Special Problems for ME 200 - Spring 2011 Problems Due on April 11, 2011 SP30: Air at 5 bar and 177 C is expanded through a turbine to 1 bar and 27 C. The mass flow rate of air through the turbine is 2 kg/s. Stray heat loss of 53.22 kW occurs to a surrounding at 27 C. Assume the surface temperature of the turbine at which heat loss occurs to be the average of the inlet and exit air temperatures. Consider variable specific heats for air. (a) Calculate the power (kW) developed by the turbine. (b) What is the rate of entropy generation (kW/K) within the turbine? (c) Find the total rate of entropy generation (kW/K) for turbine and its surroundings. (d) Explain the difference between the magnitudes of rate of entropy generation within the turbine and for the turbine plus its surroundings. SP31: A throttle valve is used in the steam supply line of an isentropic steam turbine to control its power output. Steam at 6 MPa and 400 C (state 1) is supplied to the inlet of the throttle valve and the turbine exit pressure is 80 kPa (state 3). Consider two settings of
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