Flat plates film condensation

Chen. M.M., An Analytical Study of Laminar Film Condensation. Part 1. Flat Plates Part 2. Single and Multiple Horizontal Tubes." J. Heat Transfer, Vol. 83. pp. 48-60,1961. 

Consider a vertical flat plate exposed to a condensable vapor. If the temperature of the plate is below the saturation temperature of the vapor, condensate will form on the surface and under the action of gravity will flow down the plate. If the liquid wets the surface, a smooth film is formed, and the process is called film condensation. If the liquid does not wet the surface, droplets are formed which fall down the surface in some random fashion. This process is called dropwise condensation. In the film-condensation process the surface is blanketed by the film, which grows in thickness as it moves down the plate. A temperature gradient exists in the film, and the film represents a thermal resistance to heat transfer. In dropwise condensation a large portion of the area... 

At a distance x down a vertical, isothermal flat plate on which a saturated vapor is condensing in a continuous film, the thickness of the liquid condensate layer is 8. The heal transfer coefficient at this location on the plate is given by (a) kJS (b) Shf (c) Sh ... 

When a saturated vapor condenses on a vertical, i.sothermal flat plate in a continuous film, the rale of heat transfer is proportional to... 

The Reynolds number Re = wm 6/z/L for the condensation on a vertical tube can, due to the mass balance M = wm dn 8 gL and with r/L = i/LgL, also be written as Re = M/(d,TT i]L ). As the tube diameter d, on which the calculations from Fig. 4.12 are based, is much larger than the assumed thickness of the film, the curvature of the condensate film has no effect on the heat transfer. The results also hold for condensation on a vertical flat plate, with the Reynolds number defined in (4.38). 

Chen, M.M. An analytical study of laminar film condensation. Part 1. Flat plates. Part 2. Single and multiple horizontal tubes. Trans. Am. Soc. Mech. Eng., Ser. C. J. Heat... 

Film thidcness S is typically two or three orders of magnitude smaller than the tube diameter it can therefore be found, for flow either inside or outside a tube, from the equation for a flat plate, Eq. (5.77). Since there is a temperature gradient in the film, the properties of the liquid are evaluated at the average film temperature 7., given by Eq. (13.11). For condensation on a vertical surface, for which cos) = 1, Eq. (5.77) becomes... 

O. A. Plumb, D. B. Burnett, and A. Shekarriz, Film Condensation on a Vertical Flat Plate in a Packed Bed, ASMEJ. Heat Transfer, (112) 235-239,1990. 

Shang and Adamek [15] recently studied laminar film condensation of saturated steam on a vertical flat plate using variable thermophysical properties and found that the Nusselt theory with the Drew [14] reference temperature cited above produces a heat transfer coefficient that is as much as 5.1 percent lower than their more correct model predicts (i.e., the Nusselt theory is conservative). 

D. Y. Shang and T. Adamek, Study on Laminar Film Condensation of Saturated Steam on a Vertical Flat Plate for Consideration of Various Physical Factors Including Variable Thermophysical Properties, Wdrme-und Stoffiibertragung, 30, pp. 89-100,1994. 

R. D. Cess, Laminar Film Condensation on a Flat Plate in the Absence of a Body Force, Z. Angew. Math. Phys., 11, pp. 426-433,1960. 

Vertical Flat Plates. Following the earlier work by Bromley [190] on cylinders (see below), Hsu and Westwater [191] derived an expression for laminar film boiling on a vertical plate that is analogous to that for laminar film condensation. The average value of hc over a plate of height L is given by... 

In principle the theory of electrical capacitance can be applied to the determination of lubricant film thickness between the bounding surfaces of two solids, but in practice the geometrical difficulties described in Section 5.1.1 for electrical resistance methods are even more troublesome for capacitance. If the solids are bounded by two flat surfaces parallel to each other, the electrical capacitance problem becomes that of a parallel-plate condenser, for which the formula is... 

Equipment used for thin-layer electrophoresis is practically the same as that used for separations on paper, cellulose acetate and ion exchange papers. Usually cooling is introduced into the equipment. Thus, e.g., a water-cooled flat aluminium (dural, brass) block is insulated by means of a replaceable glass plate or plastic film. The thin-layer plate is located on the insulated block and paper wicks ensure the contact with electrode vessels. A polyethylene sheet is placed between the top of the layer and the lid. This protects the surface of the layer from drops of condensed moisture that condense on the lid. A sheet of plate glass covers the whole chamber. If precoated plastic thin-layer sheets are used, the apparatus of the immersed type can be used [78]. Elution of spots, and the general practice in thin-layer electrophoresis is the same as in thin-layer chromatography. 

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