9- A tube bank consists of 300 tubes at a distance of 6cm between the centerlines of any two adjacent tubes. Air approaches the tube bank in the normal direction at 20C and 1atm with a mean velocity of 6m/s. There are 20 rows in the flow direction with 15 tubes in each row with an average surface temperature of 140C. For an outer tube diameter of 2cm, determine the average heat transfer coefficient. Evaluate the air properties at an assumed mean temperature of 70C and 1atm. Evaluate the total heat transfer if the tube length equals 2m