Question

# 10. Air is to be heated by passing it over a bank of 2.8-m-long tubes inside...

10. Air is to be heated by passing it over a bank of 2.8-m-long tubes inside which steam is condensing at 90ºC. Air approaches the tube bank in the normal direction at 20ºC and 1 atm with a mean velocity of 5.2 m/s. The outer diameter of the tubes is 1.6 cm, and the tubes are arranged staggered with longitudinal and transverse pitches of SL = ST= 4 cm. There are 30 rows in the flow direction with 10 tubes in each row.

a. The Reynold number based on the maximum velocity.                                         [5 marks]
b. The heat transfer convection coefficient.                                                               [7 marks]
c. The air temperature when it exits the tubes bank.                                                   [7 marks]
d. The rate of heat transfer per unit length of the tubes.                                             [2 marks]
Read the properties of air at an assumed mean temperature, Tm = 40oC.   [3 marks]

Solution: