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Solution
The conversion factors for the units used in the calculation of the dimensionless numbers
below are
F1 = 0.001; F2 = 1000; F3=3600
The Graetz number Gz is calculated from
with G in kg/h and L in mm. Using the values given above, Gz =186.51. The Reynolds
number is obtained from
with Ve in m/s, H* in m and p in g/cm 3 .
Using the values given above, Re = 0.03791.
With H in m and Ve in m/s we get from
and the Brinkman number Br from
Finally, the product Re • Pr • Br = 7768.06.
5.3.4 Cooling of Melt in Mold
As mentioned in Section 3.2.1, the numerical solution of the Fourier equation, Equation
3.31, is presented here for crystalline and amorphous polymers.
5.3.4.1 Crystalline Polymers
The enthalpy temperature diagram of a crystalline polymer shows that there is a sharp
enthalpy rise in the temperature region where the polymer begins to melt. This is caused
by the latent heat of fusion absorbed by the polymer when it is heated and has to be
taken into account when calculating cooling curves of crystalline polymers.
By defining an equivalent temperature for the latent heat (Figure 5.41), GLOOR [22]
calculated the temperature of a slab using the Fourier equation for the non-steady-state