Bypass curve

For the case of van de Vusse kinetics with a feed of 1 kmol/m of A, Figure 6.7 indicates that the AR boundary is composed of an arc representing a CSTR with bypass (curve C), a... 

CSTR (point O), and a CSTR followed by a PFR (curve D). Within the region bounded by the three arcs and the horizontal base line Cg = 0), product compositions can be achieved with some combination of these reactor configurations. The appropriate reactor conhguradoo along the boundary of the attainable region depends on the desired effluent concentration of A. When 1 > > 0.38 kmol/m, a CSTR with bypass (curve C) provides the maximum... 

Fig. 2. Time—temperature—transformation (TTT) diagram where A represents the cooling curve necessary to bypass crystallization. The C-shaped curve separates the amorphous soHd region from the crystalline soHd region. Terms are defined ia text.

Certain pump designs use an internal bypass orifice port to alter head-flow curve. High liquid velocities often erode the orifice, causing the pump to go farther out on the pump curve. The system head curve increase corrects the flow back up the curve. 

FIG. 10-78 Approximate performance curves for a rotary positive-displacement compressor. The safety valve in discharge line or bypass must he set to operate at a safe value determined hy construction. 

The same procedure maybe used at other pump flows to permit plotting the series of balance-point curves as has been done in Fig. 29-61. From such curves, one can establish the maximum lean pump at any total tower outflow, and combining this with the semilean-pump performance curve results in Fig. 29-55. Bypass flow plotted in Fig. 29-55 is obtained by adding simultaneous lean- and semilean-pump flows and subtracting the recovery pump-turbine flow required to make the balance point at that lean-pump flow. 

Step 8 Calculate step on the bypass valve. Now that the Ac bypass of the bypass valve is known, this must he translated into a new valve position. A similar process as described in Step 6 is used. However, in this case there is not an absolute value of c, but instead a Ac. Therefore, first determine the actual bypass bet- This is accomplished by taking the actual bypass valve position and using tlie manufacturer s curve (Figure 7-9). From this point, the method to determine the new valve position is the same as described in Step 6. 

Fig ure 7-9. The bypass valve position can also be determined from the valve s curve. 

When a pump has a motor drive, the process engineer must verify that the motor will not overload from extreme process changes. The horsepower for a centrifugal pump increases with flow. If the control valve in the discharge line fully opens or an operator opens the control valve bypass, the pump will tend to run out on its curve, giving more flow and requiring more... 

Using a cooled bypass around the compressor, or by any means possible, try to establish spread between the points. It is amazing how data points can look different and still come back to the same point on the curve when the calculations are complete. If the compressor is tied to a reactor, the points may have to be taken over quite a period of time which can be done if the instruments are maintained. Be careful of fouling when using this method. 

Figure 52 also shows that the actual recovery curve does not decrease below a certain level. This indicates that a certain amount of material is always recovered to the underflow and bypasses classification. If a comparison is made between the minimum recovery level of solids to the liquid that is recovered, they are found to be equal. Therefore it is assumed that a percent of all size fractions reports directly to the underflow as bypassed solids in equal proportion to the liquid split. Then each size fraction of the actual recovery curve is adjusted by an amount equal to the liquid recovery to produce the "corrected recovery" curve shown in Figure 52. As the Djoc point changes from one application to another, the recovery curves shift, along the horizontal axis. In order to determine a single graph which represents the corrected recovery curve, the particle size of each size fraction is divided by the Dj value and a "reduced recovery" curve can be plotted, as shown in Figure 53. Studies reported by Arterburn have shown that this curve remains constant over a wide range of cyclone diameters and operating conditions when applied to a slurry...

A typical procedure is shown in Figure 2. Other dyes besides ethidium can be used, although ethidium has an advantage in that its excitation emission bands are well removed from any protein absorbances. A standard curve can be constructed for the nucleic acid of concern and the limits of detection established. In Step 3, proteolytic enzymes may be substituted for heparin, or the step may be bypassed in the case of proteins which do not interfere. After measurement of the unknown sample the nucleic acid concentration may be simply calculated or read from the standard curve. 

