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Vapour Pressure Of Water
The vapor pressure of water is the pressure exerted by molecules of water vapor in gaseous form (whether pure or in a mixture with other gases such as air). 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. The saturation vapor pressure of water increases with increasing temperature and can be determined with the Clausius–Clapeyron relation. The boiling point of water is the temperature at which the saturated vapor pressure equals the ambient pressure. Water supercooled below its normal freezing point has a higher vapor pressure than that of ice at the same temperature and is, thus, unstable. Calculations of the (saturation) vapor pressure of water are commonly used in meteorology. The temperature-vapor pressure relation inversely describes the relation between the boilin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Torr
The torr (symbol: Torr) is a Pressure#Units, unit of pressure based on an absolute scale, defined as exactly of a standard atmosphere (unit), atmosphere (101325 Pa). Thus one torr is exactly (≈ ). Historically, one torr was intended to be the same as one "millimetre of mercury", but subsequent redefinitions of the two units of measurement, units made the torr marginally lower (by less than 0.000015%). The torr is not part of the International System of Units (SI). Even so, it is often combined with the metric prefix milli to name one millitorr (mTorr), equal to 0.001 Torr. The unit was named after Evangelista Torricelli, an Italian physicist and mathematician who discovered the principle of the barometer in 1644. Nomenclature and common errors The unit name ''torr'' is written in letter case, lower case, while its symbol ("Torr") is always written with an uppercase initial; including in combinations with prefixes and other unit symbols, as in "mTorr" (millitorr) or " ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kelvin
The kelvin (symbol: K) is the base unit for temperature in the International System of Units (SI). The Kelvin scale is an absolute temperature scale that starts at the lowest possible temperature (absolute zero), taken to be 0 K. By definition, the Celsius scale (symbol °C) and the Kelvin scale have the exact same magnitude; that is, a rise of 1 K is equal to a rise of 1 °C and vice versa, and any temperature in degrees Celsius can be converted to kelvin by adding 273.15. The 19th century British scientist Lord Kelvin first developed and proposed the scale. It was often called the "absolute Celsius" scale in the early 20th century. The kelvin was formally added to the International System of Units in 1954, defining 273.16 K to be the triple point of water. The Celsius, Fahrenheit, and Rankine scales were redefined in terms of the Kelvin scale using this definition. The 2019 revision of the SI now defines the kelvin in terms of energy by setting the Bo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lee–Kesler Method
The Lee–Kesler method allows the estimation of the saturated vapor pressure at a given temperature for all components for which the critical pressure ''P''c, the critical temperature ''T''c, and the acentric factor ''ω'' are known. Equations : \ln P_ = f^ + \omega \cdot f^ : f^=5.92714 - \frac - 1.28862 \cdot \ln T_ + 0.169347 \cdot T_^6 : f^=15.2518 - \frac-13.4721 \cdot \ln T_ + 0.43577 \cdot T_^6 with :P_=\frac ( reduced pressure) and T_=\frac ( reduced temperature). Typical errors The prediction error can be up to 10% for polar components and small pressures and the calculated pressure is typically too low. For pressures above 1 bar, that means, above the normal boiling point, the typical errors are below 2%. Example calculation For benzene with * ''T''c = 562.12 KBrunner E., Thies M.C., Schneider G.M., ''J.Supercrit. Fluids'', 39(2), 160–173, 2006 * ''P''c = 4898 kPa * ''T''b = 353.15 K * ''ω'' = 0.2120 Dortmund Data Bank the following calculati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gas Laws
The laws describing the behaviour of gases under fixed pressure, volume, amount of gas, and absolute temperature conditions are called gas laws. The basic gas laws were discovered by the end of the 18th century when scientists found out that relationships between pressure, volume and temperature of a sample of gas could be obtained which would hold to approximation for all gases. The combination of several empirical gas laws led to the development of the ideal gas law. The ideal gas law was later found to be consistent with atomic and kinetic theory. History In 1643, the Italian physicist and mathematician, Evangelista Torricelli, who for a few months had acted as Galileo Galilei's secretary, conducted a celebrated experiment in Florence. He demonstrated that a column of mercury in an inverted tube can be supported by the pressure of air outside of the tube, with the creation of a small section of vacuum above the mercury. This experiment essentially paved the way towards ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dew Point
