A 10-ft-diameter insulated spherical balloon contains air at 180 psia and 70F. A special valve allows the

Question:

A 10-ft-diameter insulated spherical balloon contains air at 180 psia and 70°F. A special valve allows the air to leave at a constant rate of 0.4 lbm/s. Calculate the temperature and pressure after
a) 8 minutes
b) 15 minutes. Estimate the time needed for the temperature to reach - 20°F.