1. Air at 25 psia is to be heated from 60 to 100 F in a smooth, 3/4-in.-ID tube whose surface is held at a constant temperature of 120 F. What is the length of the tube required for an air velocity of...

1. Air at 25 psia is to be heated from 60 to 100F in a smooth, 3/4-in.-ID tube whose surface is held at a constant temperature of 120F. What is the length of the tube required for an air velocity of 25 fps? At 15 fps?

2. Air, at 322 K, enters a rectangular duct with a mass velocity of 29:4 kg/sm². The duct measures 0.61 m by 1.22 m and its walls are at 300 K.

Determine the rate of heat loss by the air per meter of duct length and the corresponding decrease in air temperature per meter.