Magnitude of pressure drop

A third factor is the ease with which various membrane materials can be fabricated into a particular module design. Almost ah membranes can be formed into plate-and-frame, spiral, and tubular modules, but many membrane materials caimot be fabricated into hollow-fine fibers or capihary fibers. Finahy, the suitabiHty of the module design for high pressure operation and the relative magnitude of pressure drops on the feed and permeate sides of the membrane can sometimes be important considerations. 

Suitable computational models for each of the layers discussed above were developed on the basis of available information and a time scale analysis of flow in OXY reactors (see Ranade, 1999b for more details). Because of the magnitude of pressure drop across the grid, it was found necessary to employ compressible flow equations. An ideal gas assumption was used to calculate the density of gas at any point (as a... 

The pressure drop reduction is said to occur due to the ball-bearing effect of the particulates. The magnitude of pressure drop reduction is a function of particle size and particle characteristics (e.g., density). However, some researchers argue that it is an unsteady-state phenomenon on that cannot be relied on to occur consistently. 

Sharp rate of rise of pressure drop. A sharp rate of rise of pressure drop with vapor rate may be an even more sensitive flooding indicator than the magnitude of pressure drop. The flood point can be inferred from a plot of pressure drop against vapor or liquid flow rate, and is the point where the slope of the curve changes significantly (Figs. 14.3,14.4). In tray columns, the slope change can be relatively mild (curve 1 in Fig,... 

FIGURE 9.23 Relative Magnitude of Pressure Drop Contributions as a Function of Exposed Channel Length for (a) Low Flow (0.005 kg/s) and (b) High Flow (0.025 kg/s). 

Ultimately, the particles will stream with the fluid and the bed will cease to exist. This occurs in (E). Figure 28 (A) shows a column that is traversed counter gravity-wise by a gas with a superficial velocity, u. A pressure drop equal to APj, will result, and the magnitude of the drop will be determined by the fluid rate and the characteristics of the bed. As the gas velocity is increased, the pressure drop will rise. 

The amount of air liberated each time the pressure had been lowered depended, of course, on the magnitude of the drop in pressure The greater the reduction in pressure, the more air was liberated. 

Figure 12 shows some results of pressure drop measurements over a 1-m-long internally finned round tube (4-mm internal diameter, six fins, fm height 1 mm, fin thickness 0.5 mm) with a cutoff angle at the bottom end of 60 . With n-decane as the liquid and air at ambient temperature and pressure as the gas, the pressure drop increases steadily with increasing gas velocity until a certain critical gas velocity is reached. Below this critical velocity, the pressure drop is low, viz., orders of magnitude lower than in a fixed bed of catalyst under comparable conditions. It can also be seen that under these conditions the superficial velocity of the liquid in the internally finned tube has little effect on the pressure drop. 

Motion pictures were taken of the surface of the liquid oxygen during both tests 7 and 8. The film from test 7 was taken while the level was in the tank dome within 10 to 15 in. of the top. From the film it was estimated that the cessation of boiling due to pressurization caused the surface to become quiescent at a level 1 to 2 in. lower than the boiling surface. Liquid—gas detector probes which were 1 in. apart indicated the same magnitude of level drop. 

A slit die is designed on the assumption that the material is Newtonian, using apparent viscous properties derived from capillary rheometer measurements, at a particular wall shear stress, to calculate the volumetric flow rate through the slit for the same wall shear stress. Using the correction factors already derived, obtain an expression for the error involved in this procedure due to the melt being non-Newtonian. Also obtain an expression for the error in pressure drop calculated on the same basis. What is the magnitude of the error in each case for a typical power law index n = 0.377... 

---