We often post articles and other news on our LinkedIn page, so please go and follow to keep up to date or for any pump queries you may have please contact us. Viscosity Comparison (centipoise 20 degrees C)Ĭentipoise (cP) = Centistokes (cSt) x S.G.Ĭentistoke (cSt) = Centipoise (cP) / S.G. There are ways to calculate (or ascertain from charts) but that is beyond the remit of this paper, so for practical purposes:Īssoma pump can handle is 150 cP (due to torque transmission through the magnets)Ĭrest can handle is 300 cp (under certain circumstances higher values may be tolerated Anything over 25cP will have a significant effect on the performance of a centrifugal pumps. Viscosity will have significant effects on flow rates and pressure capabilities of centrifugal pumps as well shaft torque and available power, the efficiency will obviously be lower. When shear is applied to non-Newtonian fluids, the viscosity of the fluid changes (e.g. Non-Newtonian fluids are the opposite of Newtonian fluids. In simple terms, a Newtonian fluid’s viscosity remains constant, no matter the amount of shear applied for a constant temperature (e.g. Kinematic viscosity is used to measure Newtonian liquids, dynamic viscosity for non-Newtonian liquids. Therefore, we say that steel has a greater density than ice. They may be the same size, but the steel cube weighs more than the ice cube. Think about an 1cm3 ice cube and a 1cm3 cube of steel. A poise (P) is a unit of dynamic (absolute) viscosity in the centimeter gram second (CGS) system of units. The formula for the conversion is:ĭensity is the ratio of the mass (or weight) of the sample divided by the volume of the sample. Density actually provides a way to convert between a kinematic and a dynamic viscosity measurement. What’s the difference between dynamic and kinematic viscosity?Ī basic difference between the dynamic and kinematic viscosity measurements is density. The unit of measure of kinematic viscosity is Centistokes (cSt). So kinematic viscosity is the measure of a fluid’s inherent resistance to flow when no external force, except gravity, is acting on it. The other way is to measure the resistive flow of a fluid under the weight of gravity. This is dynamic viscosity and the unit of measure for dynamic viscosity is Centipoise (cP) One way is to measure a fluid’s resistance to flow when an external force is applied. If we know the and values for a given polymer solution the intrinsic viscosity and molecular weight can be calculate using the above equation.When people talk about understanding viscosity, they are talking about one of two things: dynamic (also known as absolute) viscosity or kinematic viscosity. Where is the intrinsic viscosity, is Molecular weight, and are constants for a particular polymer solvent system. The molecular weight of the polymer solution is very high so the viscosity of polymer solution is very high compared to that of pure solvent.įrom the Mark-Houwink equation the relationship among the molecular weight and viscosity are given below The molecular weight of the polymer is measured by using viscometer and the molecular weight obtained by this technique is called viscosity average molecular weight. The unknown composition can be determined by plotting a graph for the time of flow and compositions. In this method the flow times are measured for different known compositions and a graph is plot for time of flow and compositions. The time of flow of liquid depends on the viscosity and composition. Various mixtures of two non-interacting liquids viscosities will lie among the viscosities of those pure components. And η 1 is the coefficient of viscosity of water.įor a given liquid η has a specific value at the same temperature. Here t 1 and t 2 are the time of flow of the liquids and ρ 1 and ρ 2 are the respective densities. Then the coefficient of viscosity of liquid (η 2) is given by equation In this method viscosity of liquid is measured by comparing the flow times of two liquids of equal volumes using same viscometer.Ĭonsider two liquids are passing through a capillary of same viscometer. The Ostwald method is a simple method for the measurement of viscosity, in which viscosity of liquid is measured by comparing the viscosity of an unknown liquid with that of liquid whose viscosity is known. Many methods are available for measuring viscosity of polymer solution. It is due to the internal friction of molecules and mainly depends on the nature & temperature of the liquid. Viscosity is an internal property of a fluid that offers resistance to flow. Determine the viscosity average molecular weight of a polymer.Absolute viscosity of juice is 2.12 ×10-3 kg m-1 s-1, and specific cake. Determine the absolute viscosity of Polymer solutions of different concentrations The given figure consists of 16 unit squares arranged as shown.
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