Argon gas expands in an adiabatic turbine steadily from and 800 kPa to 80 kPa at a rate of 2.5 kg/s. For isentropic efficiency of 88 percent, the power produced by the turbine is (a) 240 kW (b) 361 kW (c) 414 kW (d) 602 kW (e) 777 kW
Step 11 of 2
The final temperature for an isentropic process is:
The actual final temperature is obtained from the efficiency:
The power output is obtained from the energy balance:
Recommended textbook solutions
A gas-turbine power plant operates on the simple Brayton cycle between the pressure limits of 100 and 1600 kPa. The working fluid is air, which enters the compressor at at a rate of and leaves the turbine at Assuming a compressor isentropic efficiency of 85 percent and a turbine isentropic efficiency of 88 percent, determine (a) the net power output, (b) the back work ratio, and (c) the thermal efficiency. Use constant specific heats with and k=1.35.
An ideal Otto cycle has a compression ratio of 8. At the beginning of the compression process, air is at 95 kPa and and 750 kJ/kg of heat is transferred to air during the constant-volume heat-addition process. Taking into account the variation of specific heats with temperature, determine (a) the pressure and temperature at the end of the heat-addition process. (b) the net work output, (c) the thermal efficiency, and (d) the mean effective pressure for the cycle.
A gas turbine for an automobile is designed with a regenerator. Air enters the compressor of this engine at 100 kPa and . The compressor pressure ratio is 8, the maximum cycle temperature is and the cold airstream leaves the regenerator cooler than the hot airstream at the inlet of the regenerator. The cycle produces 150 kW. The compressor isentropic efficiency is 87 percent, and the turbine isentropic efficiency is 93 percent. Determine the exergy destruction for each of the processes of the cycle. The temperature of the hot reservoir is the same as the maximum cycle temperature, and the temperature of the cold reservoir is the same as the minimum cycle temperature. Use constant specific heats at room temperature.
A commercial refrigerator with refrigerant-134a as the working fluid is used to keep the refrigerated space at -35C by rejecting waste heat to cooling water that enters the condenser at 18C at a rate of 0.25 kg/s and leaves at 26C. The refrigerant enters the condenser at 1.2 MPa and 50C and leaves at the same pressure subcooled by 5C. If the compressor consumes 3.3 kW of power, determine (a) the mass flow rate of the refrigerant, (b) the refrigeration load, (c) the COP, and (d) the minimum power input to the compressor for the same refrigeration load.