increases downstream, the Reynolds number formed with the film thickness increases. The initially flat film becomes wavy and is eventually transformed from a laminar to a turbulent film the heat transfer is significantly better than in the laminar film. The heat transfer in turbulent film condensation was first calculated approximately by Grigull [4.14], who applied the Prandtl analogy for pipe flow to the turbulent condensate film. In addition to the quantities for laminar film condensation the Prandtl number appears as a new parameter. The results can not be represented explicitly. In order to obtain a clear representation, we will now define the Reynolds number of the condensate film... 

In the calculation of heat transfer in the transition region between laminar and turbulent film condensation, empirical interpolation formulae are well established. One of these types of formulae is... 

With these estimated values the vapour side heat transfer coefficient aG and the mass transfer coefficient [3G can be calculated. Just as the heat transfer coefficient aL of the condensate film is also known, which in laminar film condensation is yielded from Nusselt s film condensation theory (4.39), and for turbulent film condensation from (4.41). From (4.67) the temperature... 

Turbulent film condensation on vertical or inclined plates and on the inside or outside of vertical tubes. 

Transition region between laminar and turbulent film condensation. 

Turbulent film condensation of vapour flowing in tubes. 

Various semiempirical models exist in the literature to predict turbulent film condensation [20-23]. Butterworth [18] recommends the result of Labuntsov [23] for the local coefficient... 

Rohsenow et al. [21] extended the analysis into the turbulent film regime using the heat transfer-momentum analogy. The results for a downward flowing vapor are shown in Fig. 14.7 for Prf = 1.0 and 10.0. At high vapor velocities, as the dimensionless shear stress x increases, the transition to turbulence occurs at smaller values of the film Reynolds number (Eq. 14.31) as represented by the dashed lines. The influence of x on both laminar and turbulent film condensation is evident. 

Dhir and Lienhard [118] studied laminar film condensation on two-dimensional isothermal surfaces for which boundary layer similarity solutions exist and found that a similarity solution exists for body shapes that give g(x) = x". Nakayama and Koyama [119] extended the analysis of arbitrarily shaped bodies to include turbulent film condensation. 

H. Uehara, E. Kinosita, and S. Matsuda, Theoretical Study on Turbulent Film Condensation on a Vertical Plate, Proc. ASMEIJSME Thermal Eng. Conf, Maui, 2, pp. 391-397,1995. 

A. Nakayama and H. Koyama, An Integral Treatment of Laminar and Turbulent Film Condensation on Bodies of Arbitrary Geometrical Configuration, 7 Heat Transfer, 107, pp. 417-423,1985. 

Rohsenow, W.M., Webber, J.H., and Ling, A.H. (1956) Effect of vapor velocity on laminar and turbulent film condensation. Journal of Heat Transfer-Transactions of the ASME, 78, 1637-1643. 

Vertical In-Shell Condensers Condensers are often designed so that condensation occurs on the outside of vertical tubes. Equation (5-88) is valid as long as the condensate film is laminar. When it becomes turbulent. Fig. 5-10 or Colburns equation [Tran.s. Am. Jn.st. Chem. Ertg., 30, 187 (1933-1934) maybe used. 

Figure 10-67B. Correlation of McAdams representing the condensing film coefficient on the outside of vertical tubes, integrated for the entire tube length. This represents the streamline transition and turbulent flow conditions for Prandtl numbers 1 and 5. Do not extrapolate Prandtl numbers, Pr beyond 5. (Used by permission Engineering Data Book II 1984, Wolverine Tube, Inc.)...

Devore has presented useful charts for solving a multi-tuhe condenser design as shown in Figures 10-68,10-69, and 10-70. Figure 10-71 is useful for condensing steam. The charts all follow Nusselt s basic presentation however, a correction for turbulence of the film and other deviations is included. 

For conditions of turbulent flow the transfer coefficient for the water side, hi = u<>. Ri the scale resistance is constant, and h the coefficient for the condensate film is almost independent of the water velocity. Thus, equation 9.201 reduces to ... 

The basic equations for filmwise condensation were derived by Nusselt (1916), and his equations form the basis for practical condenser design. The basic Nusselt equations are derived in Volume 1, Chapter 9. In the Nusselt model of condensation laminar flow is assumed in the film, and heat transfer is assumed to take place entirely by conduction through the film. In practical condensers the Nusselt model will strictly only apply at low liquid and vapour rates, and where the flowing condensate film is undisturbed. Turbulence can be induced in the liquid film at high liquid rates, and by shear at high vapour rates. This will generally increase the rate of heat transfer over that predicted using the Nusselt model. The effect of vapour shear and film turbulence are discussed in Volume 1, Chapter 9, see also Butterworth (1978) and Taborek (1974). 

Above a Reynolds number of around 2000, the condensate film becomes turbulent. The effect of turbulence in the condensate film was investigated by Colburn (1934) and Colburn s results are generally used for condenser design, Figure 12.43. Equation 12.51 is also shown on Figure 12.43. The Prandtl number for the condensate film is given by ... 

Specific correlations of individual film coefficients necessarily are restricted in scope. Among the distinctions that are made are those of geometry, whether inside or outside of tubes for instance, or the shapes of the heat transfer surfaces free or forced convection laminar or turbulent flow liquids, gases, liquid metals, non-Newtonian fluids pure substances or mixtures completely or partially condensable air, water, refrigerants, or other specific substances fluidized or fixed particles combined convection and radiation and others. In spite of such qualifications, it should be... 

Carpenter and Colburn (C3, C12), 1951 Review of research on film condensation shows importance of gas stream effects, waves, transition to turbulence, etc. 

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