Lee-Kesler approach

For high-precision equations of state, there is currently no simple method available to apply them to mixtures where their advantages are maintained. For special mixtures such as natural gas, the development of a special equation has been considered to be useful [2]. For a few cases, the Lee-Kesler approach [3, 4],... 

The Pitzer-Lee-Kesler approach can be also used for polar compounds at higher pressures. The accuracy, however, decreases with increasing polarity and the presence of hydrogen bonding. 

For polar systems at high pressures the cubic equations of state modified for polar compounds (Section 14.7.3), and for still higher ones the Pitzer-Lee-Kesler approach, give the most reliable results. The accuracy is poorer, however, Aan that of the previous cases. 

For enthalpy and entropy departure values of nonpolar/weakly polar mixtures, the cubic EoS discussed here give reasonable accuracy up to moderate pressures. At higher pressures, the Pitzer-Lee-Kesler approach should be used. 

The Kesler-Lee correlations for liquid and vapour phase heat capacities of petroleum fluids are used for estimating the respective enthalpies at temperatures of interest. The Lee-Kesler corresponding-states method is used for obtaining estimates of the heats of vaporization and for developing the saturation envelope enthalpies. This method uses the Curl and Pitzer approach and calculates various thermodynamic properties by representing the compressibility factor of any fluid in terms of a simple fluid and a reference fluid as follows ... 

The Lee-Kesler method for correlating gas phase properties (reference equation and corresponding states approach) has been extended to vapor-liquid equilibria calculations. The calculation of accurate phase equilibria results is more difficult than for the properties of single phase fluids. 

The vapor pressure of pseudocomponents is also an important property when an equation-of-state approach is not used. All other approaches to process thermo-dynamics require some form of vapor-pressure correlation. The vapor pressure for pure hydrocarbons has been extensively tabulated in many component databases such as DIPPR (Design Institute for Physical Property Research, American Institute of Chemical Engineers) and significant libraries are available in modern process modeling software. Several correlations are available in the literature for the vapor pressure of pseudocomponents. It is important to recall that the vapor pressure and heat vaporization are related through the Clausius-Clapeyron [17] Equation (Equation (1-46)). This relationship imposes a constraint if we wish the model to be thermodynamically consistent In general, most of the popular correlations for vapor pressure such as the Lee-Kesler [9,10] agree well with heat of vaporization correlations and maintain thermodynamic consistency. We present the Lee-Kesler vapor pressure correlation in Equation (1.47). 

First, extensive PVT data are needed for the evaluation of the eight parameters. Such data, as we have mentioned, are available for a few compounds only. A generalized form, developed by Lee and Kesler is available, however. (This form, by the way, has been used for the development of the Lee-Kesler tables used in combination with Pitzer s corresponding states approach.)... 

The Pitzer corresponding states approach, with the Lee-Kesler Tables of Appendix D, and the cubic equations of state of Table 8.3 give reasonable accuracy for nonpolar/weakly polar compounds. 

At higher pressures and for nonpolar compounds, cubic EoS can be used except close to the critical temperature. More reliable results in this region can be obtained with Pitzer s corresponding states approach, combined with the Lee-Kesler Tables, which should be also used at high pressures. [While the Tables cannot be easily adapted for computer use, the generalized BWR EoS, from which these Tables (Appendix D) were developed, can be used for this purpose.]... 

There are a number of reliable estimating techniques for obtaining pure-component hq uid heat capacity as a function of tem )erature, including Ruzicka and Dolmalsld, Tarakad and Danner, " and Lee and Kesler. These methods are somewhat compheated. The relatively single atomic group contribution approach of Chueh and Swanson for liquid heat capacity at 29.3.15 K is presented here ... 

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