Heat Transfer
CONVECTION HEAT TRANSFER
Recalling Equation 2-3:
Q
UoAoDTo
where Uo is defined in Figure 6.
An example of this concept applied to cylindrical geometry is illustrated by Figure 7, which
shows a typical combined heat transfer situation.
Figure 7 Combined Heat Transfer
Using the figure representing flow in a pipe, heat transfer by convection occurs between
temperatures T1 and T2; heat transfer by conduction occurs between temperatures T2 and T3; and
heat transfer occurs by convection between temperatures T3 and T4. Thus, there are three
processes involved. Each has an associated heat transfer coefficient, cross-sectional area for heat
transfer, and temperature difference. The basic relationships for these three processes can be
expressed using Equations 2-5 and 2-9.
Q
h1A1 (T1
T2 )
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