Air at 2 atm and 200◦C is heated as it flows through a tube with a diameter of 1 in  (2.5 cm) at a velocity of 10 m/s. Calculate the heat transfer per unit length of tube if a  constant-heat-flux condition is maintained at the wall and the wall temperature is 20◦C  above the air temperature, all along the length of the tube. How much would the bulk  temperature increase over a 3-m length of the tube?