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发表于 2013-3-4 09:15:12
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在帮助文件中有各个方法的介绍。以SRK 为例
SRK
The SRK property method uses the Soave-Redlich-Kwong (SRK) cubic equation of state for all thermodynamic properties with option to improve liquid molar volume using volume correction.
This method has the following options:
Peneloux-Rauzy method for liquid molar volume correction which results in more accurate liquid molar volume
NBS Steam Table for calculating properties of water for better accuracy
Kabadi-Danner mixing rules when dealing with water-hydrocarbon systems (See SRK-KD)
Composition-independent fugacity coefficient for faster convergence in equation-based modeling
Modified lij parameters in the SRK-ML model.
When using the SRK method, please select STEAMNBS as the free-water method. The NBS steam table provides greater accuracy and SRK is designed to work with it. The enthalpy, entropy, Gibbs energy, and molar volume of water are calculated from the steam tables. The total properties are mole-fraction averages of these values with the properties calculated by the equation of state for other components. Fugacity coefficient is not affected.
Refer to the tables labeled Parameters Required for the SRK Property Method below and Parameters Required for Common Models for thermodynamic and transport property models, and required parameters for this property method.
This property method is comparable to other property methods based on cubic equations of state. It is recommended for gas-processing, refinery, and petrochemical applications. Example applications include gas plants, crude towers, and ethylene plants.
The SRK property method has built-in pure component and binary parameters for use in modeling the ethylene process. The built-in parameters are stored in the Ethylene databank. For other systems, you must supply pure component and binary parameters. You can use the Data Regression System (DRS) to determine the binary parameters from experimental phase equilibrium data (binary VLE and LLE data).
Mixture Types
Use the SRK property method for nonpolar or mildly polar mixtures. Examples are hydrocarbons and light gases, such as carbon dioxide, hydrogen sulfide, and hydrogen. For systems with polar components, such as alcohols, use the SR-POLAR, WILSON, NRTL, VANLAAR, or UNIQUAC property methods, or specify values for the lij parameters. This property method is particularly suitable in the high temperature and high pressure regions, such as in hydrocarbon processing applications or supercritical extractions.
With the Kabadi-Danner mixing rules, this property method can be used to model water-hydrocarbon immiscibility.
Range
You can expect reasonable results at all temperatures and pressures. The SRK property method is consistent in the critical region. Therefore, unlike the activity coefficient property methods, it does not exhibit anomalous behavior. Results are least accurate in the region near the mixture critical point.
(CPIG or CPIGDP) and
SRKTC, SRKPC, SRKOMG
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