A New General Correlation for the Influence Parameter in Density Gradient Theory and Peng-Robinson Equation of State for N-Alkanes

A new analytical expression is proposed for the reduced influence parameter in Density Gradient Theory when combined with the Peng-Robinson equation of state for 32 n-alkanes. It contains the critical and triple point temperature values for each fluid as input and three adjustable coefficients. The new analytical expression contains the two-coefficients Zuo and Stenby and Miqueu et al.correlations as particular cases, and it is a modification of the previously published Cachadiña et al. correlation. Initially, the correlation coefficients for each fluid were obtained by fitting selected values for surface tension, and the results were comparable to other specific correlations reported in the literature. The overall mean absolute percentage deviation (OMAPD) between the selected and calculated data is just 0.79% Then, a general correlation including six adjustable coefficients valid for all the considered n-alkanes is proposed. It includes the radius of gyration as a new input parameter for each fluid. In this case, the OMAPD is 1.78\%. The use of other fluid properties as inputs is also briefly discussed.