HANSER Hanser Publishers, Munich • Hanser Gardner Publications ...
HANSER Hanser Publishers, Munich • Hanser Gardner Publications ...
HANSER Hanser Publishers, Munich • Hanser Gardner Publications ...
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5.3.1 Pressure Drop in Runner<br />
As the following example shows, the pressure drop along the runner of an injection mold<br />
can be calculated from the same relationships used for dimensioning extrusion dies.<br />
Example<br />
For the following conditions, the isothermal pressure drop Ap0 and the adiabatic pressure<br />
drop Ap are to be determined:<br />
For polystyrene with the following viscosity constants according to Equation 1.36,<br />
Section 1.3.7.3:<br />
A0 = 4.4475<br />
A1 = -0.4983<br />
A2 = -0.1743<br />
A3 = 0.03594<br />
A4 = -0.002196<br />
C1 = 4.285<br />
C2 =133.2<br />
T0 = 190 0 C<br />
flow rate rh = 330.4 kg/h<br />
melt density pm = 1.12 g/cm 3<br />
specific heat cpm= 1.6 kj/(kg <strong>•</strong> K)<br />
melt temperature T =230 0 C<br />
length of the runner L =101.6 mm<br />
radius of the runner R =5.08 mm<br />
Solution<br />
a) Isothermal flow<br />
Yz from Equation 1.19:<br />
(Q = volume flow rate cm /s)<br />
aT from Equation 1.35:<br />
n from Equation 1.37:<br />
7]a from Equation 1.36: