The outside wall surface of a 25 mm diameter metal tube (k=42 W/m*K) is maintained at 120 C. The tube is located in a room at 25 C and the convective heat transfer coefficient is 34 W/m^2*K. We'd like to increase heat transfer from the tube by adding fins that are 3 mm thick and 18 mm long, made of the same material as the tube. What will be the percentage increase in heat transfer if we add the following types of fins?
a) 12 straight fins positioned longitudinally parallel to the axis of the tube
b) Circular fins having the same total surface area as the twelve fins in the case a answer for both is about 500 words.