Problem 5 The working fluid of a liquid-vapor cycle is 1kg of R-134a. The cycle operates between two pressures 80 kPa and 3 MPa. • Process A-B: An isobaric compression at the high pressure to a saturated liquid. •Process B-C: An iso-entropic process from the high pressure to the low pressure. • Process C-D: An isobaric expansion at the low pressure to a saturated vapor. •Process D-A: An iso-entropic process from the low pressure to the high pressure. a) Using the thermodynamic tables provided on Brightspace, make a table of the temperature, pressure, volume, internal energy, enthalpy, entropy and quality factor (T, P, V, U, H, S & x) at the start of each process. b) Make a table of the change in internal energy, heat flow, work done, change in enthalpy, and change in entropy (AU, Q, W, AH, AS) during each leg of the cycle. c) Sketch well-labelled P-V & T-S diagrams (indicating processes, lines of constant pressure and/or temperature, the saturation dome, heat flow, work, etc.) d) Calculate the coefficient of performance of the cycle (QL/W). e) Draw the cycle on the p-h Diagram for R134a provided. f) Why do the values of h & s differ between the thermodynamic tables provided on Brightspace and the p-h diagram provided? (Hint: The p-h diagram states the reason) How would you align the values between the tables and the diagram? p (kPa) 4000 8-8-8 86'0 8-8 p-h Diagram for R134a Reference state: h/(kJ kg)=200 and s/(kJ K·kg) = 1.00 for saturated liquid at T = 0°C. 2000 1000 700 400 P200 7070 40 -30 TIC s/(kJ K·kg¹) v/(m³.kg¹) Quality -20 40 50 0.1 0.2 122 20 10 -10 0.3 10 1.14 1.181 22 1.30 1.34 1.38 1.421 90 80 70 60 50 40 30 20 44 0.4 0.5 0.6 0.7 0.8 0.9 100 200 300 -50 -40 -30 20 -10 h/(kJ.kg¹) 400 0 1.461 100 80 1.50 110 50 10 20 30 40 1.54 120 20 58 500 62 110 1.66 0.002 1.70 1.74 1.78° 0.005 1.82 1.86 1.90 0.01 1.94 0.02 1.98 2.02 0.05 2.06 2.10 0.1 2.14 218 02 2.22 0.5 2.26 2.30 2.34
Problem 5 The working fluid of a liquid-vapor cycle is 1kg of R-134a. The cycle operates between two pressures 80 kPa and 3 MPa. • Process A-B: An isobaric compression at the high pressure to a saturated liquid. •Process B-C: An iso-entropic process from the high pressure to the low pressure. • Process C-D: An isobaric expansion at the low pressure to a saturated vapor. •Process D-A: An iso-entropic process from the low pressure to the high pressure. a) Using the thermodynamic tables provided on Brightspace, make a table of the temperature, pressure, volume, internal energy, enthalpy, entropy and quality factor (T, P, V, U, H, S & x) at the start of each process. b) Make a table of the change in internal energy, heat flow, work done, change in enthalpy, and change in entropy (AU, Q, W, AH, AS) during each leg of the cycle. c) Sketch well-labelled P-V & T-S diagrams (indicating processes, lines of constant pressure and/or temperature, the saturation dome, heat flow, work, etc.) d) Calculate the coefficient of performance of the cycle (QL/W). e) Draw the cycle on the p-h Diagram for R134a provided. f) Why do the values of h & s differ between the thermodynamic tables provided on Brightspace and the p-h diagram provided? (Hint: The p-h diagram states the reason) How would you align the values between the tables and the diagram? p (kPa) 4000 8-8-8 86'0 8-8 p-h Diagram for R134a Reference state: h/(kJ kg)=200 and s/(kJ K·kg) = 1.00 for saturated liquid at T = 0°C. 2000 1000 700 400 P200 7070 40 -30 TIC s/(kJ K·kg¹) v/(m³.kg¹) Quality -20 40 50 0.1 0.2 122 20 10 -10 0.3 10 1.14 1.181 22 1.30 1.34 1.38 1.421 90 80 70 60 50 40 30 20 44 0.4 0.5 0.6 0.7 0.8 0.9 100 200 300 -50 -40 -30 20 -10 h/(kJ.kg¹) 400 0 1.461 100 80 1.50 110 50 10 20 30 40 1.54 120 20 58 500 62 110 1.66 0.002 1.70 1.74 1.78° 0.005 1.82 1.86 1.90 0.01 1.94 0.02 1.98 2.02 0.05 2.06 2.10 0.1 2.14 218 02 2.22 0.5 2.26 2.30 2.34
Refrigeration and Air Conditioning Technology (MindTap Course List)
8th Edition
ISBN:9781305578296
Author:John Tomczyk, Eugene Silberstein, Bill Whitman, Bill Johnson
Publisher:John Tomczyk, Eugene Silberstein, Bill Whitman, Bill Johnson
Chapter28: Special Refrigeration Applications
Section: Chapter Questions
Problem 15RQ: Why is two-stage compression popular for extra-low-temperature refrigeration systems?
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Transcribed Image Text:Problem 5
The working fluid of a liquid-vapor cycle is 1kg of R-134a. The cycle operates between two pressures 80 kPa and
3 MPa.
• Process A-B: An isobaric compression at the high pressure to a saturated liquid.
•Process B-C: An iso-entropic process from the high pressure to the low pressure.
• Process C-D: An isobaric expansion at the low pressure to a saturated vapor.
•Process D-A: An iso-entropic process from the low pressure to the high pressure.
a) Using the thermodynamic tables provided on Brightspace, make a table of the temperature, pressure,
volume, internal energy, enthalpy, entropy and quality factor (T, P, V, U, H, S & x) at the start of each process.
b) Make a table of the change in internal energy, heat flow, work done, change in enthalpy, and change in
entropy (AU, Q, W, AH, AS) during each leg of the cycle.
c) Sketch well-labelled P-V & T-S diagrams (indicating processes, lines of constant pressure and/or temperature,
the saturation dome, heat flow, work, etc.)
d) Calculate the coefficient of performance of the cycle (QL/W).
e) Draw the cycle on the p-h Diagram for R134a provided.
f) Why do the values of h & s differ between the thermodynamic tables provided on Brightspace and the p-h
diagram provided? (Hint: The p-h diagram states the reason) How would you align the values between the tables
and the diagram?
Transcribed Image Text:p (kPa)
4000
8-8-8
86'0
8-8
p-h Diagram for R134a
Reference state:
h/(kJ kg)=200 and s/(kJ K·kg) = 1.00
for saturated liquid at T = 0°C.
2000
1000
700
400
P200
7070
40
-30
TIC
s/(kJ K·kg¹)
v/(m³.kg¹)
Quality
-20
40
50
0.1
0.2
122
20
10
-10
0.3
10
1.14
1.181
22
1.30
1.34
1.38
1.421
90
80
70
60
50
40
30
20
44
0.4
0.5
0.6
0.7
0.8
0.9
100
200
300
-50
-40
-30
20
-10
h/(kJ.kg¹)
400
0
1.461
100
80
1.50
110
50
10
20
30
40
1.54
120
20
58
500
62
110
1.66
0.002
1.70
1.74
1.78°
0.005
1.82
1.86
1.90 0.01
1.94
0.02
1.98
2.02
0.05
2.06
2.10
0.1
2.14
218 02
2.22
0.5
2.26
2.30
2.34
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