Effect of pressure on fluid viscosity

Various methods for calculating the influence of temperature on the viscosity of pure fluids have been presented in the dossier. "Viscosity. Methods of estimation for fluids" and experimental or calculated data have been tabulated for many inorganic and organic compounds in the [K 480] file "Viscosity. Gases at atmospheric pressure".

Pressure also has a significant effect on fluid viscosity. Viscosity variation always results in an increase in viscosity with pressure, but its significance varies greatly from one region of the pressure-temperature phase diagram to another. The literature contains numerous models for predicting viscosity, ranging from theoretical developments to empirical correlations. In the , we have seen that accurate semi-theoretical models for predicting the viscosity of dilute gases have been developed on the basis of gas kinetic theory and Chapman-Enskog theory. On the other hand, the complexity of intermolecular forces involved in dense fluids makes a semitheoretical description based on statistical mechanics concepts extremely difficult.

In the second part will develop methods for calculating the viscosity of pure gases as a function of temperature, pressure or density.

In the third part will develop methods for calculating the viscosity of pure liquids as a function of temperature, pressure or density.

Finally, in a separate dossier, we report on tables showing the viscosity of inorganic and organic substances as a function of temperature and pressure.