7/28/2023 0 Comments Greater viscosity examples![]() ![]() These pumps operate slower and generate more shear.įriction determines the choice and size of pipes, filters, valves and instrumentation. The best type of pumps in the industry for more viscous fluids are positive displacement pumps (different types of these pumps are available depending on the application at hand). With fluids of greater viscosity, pumps need adjustment to account for their resistance to shear. Typically, centrifugal pumps are used for low viscosity fluids because of the high shear generated, which as defined makes a thinner liquid that’s easier to pump. Once you know the viscosity, (as well as some other operating parameters) you can choose the type of pump needed. An overview definition of these fluids is that they are are viscous if still, but will thin with time and agitation. Glues, soaps and starches belong to this group. These are complex, both to define and deal with in pumping. The last group falls into this category and is called thixotropic fluids. Temperature and time also have a bearing on liquid viscosity, making for a variety of complex, non-Newtonian fluids. ![]() With non-Newtonian fluids, the impact on viscosity happens in one of a few ways: if the viscosity increases with shear, it’s called dilatant, for example, quicksand if viscosity reduces with shear, it’s called pseudoplastic, like regular paints. Suspensions, slurries and gels are examples of non-Newtonian fluids. Gasoline, water, alcohol, and oils are examples of Newtonian fluids. ![]() This means when shear is applied the viscosity of the fluid changes. (Shear is defined as the amount force that is applied parallel-ly, creating friction between the particles of the fluid because of its viscosity.) Non-Newtonian fluids, therefore, are the opposite. Newtonian fluids have a viscosity that remains constant, regardless of the amount of shear applied. Understanding viscosity (and other properties of fluids) and the reactions between the fluids and the material of the equipment will help you select the right type and size of equipment to get the best performance.īroadly, fluids are classified into Newtonian and non-Newtonian fluids. Whether it’s pipes to transfer liquids, pumps to mix and move them or the different types of filters needed, the viscosity of the fluid is a factor that will determine the equipment you need. In contrast with gases, there is no systematic microscopic theory for liquid viscosity.While selecting your equipment for pumping fluids, it’s important to have a full understanding the properties of the fluids that will pass through it. Here dynamic viscosity is denoted by μ (K) 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.
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