How to Calculate and Solve for Pressure Gradient | Polymer & Textile

The image above represents pressure gradient.

To compute for pressure gradient, four essential parameters are needed and these parameters are value (α), viscosity (μ), screw rotation speed (N) and proportionality constant that depends on screw geometry (B).

The formula for calculating pressure gradient:

ΔP = αμN / B

Where;

ΔP = Pressure Gradient
α = Value
μ = Viscosity
N = Screw Rotation Speed
B = Proportionality Constant that Depends on Screw Geometry

Let’s solve an example;
Find the pressure gradient when the value is 2, viscosity is 9, screw rotation speed is 20 and proportionality constant that depends on screw geometry is 24.

This implies that;

α = Value = 2
μ = Viscosity = 9
N = Screw Rotation Speed = 20
B = Proportionality Constant that Depends on Screw Geometry = 24

ΔP = αμN / B
ΔP = (2)(9)(20) / 24
ΔP = 360 / 24
ΔP = 15

Therefore, the pressure gradient is 15.

Calculating the Value when the Pressure Gradient, Viscosity, Screw Rotation Speed and Proportionality Constant that Depends on Screw Geometry is Given.

α = ΔP x B / μN

Where;

α = Value
ΔP = Pressure Gradient
μ = Viscosity
N = Screw Rotation Speed
B = Proportionality Constant that Depends on Screw Geometry

Let’s solve an example;
Find the value when the pressure gradient is 20, viscosity is 5, screw rotation speed is 11 and the proportionality constant that depends on screw geometry is 7.

This implies that;

ΔP = Pressure Gradient = 20
μ = Viscosity = 5
N = Screw Rotation Speed = 11
B = Proportionality Constant that Depends on Screw Geometry = 7

α = ΔP x B / μN
α = 20 x 7 / (5)(11)
α = 140 / 55
α = 2.54

Therefore, the value is 2.54.

Continue reading How to Calculate and Solve for Pressure Gradient | Polymer & Textile

How to Calculate and Solve for Apparent Shear Stress | Slit Die | Polymer & Textile

The image above represents the apparent shear stress | slit die.

To compute for apparent shear stress | slit die, three essential parameters are needed and these parameters are height of die (h), pressure gradient (ΔP) and flow length (L).

The formula for calculating the apparent shear stress | slit die:

τapp = h . ΔP / 2L

Where:

τapp = Apparent Shear Stress | Slit Die
h = Height of Die
ΔP = Pressure Gradient
L = Flow Length

Let’s solve an example;
Find the apparent shear stress | slit die when the height of die is 7, pressure gradient is 12 and the flow length is 16.

This implies that;

h = Height of Die = 7
ΔP = Pressure Gradient = 12
L = Flow Length = 16

τapp = h . ΔP / 2L
τapp = 7 . (12) / 2(16)
τapp = 84 / 32
τapp = 2.625

Therefore, the apparent shear stress is 2.625.

Calculating the Height of Die when the Apparent Shear Stress, Pressure Gradient and the Flow Length is Given.

h = τapp x 2L / ΔP

Where:

h = Height of Die
τapp = Apparent Shear Stress | Slit Die
ΔP = Pressure Gradient
L = Flow Length

Let’s solve an example;
Find the height of die when the apparent shear stress | slit die is 32, the pressure gradient is 10 and the flow length is 8.

This implies that;

τapp = Apparent Shear Stress | Slit Die = 32
ΔP = Pressure Gradient = 10
L = Flow Length = 8

h = τapp x 2L / ΔP
h = 32 x 2 (8) / 10
h = 32 x 16 / 10
h = 512 / 10
h = 51.2

Therefore, the height of die is 51.2.

Continue reading How to Calculate and Solve for Apparent Shear Stress | Slit Die | Polymer & Textile