A circumferential fin of rectangular profile is constructed of a material having k = 55W/m C

Question:

A circumferential fin of rectangular profile is constructed of a material having k = 55W/m ∙ ºC and is installed on a tube having a diameter of 3 cm. The length of fin is 3 cm and the thickness is 2 mm. If the fin is exposed to a convection environment at 20ºC with a convection coefficient of 68 W/m2 ∙ ºC and the tube wall temperature is 100ºC, calculate the heat lost by the fin.