Vapor flow suppression

The lower velocity in the throat does not affect the jet s performance, as long as the velocity remains above the speed of sound. If the velocity in the throat falls below the speed of sound, we say that the jet has been forced out of critical flow. The sonic pressure boost is lost. As soon as the sonic boost is lost, the pressure in the vacuum tower suddenly increases. This partly suppresses vapor flow from the vacuum tower. The reduced vapor flow slightly unloads condenser 1 and jet 2 shown in Fig. 16.2. This briefly draws down the discharge pressure from jet 1. The pressure in the diffuser throat declines. The diffuser throat velocity increases back to, or above, sonic velocity. Critical flow is restored, and so is the sonic boost. The compression ratio of the jet is restored, and the vacuum tower pressure is pulled down. This sucks more vapor out of the vacuum tower, and increases the loads on condenser 1 and... 

Option Three—Inject cold water into the condensate rim-down to suppress vaporization. To suppress vaporization of 320°F condensate, as shown in Fig. 13.3, enough 70°F water (i.e., 25 percent of the condensate flow rate) would have to be injected. I have done this as well, with good results. 

Relevant only for a small fuel time constant and under low pressure Various modes of dynamic flow redistribution Occurs with steam injection into vapor suppression pools Very-low-frequency periodic process (-0.1 Hz)... 

But, dear reader, do not forget that when the steam inlet pressure-control valve is 100 percent open, any further increase of cool softened-water flow will suppress the deaerator s pressure. When the pressure of a vapor goes down, its volume goes up ... 

Liquid Flow Patterns on Large Trays The most popular theoretical models (below) postulate that liquid crosses the tray in plug flow with superimposed backmixing, and that the vapor is perfectly mixed. Increasing tray diameter promotes liquid plug flow and suppresses backmixing. 

Figure 12 under the counter-flow mode at 0.5 A/cm2. The index with the MPL is larger than that without the MPL for an index of 0-1 as depicted in Fig. 12. This result also shows that the MPL enhances water back-transport from the cathode side to the anode side. However, when the index is negative, meaning that the internal water circulation from the anode channel to the cathode channel, the index with the MPL is slightly higher than the index without the MPL. Therefore, the MPL at the cathode suppressed water vapor absorption at the anode, which is explainable by membrane hydration attributable to the MPL at the cathode. Consequently, the MPL promotes membrane hydration, leading less internal water circulation from the anode to the cathode side.

Most popular theoretical models (such as the AlChE and the Chan and Fair models, Sec. 7.2.1) postulate that liquid crosses the tray in plug flow (Fig. 7.7a) with superimposed backmixing, and that vapor is perfectly mixed. Increasing tray diameter promotes liquid plug flow and suppresses backmixing. This should enhance efficiency in large-diameter columns, but such enhancement has not been observed (147,148). Liquid maldistribution is the common explanation to the observation. 

It was supposed, that for a high vapor velocity and a thin liquid film the influence of gravity is small and the correlation for up flow was used. Total boiling suppression occurs when mass quality more than 0.3 for a film thickness less than 60 pm. That value is close to the bubble departure diameter observed for flow boiling in a film. When the film thickness is smaller than the critical one, the forced convection occurs with a small heat transfer coefficient. The crisis of the heat transfer was observed for a complete liquid evaporation on a heated wall. While the mass quality less than 0.3, we have the cell or slug flow mode, so boiling is not suppressed. 

Fig. 5 Boiling in a narrow vertical tube. (A) Boiling suppressed by head, natural convection is shown (B) bubble formation (C) slug formation due to bubble coagulation (D) fully developed slug flow (E) breakdown of slugs at high vapor rates (F) annular-flow-climbing film.

With a view to test the practical implementation of the design, a set of scenarios was devised (Table 1). We started with case B1 where the cold feed, Fi, was suppressed. All the feed flow is now supplied through F2, which explains the high value for the energy demand Q. In B2 the feed condition was changed to saturated vapor (q2 = 0) which substantially reduces the energy supplied and, consequently, the product purity. 

---