
Natural Convection Heat Transfer 297
with the boundary conditions
ff T()() *( )ηη η== == ==00001′ and
,
. (12.40)
The numerical solutions of these equations for Pr = 0.1, 1, and 10 are shown in
Figure 12.5. It is seen that the thermal and momentum diffusions are deeper, and the
boundary layers are thicker, for the smaller Prandtl number uids.
The local Nusselt number at a distance x from the leading edge of the plate is
Nu
*
**
*
x
ff
y
hx
k
hL
k
x
L
T
y
x
L
y
yy
== =−
∂
∂
=−
∂
∂
∂
∂
∂
=
××
0
η TTx
L
*
.
∂
=
η
η 0
×
Note that (∂T*/∂η)
η = 0
is a function of the Prandtl number only. Therefore, if
g(Pr) = −(∂T*/∂η)
η = 0
,
(12.41)
The follo ...