Chapter 7, Problem 7.49P

Water at 10 bar, 240°C enters a turbine operating at steady state and exits at 4 bar. Stray heat transfer and kinetic and potential energy effects are negligible. A hard-to-read data sheet indicates that the quality at the turbine exit is 49%. Determine the entropy production in Joules/kg. K.

A balloon filled with helium at 20°C, 1 bar and a volume of 0.5 m³ is moving with a velocity of 15 m/s at an elevation of 0.5 km relative to an exergy reference environment for which To = 20°C, po = 1 bar. Using the ideal gas model with k = 1.67, determine the specific exergy of the helium, in kJ.

Carbon dioxide (CO2) at 1 bar, 300 K enters a compressor operating at steady state and is compressed adiabatically to an exit state of 10 bar, 550 K. The CO2 is modeled as an ideal gas, and kinetic and potential energy effects are negligible. For the compressor, determine: (a) the work input, in kJ per kg of CO2 flowing, (b) the rate of entropy production, in kJ/K per kg of CO2 flowing, and (c) the percent isentropic compressor efficiency. Part A Determine the work input, in kJ per kg of CO2 flowing. W. cy kJ/kg Save for Later Attempts: 0 of 1 used Submit Answer Part B The parts of this question must be completed in order. This part will be available when you complete the part above. Part C The parts of this question must be completed in order. This part will be available when you complete the part above.

Carbon dioxide (CO2) at 1 bar, 300 K enters a compressor operating at steady state and is compressed adiabatically to an exit state of 10 bar, 530 K. The CO2 is modeled as an ideal gas, and kinetic and potential energy effects are negligible. For the compressor, determine: (a) the work input, in kJ per kg of CO2 flowing, (b) the rate of entropy production, in kJ/K per kg of CO2 flowing, and (c) the percent isentropic compressor efficiency.

Consider 0.75 kg of N2 at 300 K, 1 bar contained in a rigid tank connected by a valve to another rigid tank holding 0.3 kg of CO2 at 300 K, 1 bar. The valve is opened and gases are allowed to mix, achieving an equilibrium state at 280 K.   determine the entropy change of each gas and of the overall system, in kJ/K.

Thermo

Nitrogen (N₂) enters a well-insulated diffuser operating at steady state at 0.656 bar, 275 K with a velocity of 282 m/s. The inlet area is 4.8 x 10-3 m². At the diffuser exit, the pressure is 0.9 bar and the velocity is 80 m/s. The nitrogen behaves as an ideal gas with k = 1.4. (a) Determine the exit temperature, in K, and the exit area, in m². (b) For a control volume enclosing the diffuser, determine the rate of entropy production, in kW/K.

An open feedwater heater is a direct-contact heat exchanger used in vapor power plants. Shown in the figure below are operating data for an open feedwater heater with H2O as the working fluid operating at steady state, where T1 = 41 °C.   Ignoring stray heat transfer from the outside of the heat exchanger to its surroundings and kinetic and potential energy effects, determine the rate of entropy production, in kW/K.

Water vapor at 10 MPa, 600°C enters a turbine operating at a steady state with a volumetric flow rate of 0.36 m3/sand exits at 0.1 bar and a quality of 92%. Stray heat transfer and kinetic and potential energy effects are negligible. Determine for the turbine (a) the mass flow rate, in kg/s, (b) the power developed by the turbine, in MW, (c) the rate at which entropy is produced, in kW/K, and (d) the isentropic turbine efficiency. Show this expansion process on a T-s diagram.