Concept explainers
a)
The final equilibrium temperature.
a)
Answer to Problem 92P
The final equilibrium temperature 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 mass of the air.
Here, mass of the air is
Conclusion:
Substitute 0 for
Here, mass of the air is
From the Table A-2, “Ideal-gas specific heats of various common gases”, obtain the properties for air.
From the Table A-3, “Properties of common liquids, solids, and foods”, the specific heat of water
Substitute
Substitute
Thus, the final equilibrium temperature is
b)
The amount of heat transfer to the air.
b)
Answer to Problem 92P
The amount of heat transfer to the air is
Explanation of Solution
Write the expression to calculate the heat transfer
Conclusion:
Substitute
Thus, the amount of heat transfer to the air is
c)
The entropy generation.
c)
Answer to Problem 92P
The entropy generation is
Explanation of Solution
Write the expression for the entropy balance equation of the system.
Here, rate of net entropy in is
Write the expression to calculate the final pressure
Here, final temparature is
Conclusion:
Substitute
Substitute 0 for
Substitute
Thus, the entropy generation is
Want to see more full solutions like this?
Chapter 7 Solutions
Thermodynamics: An Engineering Approach
- Consider steady heat transfer through a 5-m × 7-m brick wall of a house of thickness 30 cm. On a day when the temperature of the outdoors is 0°C, the house is maintained at 27°C. The temperatures of the inner and outer surfaces of the brick wall are measured to be 20°C and 5°C, respectively, and the rate of heat transfer through the wall is 1035 W. Determine the rate of entropy generation in the wall and the rate of total entropy generation associated with this heat transfer process.arrow_forward9 kg of Refrigerant 134-a is initially at 26.69°C with enthalpy of 100 kJ/kg. Heat is transferred to the refrigerant under a constant-pressure process until the entropy of the refrigerant reaches 0.9795 kJ/kg.K.(i) Determine the final temperature of the refrigerant(ii) Calculate the boundary work, Wb, in kJ.Assist your answer with a proper P-v diagram indicating the properties,process, and boundary work region clearly.(iii) Explain the reason behind the high amount of boundary work obtained in (ii).Assist your explanation with relevant sketching.arrow_forwardA rigid tank contains 5 kg of saturated vapor steam at 100°C. The steam is cooled to the ambient temperature of 25°C.(a) Sketch the process with respect to the saturation lines on a T-v diagram.(b) Determine the entropy change of the steam, in kJ/K.(c) For the steam and its surroundings, determine the total entropy change associated with this process, in kJ/K.arrow_forward
- A 30-kg aluminum block initially at 140°C is brought into contact with a 40-kg block of iron at 60°C in an insulated enclosure. Determine the final equilibrium temperature and the total entropy change for this process.arrow_forwardtwo aluminum ingots, one weighing 1.5 kg at 450 degrees celsius while the other is 1.1 kg at 250 degrees celsius, are placed in an insulated enclosure. assuming there is no heat transfer from the ingots to the enclosure material, determine the final temperature and the entropy associated with the process.arrow_forwardWhat is entropy and its application?arrow_forward
- A well-insulated 4-m × 4-m × 5-m room initially at 10°C is heated by the radiator of a steam heating system. The radiator has a volume of 15 L and is filled with superheated vapor at 200 kPa and 200°C. At this moment both the inlet and the exit valves to the radiator are closed. A 120-W fan is used to distribute the air in the room. The pressure of the steam is observed to drop to 100 kPa after 30 min as a result of heat transfer to the room. Assuming constant specific heats for air at room temperature, determine the average temperature of air in 30 min.arrow_forwardA well-insulated 4-m × 4-m × 5-m room initially at 10°C is heated by the radiator of a steam heating system. The radiator has a volume of 15 L and is filled with superheated vapor at 200 kPa and 200°C. At this moment both the inlet and the exit valves to the radiator are closed. A 120-W fan is used to distribute the air in the room. The pressure of the steam is observed to drop to 100 kPa after 30 min as a result of heat transfer to the room. Assuming constant specific heats for air at room temperature, determine the entropy change of the air in the room.arrow_forwardA well-insulated 4-m × 4-m × 5-m room initially at 10°C is heated by the radiator of a steam heating system. The radiator has a volume of 15 L and is filled with superheated vapor at 200 kPa and 200°C. At this moment both the inlet and the exit valves to the radiator are closed. A 120-W fan is used to distribute the air in the room. The pressure of the steam is observed to drop to 100 kPa after 30 min as a result of heat transfer to the room. Assuming constant specific heats for air at room temperature, determine . the entropy generated during this process, in kJ/K. Assume the air pressure in the room remains constant at 100 kPa at all times.arrow_forward
- In a container with a fixed volume of 0.5 m3, initially there is refrigerant -134a at a pressure of 200 kPa and a dryness fraction of 40%. Later, heat is transferred from a source at 35°C to the refrigerant until its pressure rises to 400 kPa. Calculate the entropy changes of the system, the surroundings, and the universe during the phase change.arrow_forwardThe fluid is heated from 125 degrees Fahrenheit to 225 degrees Fahrenheit. Consider an ideal gas with the following characteristics: R = 85 ft-lbf/lbm-R Cp = 0.35 + 0.000325T BTU/lbm-R If the heating is at constant volume, compute for (a) the change in internal energy, (b) the change in enthalpy, and (c) the change in entropy. If the heating is at constant pressure, compute for (d) the change in entropy, and (e) the value of k at 160 degrees Celsius. If the fluid undergoes an isentropic process, determine (f) non-flow work and (g) steady-flow work. (For item f and g, use the value of k at 160 degrees Celsius). Note: The unit should be in metric system. Should have given, required and the solution.arrow_forwardConsider a piston–cylinder assembly that initially contains 0.5 kg of steam at 400°C and 100 bar. For the isothermal expansion of the steam in this system to a final pressure of 1 bar, determine the following: (a) What is the maximum possible work (in [kJ]) that can be obtained during this process and the entropy change of the surroundings (in [kJ/K])? (b) Repeat part (a) using the ideal gas model for steam. Compare your answers.arrow_forward
- Elements Of ElectromagneticsMechanical EngineeringISBN:9780190698614Author:Sadiku, Matthew N. O.Publisher:Oxford University PressMechanics of Materials (10th Edition)Mechanical EngineeringISBN:9780134319650Author:Russell C. HibbelerPublisher:PEARSONThermodynamics: An Engineering ApproachMechanical EngineeringISBN:9781259822674Author:Yunus A. Cengel Dr., Michael A. BolesPublisher:McGraw-Hill Education
- Control Systems EngineeringMechanical EngineeringISBN:9781118170519Author:Norman S. NisePublisher:WILEYMechanics of Materials (MindTap Course List)Mechanical EngineeringISBN:9781337093347Author:Barry J. Goodno, James M. GerePublisher:Cengage LearningEngineering Mechanics: StaticsMechanical EngineeringISBN:9781118807330Author:James L. Meriam, L. G. Kraige, J. N. BoltonPublisher:WILEY