Total pressure, effect

The ambiguity of the total pressure effect can be seen by a comparison of the gas-phase- and liquid-phase-controlled cases when the gas phase controls, the liquid-phase resistance is negligible and Kg( = K npf is independent of the total pressure. For this case the coefficient K g< is inversely proportional to the total system pressure as shown in Eq. (14-66). On the other hand, when the liquid phase controls, the correct equation is... 

Thermal relaxation of the samples under pressure at room temperature (Fietz et al. 1996) for sufficient time gives the total pressure effect consisting of the intrinsic and the oxygen-ordering pressure effect... 

Fig. 57. dependence on pressure as a function of nonstoichiometry. Solid symbols, total pressure effect (intrinsic and oxygen ordering) after annealing at room temperature, Open symbols, intrinsic pressure effect after annealing at 100 K. Data from Fietz et al. (1994, 1996), Benischke et al. (1992) and D yakonov et al. (1996). After Fietz et al. (1996). 

A Posteriori Modei Discrimination. Several discrimination criteria can be used in the case no additional experimental information can be acquired. A first criterion has already been discussed in Section 3.1.2, that is, investigating the total pressure effect on the initial reaction rate potentially allows identifying the RDS in a reaction mechanism. Similar tests can be defined in which the rate equation is rearranged into a particular form to give a linear relationship between dependent and independent variables. 

The binary adsorption data clearly demonstrates the existence of a total pressure range in which the capacity of an adsorbent for CH4 and N2 is maximum. The "adsorption enhancement factor" correlationfor N2 andCH4, though restricted to one temperature in this investigation, should be useful in predicting capacities and total pressure effect on other adsorbents as well as providing a basis for evaluating theoretical ehancement curves. 

Total pressure effects on equilibria with transition state or monomer dissolved in amorphous Dolvmer. 

Table 9. Gas phase ethylene butene polymerization (85 C 10 bar total pressure) effect of butene content and ELB on the melt-flow ratio. The solid catalyst used cotnains dlbutylphtalate as an internal Lewis base.

With M = He, experimeuts were carried out between 255 K aud 273 K with a few millibar NO2 at total pressures between 300 mbar aud 200 bar. Temperature jumps on the order of 1 K were effected by pulsed irradiation (< 1 pS) with a CO2 laser at 9.2- 9.6pm aud with SiF or perfluorocyclobutaue as primary IR absorbers (< 1 mbar). Under these conditions, the dissociation of N2O4 occurs within the irradiated volume on a time scale of a few hundred microseconds. NO2 aud N2O4 were monitored simultaneously by recording the time-dependent UV absorption signal at 420 run aud 253 run, respectively. The recombination rate constant can be obtained from the effective first-order relaxation time, A derivation analogous to (equation (B2.5.9). equation (B2.5.10). equation (B2.5.11) and equation (B2.5.12)) yield... 

Increasing or decreasing the partial pressure of a gas is the same as increasing or decreasing its concentration. The effect on a reaction s equilibrium position can be analyzed as described in the preceding example for aqueous solutes. Since the concentration of a gas depends on its partial pressure, and not on the total pressure of the system, adding or removing an inert gas has no effect on the equilibrium position of a gas-phase reaction. 

The effective saturation depth,, represents the depth of water under which the total pressure (hydrostatic plus atmospheric) would produce a saturation concentration equal to for water ia contact with air at 100% relative humidity. This can be calculated usiag the above equation, based on a spatial average value of T, measured by a clean water test. For design purposes,, can be estimated from clean water test results on similar systems, and it can range from 5 to 50% of tank Hquid depth. Effective depth values for coarse bubble diffused air, fine bubble diffused air, and low speed surface aerators are 26 to 34%, 21 to 44%, and 5 to 7%, of the Hquid depth, respectively. 

Vapor pressure is the most important of the basic thermodynamic properties affec ting liquids and vapors. The vapor pressure is the pressure exerted by a pure component at equilibrium at any temperature when both liquid and vapor phases exist and thus extends from a minimum at the triple point temperature to a maximum at the critical temperature, the critical pressure. This section briefly reviews methods for both correlating vapor pressure data and for predicting vapor pressure of pure compounds. Except at very high total pressures (above about 10 MPa), there is no effect of total pressure on vapor pressure. If such an effect is present, a correction, the Poynting correction, can be applied. The pressure exerted above a solid-vapor mixture may also be called vapor pressure but is normallv only available as experimental data for common compounds that sublime. 

