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The Pressure Drop Calculator estimates the amount of pressure required to dispense a material through a given material dispense system.
Several assumptions are used that may alter the estimation from the actual results. The calculations assume the following about the material and its system:
- Newtonian Fluid
- Non-compressible Fluid
- No Gravity
- No Friction Containers
- Laminar Flow
Required Flow Rate (Q) is volumetric dispense rate. This can be calculated using the Gasket Material Calculator
Dynamic Viscosity (μ) is the viscosity of the Newtonian fluid. This is usually given by the material manufacturer but can also be measured using a viscometer.
Specific Gravity (ρ) is a coefficient that relates the material's density to the density of water. A Specific Gravity greater than 1 indicates that the material is more dense than water.
Container describes the vessel which holds the material. A coefficient relating the length and diameter of all the elements of the container is used to calculate the pressure drop associated with the container. Off-machine containers use a regulator after the pressure pump, so their coefficient is zero.
Hose (L, D) describes a hose used to connect parts of a dispense system. The length and diameter are directly used in the pressure drop calculations. The Elbows are used to approximate additional pressure drops through the elbows.
Tip (L) is the length of the tip of the dispense system.
Inner Diameter (D) is the inner diameter of the tip.
The pressure drop is calculated across each component, and the total pressure drop is the sum of each of the components. Each component is represented as a pipe with a Length and Diameter.
The container uses a pre-calculated Length and a Diameter of 1.
Hoses use the specified Length and Diameter. The Length is offset by the number of elbows using this equation:
(Equivalent Length) = (Length) + 30 * (Number Of Elbows) * (Diameter)
The tip uses the specified Length and Diameter. A taper tip uses an equivalent Length of 0.626.
Pressure drop across the representative pipe is calculated according to this equation:
8 ρ Q2 L
Δp = --------- * λ * ---
π2 D4 D
Where
ρ (rho) is Specific Gravity
Q is the volumetric flow rate
π (pi) is 3.14159...
D is the diameter of the pipe
λ (lambda) is the coefficient of friction
L is the length of the pipe
To estimate λ, we first find the estimated velocity, V.
V = 4Q / (π * D2)
We then find Reynold's Number, Re.
Re = V * D * ρ / μ
Finally, we use the lesser of two possible λ calculations:
λ = 64 / Re
λ = 0.3164 / (Re0.25)
The appropriate values are substituted into the pipe equation and the resulting pressure drop is displayed.
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