Unformatted text preview: ME 312 HOMEWORK SET # 2
Spring 2009 Due: Thursday 16 April EXAM I: 16 April Show a_ll work for full credit. #1. Air is compressed by an adiabatic compressor from 1 bar and 12 °C to a pressure of 8 bar at a steady
rate of 0.2 kg/s. The isentropic efﬁciency of the compressor is 80%. Assuming constant speciﬁc heat, determine a) the exit temperature of the air, b) the required power input to the compressor, in kW.
Show the process on a T—s diagram. #2. A gasturbine power plant operates on an airstandard cycle between pressure limits of 1 and 6 bars.
The compressor inlet air temperature is 22 °C and the temperature limitation on the turbine is 747 °C.
The compressor and turbine isentropic efﬁciencies are 84 and 87 percent, respectively.
If the mass ﬂow rate of the cycle is 4.601 kg/s,
a) Show the actual cycle on a T—s diagram. Label each state.
b) Complete the following table:
Description m“ h (We)
 Compressor inlet
2
3
c) Complete the following table and energy balance: ——————
———_— —_———_
4 _) 1 Heat Exchanger Totals: kJ/kg kJ/kg kJ/kg kJ/kg d) Find the cycle efﬁciency, backwork ratio and the power in kW produced by the cycle. 6) Find the change in availability (exergy) Aw for each process and complete an availability
accounting if T0 = 17 °C: Input: Work input at the compressor: kJ/kg
Aw for the heat addition: kJ/kg Total: kJ/kg
Output: Work output at the turbine: kJ/kg
Aw for the heat rejection: kJ/kg
Availability destruction (turbine & compressor): kJ/kg Total: kJ/kg What percent available energy is lost to the environment by heat transfer?
What percent available energy is lost due to entropy generation? ...
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 Spring '11
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