
260 Heat Transfer: Thermal Management of Electronics
Consider a small section of an internal ow with length dx, perimeter P, and surface
area dA = Pdx as shown in Figure 11.5. Fluid with the mean temperature T
m
enters this
volume and leaves it with the mean temperature T
m
+ dT
m
. An energy balance gives the
convection heat transfer rate to the uid passing through this small control volume,
(11.20)
The total convection heat transfer rate from the inlet to the exhaust can be calcu-
lated by integrating this over the entire length of the ow. If T
i
and T
e
are the uid
mean temperatures at inlet and exhaust, and C
p,ave
is the ...