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where temperature T is in degrees Celsius (°C) and saturation vapor pressure P is in kilopascals (kPa). According to Monteith and Unsworth, "Values of saturation vapour pressure from Tetens' formula are within 1 Pa of exact values up to 35 °C." Murray (1967) provides Tetens' equation for temperatures below 0 °C: [3]
The fugacity of a condensed phase (liquid or solid) is defined the same way as for a gas: = and = It is difficult to measure fugacity in a condensed phase directly; but if the condensed phase is saturated (in equilibrium with the vapor phase), the chemical potentials of the two phases are equal (μ c = μ g).
One pascal is one newton per square meter (N·m −2 or kg·m −1 ·s −2). Experimental measurement of vapor pressure is a simple procedure for common pressures between 1 and 200 kPa. [2] The most accurate results are obtained near the boiling point of the substance; measurements smaller than 1 kPa are subject to major errors. Procedures ...
The Köhler curve is the visual representation of the Köhler equation. It shows the saturation ratio – or the supersaturation = % – at which the droplet is in equilibrium with the environment over a range of droplet diameters. The exact shape of the curve is dependent upon the amount and composition of the solutes present in the atmosphere.
The Arden Buck equations are a group of empirical correlations that relate the saturation vapor pressure to temperature for moist air. The curve fits have been optimized for more accuracy than the Goff–Gratch equation in the range −80 to 50 °C (−112 to 122 °F). [1]
Such VLE diagrams are square with a diagonal line running from the (x 1 = 0, y 1 = 0) corner to the (x 1 = 1, y 1 = 1) corner for reference. These types of VLE diagrams are used in the McCabe–Thiele method to determine the number of equilibrium stages (or theoretical plates ) needed to distill a given composition binary feed mixture into one ...
The saturation with respect to water cannot be measured much below –50 °C, so manufacturers should use one of the following expressions for calculating saturation vapour pressure relative to water at the lowest temperatures – Wexler (1976, 1977), [1] [2] reported by Flatau et al. (1992)., [3] Hyland and Wexler (1983) or Sonntag (1994 ...
The saturation vapor pressure is the pressure at which water vapor is in thermodynamic equilibrium with its condensed state. At pressures higher than saturation vapor pressure, water will condense , while at lower pressures it will evaporate or sublimate .