Flow rate pressure characteristic

Flow rate pressure characteristic The relationship between the flow rate and a given pressure differential. 

Recently elaborated methods for predicting volumetric flow rate/pressure characteristics, extrudate structures, and determining high and low limits of optimal processing, can now be used in industrial processing of plastics. 

Rotation of the core at Q = 70 min-1 shifted flow rate/pressure characteristics of extrusion curves upwards and to the left, the result of which was a notable drop of (AP)70 compared to (AP)0 (indexes used here correspond to the speed of core s rotation). Increase in (AP)70 up to values of (AP)0 due to higher speed of the screw allowed as increase is the extruder s capacity by 40-80 % (depending on the nature and content of the filler). Results very much similar to that were obtained later in experiments with filled PVC-based compositions 36). Pressure in the head can be reduced by not less than 20-30 % at a constant extrusion rate, experiments with filled PVC-based compositions 36). Pressure in the head can be reduced by not less than 20-30% at a constant extrusion rate. 

Figure 6.15(a) shows the linear flow rate-pressure characteristic Q-p) on the basis of equation (6.126). Two points on the Q-p graph characterize the capability of the EO microchannel to work as a micropump. One is the free-flow capability (Geo) obtained at zero back pressure, = 0. The other is the zero-flow pressure capability, or EO pressure, (/ eo)> defined as the back pressure needed to exactly cancel the EO flow. At free flow, p = 0 and we have... 

Figure 6.15 (a) The flow rate-pressure characteristic for an ideal EO flow with back pressure p. (b) The flow profile m in a cylindrical microchannel at the electroosmotic pressnre where the net flow rate is zero (Q = 0)... 

Because of the complexity of designs and performance characteristics, it is difficult to select the optimum atomizer for a given appHcation. The best approach is to consult and work with atomizer manufacturers. Their technical staffs are familiar with diverse appHcations and can provide valuable assistance. However, they will usually require the foUowing information properties of the Hquid to be atomized, eg, density, viscosity, and surface tension operating conditions, such as flow rate, pressure, and temperature range required mean droplet size and size distribution desired spray pattern spray angle requirement ambient environment flow field velocity requirements dimensional restrictions flow rate tolerance material to be used for atomizer constmction cost and safety considerations. 

The flow rate-pressure drop measurements shown in Table 3.1 were made in a horizontal tube having an internal diameter d, = 6 mm, the pressure drop being measured between two tappings 2.00 m apart. The density of the fluid, p, was 870 kg/m3. Determine the wall shear stress-flow characteristic curve and the shear stress-true shear rate curve for this material. 

Before closing this chapter, we feel that it is useful to list in tabular form some isothermal pressure-flow relationships commonly used in die flow simulations. Tables 12.1 and 12.2 deal with flow relationships for the parallel-plate and circular tube channels using Newtonian (N), Power Law (P), and Ellis (E) model fluids. Table 12.3 covers concentric annular channels using Newtonian and Power Law model fluids. Table 12.4 contains volumetric flow rate-pressure drop (die characteristic) relationships only, which are arrived at by numerical solutions, for Newtonian fluid flow in eccentric annular, elliptical, equilateral, isosceles triangular, semicircular, and circular sector and conical channels. In addition, Q versus AP relationships for rectangular and square channels for Newtonian model fluids are given. Finally, Fig. 12.51 presents shape factors for Newtonian fluids flowing in various common shape channels. The shape factor Mq is based on parallel-plate pressure flow, namely,... 

Show how the valve effective characteristic is related to pressure drop. Figure 19.14 shows the inherent and effective characteristics of typical linear, equal-percentage, and on-off control valves. The inherent characteristic is the theoretical performance of the valve. If a valve is to operate at a constant load without changes in the flow rate, the characteristic of the valve is not important, since only one operating point of the valve is used. 

