Question: Air enters a heat exchanger with a velocity of 120 m/s and a temperature and pressure of 225°C and 2.5 MPa. Heat is removed from the air in the heat exchanger and the air leaves with a velocity 30 m/s at a temperature and pressure of 80°C and 2.45 MPa. Find the heat removed per kilogram of air flowing through the heat exchanger and the density of the air at the inlet and the exit to the heat exchanger.