Pressure Drop over the Spinning Holes

For the calculation of shear rate it is essential to convert accurately to meters and seconds in order to obtain shear rate in reciprocal seconds (s ). The formula is given by Eq. (5), with Oy = 1.74 cm min and D = 500 pm. 

We can now calculate the pressure drop over the spinning hole with Poiseuille s 

The result is 3119335 Pa = 31 bar. The pressure drop over the much wider back- 

This is a reasonable pressure drop not too high, but also not too low, because this would lead to an uneven distribution of the flow over the holes, which would result in filament titer differences within a yam bundle. For a lower melt viscosity (for example, 100 Pa s), narrower spinning holes (350 pm) would have been necessary. 

The pressure drop over the filter package would add 30-50 bar, resulting in an initial pressure drop over the spinning assembly of 60-85 bar. The pressure drop over the filter does increase during the lifetime of the spinning assembly. The assembly would be taken out of the machine at 200-250 bar. 

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