Flow Rate and a Pressure Gradient Along the Capillary

Volumetric Flow Rate and a Pressure Gradient Along the Capillary 

It should be noted that the shear rate is related to the volumetric flow rate. In a capillary rheometer, for example, the shear rate at the capillary wall is related to the 

D or r is the diameter or the radius of the die, respectively (mm), and 2 is a volumetric flow rate, that is, quantity of fluid extruded per time (mm /s). 

Let us give some examples, using two different systems, in millimeters and inches. 

Example one At the volumetric flow rate of 1 cm (1000 mm )/s and a die diameter of 1 mm (0.1 cm), the shear rate is 1.02X10 s. Note that the shear rate is measured in reciprocal seconds (1/s, or s ). 

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