slader Annular aluminum fins of rectangular profile are attached to a circular tube having an outside diameter of 50 mm and an outer surface temperature of 250°C. The fins are 4 mm thick and 30 mm long. The system is in ambient air at a temperature of 20°C, and the surface convection coefficient is 40 W/m2·K. (a) What are the fin efficiency and effectiveness? (b) If there are 125 such fins per meter of tube length, what is the rate of heat transfer per unit length if tube?