Viscosity Measurement Principle

Viscosity Measurement Principle

The liquid flows through a pipe
A parabolic velocity distribution in a tube
Hagen-Poisee's Law (Gravity-Driven Flow)
Vkin = C * t; C = pr4hg / (8Vl)
C: Capillary constant
R: the radius of the capillary
H: height of liquid column
V: the volume of liquid passing through the capillary at time t
L: the length of the capillary

Principle of capillary viscosity measurement
     Measure a given volume of sample through a capillary of a known size at a given temperature and at accurate time.
     Good external conditions:
1. Temperature fluctuation: <0.1 ° C requires constant temperature bath
2. Precise timing function
3. Excellent cleanliness of the capillary
4. Sample dust and particles

Measurement of Ubbelohde viscometer

Determine the correct capillary
Vkin = C * t
     According to a given viscosity and standard, (recommended) 100 seconds of measurement time, (minimum time of about 60 seconds), you can determine the required Ubbelohde viscometer
For example: Vkin = 35 mm2 / sec
     T = 100 seconds should be used
    Constant K = 0.3; type IIc
     The capillary viscometer can not be measured: non-Newton-liquid rheological properties (eg paste, polymer melt, concentrated latex and solution) can measure: pure, organic mixtures and inorganic liquids (eg water, Polymer, protein or other organic dilute solution, (mineral) oil; capillary viscometer has a very high accuracy (<0.1%), the conditions required for the temperature stability <0.1 degrees!

The basic formula of Kinematic viscosity

Rules
Well-known rules:
     According to ISO3105 and ASTM445 / 446 minimum flow time should be not less than 200 seconds
People do not know but the important rules:
     According to ISO3105 and ASTM445 / 446 if the "kinetic energy correction", then the minimum flow time can be less than 200 seconds.
For the "kinetic energy correction" method, the flow time is reduced to 40 ... 60 seconds is possible to meet all the criteria and save time! But the kinetic correction value can not be greater than 3% of the outflow time t (ie ⊿t / t ≯ 3%)
Uzbek and other types of capillary viscometer