Inclination angle, condensation

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)]. 

One way of preventing inundation of condensate on lower tubes is to incline the tube bundle with respect to the horizontal. As the inclination angle increases, a critical value is reached where the condensate no longer drips off the tube but instead clings to the tube and flows to its base. Shklover and Buevich [66] conducted an experimental investigation of steam condensation in an inclined bundle of tubes and recommend an inclination angle of 5°. 

Shigechi et al. [112] conducted a boundary layer analysis of this problem and included momentum and convection effects in the condensate film. They obtained different solutions using as a boundary condition various inclination angles of the liquid-vapor interface at the plate edge. Their maximum average Nusselt number was found to agree well with Eq. 14.98. Chiou et al. [214] included surface tension in their model and showed that heat transfer decreases in relation to Eq. 14.98 as the surface tension of the condensate increases. 

Add 60 ml. of concentrated hydrochloric acid with shaking to 30 ml. of aniline in the flask, cool the mixture to about 50, and then add 45 ml. of paraldehyde and some fragments of unglazed porcelain assemble the apparatus without delay in a fume-cupboard with the condenser inclined at an angle of about 60°. 

For evaporation at the boiling point either a conical flask with a short Pyrex funnel in the mouth or a round-bottomed flask inclined at an angle of about 45° may be employed in the latter the drops of liquid, etc., thrown up by the ebullition or by effervescence will be retained by striking the inside of the flask, while gas and vapour will escape freely. When organic solvents are employed the flask should be fitted with a swan-neck tube and a condenser so that the solvent is recovered. 

When the filming amine condenses, the hydrophilic polar radical of the molecule (the head) adsorbs onto the metal surface and the hydrophobic, long chain (the tail) is directed at a 90° angle of inclination away from the metal surface. Provided the feed rate is adequate, the critical concentration is eventually reached and a continuous monomolecular surface film is formed. At this stage, the physical size of the interstices between the polar groups is smaller than the molecules of water, carbon dioxide, or oxygen, and these molecules are thus physically prevented from reaching the metal surface. 

Benzene vapour, at atmospheric pressure, condenses on a plane surface 2 m long and I m wide, maintained at 300 K and inclined at an angle of 45° to the horizontal. Plot the thickness of the condensate film and the point heat transfer coefficient against distance from the top of the surface. 

If a pure product is desired, the tube is sealed off at the first constriction after all of the pentachloride has been decomposed. The product is shaken into bulb D, the tube inclined at an angle of 45°, and the chloride sublimed under reduced pressure at a temperature of 450°C. An asbestos shield placed at the point where the tube enters the furnace will assure condensation of trichloride just beyond the edge of the furnace. The product is sublimed twice, allowed to cool to room temperature, and the tube broken just above and below the point where the trichloride has formed. The dark-red crystalline mass may be powdered, transferred to a weighing bottle, and stored in a desiccator without fear of decomposition. Exposure to direct sunlight should be avoided because of the formation of oxychlorides under such conditions. The yield is usually about 60 to 65 per cent based upon the quantity of rhenium used. In one experiment, 38 g. of twice resublimed rhenium trichloride was prepared with a yield of 68 per cent. 

The above analysis of condensation on a vertical plate can be easily extended to condensation on an inclined plate. Consider a plate inclined at an angle, 0, with respect to the gravity vector as shown in Fig. 11.10. 

The carbon dioxide leading tube was configured in such a way, that the thickness of the condensate film at the outside of this tube does not influence the heat transfer measurements, regardless of the angle of inclination. For that purpose the tube has been finned on the outside. The geometry of those fins as well as the distances between them have been chosen in such a way, that the temperature differences on the outer wall along the tube never exceed 0.5°C, regardless of the inclination of the tube. 

Equation l,p-22 was developed for vertical plates, but it can also be used for laminar fififi eondensation on the upper surfaces of plates that are inclined by an angle S.ifrom the vertical, by replacing g in that equation by g cos (Fig, 10-27). This approximatiot) gives satisfactory results especially for d 60 . Note that the condensation heat transfer coefficients on vertical and inclined plates are related to each other by... 

Equations for vertical plates can also be used for laminar film condensation on Ihc upper surfaces of the plates that are inclined by an angle 0 from llie vertical, by replacing g in that equation by g cos 9. Vertical plate equations can also be used to calculate the average heat transfer coefl icieni for laminar film condensation on the outer surfaces of vertical tubes provided that the tube diameter is large relative to the thickness of the liquid film. 

If subcooling of the condensate or superheating of the vapour is considered, then in place of the enthalpy of vaporization Ahv the enthalpy difference Ah s according to (4.29) is used. If the condensation surface is inclined at an angle 7 to the vertical, the acceleration due to gravity g is replaced by its component g cos 7 parallel to the wall. 

If the wall is inclined at an angle 7 to the vertical then the acceleration due to gravity g has to be replaced by its component parallel to the wall g cos 7 with 0 < 7 < 7r/2. The equation also holds for condensation of quiescent vapours on the inside or outside of a vertical tube, if the diameter of the tube is large in comparison to the film thickness. The width b has to be replaced by b = ir d. If a deviation of 1 % from the values from Nusselt s film condensation theory is permitted, then the equation is valid up to a Reynolds number... 

The ethyl malonic acid is placed in a small fractionating flask provided with a long condensing tube supported in an oil-bath at an oblique angle, so that its outlet tube is inclined upward. The mouth is closed by a cork bearing a thermometer. The acid is heated at 180°, until carbon dioxide is no longer evolved, which will require about a half-hour. The residue is distilled from the same flask in the usual way the butyric acid passes over between 162-163°. Yield, about 80-90% of the theory. 

The condenser is inclined at a 30° angle with F at the lower end and surrounded by ice. Water, heated to 80°, is run through E. With the aid of a very slow stream of carbon dioxide the phosphonium iodide sublimes into F as well-formed crystals. Tliis requires 2 or 3 hours. Yield 28 to 34 g. (50 to 60 per cent). 

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