8-61 Steam enters a diffuser at 10 kPa and 50C with a velocity of 300 m/s and exits as saturated vapor at 50C and 70 m/s. The exit area of the diffuser is 3 m. Determine (a) the mass flow rate of the steam and (b) the wasted work potential during this process. Assume the surroundings to be at 25C. 8-62E Air is compressed steadily by a compressor from 14.7 psia and 60F to 100 psia and 480F at a rate of 22 lbm/min. Assuming the surroundings to be at 60F, deter- mine the minimum power input to the compressor. Assume air to be an ideal gas with variable specific heats, and neglect the changes in kinetic and potential energies. 8-63 Steam enters an adiabatic turbine at 6 MPa, 600C, and 80 m/s and leaves at 50 kPa, 100C, and 140 m/s. If the power output of the turbine is 5 MW, determine (a) the reversible power output and (b) the second-law efficiency of the turbine. Assume the surroundings to be at 25C. Answers: (a) 5.84 MW, (b) 85.6 percent 80 m/s 6 MPa 600C STEAM 5 MW 50 kPa 100C 140 m/s FIGURE P8-63 8-64 Steam is throttled from 9 MPa and 500C to a pres- sure of 7 MPa. Determine the decrease in exergy of the steam during this process. Assume the surroundings to be at 25C. Answer: 32.3 kJ/kg 8-65 Combustion gases enter a gas turbine at 900C, 800 kPa, and 100 m/s and leave at 650C, 400 kPa, and 220 m/s. Taking c, 1.15 kJ/kg C and k = 1.3 for the combustion gases, determine (a) the exergy of the combustion gases at the turbine inlet and (b) the work output of the turbine under reversible conditions. Assume the surroundings to be at 25C and 100 kPa. Can this turbine be adiabatic? 8-61 Steam enters a diffuser at 10 kPa and 50C with a velocity of 300 m/s and exits as saturated vapor at 50C and 70 m/s. The exit area of the diffuser is 3 m. Determine (a) the mass flow rate of the steam and (b) the wasted work potential during this process. Assume the surroundings to be at 25C. 8-62E Air is compressed steadily by a compressor from 14.7 psia and 60F to 100 psia and 480F at a rate of 22 lbm/min. Assuming the surroundings to be at 60F, deter- mine the minimum power input to the compressor. Assume air to be an ideal gas with variable specific heats, and neglect the changes in kinetic and potential energies. 8-63 Steam enters an adiabatic turbine at 6 MPa, 600C, and 80 m/s and leaves at 50 kPa, 100C, and 140 m/s. If the power output of the turbine is 5 MW, determine (a) the reversible power output and (b) the second-law efficiency of the turbine. Assume the surroundings to be at 25C. Answers: (a) 5.84 MW, (b) 85.6 percent 80 m/s 6 MPa 600C STEAM 5 MW 50 kPa 100C 140 m/s FIGURE P8-63 8-64 Steam is throttled from 9 MPa and 500C to a pres- sure of 7 MPa. Determine the decrease in exergy of the steam during this process. Assume the surroundings to be at 25C. Answer: 32.3 kJ/kg 8-65 Combustion gases enter a gas turbine at 900C, 800 kPa, and 100 m/s and leave at 650C, 400 kPa, and 220 m/s. Taking c, 1.15 kJ/kg C and k = 1.3 for the combustion gases, determine (a) the exergy of the combustion gases at the turbine inlet and (b) the work output of the turbine under reversible conditions. Assume the surroundings to be at 25C and 100 kPa. Can this turbine be adiabatic?