![]() In liquids, viscous forces are caused by molecules exerting attractive forces on each other across layers of flow. Hence, gaseous viscosity increases with temperature. Since the momentum transfer is caused by free motion of gas molecules between collisions, increasing thermal agitation of the molecules results in a larger viscosity. This transfer of momentum can be thought of as a frictional force between layers of flow. Viscosity in gases arises from molecules traversing layers of flow and transferring momentum between layers. The formulas given are valid only for an absolute temperature scale therefore, unless stated otherwise temperatures are in kelvins. Here dynamic viscosity is denoted by μ \mu and kinematic viscosity by ν \nu. Engineering problems of this type fall under the purview of tribology. Understanding the temperature dependence of viscosity is important for many applications, for instance engineering lubricants that perform well under varying temperature conditions (such as in a car engine), since the performance of a lubricant depends in part on its viscosity. This article discusses several models of this dependence, ranging from rigorous first-principles calculations for monatomic gases, to empirical correlations for liquids. In liquids it usually decreases with increasing temperature, whereas, in most gases, viscosity increases with increasing temperature. Viscosity depends strongly on temperature. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |