Mount the BS U – Tube viscometer in the constant temperature bath keeping tube L vertical.G1 = acceleration of gravity at the calibrator laboratory G2 = acceleration of gravity at the testing laboratory If the visco meter is used at a location other than the calibrating laboratory the constant ‘C’ should be corrected for the difference in the acceleration of gravity ‘g’ at the two locations as followsĬ2 = Calibration constant in the testing laboratoryĬ1 = Calibration constant in the calibration laboratory.V =Viscosity in centistokes for the standard liquid Measure to within 0.5 seconds the time required for the leading edge of the meniscus to pass from the first timing mark to the second.Allow the charged viscometer to remain in the bath long enough to reach the main test temperature.Place the charged viscometer in the bath maintained at a temperature within 0.10 C.Charge the clean dry viscometer by pouring the known viscosity material.Any liquid of known viscosity may be used for calibration of viscometer.Stopwatch capable of being read up to 0.5 seconds.The thermometer of capacity 90˚ C and with an accuracy of 0.10 C.Provision shall be made for visibility of the viscometer and the thermometer.A suitable bath for immersion of viscometer so that the liquid reservoir or top of the capillary whichever is uppermost is at least 2 cm below the upper bath level.
Kinematic viscosity free#
The viscometer shall be made of clear borosilicate or other heat resistant glass free from visible defects.B S U - Tube Modified Reverse Flow Viscometer.Kinematic viscosity is defined as the quotient of the absolute or dynamic viscosity divided by the density of the liquid both at the same temperature.For incompressible liquids, the densities are independent of pressure and hence kinematic viscosities for incompressible liquids only depend on temperature. EnggCyclopedia's viscosity calculators for Liquids and Vapors can be used to quickly determine the viscosity at a given temperature.įor compressible fluids (gases) the densities depend on pressure of the system and hence kinematic viscosities of gases are also dependent on pressure. Variation of absolute viscosities with fluid temperatureĪbsolute liquid and vapor viscosities are strong functions of liquid temperatures. Hence kinematic viscosity of a fluid is also dependent only in the state of the fluid and not the flowrate. It should be noted that absolute viscosity (µ) and density (ρ) are both fluid properties dependent only of the state of the fluid (pressure and temperature). This ratio is known as kinematic viscosity (ν) of a fluid. Hence the ratio of viscous forces to inertial forces in the fluid is represented by (absolute viscosity / density). Viscous forces are represented by a density of the fluid and viscous forces are represented by the absolute or dynamic viscosity of the fluid. In some cases the ratio of viscous forces and inertial forces in a fluid flow is considered to be important. Unit of viscous stress are same as units of pressure. Newton's law stands for viscous force per unit area of the fluid, which is represented by viscous stress. Here, the negative sign indicates direction opposite to the fluid flow and µ is the absolute viscosity or dynamic viscosity of the fluid which acts as a proportionality constant. Velocity Gradient = dV/dy ≈ ΔV/Δy (as Δy→0)
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