In this situation, if the pressure filtration stays unchanged, the filtrate rate will decrease with time. When unacceptable values of the filtrate rate are reached, the process must be stopped and the membrane cleaned or replaced. This mode of operation is uneconomical. One solution to this problem is to increase the transmembrane pressure in order to maintain the flow rate but, in this case, the pumping flow rate has to be reduced because pumps generally present a pre-established and characteristic flow rate-pressure relation which is, a priori, unchangeable. Consequently, when the pressure is continuously increased, the clogging rate will increase faster than when a high tangential velocity is used in the unit. 

The development of a chromatographic procedure for an unknown sample (mixture) requires the selection of a variety of experimental conditions (type and composition of the mobile phase, characteristics of the column and the stationary phase, temperature, flow-rate, pressure, type of gradient, etc.). This problem was traditionally solved in an empirical way and with the aid of the vast literature on similar situations already dealt with. The last few years have seen attempts at the rationalization and automation of the optimization of chromatographic processes which have resulted In Interesting systematic approaches of great use. The monographs by Berridge [56], devoted to HPLC, and that by Shoenmakers [57], which deals with both HPLC and GC, represent the most systematic and complete compilations in this field at present. 

Design considerations for vascular access devices include ease of handling, insertion, and use minimal thrombotic and other biocompatibility-related complications stmctural and operational reliability over time and optimization for application-specific performance issues (Canaud et al., 2000). Three different catheter tips are shown in Fig. 20.10 to illustrate these variations in design and structure. Because of the distinct characteristics of the different treatments and agents deployed through catheters, it is not practical to provide specific values for flow rates, pressure drops, viscosities, and other important transport properties. 

As with other separation equipment, the main characteristics of filters are the flow rate-pressure drop relationships and other performance characteristics such as the separation efficiency. In filtration however, these relationships are more complex as there are many variables and factors (cake thickness, mass of cake per unit area, specific cake resistance etc.) which greatly influence the process. 

Equations (4.2), (4.3), and (4.4) are for the fuel channel, water rod channel, and outside core, respectively. The governing equations are discretized using the upwind difference scheme and the full implicit scheme. The boundary conditions are the feedwater flow rate, the feedwater temperature, and the mrbine inlet flow rate. The characteristic of the turbine control valve, expressed as the change of steam flow rate, is shown in Fig. 4.4 [6]. The feedwater flow rate changes with the core pressure as shown in Fig. 4.5 [6]. 

FIG. A-75 Pressure loss versus volume flow rate filter characteristic. (Source Altair Filters International Limited.)... 

Variable-Area Flow Meters. In variable-head flow meters, the pressure differential varies with flow rate across a constant restriction. In variable-area meters, the differential is maintained constant and the restriction area allowed to change in proportion to the flow rate. A variable-area meter is thus essentially a form of variable orifice. In its most common form, a variable-area meter consists of a tapered tube mounted vertically and containing a float that is free to move in the tube. When flow is introduced into the small diameter bottom end, the float rises to a point of dynamic equiHbrium at which the pressure differential across the float balances the weight of the float less its buoyancy. The shape and weight of the float, the relative diameters of tube and float, and the variation of the tube diameter with elevation all determine the performance characteristics of the meter for a specific set of fluid conditions. A ball float in a conical constant-taper glass tube is the most common design it is widely used in the measurement of low flow rates at essentially constant viscosity. The flow rate is normally deterrnined visually by float position relative to an etched scale on the side of the tube. Such a meter is simple and inexpensive but, with care in manufacture and caHbration, can provide rea dings accurate to within several percent of full-scale flow for either Hquid or gas. 

Although it has been common practice to specify the pressure loss in ordinary valves in terms of either equivalent length of straight pipe of the same size or velocity head loss, it is becoming more common to specify flow rate and pressure drop characteristics in the same terms as has been the practice for valves designed specifically for control service, namely, in terms of the valve coefficient, C. The flow coefficient of a valve is defined as the volume of Hquid at a specified density that flows through the fully opened valve with a unit pressure drop, eg, = 1 when 3.79 L/min (1 gal /min) pass through the valve... 

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