عنوان مقاله [English]
نویسندگان [English]چکیده [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 lubricants are crucial for most industrial applications. In this work, available literature viscosity data of synthetic lubricants including aliphatic polyol esters on a wide pressure and temperature range used to study the pressure and temperature dependence of the viscosity. The experimental values were correlated with two linear equations, 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 degree of branching of the molecules. For the studied polyol esters, it has been observed that the and increase with the size of the molecule. The values of and are also increase with the branching of the chains of aliphatic polyol esters. In addition, our recent proposed equation is used to represent both the temperature and pressure dependence of the viscosity and demonstrated good correlation with the experimental data.