How do you calculate rotational viscosity?
Rotational viscometers measure the viscosity of the sample by turning a spindle in a cup. The viscosity is determined through the measurement of the torque on a vertical shaft that rotates a spindle. Two different setups are used when measuring viscosity using a rotational viscometer: Spring-type instruments.
What does rotational viscometer measure?
Rotational Viscometer: A viscometer is an instrument used to measure the viscosity of a fluid which is also called viscosimeter. From: Drilling Engineering, 2021.
Do we measure torque in rotational viscometer?
Rotational viscometers have become a standard in virtually all industries. They measure viscosity by sensing the torque required to rotate a spindle at constant speed while immersed in fluid. The torque is proportional to the viscous drag on the spindle; thus the sample viscosity.
What is angular viscosity?
Viscosity is usually described as the property of a fluid which determines the rate at which local momentum differences are equilibrated. Rotational viscosity is a property of a fluid which determines the rate at which local angular momentum differences are equilibrated.
How is torque related to viscosity?
The torque will vary in viscosity at the time of mixing as the motor speed is constant, and so the operator can establish the relative viscosity of the mixture. The type and size of the paddle control the relationship between the absolute viscosity and the torque, where the paddle will be designed to ensure mixing.
Why do we use rotational viscometer?
Rotational viscometers are designed to measure viscosity by analyzing the torque required to rotate a spindle submerged in a fluid at a constant speed. The continuous rotation of the spindle ensures calculations are made over time, allowing time-dependent fluid analysis.
What is the percentage on viscometer?
Repeatability and precision. Brookfield viscometers have a guaranteed accuracy of + -1% relative to the full scale value of the moving / speed combination used. The repeatability of the measurement is given at + -0.2 %. The precision is therefore one graduation out of 100, including 1 % Full Scale Range FSR.
How is viscometer constant calculated?
The calibration constant for the viscometer at 100°C can now be calculated using the same equation. Viscometer No. (cP) multiply the kinematic viscosity in mm2 /s( cSt) by the density in grams per milliliter. shown below are based on a coefficient of thermal expansion typical to that for a mineral oil.
How do you calculate viscosity torque?
The viscous coefficient, k , is said to relate viscous torque to angular velocity in the following manner, τ=−kω. A new relationship can be studied by adding areas of resistance, or rigid flags, over which the viscous force is acting, to increase drag.
How do you convert shear to RPM?
When we perform rheological experiments with a viscometer, usually it gives us shear stress values corresponding to particular revolution per minute (rpm). Then we convert rpm into a shear rate by multiplying a factor 1.7. After that we have a set of values shear stress and shear rate.
What is the unit of viscometer constant?
The S.l. unit of viscosity is 1 pascal second, and is equal to 10 poises. One centistokcs is equal to one millimeter squared per second. The viscometer constant at other temperatures can be obtained by interpolation or extrapolation.
What is the relation between torque and viscosity?
Does viscosity change with RPM?
Viscosity measurements are made at two separate speeds, normally an order of magnitude apart, such as 50 rpm and 5 rpm. The viscosity value at 5 rpm is divided by the viscosity value at 50 rpm. For a pseudoplastic material, the ratio of the two viscosities is a number that is greater than 1.
What is the formula for rotational viscometer?
1 Rotational viscometer (10–10 6 Pa s) Of all measuring methods, mostly rotational viscometers (10–106 Pa s) are used. They operate according to the following physical principle: (4.15) η = 1 4 π L ( 1 r 2 − 1 R 2) T ω, where T is the moment of rotation, L is the length of the spindle, R is the cylinder radius,
What is the most popular rotational viscometer?
The most popular rotational viscometer is the Couette concentric-cylinder viscometer. Fluid is placed in the annulus between two concentric cylinders (regarded as infinite in the interpretation of data), which are in relative rotation about their common axis.
How do you measure viscosity with a spindle viscometer?
In the spindle viscometer, the viscosity is determined byrotating a spindle (for example, cylinder- or disc-shaped,as shown in Figures 2.2.10.-5 and 2.2.10.-6, respectively)immersed in the liquid. Relative values of viscosity(or apparent viscosity) can be directly calculated usingconversion factors from the scale reading at a givenrotational speed.
Which viscometer configuration should I choose for viscosity testing?
Liquid up to semi-solid samples are suitable for viscosity testing with rotational viscometers. Since there are various rotational viscometers and numerous corresponding spindles on the market, this article should give guidelines for choosing the relevant configuration.