عنوان مقاله [English]
Viscosity is one of the most important properties of lubricants, which affect the processes of heat and mass transfer. The temperature and pressure dependence of the viscosity of the lubricants are essential for most industrial applications. In this study, available viscosity data from the literature on broad pressure and temperature ranges for synthetic lubricants including polyalkylene glycols are used to study the pressure and temperature dependence of the viscosity. The experimental values were correlated with two linear relations, as a function of temperature and pressure. These simple and accurate linear equations provide reliable extrapolation of viscosity data for studied lubricants. Based on these correlations, the pressure and temperature viscosity coefficients ( and ) have been determined for these fluids. For studied lubricants, values decrease as the temperature or pressure increase. The coefficient decreases with the temperature and increases with the pressure. The values of and are dependent on the size and the type of functional groups of the molecules. For the studied polyalkylene glycols, it has been observed that the and increase with the size of the molecule. The highest and values in the studied polyalkylene glycols have been obtained for the lubricant with hydroxyl end group.