Page 63 - Advances in Textile Biotechnology

42 Advances in textile biotechnology

whereas the slow part of the curve shows the relatively slow diffusion
process. A value for the squeezing factor α can be obtained by a short cut
method that approximates the two regimes by straight lines. as shown in
Fig. 2.8.
It can be argued that the E value at the cross point is also the value of
α. It is the point where convective transport is changed into diffusion trans-
port. The angle of the fast regime of the curve is proportional to the Pe
number as indicated in Fig. 2.8 because Pe represents the rate of fabric
deformation and thus the rate of convectional transport.
To clarify the concepts of the squeezing factor α and the Pe number,
Fig. 2.9 and 2.10 may be helpful. In Fig. 2.9, three curves have been drawn,

1

a

E

Pe

0
0 Time
2.8 Short-cut method to determine the value of the squeezing factor α
graphically.

1
a = a = a
1 2 3

E

Pe 3
Pe
2
Pe 1
0
0 Time
2.9 Three curves representing the transport of enzymes into a fabric
as a function of time for different values of Pe and identical values
of α.

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