تاثير دما و فشار بر گرانروي روان سازهاي پلي‌اُل استري آليفاتيك

The Effect of Temperature and Pressure on the Viscosity of Aliphatic Polyol Esters Lubricants

يكي از مهم­ترين ويژگي روان­ سازها كه نقش مهمي در فرايندهاي گرما و انتقال جرم دارد، گرانروي است. بررسي وابستگي فشاري و دمايي گرانروي روان ­سازها براي بسياري از كاربردهاي صنعتي لازم است. در اين پژوهش، براي بررسي وابستگي فشاري و دمايي گرانروي روان سازهاي تهيه شده شامل پلي ال استر­هاي آليفاتيك، داده ­هاي گرانروي قابل دسترس در گزارش هاي علمي در گستره وسيعي از فشار و دما مورد استفاده قرار گرفت. مقادير تجربي با دو معادله­ خطي به صورت تابعي از فشار و دما توصيف شده ­اند. اين معادله­ هاي خطي، ساده و دقيق امكان برونيابي قابل اعتماد داده­ هاي گران روي براي روان­ سازهاي مورد مطالعه را فراهم مي­ كنند. افزون براين ­ها، معادل ه­اي كه در سال ­هاي اخير براي نشان دادن وابستگي همزمان گرانروي به دما و فشار براي مايع­ه اي يوني پيشنهاد شده بود، براي روان­ سازها به كارگرفته و نشان داده شد كه همبستگي مناسبي با داده ­هاي تجربي دارند.

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.