(a)
The power output of the turbine.
(a)
Answer to Problem 95RP
The power output of the turbine is
Explanation of Solution
Write the energy rate balance equation for one inlet and one outlet system.
Here, the rate of heat transfer is
The argon flows at steady state through the turbine. Hence, the rate of change in net energy of the system becomes zero.
Heat loss occurs to the surrounding at the exit. Neglect the potential energy changes. The work done is by the system (turbine) and the work done on the system is zero i.e.
The Equations (II) reduced as follows to obtain the work input.
Here, the
Write formula for enthalpy departure factor
Here, the enthalpy at ideal gas state is
Rearrange the Equation (III) to obtain
Refer Equation (IV) express as two states of enthalpy difference (initial and final).
The change in enthalpy at ideal state is expressed as follow.
Here, the specific heat is
Substitute
Refer Table A-1E, “Molar mass, gas constant, and critical-point properties”.
The critical temperature and pressure of argon gas is as follows.
The reduced pressure
The reduced pressure
At initial:
Refer Figure A-29, “Generalized enthalpy departure chart”.
The enthalpy departure factor
Refer Figure A-30, “Generalized entropy departure chart”.
The entropy departure factor
At final:
Refer Figure A-29E, “Generalized enthalpy departure chart”.
The enthalpy departure factor
Refer Figure A-30, “Generalized entropy departure chart”.
The entropy departure factor
Refer Table A-2E, “Ideal-gas specific heats of various common gases”.
The specific heat at constant pressure of argon is
The gas constant of argon is
Conclusion:
Substitute 0.04 for
Substitute
Thus, the power output of the turbine is
(b)
The exergy destruction associated with the process.
(b)
Answer to Problem 95RP
The exergy destruction associate with process is
Explanation of Solution
Write the entropy balance equation for closed system.
Here, the entropy input is
Rewrite the Equation (VII) as follows by substituting 0 for
Here, mass flow rate is
Write the formula for change in entropy
Here, the gas constant is R, the specific heat at constant pressure is
Write the formula for change in entropy
Here, the entropy departure factor is
Write the formula for exergy destruction associate with process.
Substitute
Conclusion:
Substitute
Substitute
Substitute
Thus, the exergy destruction associate with process is
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Chapter 12 Solutions
Thermodynamics: An Engineering Approach
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