Curve rate-pressure

Read, F, for the approximate calculated Cs, ft/sec from Table 9-37 at calculated liquid rate, Ib/hr-ft. Then read Y from IMTP Packing Pressure Drop chart. Figure 9-2IG and then read curves showing pressure drop, (may require interpolation). 

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. 

When data are available in the form of the flow rate-pressure gradient relationship obtained in a small diameter tube, direct scale-up for flow in larger pipes can be done. It is not necessary to determine the r-y curve with the true value of y calculated from the Rabinowitsch-Mooney equation (equation 3.20). 

Horizontal centrifugal pumps should provide 150% of the rated capacity at 65% of the rated pressure, with a shutoff head of not more than 120% of the rated pressure. This pump should be used only when suction supply is under a positive head. Suction pipes should be designed to preclude the formation of air bubbles. A characteristic curve for a rated fire water pump is shown in Figure 7-15. 

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 10.17. Development of the BET-mtrogen surface area during the dehydration, by CRTA, of a sample of fine gibbsite, 1 pm gram size. CRTA conditions controlled pressure indicated in mbar on the curve rate of dehydration, 11.4 mg IT1 g"1 (Rouquerol and Ganteaume, 1977).

Figure 3. After the initial desorption, curve (a) is loaded during cooling with 5 K/min, while the absorption in (b) is supported by keeping the sample at constant T = 160°C for 100 min. The subsequent desorption is performed with a heating rate of 5 K/min for both curves. Hydrogen pressure is 1 bar. For better visibility, the absorption curves have been shifted. From Ref. [9].

The mean pore size and pore size distribution can be evaluated by performing this measurement by a stepwise increase of the pressure. In this case the gas flow across the wet defect-free membrane is recorded (Fig. 4.18) as a function of the applied pressure difference across the sample ("wet curve"). The point of first flow is identified as the "bubble point". This continues until the smallest detectable pore is reached. Then the flow rate response corresponds to the situation in a completely dry sample. The measurement of gas flow through the same membrane in a dry state gives a linear function of the applied pressure difference ("dry curve"). The pressure at which the "half-dry" curve intersects with the "wet" curve can be used to calculate an average pore diameter. Pore number distributions can also be derived from flow distribution curves. 

Examination of Figures 12.7 and 12.8 shows that the 1-bar curve on Figure 12.8 corresponds exactly to the 0.1 bar curve in Figure 12.7 except that in Figure 12.8 productivity is about one tenth that in Figure 12.7. This is due to the fact that the amount that can be converted, defined on the total feed rate of reactants, is reduced by a factor of ten by the introduction of the diluent. Curves at pressures other than 1 bar show the effects of decreasing rates of reaction due to dilution. Similarly intertwined curves would be observed at zero dilution on Figure 12.7 at pressures one tenth of those in... 

As an alternative to direct heat transfer measurements it is possible to use changes in pressure drop brought about by the presence of the deposit. The pressure drop is increased for a given flow rate by virtue of the reduced flow area in the fouled condition and the rough character of the deposit. The shape of the curve relating pressure drop with time will in general, follow an asymptotic shape so that the time to reach the asymptotic fouling resistance may be determined. The method is often combined with the direct measurement of thickness of the deposit layer. 

A freshly prepared high-vacuum film always showed a higher decomposition rate than one which had been used in a decomposition experiment. The shapes of all curves of pressure increase against time were similar, and the curves for subsequent experiments could be superimposed on the first by a simple change of scale on the pressure axis. If the reciprocal of the scale factor is taken as a measure of the activity of the film, the data of Table II are obtained for a series of consecutive experiments on the same film. The activ-... 

Where the driven machine is a centrifugal type i.e. pump or compressor, the shaft power may be taken as that which occurs at the end of curve operating point. This rule-of-thumb point is defined as being 125% of the power required at the maximum operating efficiency point on the designed curve of pressure (head) versus fluid flow rate, at the rated shaft speed. 

Figure 5. The wear of the tissue with time (For all experiments the plate was made to oscillate at an average velocity of 0.52 M/min. The abscissas can therefore be converted to distance slid.) Curve A pressure on the tissue alternated equally between 0.69 and 6.9 MN/m at a frequency of 0.02 Hz. Curve B the pressure was alternated equally between 0.69 and 4.14 MN/m at a frequency of 0.02 Hz. Note the initial higher wear rates and the two steady state rates of Curve B.

Using lower flow rate, efficiency is in general better, but the Van Deemter curve is non-uniform. It depends essentially on the particle size, the nature of the stationary phase, the structure of the solute and the temperature. For small particle sizes (3-5 Xm) the minimum is relatively flat and the slope of the Van Deemter curve is not steep. In reality, this means, that with 3-5 pm columns it is possible to work at higher flow rates - pressure permitting. The chromatographic analysis is faster and you do not lose a lot in separation performance. A decreased flow rate would not lead to a noticeable improvement of the separation. (A note in parenthesis for those interested improving... 

The column diameter is sized to operate at 65% to 90% of flooding or to have a given pressure drop per foot of packing. Flooding can be more easily measured in a packed column than in a plate column and is usually signaled by a break in the curve of pressure drop vs. gas flow rate. 

Figure 5. Calculated homogeneous nucleation rate in superheated diethyl ether T = 193.5 C). The labels on each curve are pressures in bar [71, 5].

This method makes use of comparison between the theoretical and the experimental initial rate curves. Rate equations derived from the mechanisms described above were expressed as a function of total pressure (Pt) and conversion (X). Then the substitution of X= gave the parametric form of the initial rate (lO) which is plotted against total pressure in Figure 1. 

---