Chapter 7, Problem 7.72P

Consider 5.0 pounds per minute of water vapor at 100 lbf/in², 500°F, and a velocity of 100 ft/s entering a nozzle operating at steady state and expanding adiabatically to the exit, where the pressure is 40 lbf/in2. The isentropic nozzle efficiency is 85.0%. Determine the velocity of the steam at the exit, in ft/s, and the rate of entropy production, in Btu/min.°R.

Figure PZ55 and the accompanying table provide the schematic and steady-state operating data for a flash 7.55 chamber fitted with an inlet valve that produces saturated vapor and saturated liquid streams from a single entering stream of liquid water. Stray heat transfer and the effects of motion and gravity are negligible. Determine (a) the mass flow rate, in Ib/s, for each of the streams exiting the flash chamber and (b) the total rate of exergy destruction, in Btu/s. Let To = 77°F, Po =1 atm State Condition T(°F) p(lbf/in.°) h(Btu/lb) s(Btu/lb R) liquid 300 80 269.7 1 0.4372 1.6996 30 1164.3 2 sat. vapor 3 sat. liquid 218.9 0.3682 30 2 Saturated vapor P2=30 lbf/in.2 Flash chamber Valve =100 lb/s T 300°F P=80 lbf/in.2 Saturated liquid,A+ P3=30 lbf/in.2 3 FIGURE P7.55

Figure shows a simple vapor power plant operating at steady state with water as the working fluid. Data at key locations are given on the figure. The mass flow rate of the water circulating through the components is 109 kg/s. Stray heat transfer and kinetic and potential energy effects can be ignored. Determine: (a) the mass flow rate of the cooling water, in kg/s. (b) the thermal efficiency. (c) the rates of entropy production, each in kW/K, for the turbine, condenser, and pump. (d) Using the results of part (c), place the components in rank order, beginning with the component contributing most to inefficient operation of the overall system. verl

Saturated water vapor at 300°F enters a compressor operating at steady state with a mass flow rate of 5 lb/s and is compressed adiabatically to 800 lbf/in.² If the power input is 2150 hp, determine for the compressor: (a) the percent isentropic compressor efficiency and (b) the rate of entropy production, in hp/°R. Ignore kinetic and potential energy effects.

Saturated water vapor at 300°F enters a compressor operating at steady state with a mass flow rate of 5 lb/s and is compressed adiabatically to 750 lbf/in.2If the power input is 2150 hp, determine for the compressor:(a) the percent isentropic compressor efficiency and(b) the rate of entropy production, in hp/°R.Ignore kinetic and potential energy effects.

Consider 5.2 pounds per minute of water vapor at 100 lbf/in², 500°F, and a velocity of 100 ft/s entering a nozzle operating at steady state and expanding adiabatically to the exit, where the pressure is 40 lb/in². The isentropic nozzle efficiency is 85.0%. Determine the velocity of the steam at the exit, in ft/s, and the rate of entropy production, in Btu/min.°R. Step 1 Determine the velocity of the steam at the exit, in ft/s. Your answer is correct. V₂ = 1907.37033530460465 ft/s Hint Step 2 * Your answer is incorrect. Determine the rate of entropy production, in Btu/min.°R. Attempts: 2 of 3 used

Saturated water vapor at 300°F enters a compressor operating at steady state with a mass flow rate of 5 Ib/s and is compressed adiabatically to 650 lbf/in.? If the power input is 2150 hp, determine for the compressor: (a) the percent isentropic compressor efficiency and (b) the rate of entropy production, in hp/ R. Ignore kinetic and potential energy effects.

11. thermodynamics

A system consists of 2 kg of water at 100°C and 1 bar. Determine the exergy, in kJ, if the system is at rest and zero elevation relative to an exergy reference environment for which To = 20°C, po =1 bar.