Superheated vapor illustration

The condition of the feed as it enters the column has an effect on the number of trays, reflux requirements and heat duties for a given separation. Figure 8-15 illustrates the possible situations, i.e., sub-cooled liquid feed, feed at the boiling point of the column feed tray, part vapor and part liquid, all vapor but not superheated, and superheated vapor. The thermal condition is designated as q, and... 

Use other data in the superheated vapor steam tables to calculate the fugacity of steam at 300" C and 8 MPa. and check the answer obtained in the previous illustration. 

The calculation of the heat transfer coefficient and the driving temperature difference is not difficult for a one tube pass product cooler, see Fig. 7.4-4 left which illustrates a cocurrent flow of the product flow and the flow of the cooling agent. However, things are much more complex for condensers with an entering stream of a superheated vapor. In such exchangers the heat transfer and the heat flow Q are appreciably reduced by an increasing amount of noncondensable... 

Up to this point we have considered conplete distillation columns with at least two sections. Columns with only a stripping section or only an enriching section are also commonly used. These are illustrated in Figures 4-24A and B. When only a stripping section is used, the feed must be a subcooled or saturated liquid. No reflux is used. A very pure bottoms product can be obtained but the vapor distillate will not be pure. In the enriching or rectifying column, on the other hand, the feed is a superheated vapor or a... 

The screw and nut parts have the opposite characteristics. It is not difficult to reach their crevices (internal and external threads) with cleaning fluid. They are not difficult to dry, and the need for superheated vapor was only for illustration. 

Both T-xy and P-xy are useful in illustrating the concepts of bubble point, dew point, superheated vapor, and subcooled liquid. Consider the P-xy diagrams sketched in Figure 2.10. Suppose we have a mixture with composition z, and we hold it at the sartK temperature T for which the diagram was drawn. If we impose a very high pressure on the mixture, we will be above the x versus P curve (saturated-liquid line) and no vapor will be present. There will be only... 

The steam enters as a superheated vapor, and does not condense signiflcantly in the turbine. If the steam were saturated when it entered the turbine, a significant fraction of hquid would be formed when the temperature dropped isentropicaUy. The dashed fine on the Ts diagram illustrates this case. This option is impractical, since too much hquid causes erosion and wear of the turbine blades. 

However, other types of feed are obviously possible, as illustrated schematically in Fig. 12.3-2. For example, if the feed is a cold liquid that is below the saturation temperature at the composition on that stage, then the feed will necessarily condense some of the vapor rising up through the column. In this case, G will be greater than G. In the same sense, if the feed is a superheated vapor, then it will vaporize some of the liquid moving down the column, and L will be greater than L. ... 

If the steam leaves the turbine part liquid and vapor, the properties of the exit stream are determined by a mass fraction average of the properties of pure liquid and vapor as given by Equation 5.11.11 to 5.11.13. According to the phase mle, these properties are a function of one thermodynamic variable. Because the inlet steam is superheated, the properties depend on two variables as given by Equation 5.11.14 and 5.11.17. Problem 5.3 illustrates the calculation procediue given in Table 5.12. 

Isotherms on an A-V diagram are useful to illustrate the origin of p-V diagrams, superheated liquids and subcooled vapors in metastable states, unstable states between the spinodal points, critical points, and the requirement of mechanical stability. It is reasonable to assume that the slope of A vs. V at constant temperamre and composition is negative, because... 

The materials are available at 305°F, and the vapor is not superheated. Water is available ai 72, and it will be heated to 120 F. Pr ure at the top of the tower is 10 psi. This example is primarily an illustration of Ihe organization of computations, and hence specific heats and latent heats have not been corrected to the values shown in this edition. 

---