There are several models available for calculating the viscosity of pure substances in the gas and liquid phases. Currently, in MATLAB, there are two separate programs that utilize these models in calculating viscosity of a pure substance: one for the vapor phase and one for the liquid phase. In this project, we have developed a MATLAB progam which combines these MATLAB programs so that the user can specify the temperature and state (vapor or liquid) of the component. The value for the corresponding viscosity is returned.

Program mucalc in MATLAB uses the Chapman-Enskog theory which was developed in the early 20th century. This theory is a kinetic theory for monatomic gases at low density. The Chapman-Enskog theory in combination with Lennard-Jones parameters leads to the following equation (given by Bird, Stewart, and Lightfoot):

where: mu=viscosity (in units of kg/m/s)

M=molecular weight

T=temperature (converted into Kelvin)

sigma=collision diameter of molecule (in Angstroms, Lennard-Jones parameter specific to each substance)

omega=collision integral for viscosity (Lennard-Jones parameter, calculated in program omegacalc)

Note: Although the Chapman-Enskog equation was developed for monatomic gases it has also been shown to work well for polyatomic gases, thus it is applicable to the gases that are used in the start301 database.

There are several models available for calculation of the viscosity of pure liquids. Program liqmucalc uses the following model (given by Reid, Prausnitz, and Poling):

ln(viscosity)= A+ B/T+ C*T+ D*T^2

where: T is in Kelvin

A, B, C, D are constants specific to each liquid that Van Velzen et al., Yaws et al., and Duhne have published to allow an estimation of viscosities for liquids in which experimental data exist