- 积分
- 91
- 注册时间
- 2012-12-11
- 积分
- 91
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chemcad 中NRTL方程简介：
Liquid phase activity coefficients are calculated by NRTL equation.
NRTL Equation The NRTL equation has the following form:
where:
The most common usage of the NRTL equation is the three-parameter equation.
The NRTL equation may be used either as a three-parameter (Bji, Bij, and αij only), as a five-parameter (Aji, Aij, Bji, Bij, and αij), seven-parameter (Aji, Aij, Bji, Bij, Cji, Cij, and αij), or nine-parameter equation (Aji, Aij, Bji, Bij, Cji, Cij, Dji, Dij, and αij).
Converting Binary Parameters (BIPs) from Literature Many data sources use the DECHEMA equation whereas CHEMCAD divides the actual BIPs by RT. To use BIPs from a source using the alternate format, divide by R (1.97842) for the proper value and divide by T to identify the proper BIP.
For example: Using data from DECHEMA, if A12 = A +B *T, then CHEMCAD BIPs are Bij= A / R and Aij = B / R.
Regressing BIPs Use the Thermophysical menu command Regress BIPs. When regressing BIPs for NRTL in the default condition, CHEMCAD calculates only Bij, Bji, and αij. Aij and Aji are set to zero. If you want to calculate all five BIPs during the regression, include initial estimates for all BIPs on the Regress NRTL Parameters screen during the regression analysis.
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