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 gas-turbine power plant operates on an air-standard 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
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, back-work 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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