SpecialProblems29-31

SpecialProblems29-31 - Air enters the compressor at 98 kPa...

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Special Problems for ME 200 – Fall 2011 Special Problems 29, 30, and 31 Due Friday, November 11, 2011 SP29: Refrigerant 134a enters the compressor of refrigerator at 2.8 bar and 20 C at the rate of 0.1 kg/s. The compressor requires 4 kW power input and the refrigerant exits the compressor at 14 bar and 70 C. The surrounding temperature is 30 C and the average surface temperature of the compressor is 45 C. (a) Calculate the total entropy generation (kW/K) during the process. (b) Show the compression process on T-s diagram. Label the states, show property values, and appropriate lines of constant pressure. SP30: An adiabatic air compressor is powered by an adiabatic steam turbine which also drives an electric generator. Steam flows through the turbine at the rate of 25 kg/s; it enters at 12.5 MPa and 500 C and exits at 10 kPa with a quality of 92%.
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Unformatted text preview: Air enters the compressor at 98 kPa and 295 K at steady rate of 10 kg/s and exits at 1 MPa and 620 K. Consider variable specific heats for air. (a) Calculate the net power (MW) delivered to the generator. (b) Determine the rate of entropy generation (kW/K) within the steam turbine as well as the air compressor. SP31: Air flows steadily through a turbine at the rate of 2 kg/s and expands from 3 bar and 117 C to 1 bar and 30 C. Consider variable specific heats for air. (a) What is the maximum possible power output (kW) of the turbine? (b) Calculate the isentropic efficiency (%) of the turbine. (c) Determine the rate of entropy generation (kW/K) for the turbine. (d) Show the actual and isentropic expansion processes on T-s diagram. Label the states, show temperature values, and appropriate lines of constant pressure....
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