In order to properly analyze the external flow, the fins must be considered in the calculations. Fig. 5 shows the actual geometry of the fins in between each row of tubes. Since the fins are actually extremely narrow sinusoidal waves, they can be assumed to be straight, rectangular fins. In addition, the fins are assumed to be half the height in order to assume that the tip is adiabatic. Fig. 6 shows a detailed diagram of a segment of the tubes with both heat transfer processes.