Shaped Ducts

In very built up areas, telephone cables are laid in ducts that mostly consist of shaped duct blocks. This means that cables running parallel to tramway tracks cannot be avoided. Metal-sheathed cables with poor coating, or with none at all, are then heavily exposed to stray currents from the tramway [5,6]. 

This requires the calculation of the phase Reynolds number and Prandtl number. This method of evaluating the wall heat flux is exactly the same as that commonly used for evaluating the heat flux for single-phase flow in an irregularly shaped duct. 

Field-flow fractionation is a separation method which was introduced by Giddings18 around 1960. The polymer solution flows in a flat ribbon-shaped duct, (see Fig. 1.20). A field perpendicular to the plane of the ribbon interacts with the polymers this field may be a thermal gradient (or more simply the gravitation field). 

A stadium-shaped duct and a modified stadium-shaped duct are displayed in the insets of Fig. 5.57. Zarling [288] has obtained the / Re and NuHi for fully developed laminar flow in stadium-shaped ducts. Cheng and Jamil [289] have determined the/Re and Nu for the mod-... 

FIGURE 5S7 Fully developed / Re and NuH) for stadium-shaped and modified stadium-shaped ducts [1]. 

A moon-shaped duct is depicted in Fig. 5.58. Shah and London [1] have determined the fully developed / Re and the velocity profile for moon-shaped ducts. These follow ... 

A cusped duct, also referred to as a star-shaped duct, such as the one shown in Fig. 5.62, is made up of concave circular arcs. The fully developed/Re, NuHi, and NuT, in laminar flow are given in Table 5.64, in which n is the number of the concave circular arcs in the cusped ducts. The values for/Re, NuT, and Num are taken from Shah and London [1], Dong et al. [292], and... 

B. D. Bowen, Laminar Flow in Unusual-Shaped Ducts, B.S. thesis, University of British Columbia, Vancouver, 1967. 

Fig. 2.7. Flat die of equipment for 5 m wide HDPE geomembranes. The die is fed by two extmders, connections far right The arrangement of the countersink screws on the top indicates the line of the coathanger-shaped duct. The choker bar can be adjusted by tlie nuts of the protruding bolts, and the die lips can be adjusted by the hexagon socket screws on the far left. The carpet of molten material leaves the die lip horizontally and is pulled into the gap between the two bottom rollers of the polishing roll stack. This and the following two figures courtesy Naue GmbH Co. KG...

The mixed flow dryer is a continuous dryer shown in Figure 21.15. The dryer consists of one or two rectangular columns. A typical column is 762 mm thick. A series of inverted V-shaped ducts are staggered traversal within the column. One row of these ducts are open to the inside plenum of the dryer and the other group are open to the outside. Grain flows from top to the bottom around these duets. In this design, grain is mixed somewhat as it flows downward. 

The scram system of the CIRENE reactor consists, as previously mentioned, in a number of tubes passing through the core and allowing injection of a poisoned liquid. Each of these tubes is a branch of a U-shaped duct, the other branch being placed outside the core. In operation the liquid column is maintained in the outside branch by an overpressure of the cover gas inside the in-core branch, which balances the hydrostatic head. 

However, confining surfaces increase the danger resulting in a hydrogen+air cloud explosion. It has been shown in [6] that when a H2 + air mixture is ignited in a U-shaped semi-open duct of 90 m volume, the combustion velocity can reach 80 m/ s and compression wave overpressure AP = 2 10" Pa. The turbulence artificially generated in U-shaped duct may cause transition of deflagration to detonation. 

The U-shaped duct and dimensions used in the large-scale experiments are shown in Fig. 5.2. 

HAM combustion behavior greatly depends on the configuration of a volume filled with a combustible mixture. Let us analyze the experimental data obtained in a semi-confined U-shaped duct [11-13], the general view is shown in Fig. 9.22. The HAM contained 37 1% H2 at normal temperature and pressure conditions in these experiments. Three typical cases were distinguished ... 

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