Vapor pressure of subcooled liquid

As mentioned before, POP transport in the environment depends on their physicochemical properties [40-54], and these include saturated vapor pressure, solubility, Henry s law constant, octanol-water, octanol-air, and organic carbon-water partition coefficients. The saturated vapor pressure characterizes the capability of a substance to be transferred to the gaseous state. Eollowing the study of Wania and Mackay [40], the efficiency of POP condensation with subcooled liquid pressure (p°L) at 25°C above 1 Pa is very low. POPs with a vapor pressure between 1 and 10" Pa are condensed at a temperature of about -30°C and their deposition may be expected mostly in the polar latitudes. POPs with a vapor pressure of subcooled liquid from 10" to 10" Pa are condensed at a temperature above 0°C and they may reach to the middle latitudes. EinaUy, POPs of low volatility with a vapor pressure of subcooled liquid below 10" Pa are practically not vaporized and these substances may be transported and deposited as fine aerosols or coarse particles [39]. Using the vapor pressure of the subcooled liquid it is possible to characterize the partitioning of a POP between the gas phase and the solid phase of the atmospheric aerosol. The POPs having a lower vapor pressure are better bound with... 

If you are very careful to use very pure water, and to exclude all crystallization nuclei, it is possible to subcool liquid water to temperatures far below its equilibrium freezing point (see Figure 5.8). a. Estimate the vapor pressure of subcooled liquid water at — 10°C, using the Clausius-Clapeyron equation, starting at the triple poinL at which point... 

From Table I, the specific volume of saturated water vapor with respect to ice at 5 F is 11 550 fl /lb from which IF , jp = 0.000 086 6, but the observed water dew point was in equilibrium with subcooled liquid water at 5 F. From Table I (data from International Critical Tables ), the vapor pressures of subcooled liquid water and of ice at 5 F (-15 C) are 1.436 mm and 1.241 mm Hg, respectively. 

Since the vapor pressure of subcooled liquid water is greater than ice at the same temperature, the weight per cubic foot of water vapor in equilibrium with liquid water will be proportionately larger than the value calculated from the specific volume read from the table, which is for equilibrium with ice. 

Answer—yes But why Well, the liquid is cooled by 5°F after it leaves the drum. The cooled liquid is not in equilibrium with the vapor in the drum. It has been subcooled by 5°F. This means that the bubble-point liquid has been cooled, without altering its composition. The vapor pressure of the liquid has been reduced. As can be seen in Fig. 25.3, subcooling this particular liquid by 5°F reduces its vapor pressure by about 2 psi. As the specific gravity of the liquid is 0.58, this is equivalent to an increase in the NPSH by 8 ft. Once again, our objective is to increase the flow from 250 to 300 GPM. Figure 25.2 tells us that the required NPSH increases from 20 to 26 ft. However, when we subcool the liquid by 5°F, the available NPSH increases from 20 to 28 ft. As the available NPSH now exceeds the required NPSH by 2 ft, the flow can be increased without risk of pump cavitation. 

Saturated vapor pressure of a pure solid substance (Ps) or of its subcooled liquid (Pl) is an indicator of the substance volatility. These and other physical-chemical properties and distribution coefficients can be found in the handbook (Mackay et al., 1992b). 

Odabasi, M., Cetin, B., and Sofuoglu, A. Henry s law constant, octanol-air partition coefficient and subcooled liquid vapor pressure of carbazole as a function of temperature Application to gas/particle partitioning in the atmosphere, Chemosphere, 62(7) 1087-1096, 2006. 

Eq. 4-9 is known as the Antoine equation. It has been widely used to regress experimental data. Values for A, B, and C can be found for many compounds in the literature (e.g., Lide, 1995, Daubert, 1997). Note, however, that when using Eqs. 4-8 and 4-9 to extrapolate vapor pressure data below the melting point, one gets an estimate of the vapor pressure of the subcooled liquid compound at that temperature (e.g., naphthalene in Fig. 4.4). 

How are the (subcooled) liquid and solid vapor pressures of a given compound at a given temperature related to each other ... 

The two isomeric polycyclic aromatic hydrocarbons phenanthrene and anthracene are solids at 25°C. Although these compounds have almost the same boiling point (see below), their vapor pressures at 25°C differ by more than one order of magnitude (see Appendix C). Explain these findings. What differences would you expect for the subcooled liquid vapor pressures of the two compounds at 25°C ... 

But, let s assume that the first microsecond after the introduction of the rat, that the liquid did vaporize. The vapor so generated, would be trapped in the reflux drum. The pressure in the drum would increase. Not by 20 psig, but just a little. The small increase in pressure in the reflux drum would push up the liquid level in the condenser. The surface area of the condenser, available to subcool the liquid, would increase. The liquid temperature would be reduced. As the subcooled liquid flowed across the dead rat, its pressure would drop. The liquid s pressure would fall, to exactly that pressure that corresponds to the vapor pressure of the butane, at the temperature in the reflux drum. 

This figure is another example of a phase diagram, drawn here for a constant pressure of 70 kPa. The t - y, curve represents states of saturated vapor, with states of superheated vapor lying above it The t — x, curve represents states of saturated liquid, with states of subcooled liquid lying below iL The two-phase region lies between these curves. 

With reference to the txy diagram, we describe the course of a constant-pressure heating process leading from a state of subcooled liquid at point a to a state of superheated vapor at point d. The path shown on the figure is for a constant composition of 60 mole percent acetonitrile. The temperature of the liquid increases as the result of heating from point a to point b, where the first bubble of vapor appears. Thus point b is a bubble point, and the t - x, curve is the locus of bubble points. 

Consider a rise in liquid subcooling. Initially, this will lower the vapor pressure of the condensed liquid and, therefore, the pressure in the liquid compartment. The pressure difference between the top of the column and the liquid compartment will rise. This will enhance overhead vapor flow while retarding reflux flow. 

For adsorption and absorption, the dependence of Kp on the subcooled liquid vapor pressure of different compounds has been demonstrated by plotting log Kp vs. log pL° (Pankow 1987 Pankow and Bidleman 1991, 1992 Cotham and Bidleman 1995). The correlation could be shown as... 

Both mechanisms and their combination have a similar linear relationship between log Kp and the logarithm of subcooled liquid vapor pressure P (Pankow and Bidleman 1992 Pankow 1994), i.e.,... 

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