# 02.03 Work Associated with Flow

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### Energy and Enthalpy Concepts

Energy and Enthalpy Misunderstandings (LearnChemE.com) (3:20) Three examples related to enthalpy and work changes that are often confusing...
Comprehension Questions:
1. During one stroke of a steam engine, the pressure inside the (~frictionless) cylinder is maintained at 3MPa from a supply line at 500 C while the pressure created by the force on the cam shaft and atmosphere combined is 2.5 MPa.  The volume swept by the cylinder during one stroke is 10 L.  Compute the work achieved by this process (kJ).
2. Was there any "lost work" in the above process? If so, compute its magnitude (kJ) and explain where those kJ are now.
3. Consider N2 in a closed cylinder with a piston initially at 1 bar and 300K. The system is heated to 400K such that the piston moves to maintain constant pressure. Is it true that Q = Cp dT for this system or should it be Cv dT or something else? Explain using a detailed analysis of the energy balance.