Concept explainers
(a)
The final temperature in the cylinder at equilibrium condition.
(a)
Answer to Problem 107RP
The final temperature in the cylinder at equilibrium condition is
Explanation of Solution
Write the ideal gas equation to calculate the mass of the gas
Here, initial pressure of the gas is
Write the energy balance equation for the entire system considering it as a stationary closed system.
Here, net energy input to the system is
Conclusion:
Refer the Table A-1E of “Molar mass, gas constant, and critical-point properties”, obtain the gas constants of Nitrogen and Helium as
Refer the Table A-2E of “Ideal-gas specific heats of various common gases”, obtain the specific heats of Nitrogen, copper, and Helium as
Substitute
Substitute
Calculate the temperature of piston as the average temperature of nitrogen and helium
Substitute
Thus, the final temperature in the cylinder at equilibrium condition is
Final temperature at equilibrium condition is same even if the piston is restricted from moving.
(b)
The amount of wasted work potential for the process.
The amount of wasted work potential for the process when piston is restricted from moving.
(b)
Answer to Problem 107RP
The amount of wasted work potential for the process is
The amount of wasted work potential for the process when piston is restricted from moving is
Explanation of Solution
Write the expression to calculate the total number of moles in the cylinder
Write the expression to calculate the pressure from ideal gas expression.
Here, universal gas constant is
Write the entropy generation
Here, entropy input to the system is
Write the expression to calculate the exergy destroyed
Here, the surrounding’s temperature is
Write the formula to calculate the entropy generation when the piston is restricted to move.
Conclusion:
Refer the Table A-1E of “Molar mass, gas constant, and critical-point properties”, obtain the molar masses of Nitrogen and Helium as
Substitute
Substitute
Substitute
Substitute
Thus, the amount of wasted work potential for the process is
Substitute
Substitute
Thus, the amount of wasted work potential for the process when piston is restricted from moving is
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Chapter 8 Solutions
Thermodynamics: An Engineering Approach
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