Chapter 6, Problem 6.52CU

The entropy change of a system can be negative, but the entropy generation cannot.

When two systems are in contact, the entropy transfer from the warmer system is equal to the entropy transfer into the cooler one at the point of contact. That is, no entropy can be created or destroyed at the boundary since the boundary has no thickness and occupies no volume.

Steam enters a turbine operating at a steady state at a pressure of 4 MPa, at temperature of 400 degrees Celcius, and a velocity of 200m/s . Saturated vapor exits at 100 degrees Celcius with a velocity of 100 m/s. Heat transfer from the turbine to its surroundings takes place at the rate of 20 kJ/kg of steam at a location where the average surface temperature is 350K. (a) Write the energy and entropy balance equations for a control volume the includes only the turbine and its contents (b) Determine the work produced, in kJ/kg of steam flowing. (c) For a control volume that includes only the turbine and its contents, calculate the rate of entropy production in kJ/kg*K (d) Assume the turbine described above is located in a factory where  the ambient temperature is 27 degrees Celcius. Determine the rate of entropy production in kj/kg*Kof steam, for an inlarged control volume that included the turbine and enough of its immediate surroundings so that heat transfer takes place from the…