Page 277 - Modelling in Transport Phenomena A Conceptual Approach

8.2. ENERGY TRANSPORT WITHOUT CONVECTION 257

Right-side of the wall
The Reynolds number is

LchVoo
Re = -
U

The use of Eq. (E) in Table 4.2 gives
(Nu) = (0.037Re;/' - 871) Pr1/3
= [0.037(12.1 x 106)4/5 - 8711 (0.72)1/3 = 14,596 (6)

Therefore, the average heat transfer coefficient is

= (14,596) ( 23'28i = 34W/ m2. K (7)

a) Substitution of the numerical values into Eq. (1) gives

Now we have to calculate the surface temperatures and check whether it is appropri-
ate to evaluate physical properties at the fluid temperatures. The electrical circuit
analogy for this problem is shown below:

1 L I
A<hA> Ak A<hg>

-Q

The surface temperatures TI and T2 can be calculated as
Q
TI = TA - -
A (hA)
= 50 - 4956 - 42 oc (9)
(30) (20.8) -