Condensation Flat Plate

Platten-gewebe, n. lamellar tissue, -glimmer, m. sheet mica, -gummi, n. plate rubber sheet rubber, -kaik, m. slab limestone, -kautschuk, n. plate rubber sheet rubber, -kondensator, m. (Elec.) plate condenser, -kultur, /. plate culture, -kupfer, n. sheet copper, -pulver, n. (Expl.) rolled powder, flake powder, -achale, /. flat dish, specif. Petri dish, -turm, m. plate column, plate tower, -zink, n. slab zinc, plattgedriickt, a. flat-pressed, flattened, plattieren, jj.t. plate clad. 

Boundary-layer separation and Reynolds flux. Kutateladze and Leont ev (1964, 1966) suggested that the flow boiling crisis can be analyzed using the concept of boundary-layer separation (blowoff) from a permeable flat plate with gas injection (without condensation), as shown in Figure 5.14. Kutateladze and Leont ev (1966) also give the critical condition of boundary layer separation from a flat plate with isothermal injection of the same fluid as... 

The classical electrostatic balance is the Millikan condenser, which was first used to measure the charge on the electron in the famous Millikan oil-drop experiment. In principle, the device can be used to levitate a small charged mass by using the electrical field generated by two flat plates to... 

This formula is valid for flat plates and cylindrical tubes of diameter larger than around 1/8 inch. In both cases the inclination angle should be lower than 90°. Additionally, Pr > 0,5 and [c (Ts - To) / ifc] < 1. A better approximation can be obtained when the condensate viscosity is calculated at [7o + 0,31 (Ts - 7 0)]. 

Eqs. (11.55) and (11.57) are valid for laminar flow. If flat plate flow is used as a rough guide, it will be seen that these equations can be expected to yield accurate results for about Re < 60. This Reynolds number is twice the value for a flat plate because condensation occurs on both sides of the tube. 

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... 

Saturaied aruraonia vapor at 30°C is passed over 20 vertical flat plates, each of which is 10 cm high and 15 cm wide. The average surface temperature of the plates is 10°C. Estimate the average heal transfer coefficient and the rate of ammonia condensation. 

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... 

Plate evaporators may be constructed of flat plates or corrugated plates, the latter providing an extended heat transfer surface and improved structural rigidity. Two basic types of heat exchangers are used for evaporation systems plate-and-frame and spiral-plate evaporators. Plate units are sometimes used because of the theory that scale will flake off such surfaces, which can flex more readily than curved tubular surfaces. In some plate evaporators, flat surfaces are used, each side of which can serve alternately as the liquor side and the steam side. Scale deposited while in contact with the liquor can then be dissolved while in contact with the steam condensate. There are still potential scaling problems, however. Scale may form in the valves needed for cycling the fluids and the steam condensate simply does not easily dissolve the seale produced. 

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). 

Rose [47, 48] has suggested an approximate solution for forced convection condensation along a flat plate in the presence of noncondensable gas using an analogy between heat and mass transfer. He points out that, in this situation, the diffusion problem for the vapor-gas... 

Effect of Noncondensable Gas. As described earlier, Rose [47, 48] has suggested an approximate method to calculate condensation heat transfer in the presence of a noncondensable gas. For forced convection over a single horizontal tube, he recommends the following relationship (similar to Eq. 14.52 for a flat plate) that relates the mean condensation rate to the free stream conditions ... 

Condensation in vertical tubes depends on the vapor flow direction and its magnitude. During downflow of vapor, if the vapor velocity is very low, then the condensate flow is controlled by gravity, and the Nusselt results for a vertical flat plate are applicable (unless the tube inside diameter is very small and tube wall curvature effects become important [36]). 

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. 

J. W. Rose, Approximate Equations for Forced-Convection Condensation in the Presence of a Noncondensing Gas on a Flat Plate and Horizontal Tube, Int. J. Heat Mass Transfer, 23, pp. 539-546, 1980. 

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... 

Figure 8. Flat plate condenser and rotating disk assembly in multistage test unit...

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