A shell and tube heat exchanger is designed to warm air from the environment by condensing steam that is passed through the tubes on the other side. The maximum air fl ow is 30 kg/min, and the air is inlet at the temperature and pressure of the environment, 285 K and 1 bar, respectively.
The steam fl ows through the system at a pressure of 10 bar and a fl ow rate of 3 kg/min.
The quality of the steam at the inlet is 0.9, and at the exit is 0.2.

(a) Calculate the lost work during this process using the “Exergy Method” by calculating the difference in exthalpy between the initial and fi nal states.

(b) Calculate the lost work during this process using the entropy change of the universe, i.e., Equation (3.41).