A Rankine cycle is used to produce power. It has a mass flow rate of 50 kg/s of steam. Assume both the turbine has an efficiency of 75%, the pump has an efficiency of 80%, and that the condenser has a the pump. You are going to use EES to figure out what condition the steam should be heated to in order to have the best power cycle efficiency. Assume the maximum temperature possible is 1500°R, and the maximum pressure possible is 80 atmospheres due to materials limitations.
1. Assume the high temperature in your cycle is 1000°R. Assume the high pressure is 10 atm. Solve your EES code for this single case to find the cycle efficiency.
2. Determine the entropy production in each component. Assume a boundary temperature of 50°F on the cold side and Thigh on the hot side. Note that if each component is possible, then the entire cycle is possible.
3. Now you will use a parametric table to vary Thigh from 1000°R to 1500°R and see how the cycle efficiency changes, as well as the entropy production in each component. Comment out the setting of Thigh in your EES code. Create a parametric table (Tables->New Parametric Table). Add Thigh, Phigh, eta, and the entropy production for each component to your table. Fill in the 10 table values for Thigh from 1000°R to 1500°R and then hit the green button on the parametric table to solve.
4. Next, create a second parametric table that varies the pressure from 10 atm to 80 atm while holding the high temperature at 1500°R. (Set Thigh=1500, comment out Phigh in your code. Vary Phigh in table) Add Thigh, Phigh, eta, and the entropy production for each component to your table.
5. What temperature and pressure would we want to operate at for maximum cycle efficiency?
6. What temperature and pressure would we want to operate at for minimum entropy production? (Add the entropy production of all 4 components).
Hints:
The high temperature state should always be in the superheat for this problem, so it is safe to use temperature and pressure to look up enthalpy and entropy. The state coming out of the turbine may be in the superheat and may be in the two-phase, so you will
not want to use T and P to look up any properties.