Effects of Total Pressure on Uq and The influence of total system pressure on the rate of mass transfer from a gas to a licniid or to a solid has been shown to be the same as would be predicted from stagnant-film theory as defined in Eq. (5-285), where... 

Experimental confirmations of the relative independence of kc with respecl to total pressure have been widely reported. Deviations do occur at extreme conditions. For example, Bretsznajder (Pi ediction of Ti anspoii and Othei Physical Piopeiiies of fluids, Pergamon Press, Oxford, 1971, p. 343) discusses the effects of pressure on the D bPt product and presents experimental data on the self-diffusion of CO9 which show tnat the D-p product begins to decrease at a pressure of... 

For the liquid-phase mass-transfer coefficient /cl, the effects of total system pressure can be ignored for all practical purposes. Thus, when using Kq and /cl for the design of gas absorbers or strippers, the primary pressure effects to consider will be those which affect the equilibrium curves and the values of m. If the pressure changes affect the hydrodynamics, then Icq, and a can all change significantly. 

E] Use s BoUes Fair (Ref. 75) data base to determine new effective area to use with Onda et al. (Ref. 126) correlation. Same definitions as 5-28-D. P = total pressure, atm Mq = gas, molecular weight m = local slope of equilibrium curve Lf /Gf = slope operating line Z = height of packing in feet. 

Isothermal Gas Flow in Pipes and Channels Isothermal compressible flow is often encountered in long transport lines, where there is sufficient heat transfer to maintain constant temperature. Velocities and Mach numbers are usually small, yet compressibihty effects are important when the total pressure drop is a large fraction of the absolute pressure. For an ideal gas with p = pM. JKT, integration of the differential form of the momentum or mechanical energy balance equations, assuming a constant fric tion factor/over a length L of a channel of constant cross section and hydraulic diameter D, yields,... 

Total pressure drop for horizontal gas/solid flow includes acceleration effects at the entrance to the pipe and fric tional effects beyond the entrance region. A great number of correlations for pressure gradient are available, none of which is applicable to all flow regimes. Govier and Aziz review many of these and provide recommendations on when to use them. 

Total pressure drop for vertical upflow of gases and solids includes acceleration and fric tional affec ts also found in horizontal flow, plus potential energy or hydrostatic effects. Govier and Aziz review many of the pressure drop calculation methods and provide recommendations for their use. See also Yang AIChE J., 24, 548-552 [1978]). 

Figure 6.3.2 shows the feed-forward design, in which acrolein and water were included, since previous studies had indicated some inhibition of the catalytic rates by these two substances. Inert gas pressure was kept as a variable to check for pore diffusion limitations. Since no large diffusional limitation was shown, the inert gas pressure was dropped as an independent variable in the second study of feed-back design, and replaced by total pressure. For smaller difftisional effects later tests were recommended, due to the extreme urgency of this project. 

Total pressure surveys were made downstream of the stators in both the radial and circumferential directions to determine the effect of coolant on stator losses. The wake traces for the stator with discrete holes and the stator with trailing edge slots show that there is a considerable difference in total... 

In general, the total back pressure on a balanced bellows pressure relief valve (superimposed plus built-up) should be limited to 50% of set pressure, because of the marked effect of higher back pressures on valve capacity, even when appropriate correction factors are used in sizing. In exceptional cases, such as a balanced bellows PR valve discharging into another vessel, total pressure up to 70% of set pressure may be used. 

Comparing Examples 2a and 2b we notice that the total air pressure has effects on the humidity x, partial density of dry air p total pressure or pressure of humid air, and enthalpy h. Knowing the total pressure is therefore essential in calculations of the thermodynamic properties of humid air. 

The airflow rate Q, for each air leakage path is expressed with Eqs. (7.237), (7.242), and (7.243) using the infotmation on effective leakage area, CjA, and a pressure difference across the path. The total pressure acting on an opening from the outside is the sum of the pressure due to wind, gravity forces, and mechanical ventilation performance, and the static pressure inside the building results from Eq. (7.244). 

The theory of losses is very complex. The effect of mixing on the total pressure has been investigated. The calculated results qualitatively match the measured results. Friction in impeller channel and casing decreases the total pressure. 

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