Consider the fluid conditions and overall heat transfer coefficient of Problem 11.32 for a concentric tube heat exchanger operating in parallel flow. The thin-walled separator tube has a diameter of 100 mm.

(a) Determine the required length for the exchanger.

(b) Assuming water flow inside the separator tube to be fully developed, estimate the convection heat transfer coefficient.

(c) Using the overall coefficient and the inlet temperatures from Problem 11.32, plot the heat transfer rate and fluid outlet temperatures as a function of the tube length for 60 < L < 400 m and the parallel-flow configuration.

(d) If the exchanger were operated in counter flow with the same overall coefficient and inlet temperatures, what would be the reduction in the required length relative to the value found in part (a)?

(e) For the counter flow configuration, plot the effectiveness and fluid outlet temperatures as a function of the tube length for 60 < L < 400 m.