Page 362 - APPLIED PROCESS DESIGN FOR CHEMICAL AND PETROCHEMICAL PLANTS, Volume 1, 3rd Edition

330 Applied Process Design for Chemical and Petrochemical Plants
10,000 I
� Curve Exponent System � I -
"'" ...
... A ...1.. .!.... Ont and Two Turbines on Sholl, Radial Flaw,Helical Coils, no Baffles ./ I'
0.14 0.33
B
... c 0.14 0.33 Same as A I/
... D 0.24 0.33 No Bafflts,Single Bladt Paddle (Same Results with Baffles) � I., I; �
0.40 0.30(appro1.)Sl1-Blode Turblne,Vertlcal Tubt1 Projecting into Tank
E
0.24 0.33
F 0.18 0.33 No Baffles I/ r;� .. Cummings a West, Rel. 5
No Baffles 1 Si1-Blad1 Turbine (Pitched)
(This Data about 16% -
1111 �,\\" i-r Higher far Cail and II %
,,,
Higher for Jackels than
./
�,....
...... ,,.\�
1- 1,000 ,.,.,,�.. \\\ "'""\�· Rtl.j.J
"\\'\
- �· ,,r:.°', .,,.\\t..,, ... , .I
)\ \.
�, ... ,
\
;;;--.....
,-\°'
:[: "" �,,y "\\'
:.. ,V
....__... I;' 11 i,.. � �;? ,,, .. \�
v
.,
J/ u- 1,1; � ..;,\\ci! � � !'..pc:;:::ounlap a Rushton,
Ref. 6
- - ..... .,,.�-...
100 .,,.r:.:;;.. -
,r:.6',,
. "" .... �'�
I/ �� t,t> � ,., ..........
�v '>id ��
....... �� o,\ I;
---- ·t2: � ,_\\r:., v ...... I.,
"'"i':,' �
� L" .,!; � L Uhl, Rel. g_g
� loll Jacketed!/
'9oo I II II 10,000 100,000 1,000,000
1,000
D2Np
Reynalds Number 1 -/"-
Figure 5-40. Liquid mixing heat transfer. Compiled by permission from References 3, 5, 6, and 22.
The helical coil relationship was developed using to 10,000 centipoise. Tube spacing of coil wraps of 2 to 4
four vertical baffles of;,{, T, located either outside tube diameters indicated no appreciable effect on the
the coil or inside the coil [29]. coefficient. The wider spacing gives a lower coefficient for
The addition of a second bank of similar coils for materials above 50 cp. For example, the ratio of coeffi-
additional heat transfer area, either outside or cients at 4d and 2d for water of 0.4 cp and oil of 50 cp
inside the first bank of coils will not provide twice were 0.96 and 0.88 respectively. The placement of baffles
the transfer of heat; but the effectiveness is estimat- directly adjacent to the wall gives only a 5 percent better
ed to be 70%-90% of the first bank of duplicate coefficient than if placed 1 inch off the wall or inside the
coils (assuming the same heat transfer area per helical coil. However, the power is about 10 percent lower
bank) [29]. The additional coils will provide addi- when the baffles are off the wall.
tional baffling; therefore, the need for the dimen-
sion of the vertical baffles is reduced, or they might 2. Vertical Tubes [29].
be removed entirely.
The value of, m, (an experimental exponent) Data of Dunlap and Rushton is given in [6]. This
[29) will run between 0.1 and 1.0 forµ ranging from tube design can prevent the need for vertical baffles in
600 to 0.3 cp. a tank, and the heat transfer is good.
The particular work of Oldshue and Gretton [13] on
heat transfer outside helical coils is of considerable gen- 65( 3
eral application. Refer to Equation 5-74. D 2 � wµ ( � 33
h 0 (tubes) d/k = 0.09( tP r
This is considered applicable to all sizes of tanks using r r
fi-blade flat blade turbines, even with baffles on wall or (
inside single helical coil, providing that tube diameters n2b r2 (;, rl4 (5- 75)
are of 0.018 � d/T � 0.036, with viscosity range probably