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翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Redlich–Kwong equation of state ： ウィキペディア英語版 Redlich–Kwong equation of state In physics and thermodynamics, the Redlich–Kwong equation of state is an empirical, algebraic equation that relates temperature, pressure, and volume of gases. It is generally more accurate than the van der Waals equation and the ideal gas equation at temperatures above the critical temperature. It was formulated by Otto Redlich and Joseph Neng Shun Kwong in 1949. It showed that a two-parameter, cubic equation of state could well reflect reality in many situations, standing alongside the much more complicated Beattie–Bridgeman model and Benedict–Webb–Rubin equation that were used at the time. The Redlich–Kwong equation has undergone many revisions and modifications, in order to either improve its accuracy in terms of predicting gas-phase properties of more compounds, as well as in better simulating conditions at lower temperatures, including vapor–liquid equilibria. ==Equation== The Redlich–Kwong equation is formulated as:〔 :$P\; =\; \backslash frac\; -\; \backslash frac,$ where: *''P'' is the gas pressure *''R'' is the gas constant, *''T'' is temperature, *''Vm'' is the molar volume (''V''/''n''), *''a'' is a constant that corrects for attractive potential of molecules, and *''b'' is a constant that corrects for volume. The constants are different depending on which gas is being analyzed. The constants can be calculated from the critical point data of the gas:〔 :$a\; =\; \backslash frac\backslash ,\; \backslash frac\}\; =\; 0.42748\backslash ,\; \backslash frac\},$ :$b\; =\; \backslash frac\backslash ,\; \backslash frac\; =\; 0.08664\backslash ,\; \backslash frac,$ where: *''Tc'' is the temperature at the critical point, and *''Pc'' is the pressure at the critical point. The Redlich–Kwong equation is adequate for calculation of gas phase properties when the ratio of the pressure to the critical pressure (reduced pressure) is less than about one-half of the ratio of the temperature to the critical temperature (reduced temperature): : The Redlich–Kwong equation can also be represented as an equation for the compressibility factor of a gas, as a function of temperature and pressure:〔 :$Z\; =\; \backslash frac\; =\; \backslash frac\backslash \; -\; \backslash frac\; \backslash frac$ where: *$A^2\; =\; \backslash frac^\}\; =\; \backslash frac$ *$h\; =\; \backslash frac\; =\; \backslash frac$ This equation only implicitly gives Z as a function of pressure and temperature, but is easily solved numerically, originally by graphical interpolation, or now, more easily by computer. For all Redlich–Kwong gases: :$Z\_c=$ where: *''Zc'' is the compressibility factor at the critical point From the Redlich–Kwong equation, the fugacity coefficient of a gas can be estimated:〔 :$\backslash ln\; \backslash phi\; =\; \backslash int\_0^P\; dP\}\; =\; Z\; -\; 1\; -\; \backslash ln\; -\; \backslash frac\backslash ,\; \backslash ln\; )\}$ The Redlich–Kwong equation was developed with an intent to also be applicable to mixtures of gases. In a mixture, the ''b'' term, representing the volume of the molecules, is an average of the b values of the components, weighted by the mole fractions: :$b\; =\; \backslash sum\_i$, or :$B\; =\; \backslash sum\_i$ where: *xi is the mole fraction of the ''i''th component of the mixture, *bi is the ''b'' value of the ''i''th component of the mixture, and *Bi is the ''B'' value of the ''i''th component of the mixture The constant representing the attractive forces, ''a'', is not linear with respect to mole fraction, but rather depends on the square of the mole fractions. That is: :$a\; =\; \backslash sum\_i$ where: *ai j is the attractive term between a molecule of species ''i'' and species ''j'', *xi is the mole fraction of the ''i''th component of the mixture, and *xj is the mole fraction of the ''j''th component of the mixture. It is generally assumed that the attractive cross terms are the geometric average of the individual ''a'' terms, that is: :$a\_\; =\; ()^$ In this case, the following equation for the attractive term is furnished: :$A\; =\; \backslash sum\_i$ where Ai is the ''A'' term for the ''ith component of the mixture. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Redlich–Kwong equation of state」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.