Vapor density and pressure

Historically, the first experimental determinations of the vapor densities and pressures approaching the critical region of a metal were made for mercury. Bender (1915, 1918) carried out pioneering measurements of vapor densities up to about 1400 °C. The samples in these studies were enclosed in strong fused quartz capillaries. In 1932, Birch made the first measurements of the vapor pressure of mercury and obtained realistic values for the critical temperature and pressure. Birch found values = 1460 °C and = 1610 bar, results that are remarkably close to the most accurate values available today (Table 1.1). A number of groups in various countries have contributed subsequently to the pool of pVT data currently available (Hensel and Franck, 1966, 1968 Kikoin and Senchenkov, 1967 Postill et al., 1968 Schonherr et al., 1979 Yao and Endo, 1982 Hubbard and Ross, 1983 Gotzlaff, 1988). The result is that the density data for mercury are now the most extensive and detailed available for any liquid metal. Data have been obtained by means of isothermal, isobaric, or isochoric measurements, but as we have noted in Sec. 3.5, those obtained under constant volume (isochoric conditions) tend to be preferable. In Fig. 4.10 we present a selection of equation-of-state data that we believe to be the most reliable now available for fluid... 

Experimental values of Hqg -nd Hql for a number of distillation systems of commercial interest are also readily available. Extrapolation of the data or the correlations to conditions that differ significantly from those used for the original experiments is risky. For example, pressure has a major effect on vapor density and thus can affect the hydrodynamics significantly. Changes in flow patterns affeci both mass-transfer coefficients and interfacial area. 

Spencer, W. F., Cliath, M. M. (1970) Vapor density and apparent vapor pressure of lindane (y-BHC). J. Agric. Food Chem. 18,529-530. 

The pressure is 60Torr, at which the saturation temperature of steam is 106°F. The superheat of 24°F is neglected in figuring the vapor density and velocity. 

Duarte-Garza, H.A., Hwang, C.-A., Kellerman, S., Miller, R.C., Hall, K.R., Holste, J.C. (1997a) Vapor pressure, vapor density, and liquid density for Ll-dichloro-l-fluoroethane (R-141b). J. Chem. Eng. Data 42, 497-501. 

Increases vapor density and therefore vapor-handling capacity. This leads to major reductions in column diameter and capital costs under vacuum, and to smaller reductions up to pressures of 50 to 150 psia (6). 

PVT, Vapor Density, and Virial Coefficient. In these three techniques the pressure (of a known volume and weight of gas) is measured over a temperature range. The data may be treated in two ways by assuming that the real gas is a mixture of perfect gases (each gas being one of the species), or by describing the behavior of the real gas by a virial equation. 

The most commonly measured physical property of a gas is liie pressure. Combined with the volume of the container, the pressure gives the number of moles of the gas combined with the vapor density, it gives the molecular weight of the gas. Besides the pressure, the other properties of major importance are the vapor density and the heat capacity. These three subjects will be considered here. 

It is also required to size the downcomer for adequate phase separation. One method often employed for setting downcomer design velocity is laid out in the Glitsch design manual for valve trays. Here, the downcomer design velocity is correlated from the difference between liquid and vapor densities and the system factor as described above. For many low-pressure liquids, downcomer area at the top might allow 200-250 gpm/ft at 24 in. tray spacing. 

The separation of the bulk liquid and the vapor phase is not abrupt, but as shown in Figure 6.1, there is a region where the composition, density, and pressure vary. Since 1 and 2 are defined as relative to an arbitrarily chosen dividing plane, it is in principle possible to place the dividing plane between the bulk and surface phases so that i = 0. We then have... 

Table 8.4 Vapor Density and Vapor Pressure of DDT, Its Metabolites, and Analogues...

BER/TSI] Berdonosov, S. S., Tsirel nikov, V. I., Lapitskii, A. V., Density and pressure of saturated vapors of zirconium and hafnium tetrabromides, Vestn. Mask. Univ. Ser. 2 Khim., 20, (1965), 26-29. Cited on page 177. 

The considered radial process in the bentonite annulus is a complicated one with coupled, highly nonlinear flows that involve many things. There are liquid flow and vapor flow as well as conductive and convective heat flow depending on gradients in pressure, water vapor density and temperature. The flow coefficients depend on water properties such as saturation water vapor pressure and dynamic viscosity of water. They also depend on the properties of bentonite water retention curve, hydraulic conductivity and water vapor diffusion coefficient, and thermal conductivity, all of which are functions of degree of water saturation. 

The eoncentration of solvent in a saturated vapor layer depends on temperature and vapor pressure. The coefficient of mass transfer on the air-side depends on the air velocity in the layer on the surface and Schmidt s number (includes dynamic vapor viscosity, vapor density, and diffusion coefficient). Emissions are measured in mass unit per unit of time and the amount depends on surface area and the rate of evaporation, whieh, in turn, depends on temperature, air velocity over the surface of solvent and the mass of solvent earried out on the wetted parts which have been degreased. 

Decrease column pressure to decrease vapor density and hence vapor velocity ... 

---