Poynting factor

POX. See Polyoxetane Poxvindae Poynting correction Poynting factor POY nylon yarn Pozzolans... 

At system pressures up to several tens of MPa, the fugacity coefficients, ( ) and and the Poynting factor, 7T, are usually near unity. A simplified version of equation 19 can therefore be used for the majority of vapor—Hquid equihbrium problems ... 

The exponential is known as the Poynting factor. Equation (4-277) may now be written... 

When Eq. (4-282) is applied to XT E for which the vapor phase is an ideal gas and the liquid phase is an ideal solution, it reduces to a veiy simple expression. For ideal gases, fugacity coefficients and are unity, and the right-hand side of Eq. (4-283) reduces to the Poynting factor. For the systems of interest here this factor is always veiy close to unity, and for practical purposes <1 = 1. For ideal solutions, the activity coefficients are also unity. Equation (4-282) therefore reduces to... 

The enhancement factor contains three terms supercritical phase, ideal behaviour of the pure component 2 in the vapour phase at the sublimation pressure, and the Poynting factor that describes the influence of the pressure on the fugacity of pure solid 2. 

The exponential term in eq. (2.4-16), the so-called Poynting-factor, can often be put equal to one,. In that case for a reaction in the liquid phase a simple reation between K and the composition is found ... 

Additionally usually small corrections for pressure, called Poynting factors, also belong in Eq. (13.6) and following but are omitted here. The new terms are... 

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Activity coefficients yk have traditionally been calculated from correla equations for GE/RT by application of Eq. (11.62). The excess Gibbs energy a function of Tt P, and composition, but for liquids at low to moderate, pressi it is a very weak function of P. Under these conditions, its pressure dependen and therefore the pressure dependence of the activity coefficients are usual neglected. This is consistent with our earlier omission of the Poynting factor fr... 

We could of course calculate f values by Eq. (11.67) for conditions of low-pressure VLE and combine them with experimental values of P, Tf Xj, and y, for the evaluation of activity coefficients by Eq. (11.66). However, at. low pressures (up to at least 1 bar), vapor phases usually approximate ideal gases, for which < , = 7 = 1, and the Poynting factor (represented by the exponential) differs from unity by only a few parts per thousand. Moreover, values of 4>, and tf>f differ significantly less from each other than from unity, and their influence in Eq. (11.67) tends to cancel. Thus the assumption that = 1 introduces little error for low-pressure VLE, and it reduces Eq. (11.66) to... 

Here, the exponential term is the Poynting correction factor, which may be negligible at low to moderate pressures. Disregarding the Poynting factor, Eq. (1.218) becomes... 

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The exponential term on the right-hand side of Eq. (4.12) is known as the Poynting factor. For most systems at low to moderate pressures, the Poynting factor is almost equal to one. In the case of water at 25°C ... 

This leads to a Poynting factor of 1.000714, which is essentially equal to one. If we assume that the Poynting factor is close to one, we have Raoult s law ... 

Neglecting the first term on the right side of the above equation is equivalent to assuming that the Poynting factor is equal to one. Making this assumption leads to... 

For low pressures (a few atmospheres and lower) we can apply the ideal gas model for gases and ideal mixture models for liquids. This formulation is very common in reactor technology. In some cases at higher pressures, the pressure effect on the gas phase is important. A suitable model for these systems is to use an EOS for the gas phase, and an ideal mixture model for liquids. However, in most situations at low pressures the liquid phase is more non-ideal than the gas phases. Then we will rather apply the ideal gas law for the gas phase, and excess properties for liquid mixtures. For polar mixtures at low to moderate pressures we may apply a suitable EOS for gas phases, and excess properties for liquid mixtures. All common models for excess properties are independent of pressure, and cannot be used at higher pressures. The pressure effect on the ideal (model part of the) mixture can be taken into account by the well known Poynting factor. At very high pressures we may apply proper EOS formulations for both gas and liquid mixtures, as the EOS formulations in principle are valid for all pressures. For non-volatile electrol3d es, we have to apply a suitable EOS for gas phases and excess properties for liquid mixtures. For such liquid systems a separate term is often added in the basic model to account for the effects of ions. For very dilute solutions the Debye-Htickel law may hold. For many electrolyte systems we can apply the ideal gas law for the gas phase, as the accuracy reflected by the liquid phase models is low. 

The exponential term in Equation 7-13 is a correction factor for the effect of pressure on liquid-phase fugacity and is known as the Poynting factor. In Equation 7-13, V[ can be replaced by the partial molar volume of component i in the liquid solution for greater accuracy. Eor low to moderate pressure, V is assumed as the saturated liquid molar volume at the specified temperature. Equation 7-13 is simplified to give... 

Note that the enhancement factor E has contributions from both the Poynting factor and the vapor-phase fugacity coefficient, both of which are important at high pressure, and that —> 1 as 7 —> 7 . 

Assuming that the COj-naphthalene mixture obeys the Peng-Robinson equation of state with C02-n = 0.103, estimate the.solubility of naphthalene in the CO2 supercritical fluid (SCF). Also compute the predicted enhancement factors and the contribution of the Poynting factor to the enhancement factor. 

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