Constant-flow-rate regime

As already mentioned, some instruments do not show big sensitivity changes with the carrier flow regime (see Fig. 16). With constant-flow-rate regime reproducibility is much more preserved (Fig. 17). 

Successive pol3nmer solution slugs ( 1.5 VP) separated by water injections at the same salinity were injected into porous media immersed in a thermostatic bath (30 C) at constant flow rates (v = 0.3 m/d and 0.6 m/d). At these flow rates, the wall shear rates in the pore throats Yp-p is low enough (Ypx = 4.2 s and 8.4 s calculated as suggested in Ref. 26) to ensure that the flow regime is Newtonian for the pol3n[ner solutions used. 

Figure 11.4 Image sequences of tube growth in the popping (a-h), jetting (i-l), and budding (m-p) regimes. In all experiments, aqueous cupric sulfate solution is injected into sodium silicate solution (100ml, 1 M in Si, 25°C). Injection is carried out with a syringe pump at constant flow rate (here 7.0 ml h ) through...

The second approach involves simultaneous variation of the weight of catalyst and the molal flow rate so as to maintain W/F constant. One then plots the conversion achieved versus linear velocity, as shown in Figures 6.4c and 6Ad. If the results are as indicated in Figure 6Ad, mass transfer limitations exist in the low-velocity regime. If the conversion is independent of velocity, there probably are no mass transfer limitations on the conversion rate. However, this test is also subject to the sensitivity limitations noted above. 

It is only in regime 1 that the flow rate depends on the back pressure. It will be noticed that this is only a small part of the nozzle s range of operation. Once the sonic speed has been reached at the throat (at the pressure P ), the flow becomes choked and the flow rate remains constant, for constant supply conditions, and is independent of the back pressure. 

Figure 20.12 shows a stability map of the conical preburner system investigated. In developing the stability map, the fuel flow rate is maintained constant at 0.36 g/s while the primary and secondary air flow rates are varied systematically. The flame is considered to be stable if it could be sustained for a long period of time. As shown in Fig. 20.12, unstable regimes can be noted both for low and high secondary air flow rates. 

In the stationary regime and for a non-reactive solid, the volumetric solid flow rate is constant and equal to the inlet flow rate given by the vibrating feeder (Qv ). From Eq. (1), the following ordinary differential equation is directly obtained and can be solved with a boundary condition (exit height fixed) in order to compute the bed profile along the kiln ... 

Effect of column diameter (at constant UV and percent of flood). As column diameter increases, both the liquid and vapor flow rates increase as the square of the diameter. The area for vapor flow also increases as the square of the diameter, so the vapor load remains unaffected. On the other hand, the area available for liquid flow only increases in proportion to the diameter. Therefore, the liquid rate per unit of weir length increases, the increase being proportional to the column diameter. The operating point on Fig. 6.29 will therefore shift horizontally to the right, toward the emulsion regime. Increasing the number of liquid passes on the tray reverses the above action, and shifts the operating point back to the left. 

Assuming a simple boundary layer model and a constant inlet flow rate of reactants, the growth rate of GaN is independent of reactor pressure in the mass-transport limited regime. The experimental data shown in FIGURE 2 for various reactor pressures is consistent with this behaviour. 

FIGURE 11 Hydrodynamic regimes encountered in gas-liquid flow in tubes. The liquid flow rate is constant while the gas flow rate increases, going from left to right. Gas and liquid are in cocurrent downflow. 

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