Page 126 - Modelling in Transport Phenomena A Conceptual Approach

106 CHAPTER 4. EVXLUATION OF TRANSFER COEFFICIENTS

Therefore, the required length is

L = (49.9)(1.5) = 75cm
Whitaker correlation
Substitution of Eq. (4.5-28) into Eq. (4) gives

~~0.17 ~~0.58
_- (PIPw) - 0.14
L
D- 0.06
- (45, 636)0*17(0.707)0.58 19.80 x - 0.14 ( 150 - 20)
- = 67
0.06 (23.86 x 10-6 150 - 90
Therefore, the required length is
L = (67)(1.5) = 101 cm
b) Note that Eq. (4) is also expressed in the form

The use of the Chilton-Colburn analogy, ie., f/2 = StH Pr2I3, reduces Eq. (5) to
_- 1 pr2’3 ( Tw - Tbi,, )
L
0-57 Tw - TbOut
-- (0.707)2/3 (150 - 20) =- 0.3068
1
-2 f 150 - 90 f (6)
The fiction factor can be calculated from the Chen correlation, Eq. (4.5-16)
1
3.7065 Re
where
1.1098

For various values of e/D, the calculated values of f, LID and L are given as
follows:

0 0.0053 57.9 86.9
0.001 0.0061 50.3 75.5
0.002 0.0067 45.8 68.7
0.003 0.0072 42.6 63.9
0.004 0.0077 39.8 59.7