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Problem 9-11
| Three high pressure turbines have been submitted for testing. Each operates with an inlet state of 1000 oF, 3500 psia steam. Turbine X has an exit state of 1000 psia at 660 oF and a heat loss of 7 Btu/lbm; turbine Y's exit state is 1000 psia at 635 oF with a heat loss of 12 Btu/lbm; and turbine Z's heat loss is 2 Btu/lbm with an exit state of 1000 psia at 680 oF. Summarize the test data, calculate the work output and isentropic efficiency of each turbine, and give a purchase recommendation. |
| Wx= 119.9 Btu/lbm | nx= 80.7% |
| Wy= 133.8 Btu/lbm | ny= 93.1% |
| Wz= 109.7 Btu/lbm | nz= 75.6% |
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Problem 9-21
| Calculate the thermal efficiency of a simple Rankine cycle for which steam leaves the boiler as saturated vapor at 3 x 106 N/m2 and is condensed to saturated liquid at 7000 N/m2. The pump and turbine have isentropic efficiencies of 0.6 and 0.8, respectively. The pump inlet is saturated liquid. |
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Problem 9-53
| Air is compressed from 1 atm to 300 psia. Determine the work required for an isentropic compressor and for a highly cooled compressor in which the air undergoes an isothermal process. What is the isothermal efficiency of the isentropic compressor (nt = Wt/W)? The inlet temperature is 60 oF. |
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Problem 9-73
| An ideal Brayton-cycle gas turbine with regeneration but no reheat or intercooling operates at full load with an inlet temperature to the compressor of 60 oF and an inlet temperature to the turbine of 1540 oF. The cycle is also to be operated at part load at a pressure ratio of 3.0 with a turbine inlet temperature of 1100 oF. Compare the thermal efficiency and net work output per lbm flow for the two operating points if the working fluid (air) is treated as a perfect gas and the maximum possible regeneration is obtained. |
| full load: | nt = 56.2%, Wnet = 109 Btu/lbm |
| part load: | nt = 54.3%, Wnet = 55 Btu/lbm |
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Problem 9-75
| Redo Problem 5: 9-73 using compressor and turbine isentropic efficiencies of 0.8 and 0.85, respectively, and a regenerator effectiveness (Qact/Qmax) of 0.85. |
| full load: | nt = 33.3%, Wnet = 58.9 Btu/lbm |
| part load: | nt = 27.7%, Wnet = 28.2 Btu/lbm |
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Problem 9-79
| An idealized air-standard diesel cycle has a compression ratio of 15. The energy input is idealized as a heat transfer of 700 Btu/lbm. The inlet conditions are 70 oF at 1 atm. Find the pressure and temperature at the end of each process in the cycle and determine the cycle efficiency. |
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