Pressure correction factor

Now, applying the pressure correction factor from chapter 2,... 

All relief valves are affected by reaching critical flow, which corre-spond.s to a back-pressure of about 50% of the set pressure. Pilot-operated relief valves can handle up to 50% back-pressure without any significant effect on valve capacity. Back-pressure correction factors can be obtained from the relief valve manufacturers for back-pre.ssures above 50%. API RP 520 gives a generic method for sizing a pilot-operated relief valve for sub-critical flow. 

T = flowing temperature, "R K(, = back-pressure correction factor... 

Kj = valve coefficient of discharge = 0.92 Pi = flowing pressure, psia MW = molecular weight of gas = 17,4 Z = compres-sibility factor = 0.9561 C = gas constant based on ratio of specific heats Cp/C T = flowing temperature, R Kb = back-pressure correction factor... 

Figure 10-109. Pressure correction factor. (Used by permission Chen, Ning Hsing. Chemical Engineering, V. 66, No. 5, 1959. McGraw-Hill, Inc. All rights reserved.)...

As with materials of construction correction factors, the pressure correction factors in Table 2.5 are average and only approximate and will vary, amongst other things, according to the type of equipment. Finally, its operating temperature also influences equipment capital cost. This is caused by, amongst other factors, a decrease in the allowable stress for materials of construction as the temperature increases. Table 2.6 presents typical factors to account for the operating temperature. 

Figure A8.6 BACK PRESSURE CORRECTION. FACTOR (FOR NON-CHOKED FLOW)...

The retention data described by Equation 2 are corrected from ambient conditions to the prevailing temperature and pressure conditions within the sorbent column. Use of the expansion valve at the end of the chromatographic column resulted in a negligible pressure drop across the sorbent bed, thereby simplifying the pressure correction factor used in the retention volume computations (23, 39). 

For diffusion coefficients in systems under high pressure, the method of Dawson-Khoury-Kobayashi (see Ref. [52]) suggests a relevant pressure correction factor. To estimate the molar volumes, some reliable equations of state should be applied, whereas the necessary binary diffusivities at 1 atm can be determined with one of the methods described above. 

Pressure correction factors, 62 Pressure equivalences, 111 Programmed temperature GC (PTGC), 146-149... 

Eq. 3.43 is valid for one mole of a gas only. If there are n moles of a gas occupying volume V, then, as illustrated above, the excluded volume will be given by nb and the compressible volume, therefore, will be V-nb. The pressure correction factor p for n moles, in the light of Eq. 3.41 will be proportional to n2p2, i.e., p °e n2p2 °c n2 1/V2... 

To obtain the cost at design conditions, correct the base cost for temperature, pressure, material of construction, and equipment design. In Table 2.4.1, the operating ten jerature is specified as 2,000 °F. From Table 2.10, the temperature is between 600 and 5000 C. Taking the high value, the temperature correction factor is 1.2, The pressure is at base conditions, and therefore the pressure correction factor is 1.0. Because the fiimace is constructed of carbon steel the material correction factor is also 1.0. In this case, the design factor is assume to be 1.0. Thus, from Equation 2.15.3, the furnace cost at design conditions is... 

Emissivity at a total pressure P oilier than P = 1 atm is determined by multiplying the emissivity value at 1 atm by a pressure correction factor C obtained from Figure l3-37n for water vapor. That is,... 

The pressure correction factors were determined in the preceding example to be Cf = 1.1 and = 1.4, and they do not change vdth surface temperature. Then the absorptivities of CO2 and H2O become... 

For preliminary estimates, the coefficient Kj can be taken as 0.975 for a relief valve and 0.62 for a bursting disk. The back-pressure correction factor, Ky, can initially be assumed to be 1.0 for critical flow. The combination correction factor, K, is used when a rupture disk is used upstream of the relief valve (see next section), in which case it is 0.9. If no rupture disk is used, then is 1.0. For vessels designed in accordance with AS ME BPV Code Sec. VIII, Pj = 1.1 times the maximum allowable working pressure. 

We shall assume that under flow programming conditions, the mass flow rate will be increased linearly with time (i.e., Qo(t) = (2o + 0 where Q q is the initial exit flow rate, is the exit flow rate after time t and a is the program rate. These conditions are usual for modern gas flow programming devices that utilize mass flow controllers which are computer operated. Now, if AFo is an increment of exit flow, measured at atmospheric pressure, then employing the usual pressure correction factor, the corrected gas flow (AV,) will be... 

Bateman and coworkers report a comparative analysis of six different hydraulically powered compaction simulators manufactured by a variety of vendors (Table 1), In their round-robin study, they found that the compaction simulators were comparable when operated within a moderate compression stress range of 50-2(X)MPa. However, at higher pressures, correction factors needed to be applied because of elastic distortion and differences in loading characteristics of the hydraulic systems (5). These results are not surprising since like rotary tablet presses, compaction simulators are not perfectly rigid. Therefore, compaction simulators should be properly calibrated (including corrections for mechanical flexure and electronic noise) to ensure the collection of quality experimental data. 

The hemispherical total emissivity co2(T,Pco2sm) of C02 at p = 100kPa is illustrated in Fig. 5.74. cc>2 increases slightly with rising pressure. D. Vortmeyer [5.59] presents a particularly complex pressure correction factor, which can be neglected for pressures below around 200 kPa. 

Fig. 5.76 Partial pressure correction factor Ch2o for water vapour for use in (5.195)...

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