Page 182 - Mechanical Engineers' Handbook (Volume 4)

2 Convection Heat Transfer 171

Table 13 Constants and m for Noncircular Cylinders in Cross-Flow
Geometry Re D C m
Square
3
5 10 –10 5 0.246 0.588
3
5 10 –10 5 0.102 0.675

Hexagon
3
5 10 –1.95 10 4 0.160 0.538
1.95 10 –10 5 0.0385 0.782
4

5 10 –10 5 0.153 0.638
3
Vertical plate
4 10 –1.5 10 4 0.228 0.731
3

Flow past a Sphere
For flow over a sphere, the Nusselt number is based on the sphere diameter and can be
expressed as
0.4
Nu 2 (0.4Re 0.5 0.06Re 2 / 3 )Pr ( / ) 0.25
D
s

D
D
4
for the case of 3.5 Re 8 10 , 0.7 Pr 380, and 1.0 / 3.2. The fluid

D
s
properties are calculated at the free stream temperature except , which is evaluated at the
s
surface temperature. 8
Flow across Banks of Tubes
For banks of tubes, the tube arrangement may be either staggered or aligned (Fig. 12), and
the heat-transfer coefficient for the first row is approximately equal to that for a single tube.

Figure 12 Tube arrangement.