Condensation in-tube

Boyko and Kruzhilin (1967) developed a correlation for shear-controlled condensation in tubes which is simple to use. Their correlation gives the mean coefficient between two points at which the vapour quality is known. The vapour quality x is the mass fraction of... 

In 1916, Nusselt [4.2] had already put forward a simple theory for the calculation of heat transfer in laminar film condensation in tubes and on vertical or inclined walls. This theory is known in technical literature as Nusselt s film condensation theory. It shall be explained in the following, using the example of condensation on a vertical wall. 

Film condensation in a vertical tube. To present a theoretical description of film condensation in tubes is much more difficult, since there may arise a strong dynamic interaction between the moving vapor and the flowing condensate film. If the direction of the vapor motion coincides with the direction of the condensate motion due to gravity, then, owing to viscous friction on the phase boundary, the velocity of the film flow increases, its thickness decreases, and the coefficient of convective heat transfer also increases. If the direction of the vapor motion is opposite to that of the condensate flow, then we have the opposite situation. If the vapor velocity increases, then the film may partially separate from the wall and convective heat transfer can increase sharply. 

Azer et al. [188] reported data for condensation in tubes with Kenics static mixer inserts. Substantial improvements in heat transfer coefficients were reported however, the increases in pressure drop were very large. A subsequent paper [189] presents a surface renewal model for the condensing heat transfer coefficient. With one experimentally determined constant, the correlation derived from this model is in good agreement with the experimental data. 

Condensation in coiled tubes was studied by Miropolskii and Kurbanmukhamedov [216], and condensation in tube bends was studied by Traviss and Rohsenow [217]. In both cases, modest increases in condensation rates were observed relative to straight tubes. 

During shell-side condensation in tube bundles, neighboring tubes disturb the vapor flow field and create condensate that flows from one tube to another under the action of gravity and/or vapor shear stress forces. The effects of local vapor velocity and condensate inundation must, therefore, be properly accounted for when calculating the average heat transfer in the bundle. Marto and Nunn [53], Marto [54], and Fujii [55] provide details of these phenomena. 

J. W. Palen, R. S. Kistler, and Z. F. Yang, What We Still Don t Know About Condensation in Tubes, Condensation and Condenser Design, ASME, New York, pp. 19-53,1993. 

Film condensation in tube bundles (more commonly used in shell-and-tube heat exchangers) characterize more complex physical conditions compared to condensation on a single tube. The gravity-controlled and surface-shear-stress-influenced condensate films must be modeled in different ways to accommodate combined influences of condensate drain to lower tubes (i.e., condensate inundation) and shear effects. Such a correlation, the fourth correlation from the top of Table 17.24, was proposed by Kern and modified by Butterworth [81]. 

Finely powdered magnesium germanide is placed in reaction vessel a (Fig. 232). A 50% excess of NH Br is placed in flask t. Then enough pure NH3 is condensed in tube a so that a is two-thirds filled. A slow stream of NH3 is allowed to continue to flow in order to provide agitation and NH Br is slowly added from ft by turning the little flask upward. The reaction begins immediately. 

Dolling in shell, puicess fluid in tubes Dolling in shell, condensing in tubes... 

Phosphorus(lll) oxide is prepared by passing a slow (i.e. limited) stream of air over burning white phosphorus. A mixture of the two oxides P40(, and P40,o is thereby formed the (V) oxide can be condensed out of the emerging gas stream as a solid by passing through a U tube heated in a water bath to about 330 K the more volatile (III) oxide passes on and can be condensed in a second U trap surrounded by ice. 

For an actual determination, first place in J some stable liquid the boiling-point of which is at least 50 above that of the organic liquid the pour density of which is to be measured. This difference in boiling-point is important, because it is essential that the organic liquid, when nbsequently dropped into the bottom of T, should volatilise rapidly nd so push out an equivalent volume of air before the organic vapour can diffuse up the tube T and possibly condense in the cooler ttppcr portion of the tube. Suitable liquids for use in the jacket are ter, chlorobenzene (132°), rym-tetrachloro-ethane (147 ), P ... 

There is a tendency for the water produced by the combustion to condense in the narrow neck of the combustion tube, instead of passing right over into the absorption tube. To avoid this, two movable copper hooks Q are mounted on a copper rod, which can slide in and out of a hole cut in the mortar P these may be placed over the beak of the combustion tube and conduct sufficient heat from the mortar to vaporise the water once again so that it is driven over by the Oxygen stream into the absorption tube R. 

The Mariotte bottle. l he perchlorate guard tube is attached by a length of ordinary rubber condenser tubing to the Mariotte bottle W. This is, in effect, a siphon bottle, and the lead-in tube X is a capillary provided with a tap T,. The bent capillaiy (drawn off slightly at the end) serves as exit tube it is fitted into W by a rubber bung and its level may be adjusted. 

During this process some water will have condensed in the steam-trap D and also in the distillation bulb F. If at the end of the steaming-out process, the Bunsen burner is removed from the generator A, the pressure in A will be reduced owing to steam condensation, and the liquid in F will be sucked back into D provided that the benL-over tube is carefully adjusted, the bulb F may be almost completely emptied of liquid as desired. Finally the condensed water in the steam-trap D may be run out by op ing the tap Tj. 

Into a 1-litre three-necked flask, equipped with a reflux (double surface) condenser, a mechanical stirrer (preferably of the Hershberg type. Fig. II, 7, 8) and a gas lead-in tube extending to near the bottom of the flask, place 200 g. (227 ml.) of dry benzene, 20 g. of paraformaldehyde (1) and 20 g. of finely-pulverised, anhydrous zinc chloride. Support the flask on a water bath so arranged that the level of the water in it is about... 

In a 250 ml. conical flask, fitted with an air condenser of wide bore, place 50 g. (51 -5 ml.) of acetonylacetone (see Section V,9, Note 2) and 100 g. of ammonium carbonate (lump form). Heat the mixture in an oil bath at 100° until effervescence stops (60-90 minutes) some ammonium carbonate (or carbamate) sublimes into the condenser and this must be pushed back into the reaction mixture by means of a stout glass rod. Replace the air condenser by a Liebig s condenser with wide bore inner tube and reflux the mixture gently (bath temperature, 115°) for a further 30 minutes dissolve the solid which has sublimed into the condenser in about 5 ml. of hot water and return the solution to the reaction mixture. 

---