Along, cylindrical electrical heating element of diameter d= 10 mm, length l= 0.25 m, thermal conductivity k = 240 w/m-k, density rho= 2700 kg/m3, and the specific heat c p=900 j/kg-k. the heater element is installed in a duct in which the air is flowing at a velocity of 10 m/s, and at an air temperature of 27oc. and 10 m/s, respectively. neglecting radiation, the steady state surface temperature of the rod is 3300c. a) what is the averaged heat convecition h ? b) determine per unit length of the heater, electrical energy is being dissipation rate. c) if the heater is activated from an initial temperature of 500c, estimate the time required for the surface temperature to come to 100c of its steady-state value.