Ian A. Waitz
Problem T12 (Unified Thermodynamics) (LO#4, LO#5)
Air flows in steady-state through a thermally-insulated duct that increases in area from inlet to outlet. Between the inlet and the outlet there is no external work. At the inlet to the duct, the stagnation temperature is 300K, the static pressure is 95kPa, and the velocity is 150m/s. The flow exits the duct at a static pressure of 100kPa with a velocity of 10m/s. Assume that the air behaves as an ideal gas with constant specific heats cp = 1.0035kJ/kg-K, and cv = 0.7165kJ/kg-K
a) What are the static temperature and the stagnation pressure at the duct inlet?
b) What are the stagnation temperature and stagnation pressure at the exit of the duct?
c) What is the change in entropy (per kg) from inlet to exit?
d) If the flow were to be expanded in a reversible manner in a thermally-insulated duct from the same inlet conditions to the same exit static pressure, what would be the velocity, stagnation temperature and stagnation pressure at the exit? What would be the change in entropy from inlet to exit?
