What is concentric cylinder viscometer?

The concentric cylinder (CC) viscometer is based on the basic concept of viscosity (the ratio of shear stress to the deformation or shear rate) as defined by Newton. Its principle is the measurement of the friction force on the surface of a rotating cylinder immersed in a fluid.

How do you find the viscosity of a rotational viscometer?

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 is a concentric square?

In geometry, two or more objects are said to be concentric, coaxal, or coaxial when they share the same center or axis. Circles, regular polygons and regular polyhedra, and spheres may be concentric to one another (sharing the same center point), as may cylinders (sharing the same central axis).

How does a viscometer work?

They measure the torque required to rotate a disk or bob in a fluid at a known speed. “Cup and bob” viscometers work by defining the exact volume of a sample to be sheared within a test cell; the torque required to achieve a certain rotational speed is measured and plotted.

What are the units of viscosity?

The unit of viscosity, accordingly, is newton-second per square metre, which is usually expressed as pascal-second in SI units. The viscosity of liquids decreases rapidly with an increase in temperature, and the viscosity of gases increases with an increase in temperature.

What is the principle of viscometer?

These viscometers use the principle of ‘rotational viscometry’, i.e. their measurement of product viscosity is based upon immersing a specifically selected spindle within a sample of the product followed by measurement of the torque required to rotate the spindle at a set speed whilst immersed within the product sample …

What is torque in viscosity?

Rotational viscometers use the idea that the torque required to turn an object in a fluid is a function of the viscosity of that fluid. They measure the torque required to rotate a disk or bob in a fluid at a known speed.

What is RPM in viscosity?

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 does concentric look like?

Concentric circles are circles with a common center. The region between two concentric circles of different radii is called an annulus. Any two circles can be made concentric by inversion by picking the inversion center as one of the limiting points.

How is viscosity determined in a concentric cylinder viscometer?

CONCENTRIC CYLINDER VISCOMETERS (ABSOLUTE VISCOMETERS) In the concentric cylinder viscometer (coaxial double cylinder viscometer or simply coaxial cylinder viscometer), the viscosity is determined by placing the liquid in the gap between the inner cylinder and the outer cylinder.

How to calculate the viscometer constant for a routine?

In these equations, Co = the viscometer constant when filled and tested at the same temperature T = temperature, °C B = the temperature dependence factor t, f subscripts = values at the test temperature and at the fill temperature, respectively.

What is the measurement inaccuracy of a viscometer?

Rotational viscometers are relatively easy to use but their measurement inaccuracy is at least ±10%. All types have some form of element rotating inside the liquid at a constant rate. One common version has two coaxial cylinders with the fluid to be measured contained between them.

How are rotating viscometers used to measure viscosity?

Rotating viscometers are used for measuring the viscosity of Newtonian (shear-independent viscosity) or non-Newtonian liquids (shear dependent viscosity or apparent viscosity). Rotating viscometers can be divided in 2 groups, namely absolute and relative viscometers. In absolute viscometers the flow in the measuring geometry is well defined.