Brookfield Falling Ball KF40 Uživatelský manuál stáhnout pdf (Strana 14)

Brookeld Engineering Labs., Inc. Page 14 Manual No. M11-353-A0512

III. CALCULATIONS

III.1 Dynamic Viscosity

With Newtonian liquids absolute values of the dynamic viscosity are calculated, where as,

for non-Newtonian liquids, relative values of the dynamic viscosity (apparent viscosity) are

calculated.

The dynamic viscosity is calculated according to the following equation:

Equation 1:

η = t(ρ

- ρ

)K•F

where: η dynamic viscosity [mPa•s]

t travelling time of the ball [s]

density of the ball according to the test certicate [g/cm

]

density of the sample [g/cm

]

K ball constant according to test certicate [mPa·cm

/g]

F working angle constant

Angle of inclination a

(applied to the level)

Working angle constant F

80° (DIN) 1.0

70° 0.952

60° 0.879

50° 0.778

The density and ball constant are each stated in the test certicate.

Consideration for buoyancy of the ball in the sample is accounted for by means of (ρ

-ρ

) in

equation (1).

The density of the sample can be determined by:

• referring to the material specications from the manufacturer of the uid

• measuring with a densitometer

Note: Be sure to measure the sample density at the same temperature at which the viscosity

will be measured.

The density of the sample must be determined exactly when the amount (ρ

-ρ

) becomes small.

The use of the glass ball requires the determination of the density of the sample ρ

to the 3rd

decimal position in g/cm

. For metal balls, the 2nd decimal position is sufcient. For glass

balls, the density of the measuring substance is determined to 0.001 g/cm

, for metal balls to

0.01 g/cm

1 2 ... 9 10 11 12 13 14 15 16 17 18 19

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