Concept explainers
A piston–cylinder device contains 0.85 kg of refrigerant-134a at −10°C. The piston that is free to move has a mass of 12 kg and a diameter of 25 cm. The local atmospheric pressure is 88 kPa. Now, heat is transferred to refrigerant-134a until the temperature is 15°C. Determine (a) the final pressure, (b) the change in the volume of the cylinder, and (c) the change in the enthalpy of the refrigerant-134a.
FIGURE P3–30
(a)
The final pressure of the refrigerant R-134a.
Answer to Problem 29P
The final pressure of the refrigerant R-134a is
Explanation of Solution
The final pressure is equal to the initial pressure of the refrigerant R-134a.
Here, atmospheric pressure is
Conclusion:
Substitute 88 kPa for
Thus, the final pressure of the refrigerant R-134a is
(b)
The change in the volume of the cylinder.
Answer to Problem 29P
The change in the volume of the cylinder is
Explanation of Solution
Convert the unit of initial pressure from kPa to MPa.
Write the formula of interpolation method of two variables at
Here, the variables denote by x and y are pressure and specific volume.
Calculate the initial volume of cylinder.
Here, the initial state specific volume is
Calculate the final volume of cylinder.
Here, the final state specific volume is
Calculate the change in the volume of cylinder.
Conclusion:
Refer to Table A-13, obtain the values of below variables as in Table (I) at
Pressure, MPa | Specific volume, |
0.06 | 0.35048 |
0.0904 | ? |
0.10 | 0.20743 |
Substitute 0.06 for
Thus, the specific volume of refrigerant R-134a at the initial state of 90.4 kPa and
Refer to Table A-13, obtain the values of below variables as in Table (II) at
Pressure, MPa | Enthalpy, |
0.06 | 248.60 |
0.0904 | ? |
0.10 | 247.51 |
Substitute 0.06 for
Thus, the enthalpy of refrigerant R-134a at the initial state of 90.4 kPa and
Apply spreadsheet and solve the final state specific volume at
Refer to Table A-13, obtain the values of below variables as in Table (III) at
Temperature, | Specific volume, |
10 | 0.37893 |
15 | ? |
20 | 0.39302 |
Substitute 10 for
Similarly, solve final state specific volume at
Now use interpolation method again to solve the final state specific volume at
Pressure, MPa | Specific volume, |
0.06 | 0.386 |
0.0904 | ? |
0.10 | 0.2294 |
Substitute 0.06 for
Thus, the final state specific volume at
Apply the above steps to calculate the enthalpy at
Substitute 0.85 kg for m and
Substitute 0.85 kg for m and
Substitute
Thus, the change in the volume of the cylinder is
(c)
The change in the enthalpy of the refrigerant R-134a.
Answer to Problem 29P
The change in the enthalpy of the refrigerant R-134a is
Explanation of Solution
Calculate the total enthalpy change of refrigerant R-134a.
Here, enthalpy at initial state and final state are
Conclusion:
Substitute 0.85 kg for m,
Thus, the change in the enthalpy of the refrigerant R-134a is
Want to see more full solutions like this?
Chapter 3 Solutions
Package: Thermodynamics: An Engineering Approach With 2 Semester Connect Access Card
- 25 kg of refrigerant 134a, at 300 kPa, fill a rigid container whose volume is 30 L. Determine the temperature and total enthalpy in the container. Now the container is heated, until the pressure is 700 kPa. Determine the temperature and the total enthalpy of the refrigerant when heating is complete.arrow_forwardThe increase of enthalpy of a certain gas is 141.9 kJ when the pressure increases from 103.448 kPaa to 1034.48 kPaa and the volume decreases from 0.4772 m3 to 0.0745 m3 . Determine (a) the change in internal energy and (b) the final temperature of the gas if the initial temperature is 28 oC.arrow_forwardDetermine the quality of steam at 169.06 kPa when 270 kJ/kg of energy are lost from saturated steam. What is the steam temperature?arrow_forward
- 1 lbm of carbon dioxide is heated in a constantpressure apparatus. Initially, the carbon dioxide is at 1000 psia and 200°F, and it is heated until its temperature becomes 800°F. Determine the final volume of the carbon dioxide, treating it as (a) an ideal gas and (b) a Benedict-Webb-Rubin gas.arrow_forwardDetermine the temperature, quality, and internal energy of 5 kg of water in a rigid container of volume 1 m3 at a pressure of 2 bar.arrow_forwardSteam is contained in a 4-L volume at a pressure of 1.5 MPa and a temperature of 400 C. If the pressure is held constant by expanding the volume while 20 kJ of heat is added, the final temperature is nearestarrow_forward
- Neon is compressed from 100 kPa and 20°C to 500 kPa in an isothermal compressor. Determine the change in the specific volume and specific enthalpy of neon caused by this compressionarrow_forwardA rigid vessel contains 5.0 kg of wet steam at 0.4 MPa. After the addition of 9585 kJ the steam has a pressure of 2.0 MPa and a temperature of 700°C. Determine the initial internal energy and the specific volume of the steam.arrow_forwardA 5-ft3 rigid tank contains a saturated mixture of refrigerant-134a at 50 psia. If the saturated liquid occupies 20 percent of the volume, determine the quality and the total mass of the refrigerant in the tank.arrow_forward
- The temperature of R-134a in a tank at a specified state is to be determined using the ideal gas relation, the van der Waals equation, and the refrigerant tables.arrow_forwardA student living in a 4 - m 5 - m 3 - m dormitory room turns on her 100 - W fan before she leaves the room on a summer day, hoping that the room will be cooler when she comes back in the evening. Assuming all the windows are tightly closed and disregarding any heat transfer through the walls and the windows, determine the temperature in the room when she comes back 8 h later. Use specific heat values at room temperature, and assume the room to be at 100 kPa and 20 ° C in the morning when she leaves.arrow_forwardIs the energy required to heat air from 295 to 305 K the same as the energy required to heat it from 655 to 675 K? Assume the pressure remains constant in both cases. Explain??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