A piston-cylinder apparatus contains 5 kg of H₂O initially at 1 bar and 125°C. The H₂O is then
compressed to 10 bar. During the compression process, heat transfer to a thermal energy reservoir
occurs through the walls of the cylinder such that the Hâ‚‚O temperature stays constant. The
external reservoir temperature is fixed at 77°C. Assuming that the process undergone by the H₂O is
Internally reversible, determine the following
a) The entropy change of the water (kJ/K)
b) The heat transfer out of the water to the reservoir (kJ)
c) The entropy change of the reservoir (kJ/K)
Also, is the process possible, based on the second law of thermodynamics? (Support your
answer quantitatively.)
Hint: For part b, you need to calculate the heat transfer without using the energy equation
because you don't have enough information to calculate the work separately (and there is
work done on the Hâ‚‚O when you compress it). Think about what it means for the process to be
internally reversible and isothermal, as the problem statement indicates. Does that give you a
way to calculate the heat transfer out of the water?
