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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'' = 0.2120Dortmund Data Bank the following calculation for T=Tb resul ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Saturated Vapor Pressure
Vapor pressure (or vapour pressure in English-speaking countries other than the US; American and British English spelling differences#-our, -or, see spelling differences) or equilibrium vapor pressure is defined as the pressure exerted by a vapor in thermodynamic equilibrium with its Condensation, condensed Phase (matter), phases (solid or liquid) at a given temperature in a Thermodynamic system#Closed system, closed system. The equilibrium vapor pressure is an indication of a liquid's evaporation rate. It relates to the tendency of particles to escape from the liquid (or a solid). A substance with a high vapor pressure at normal temperatures is often referred to as ''volatility (chemistry), volatile''. The pressure exhibited by vapor present above a liquid surface is known as vapor pressure. As the temperature of a liquid increases, the kinetic energy of its molecules also increases. As the kinetic energy of the molecules increases, the number of molecules transitioning into a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Critical Pressure
In thermodynamics, a critical point (or critical state) is the end point of a phase equilibrium curve. The most prominent example is the liquid–vapor critical point, the end point of the pressure–temperature curve that designates conditions under which a liquid and its vapor can coexist. At higher temperatures, the gas cannot be liquefied by pressure alone. At the critical point, defined by a ''critical temperature'' ''T''c and a ''critical pressure'' ''p''c, phase boundaries vanish. Other examples include the liquid–liquid critical points in mixtures, and the ferromagnet–paramagnet transition (Curie temperature) in the absence of an external magnetic field. Liquid–vapor critical point Overview For simplicity and clarity, the generic notion of ''critical point'' is best introduced by discussing a specific example, the vapor–liquid critical point. This was the first critical point to be discovered, and it is still the best known and most studied one. The figur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Critical Temperature
Critical or Critically may refer to: *Critical, or critical but stable, medical states **Critical, or intensive care medicine *Critical juncture, a discontinuous change studied in the social sciences. *Critical Software, a company specializing in mission and business critical information systems *Critical theory, a school of thought that critiques society and culture by applying knowledge from the social sciences and the humanities * Critically endangered, a risk status for wild species *Criticality (status), the condition of sustaining a nuclear chain reaction Art, entertainment, and media * ''Critical'' (novel), a medical thriller written by Robin Cook * ''Critical'' (TV series), a Sky 1 TV series * "Critical" (''Person of Interest''), an episode of the American television drama series ''Person of Interest'' *"Critical", a 1999 single by Zion I People *Cr1TiKaL (born 1994), an American YouTuber and Twitch streamer See also *Critic *Criticality (other) *Critical Conditi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acentric Factor
The acentric factor is a conceptual number introduced by Kenneth Pitzer in 1955, proven to be useful in the description of fluids. It has become a standard for the phase characterization of single & pure components, along with other state description parameters such as molecular weight, critical temperature, critical pressure, and critical volume (or critical compressibility). Pitzer defined from the relationship :\omega = - \log_ (p^_r) - 1, T_r = 0.7 where p^_r = \frac is the reduced saturation vapor pressure and T_r = \frac is the reduced temperature. The acentric factor is said to be a measure of the non-sphericity (centricity) of molecules. As it increases, the vapor curve is "pulled" down, resulting in higher boiling points. For many monatomic fluids, p_r^ T_r = 0.7 is close to 0.1, which leads to \omega \to 0. In many cases, T_r = 0.7 lies above the boiling temperature of liquids at atmosphere pressure. Values of can be determined for any fluid from accurate exp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reduced Pressure
In thermodynamics, the reduced properties of a fluid are a set of state variables scaled by the fluid's state properties at its critical point. These dimensionless thermodynamic coordinates, taken together with a substance's compressibility factor, provide the basis for the simplest form of the theorem of corresponding states. Reduced properties are also used to define the Peng–Robinson equation of state, a model designed to provide reasonable accuracy near the critical point. They are also used to critical exponents, which describe the behaviour of physical quantities near continuous phase transitions.Hagen Kleinert and Verena Schulte-Frohlinde, ''Critical Properties of φ4-Theories'', pp.8World Scientific (Singapore, 2001) ''(Read online a'' Reduced pressure The reduced pressure is defined as its actual pressure p divided by its critical pressure p_: :p_ = Reduced temperature The reduced temperature of a fluid is its actual temperature, divided by its critical temperatur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reduced Temperature
In thermodynamics, the reduced properties of a fluid are a set of state variables scaled by the fluid's state properties at its critical point. These dimensionless thermodynamic coordinates, taken together with a substance's compressibility factor, provide the basis for the simplest form of the theorem of corresponding states. Reduced properties are also used to define the Peng–Robinson equation of state, a model designed to provide reasonable accuracy near the critical point. They are also used to critical exponents, which describe the behaviour of physical quantities near continuous phase transitions.Hagen Kleinert and Verena Schulte-Frohlinde, ''Critical Properties of φ4-Theories'', pp.8World Scientific (Singapore, 2001) ''(Read online a'' Reduced pressure The reduced pressure is defined as its actual pressure p divided by its critical pressure p_: :p_ = Reduced temperature The reduced temperature of a fluid is its actual temperature, divided by its critical temperatur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Benzene
Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms, benzene is classed as a hydrocarbon. Benzene is a natural constituent of petroleum and is one of the elementary petrochemicals. Due to the cyclic continuous pi bonds between the carbon atoms, benzene is classed as an aromatic hydrocarbon. Benzene is a colorless and highly flammable liquid with a sweet smell, and is partially responsible for the aroma of gasoline. It is used primarily as a precursor to the manufacture of chemicals with more complex structure, such as ethylbenzene and cumene, of which billions of kilograms are produced annually. Although benzene is a major industrial chemical, it finds limited use in consumer items because of its toxicity. History Discovery The word "''benzene''" derives from "''gum benzoin''" (benzoin res ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dortmund Data Bank
The Dortmund Data Bank (short DDB) is a factual data bank for thermodynamic and thermophysical data. Its main usage is the data supply for process simulation where experimental data are the basis for the design, analysis, synthesis, and optimization of chemical processes. The DDB is used for fitting parameters for thermodynamic models like NRTL or UNIQUAC and for many different equations describing pure component properties, e.g., the Antoine equation for vapor pressures. The DDB is also used for the development and revision of predictive methods like UNIFAC and PSRK. Contents Mixture properties * Phase equilibria data ( vapor–liquid, liquid–liquid, solid–liquid), data on azeotropy and zeotropy * Mixing enthalpies * Gas solubilities * Activity coefficients at infinite dilution * Heat capacities and excess heat capacities * Volumes, densities, and excess volumes (volume effect of mixing) * Salt solubilities * Octanol-water partition coefficients * Critical data T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermodynamic Models
Thermodynamics is a branch of physics that deals with heat, Work (thermodynamics), work, and temperature, and their relation to energy, entropy, and the physical properties of matter and radiation. The behavior of these quantities is governed by the four laws of thermodynamics which convey a quantitative description using measurable macroscopic physical quantity, physical quantities, but may be explained in terms of microscopic constituents by statistical mechanics. Thermodynamics applies to a wide variety of topics in science and engineering, especially physical chemistry, biochemistry, chemical engineering and mechanical engineering, but also in other complex fields such as meteorology. Historically, thermodynamics developed out of a desire to increase the thermodynamic efficiency, efficiency of early steam engines, particularly through the work of French physicist Nicolas Léonard Sadi Carnot, Sadi Carnot (1824) who believed that engine efficiency was the key that could help ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vapour Pressure Of Water
The vapour 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 vapour pressure is the pressure at which water vapour is in thermodynamic equilibrium with its condensed state. At pressures higher than vapour pressure, water would condense, whilst at lower pressures it would evaporate or sublimate. The saturation vapour 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 vapour pressure equals the ambient pressure. Calculations of the (saturation) vapour pressure of water are commonly used in meteorology. The temperature-vapour pressure relation inversely describes the relation between the boiling point of water and the pressure. This is relevant to both pressure cooking and cooking at high altitude. An understanding of vapour pressure is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antoine Equation
The Antoine equation is a class of semi-empirical correlations describing the relation between vapor pressure and temperature for pure substances. The Antoine equation is derived from the Clausius–Clapeyron relation. The equation was presented in 1888 by the French engineer (1825–1897). Equation The Antoine equation is :\log_ p = A-\frac. where ''p'' is the vapor pressure, is temperature (in °C or in K according to the value of C) and , and are component-specific constants. The simplified form with set to zero: :\log_ p = A-\frac is the August equation, after the German physicist Ernst Ferdinand August (1795–1870). The August equation describes a linear relation between the logarithm of the pressure and the reciprocal temperature. This assumes a temperature-independent heat of vaporization. The Antoine equation allows an improved, but still inexact description of the change of the heat of vaporization with the temperature. The Antoine equation can also be transforme ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tetens Equation
The Tetens equation is an equation to calculate the saturation vapour pressure of water over liquid and ice. It is named after its creator, O. Tetens who was an early German meteorologist. He published his equation in 1930,Tetens, O. 1930. Über einige meteorologische Begriffe. Z. Geophys 6: 297-309. and while the publication itself is rather obscure, the equation is widely known among meteorologists and climatologists because of its ease of use and relative accuracy at temperatures within the normal ranges of natural weather conditions. The equation is structurally identical to the August-Roche-Magnus equation, but the coefficients differ. Formula Monteith and Unsworth (2008) provide Tetens' formula for temperatures above 0 °C:Monteith, J.L., and Unsworth, M.H. 2008. ''Principles of Environmental Physics''. Third Ed. AP, Amsterdam. http://store.elsevier.com/Principles-of-Environmental-Physics/John-Monteith/isbn-9780080924793/ ::P = 0.61078 \exp\left(\frac\right), where tem ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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