
a)
The final equilibrium temperature in the room.
a)

Answer to Problem 205RP
The final equilibrium temperature in the room is
Explanation of Solution
Write the expression for the energy balance equation for closed system.
Here, energy transfer into the control volume is
Write the expression to calculate the ideal gas equation, to find the mass of the air.
Here, mass of the air is
Conclusion:
Substitute 0 for
Here, change in internal energy in air is
From the Table A-1, “the molar mass, gas constant and critical point properties table”, select the gas constant
Substitute
From the Table A-3, “the properties of common liquids, solids and foods table”, select the specific heat at constant pressure
Substitute 1000 kg for
Thus, the final equilibrium temperature in the room is
b)
The entropy generation during the process.
b)

Answer to Problem 205RP
The entropy generation during the process is
Explanation of Solution
Write the expression for the entropy balance equation of the system.
Here, rate of net entropy in is
Conclusion:
Substitute 0 for
Here, final volume of air is
Substitute 165.4 kg for
Thus, the entropy generation during the process is
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Chapter 7 Solutions
Thermodynamics: An Engineering Approach
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