It is proposed to add pin fins to the outside surfaces of
tubes in a tube bank over which air flows. Water flows inside the tubes fast
enough to be in turbulent flow, so that hwater hair.
(a) Sketch the variation of fin efficiency f as a function
of fin length for a constant value of m (Fig. RQ4.13a).
(b) For fixed water and air temperatures, sketch the total
heat transfer rate as a function of the fin length (Fig. RQ4.13b).