Other Flow Disturbances

Accuracy Square-edged orifices and venturi tubes have been so extensively studied and standardized that reproducibihties within 1 to 2 percent can be expected between standard meters when new and clean. This is therefore the order of reliabihty to be had, if one assumes (1) accurate measurement of meter differenfial, (2) selection of the coefficient of discharge from recommended published literature, (3) accurate knowledge of fluid density, (4) accurate measurement of critical meter dimensions, (5) smooth upstream face of orifice, and (6) proper location of the meter with respect to other flow-disturbing elements in the system. Care must also be taken to avoid even sh t corrosion or fouliug during use. 

Other Flow Disturbances Other examples of deviations from fully developed, single-phase newtonian flow include nonnewtonian flow, pulsating flow, cavitation, multiphase flow, boundary layer flows, and nonisothermal flows. See Sec. 6. 

Wherever possible, the inlet piping to a gas-liquid cyclone should consist of a straight section of pipe having a length-to-inside diameter L/D) ratio not less than 10 following any upstream bends, tees or other flow disturbances. In no case should the L/D ratio drop below 5. Any upstream bend should also cause the two-phase mixture reporting to the cyclone to tmn in the same rotational direction as that within the cyclone. For example, if the gas-liquid mixture enters the cyclone in a clockwise manner in plan view, then the nearest upstream bend that lies in a horizontal plane should also make a clockwise turn. 

Figure 9 shows considerable scatter because much of the data were taken in commercial pipelines with valves, elbows, bends, and other types of flow disturbances. In the transition region of Reynolds numbers below 10,000, the dispersion coefficient rises rapidly. This can be... 

Upstream and downstream disturbances in the flow field are caused by valves, elbows, and other types of fittings. Two upstream elbows in two perpendicular planes will impart swirl in the fluid downstream. Swirl, similar to atypical velocity profiles, can lead to erroneous flow measurements. Although the effect is not as great as in upstream flow disturbances, downstream flow disturbances can also lead to erroneous flow measurements. 

Zimm 100) has extended the Rouse model to allow for intramolecular hydro-dynamic interaction, i.e., changes in medium velocity near each bead caused by the flow disturbance from other beads on the same chain. The Oseen approximation, evaluated with the beads located at their mean equilibrium positions, was used to estimate the velocity disturbances. The intensity of the disturbance depends on the parameter h ... 

The feedback control in loops 1 and 2 is combined with a feed-forward controller in loop 3 which measures the inlet, temperature T calculates the change in cooling water flow rate Few which is required to bring the reactor temperature Fback to its set point Ts and sends this signal to the feedback controller (the feed-forward controller consists of a model of the process and is therefore not of P-, PI- or PID-type). The feedforward control loop will therefore theoretically eliminate any disturbances in inlet temperature Tv The feedback part of the control system, loop 1, will compensate for any inaccuracies in the feed-forward control model as well as eliminate the effect of other, unmeasured disturbances, e.g. in inlet flow rate Fr... 

The resolution of groundwater dating (e.g., by 14C) in through-flow systems is reduced by dispersion and other flow-induced disturbances, such as deviation from piston flow. In this respect stagnant systems are advantageous because they carry the age signal of the time of burial with no further dispersion effects. 

The anisotropy of the pigment particle causes orientation along the flow pattern. If the flow pattern is parallel to the surface, an increased brilliance is achieved even to a degree that a flop effect can be observed, as in painted objects. On the other hand, flow disturbances and the merging of resin of different temperatures are frequently accentuated by metallic pigments through flow and weld lines. 

When a large change is made in Zqb,b (to 0.90), the new steady-state values of the manipulated variables were only slightly different from the base-case values. The makeup flow rates of fresh feed change Fqa increases 10 percent and Fqb decreases 10 percent. Production rates of D2 and B3 stay the same, as do other flow rates and compositions throughout the process. Thus, the steady-state sensitivity analysis suggests that this structure should handle disturbances easily. Dynamic simulations confirm that this control structure works quite well. 

One frequently suggested theory is based on the fact that the Ap protein deposit is the earlier phenomenon which would be followed, in certain subjects and in certain specific regions, by neurofibrillar degeneration. These lesions would perturb axonal flow, disturb neurotransmission and synaptic activity, then finally lead to neurone loss. However, for other authors, senile plaques and neurofibrillar degeneration are only markers of a certain type of degeneration and not the cause of the clinical signs which would be related to synaptic loss and neurone death. 

Factors that affect erosion in pipe bends include the degree of internal eUipticity and asymmetry discussed earlier, sudden chsinges in cross section, and reduction in cross-sectional area [5/]. As the radii of directional change are reduced, the erosion corrosion rate is expected to increase. Ledges, crevices, deposits, and other obstructions disturb laminar flow and result in turbulence at significant velocities [40]. Short distances less than 10 diameters after directional changes or obstructions do not allow turbulence to dissipate [52]. 

Other parameters required to permit controller tuning to be calculated are included in Figure 4.2. They include the normally expected flow disturbance (f). Some judgement should be used in selecting this value. If the plant is not yet commissioned, or historical data is not available for any other reason, then a value of 10 % of the maximum flow is a good starting point. If process data do exist then a visual inspection of flow trends (either inlet or... 

Gas chromatograph feedback controller, which uses the velocity algorithm for digital PID control, discussed in Section 12.4.3.4 to calculate flow correction factors for the monomers from the gas chromatograph measurement of the actual monomer feed composition. This controller provides the necessary integral action so that the offset between the actual reactor monomer feed composition and its set point, which may be caused by flowmeter inaccuracies or other unmeasured disturbances, is niinimized. 

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