Stiel-Thodos equation

The Jossi-Stiel-Thodos correlation is summarized in these equations ... 

The pure component databank only stores correlation coefficients for the ideal-gas or zero-density temperature dependency. In the vapor phase, properties are corrected by means of generalized equations. In the case of the thermodynamic properties, the equation of state developed by Lee Kesler (1975) is employed. For the transport properties the correlation of Stiel Thodos (1964a,b) is used for thermal conductivity and that of Jossi et al. (1962) for viscosity. Both transport property corrections employ mechanisms for differentiating between polar and nonpolar streams. 

For prediction of the vapor viscosity of pure hydrocarbons at low pressure (below Tr of 0., the method of Stiel and Thodos is the most accurate. Only the molecular weight, the critical temperature, and the critical pressure are required. Equation (2-97) with values of N from Eqs. (2-98) and (2-99) is used. 

In the equations above, the low pressure viscosity appears. This is understood to be at pressures lower than Pr < 0.6. A good correlation for this is the Stiel and Thodos [17] equation ... 

There is a method of prediction due to Stiel and Thodos that depends on the reduced density as a corrector to the low-pressure gas viscosity (/ ), and takes various forms for polar gases, according to the reduced density. This is shown in the following equations ... 

Correlating equations for the thermal conductivity. For non-polar gases, the departure of thermal conductivity, A., from the zero-pressure value, at the same temperature is given by the equations of Stiel and Thodos [17] that are valid over different gas-density ranges. These... 

The graphs for gases are also based on both experimental data and estimates. In the absence of experimental data, estimates were primarily based on correlations of Roy and Thodos Misic and Thodos and Stiel and Thodos and modified Eucken models. Experimental data and estimates were then regressed to provide the same equation for all compounds. The graphs are applicable for low pressure gas. The presented values may be adjusted to provide values at higher pressure using the methods in Reid, Prausnitz, and Poling (25). 

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