Page 302 - Modelling in Transport Phenomena A Conceptual Approach

282 CHAPTER 8. STEADY MCROSCOPIC BALANCES WITHOUT GEN.

Therefore, q approaches unity as A --t 0, indicating that the entire fin surface is at
a L
the wall temperature.
1 1 1

e A = 0.5 e

0
1 5 1

On the other hand, large values of A corresponds to cases in which the heat
transfer rate by conduction is very slow and the rate of heat transfer from the fin
surface is very rapid. Under these conditions the fin efficiency becomes
1
q=- (8.2-99)
A
Equation (8.2-99) indicates that q approaches zero as A --t 00.