Tubes inclined, condensation

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. 

Experiments have shown that Eq. (11.63) tends to underestimate the heat transfer rate from a column of tubes, and is thus conservative for design purposes. The actual heat transfer rates are enhanced by several factors not accounted for in the theoretical model discussed above. These factors include such effects as splashing of the film when it impinges on a lower tube, additional condensation on the subcooled film as it falls between tubes, and uneven run-off because of bowed or slightly inclined tubes. 

On perfectly horizontal tubes a condensed film will increase its thickness towards the bottom of the tube (Fig. 15.2). Some of the condensed liquid will fall onto lower tubes, increasing the liquid load, and decreasing the heat transfer coefficient on those tubes. Even a slight inclination of the tube is sufficient to cause the condensate to drain in the direction of the slope. A horizontal shell and tube condenser is likely to be baffled so as to force the vapor to flow horizontally across the tubes. Other flow arrangements are, however, possible. 

Armbruster and Mitrovic [62] observed that liquid falls from tube to tube in three patterns discrete droplets, jets or columns, and sheets, depending on the flow rate (i.e., film Reynolds number) and fluid properties. In addition, depending on the tube arrangement and spacing, the condensate may cause ripples, waves, and turbulence to occur in the film splashing may occur, as well as nonuniform rivulet runoff of condensate because of tube inclination or local vapor velocity effects. As a result, it is impossible to arrive at an analytical expression to describe these complex bundle phenomena. In general, the effect of inundation may be accounted for using... 

Various solutions have been used. These include orifices to regulate the flow into each tube, a blow-through steam technique with a vent condenser, complete separation of each row of tubes, and inclined tubes. 

Natural Gas Condensate in 16 Pipeline o Natural Gas,Oil and Water in 2 Oil Well Tubing o Air and Water in 1 Ver tical Tubing e Air and Lube Oil in 2 Inclined Tubing ... 

The correlation of Akers, et. al., has given good results in some industrial designs. The authors report that some vertical and inclined tube data is also correlated on the same basis. The sharp break in the data occurs around a Reynolds number of 5 X lO as shown in Figure 10-75. The mass flow rate used to correlate is the arithmetic average of inlet and oudet liquid condensate and vapor flows ... 

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. 

The Claisen flask is fixed in an inclined position and a small condenser jacket is slipped over the side tube, which slopes upwards. Atmospheric moisture is excluded by fixing a calcium chloride tube to the upper end of the side tube. Benzoylazide (12 g.) and benzene... 

Assemble an apparatus (see Fig. 21). Place the prepared vanadi-um(V) oxide into a flask and add 12 ml of freshly distilled thionyl chloride. Heat the flask in a water bath for three or four hours. Replace the reflux condenser with a dephlegmator provided with an inclined cooler (see Fig. 20). Distil off the fraction boiling at 126-127 °C by carefully heating the flask with the open flame of a burner. Transfer the collected liquid into a weighed drawn out test tube. (Wear eye protection, seal the substance in the presence of your instructor ) Weigh the ampoule with the substance and the remaining part of the tube. Calculate the yield in per cent. 

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)]. 

A. Symmetrical o-Pkthalyl Chloride A mixture of 148 g. (1 mole) of phthalic anhydride (Note 1) and 220 g. (1.06 moles) of phosphorus pentachloride (Note 2) is placed in a 500-cc. Claisen flask. The flask is equipped with a reflux condenser, the upper end of which is provided with a calcium chloride tube, and the side-arm of the flask is closed with a cork. The flask is inclined slightly so that any phosphorus oxychloride which collects in the stoppered side-arm will run back into the flask. After heating in an oil bath at 150° for twelve hours, the air condenser and the stopper in the end of the side-arm are removed, and the flask is connected to a water-cooled condenser. The temperature is then raised gradually to 250°, during which... 

Procedure, ioo c.c. of the wine are evaporated in a flask to io c.c., allowed to cool and treated with 6 c.c. of the saturated ferrous sulphate solution and 4 c.c. of concentrated sulphuric acid.1 The flask is connected with a vertical condenser about 50 cm. long and heated carefully over a small flame so that excessive frothing of the mass is avoided. The distillate is collected in two or three well-cleaned tubes, each containing 2-3 c.c. of the iodide-starch paste acidified with 2 drops of dilute sulphuric acid the tubes are inclined so that the distillate flows down the walls. In presence of nitrites, a blue ring forms at the zone of separation between the starch and the distillate. 

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. 

Air-Cooled Overhead Condensers Air-cooled overhead condensers (AOC) have been designed and installed above distillation columns as integral parts of distillation systems. The condensers generally have inclined tubes, with air flow over the finned surfaces induced by a fan. Prevailing wind affects both structural design and performance. 

B Calculate the heat flux associated with condensation on inclined and horizontal plates, vertical and hoiizonlal cylinders or spheres, and tube bundles,... 

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. 

J. C. Chato. Laminar Condensation inside Horizontal and Inclined Tube,s. ASHRAE Journal 4 (1962), p. 52. 

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