A Rankine cycle is used to generate electricity, with a total plant capacity of 65 MW. Heat from the condenser is removed using an ordinary vapor-compression refrigeration cycle. A schematic of the process is shown below. The feedwater preheater is closed. That is, there is no mixing of streams 2 and 6 in the unit. In the condenser for the Rankine cycle, streams 4 and 9 are mixed together. Heat is transfered directly from the Rankine cycle condenser to the evaporator of the refrigeration cycle. The process has the following characteristics.
• The inlet to the first turbine is at 20 MPa and 650 C.
• Steam leaves the first turbine at 7 MPa and 479.8oC .
• The input to the boiler is at 200oC (stream 7).
• The efficiency of both turbines and the compressor is 85%.
• Steam leaves the second turbine at 0.1 MPa.
The refrigeration cycle uses propane as the working fluid.
In the refrigeration cycle the evaporator operates at 10oC and the condenser operates at 50oC.
Given this information, please answer the following questions:
1. Determine the flow rate of propane in the refrigeration cycle (kg/s).
2. Determine the total work input required to the compressor (kJ/s).
3. Determine the work output of the first turbine per kg of steam.
4. Determine the ratio m1/m2.