In a real stirred tank with bypassing or short-cut flow (Fig. 3.22), highly concentrated tracer comes out early, and the residence time distribution depends on the fraction a of the flow in the bypass (Fig. 3.23). The tailing of the response curve is caused by the perfect mixing in the main part of the tank. 

More complex situations can be imagined, for example, the combination of stirred-tanks, bypassing and stagnant zones. Care must be taken to establish the model parameters carefully however and not to merely fit the tracer response data. Experimental E-curve data is given in Fig. 3.27 and a possible model for this is shown in Fig. 3.28. 

The shell-side leakage and bypass streams (see Section 12.9) will affect the mean temperature difference, but are not normally taken into account when estimating the correction factor Ft. Fisher and Parker (1969) give curves which show the effect of leakage on the correction factor for a 1 shell pass 2 tube pass exchanger. 

The minimum required NPSH on the pump curves is normally determined using water at 60°F with the discharge line fully open. However, even though a pump will run with a closed discharge line with no bypass, there will be much more recirculation within the pump if this occurs, which increases local turbulence and local velocities as well as dissipative heating, both of which increase the minimum required NPSH. This is especially true with high efficiency pumps, which have close clearances between the impeller and pump casing. 

Photolysis of diazirine 14 gave >90% of vinyl chloride, but, in accord with the observations of Tomioka, Liu, and Bonneau,17-20 photolyses in the presence of increasing quantities of TME led to a strongly curved correlation of addn/rearr vs. [TME]. And, carbene 15 was trapped by TME with, at most, 66% efficiency, so that about a third of the diazirine was converted to vinyl chloride by a 1,2-H shift that seemed to bypass the carbene. 

Water is pumped from an atmospheric tank into a vessel at 50 psig through a heat exchanger. There is a bypass around the heat exchanger. The pump has a flat curve. The heat exchanger pressure drop is 30 psi with 200 gpm of flow through it Size the pump and the two control valves so that ... 

The family of curves represented by eqn. (46) is shown in Fig. 11 and the mean and variance of both the E(f) and E(0) RTDs are as indicated in Table 5. When N assumes the value of 0, the model represents a system with complete bypassing, whilst with N equal to unity, the model reduces to a single CSTR. As N continues to increase, the spread of the E 0) curves reduces and the curve maxima, which occur when 0 = 1 —(1/N), move towards the mean value of unity. When N tends to infinity, E(0) is a dirac delta function at 0 = 1, this being the RTD of an ideal PER. The maximum value of E(0), the time at which it occurs, or any other appropriate curve property, enables the parameter N to be chosen so that the model adequately describes an experimental RTD which has been expressed in terms of dimensionless time see, for example. Sect. 66 of ref. 26 for appropriate relationships. 

Consider steps in series. In general, if all the steps are linear in concentration, then it is easy to combine them. However, if any of the steps are nonlinear, then you will get a messy overall expression. Therefore, you may try to bypass this nonlinear step in one of various ways. Approximating the versus curve by a first-order expression is probably the most useful procedure. 

Fig. 22. Particular features of age distribution curves for models which include bypassing of fluid (L13).

Survival curves in MADIT II did not separate until 9 months after enrollment, raising the question of when an ICD should be implanted after MI or revascularization. Two notable negative primary prevention trials may answer this question. The Coronary Artery Bypass Graft Patch (CABG-Patch) Trial evaluated whether primary prevention with ICD at the time of surgical revascularization in patients with EF < 35% and a positive SAECG would reduce total mortality [33]. At 32 months follow-up, no difference was found, suggesting that there is no additional benefit to ICD therapy at the time of revascularization. 

Rotary Compressors Rotary compressors are machines of the positive-displacement type. Such units are essentially constant-volume machines with variable discharge pressure. The volume can be varied only by changing the speed or by bypassing or wasting some of the capacity of the machine. The discharge pressure will vary with the resistance on the discharge side of the system. A characteristic curve typical of the form produced by these rotary units is shown in Fig. 10-93. 

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