U-tubes

If the mixture of oxygen and nitrogen dioxide is passed through a U tube in a freezing mixture the dioxide condenses mainly as N2O4 and the oxygen passes on. 

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. 

Any free bromine can be removed by passing the evolved gas through a U tube packed with glass beads covered with moist violet phosphorus (Figure 113). 

A simple mercury manometer has already been described (see Fig. II, 19, 2). Another type that is frequently employed is the U-tube manometer illustrated in Fig. 7/,2<3,1. It consists of a U-tube filled with mercury and mounted on a wooden stand. The scale B, graduated in... 

Fig. 1. Pressurized water reactor (PWR) coolant system having U-tube steam generators typical of the 3—4 loops in nuclear power plants. PWR plants having once-through steam generators contain two reactor coolant pump-steam generator loops. CVCS = chemical and volume-control system.

Liquid Manometers. Liquid manometers were used extensively by scientists in the seventeenth through the early twentieth centuries to measure pressure. The practice of expressing pressure as a certain height of Hquid evolved from this usage. The typical Hquid manometer consists of a cyclindrical glass U-tube partially fiUed with Hquid. One end is coimected to the process the other can be either open or closed (Fig. 1). 

Fig. 1. U-Tube manometer where h is the height of the ( ) Hquid employed (a) open (b) closed.

The basic design is that of the Ostwald viscometer a U-tube with two reservoir bulbs separated by a capillary, as shown in Figure 24a. The Hquid is added to the viscometer, pulled into the upper reservoir by suction, and then allowed to drain by gravity back into the lower reservoir. The time that it takes for the Hquid to pass between two etched marks, one above and one below the upper reservoir, is a measure of the viscosity. In U-tube viscometers, the effective pressure head and therefore the flow time depend on the volume of Hquid in the instmment. Hence, the conditions must be the same for each measurement. 

The fluidized-bed bioreactor (FBBT) (26) increases the capacity of existing plants. Primary effluent is passed upward through the columnar reactor filled with sand or carbon with sufficient velocity to fluidize the bed. An attached biomass develops on the bed particles. Intimate contact between the biomass and waste is provided and improved removals are reported. Oxygen is provided by a deep U-tube reactor. No biomass recirculation is required and a secondary clarifier is not necessary. 

U. Tubes, turbulent, smooth tubes, Chilton-Colburn analogy... 

The differential U tube (Fig. 10-9) shows the pressure difference between taps A and B to be... 

The inverted differential U tube, in which the manometric fluid may be a gas or a hght liquid, can be used to measure hquid pressure differentials, especially for the flow of slurries where solids tend to settle out. Additional details on the use of this manometer can be obtained from Doolittle (op. cit., p. 18). 

Closed U tubes (Fig. 10-10) using mercuiy as the manometric fluid serve to measure direclly the absolute pressure p of a fluid, provided that the space between the closed end and the mercury is substantially a perfect vacuum. 

Two-fluid U tube (Fig. 10-14). This is a highly sensitive device for measuring small gas heads. Let A be the cross-sectional area of each of the resei voirs and a that of the tube forming the U let Pi be... 

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