The dew point is the temperature the air needs to be cooled to (at constant pressure) in order to produce a relative humidity of 100%. This temperature depends on the pressure and water content of the air. When the air at a temperature above the dewpoint is cooled, its moisture capacity is reduced and airborne water vapor will Condensation, condense to form liquid water known as dew. When this occurs through the air's contact with a colder surface, dew will form on that surface. The dew point is affected by the air's humidity. The more moisture the air contains, the higher its dew point. When the temperature is below the freezing point of water, the dew point is called the frost point, as frost is formed via deposition (phase transition), deposition rather than condensation. In liquids, the analog to the dew point is the cloud point. Humidity If all the other factors influencing humidity remain constant, at ground level the relative humidity rises as the temperature falls; this ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vapor Pressure Of Water
In physics, a vapor (American English) or vapour (Commonwealth English; see spelling differences) is a substance in the gas phase at a temperature lower than its critical temperature,R. H. Petrucci, W. S. Harwood, and F. G. Herring, ''General Chemistry'', Prentice-Hall, 8th ed. 2002, p. 483–86. which means that the vapor can be condensed to a liquid by increasing the pressure on it without reducing the temperature of the vapor. A vapor is different from an aerosol. An aerosol is a suspension of tiny particles of liquid, solid, or both within a gas. For example, water has a critical temperature of , which is the highest temperature at which liquid water can exist at any pressure. In the atmosphere at ordinary temperatures gaseous water (known as water vapor) will condense into a liquid if its partial pressure is increased sufficiently. A vapor may co-exist with a liquid (or a solid). When this is true, the two phases will be in equilibrium, and the gas-partial pressure will ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Goff–Gratch Equation
The Goff–Gratch equation is one (arguably the first reliable in history) amongst many experimental correlation proposed to estimate the saturation water vapor pressure at a given temperature. Another similar equation based on more recent data is the Arden Buck equation. Historical note This equation is named after the authors of the original scientific article who described how to calculate the saturation water vapor pressure above a flat free water surface as a function of temperature (Goff and Gratch, 1946). Goff (1957) later revised his formula, and the latter was recommended for use by the World Meteorological Organization in 1988, with further corrections in 2000. The current 2015 edition of the WMO Technical Regulations (WMO-No. 49) however states in Volume 1, Part III, Section 1.2.1, that any formula or constant given in the Guide to Meteorological Instruments and Methods of Observation a.k.a. CIMO-Guide (WMO-No. 8) shall be used, and this document only contains the muc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arden Buck Equation
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 .Buck 1981 A set of several equations were developed, each of which is applicable in a different situation. Formula The equations suggested by (which are modifications of the equations in ) are: : P_\left(T \right) = 6.1121 \exp \left(\left( 18.678 - \frac \right)\left( \frac \right)\right) , over liquid water, > 0 °C : P_\left(T \right) = 6.1115 \exp \left(\left( 23.036 - \frac \right)\left( \frac \right)\right) , over ice, < 0 °C where: * is the saturation vapor pressure in * is the [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tetens Equation
Tetens may refer to: People * Alfred Tetens (1835-1903), German explorer * Axel Tetens (1892–1961), Danish Olympic wrestler * Johannes Nikolaus Tetens (1736–1807), German-Danish philosopher and scientist * Otto Tetens (1865–1945), German scientist * T.H. Tetens (1899-1976), Jewish German journalist Other uses * Tetens equation, calculates the saturation vapor pressure of water over liquid and ice See also * Teten {{surname ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kilopascal
The pascal (symbol: Pa) is the unit of pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and eve ... in the International System of Units, International System of Units (SI). It is also used to quantify internal pressure, stress (physics), stress, Young's modulus, and ultimate tensile strength. The unit, named after Blaise Pascal, is an SI coherent derived unit defined as one Newton (unit), newton per square metre (N/m2). It is also equivalent to 10 barye (10 Ba) in the Centimetre–gram–second system of units, CGS system. Common multiple units of the pascal are the hectopascal (1 hPa = 100 Pa), which is equal to one Bar (unit)#Usage, millibar, and the kilopascal (1 kPa = 1000 Pa), which is equal to one centibar. The unit of measurement called ''Standard atmo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
