Concept explainers
(a)
The final pressure of the refrigerant R-134a.
(a)
Explanation of Solution
Given:
The mass of the refrigernet
The Intial temperature of the refrigernet
The mass of the refrigernet
The diameter of the piston
The final temperature of the refrigernet is
The local atmospheric pressure
Calculation:
The final pressure is equal to the initial pressure of the refrigerant R-134a.
Thus, the final pressure of the refrigerant R-134a is
(b)
The final pressure of the refrigerant R-134a.
(b)
Explanation of Solution
Convert the unit of initial pressure from kPa to MPa.
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 |
Write the formula of interpolation method of two variables at
Here, the variables denote by x and y are pressure and specific volume.
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
Calculate the initial volume of cylinder.
Here, the initial state specific volume is
Substitute 0.85 kg for m and
Calculate the final volume of cylinder.
Here, the final state specific volume is
Substitute 0.85 kg for m and
Calculate the change in the volume of cylinder.
Substitute
Thus, the change in the volume of the cylinder is
(c)
The change in the enthalpy of the refrigerant R-134a.
(c)
Explanation of Solution
Calculate the total enthalpy change of refrigerant R-134a.
Here, enthalpy at initial state and final state are
Substitute 0.85 kg for m,
Thus, the change in the enthalpy of the refrigerant R-134a is
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