1. Air at 1 atm, 90F, and 8 ft/s enters a thin-walled tube of 4-in diameter. The tube surface temperature is maintained at 60F. Air exits the tube at 70F. Determine the length of the tube required to accomplish this process. Work in English units!
2. A box 15-cm by 50-cm at a constant surface temperature of 35C is exposed to ambient air from all sides except the base (50cm by 50 cm in a horizontal plane). The ambient air is 1 atm, 25C. Estimate the natural convection heat loss from the top of the surface as well as the side surface
3. Air at 1 atm, 25C and 8 m/s is to be heated by an in-line tube-bank with 3 rows in the flow direction and 4 tubes in each row. The outside diameter of the tubes is 0.012m with a length of 0.2 m. The surface temperature of the tubes is maintained at 350 C. Taking the air properties at 35C, calculate:
a. The air temperature and heat transfer
b. The air pressure drop across the tube-bank