Problem 6.2:
The power generation unit in your plant uses a hot exhaust gas from another process to produce work. The gas enters at 10 bar and 350 °C and exits at 1 bar and 40 °C. The process produces a net amount of work equal to 4,500 J/mol and it exchanges an unknown amount of heat with the surroundings.
a) Determine the amount of heat exchanged with the surroundings. Is this heat absorbed or rejected by the system?
b) Calculate the entropy change of the exhaust gas.
c) As a young and ambitious engineer you seek ways to improve the process. What is the maximum amount of work that you could extract from this system? Assume that the inlet and outlet conditions of the exhaust gas remain the same.
Additional data: Assume the surroundings to be at the constant temperature of 25 °C and the exhaust gas to be ideal with CP = 29.3 J/mol K.