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The cold storage room is maintained at Ti = -70 C by two stage vapor-compression refrigeration unit. In the low temperature cycle, R170 (ethane) is used as the working fluid. In the high temperature cycle, R134a is used as the working fluid. After selecting reasonable pressures for all heat exchangers, calculate evaporator capacity, COP of the system, and compressor powers. Show refrigeration cycles on P-h diagrams. Draw the T-s diagrams of R134a

The cold storage room is maintained at Ti = -70 C by two stage vapor-compression refrigeration unit. In the low temperature cycle, R170 (ethane) is used as the working fluid. In the high temperature cycle, R134a is used as the working fluid. After selecting reasonable pressures for all heat exchangers, calculate evaporator capacity, COP of the system, and compressor powers. Show refrigeration cycles on P-h diagrams. Draw the T-s diagrams of R134a

Elements Of Electromagnetics
Elements Of Electromagnetics
7th Edition
ISBN:9780190698614
Author:Sadiku, Matthew N. O.
Publisher:Sadiku, Matthew N. O.
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The cold storage room is maintained at Ti = -70 C by two stage vapor-compression refrigeration unit. In the low temperature cycle, R170 (ethane) is used as the working fluid. In the high temperature cycle, R134a is used as the working fluid. After selecting reasonable pressures for all heat exchangers, calculate evaporator capacity, COP of the system, and compressor powers. Show refrigeration cycles on P-h diagrams. Draw the T-s diagrams of R134a and R170 cycles as well. Draw schematic of refrigeration system with its components.

Note: I could not upload P-h diagram for R170 due to image upload limit. You need to use that diagram so please check it on google...

Licensed for single user. © 2009 ASHRAE, Inc. 100 20 150 200 250 300 350 400 450 500 550 R-134a 600 20 1050 -- 1000 (1,1,1,2-tetrafluoroethane) 10 Reference state: 900 600 p= 500 kg/ma -800 700 - h = 200.0 kJ/kg, s= 1.00 kJ/(kg K) for saturated liquid at 0°C 8 400 10 6 300 8 200 6 c.p. 150 4 100 2 80 60 60 2 1 40 0.8 40 30 0.6 30 4 1 0.8 20 20 0.4 0.6 15 10 0.4 10 0.2 8.0 +T=-10°C 6.0 0.2 -20 4 0.1 4.0 0.08 -30 3.0 0.1 0.06 2.0 0.08 -40 0.04 1.5 0.06 50 1.0 0.04 0.02 20 0.80 0.60 0.02 0.01 100 0.40 150 200 250 300 350 400 0.01 600 Properties computed with: NIST REFPROP 450 500 550 ENTHALPY, KJ/kg version 7.0 Based on formulation of Tillner-Roth and Baehr (1994) Fig. 8 Pressure-Enthalpy Diagram for Refrigerant 134a INT | 1100 1200 1250 .091 = 1 IN T E. 001 F110 08 F0L T I 09- -50 1450 E 0,00- =1 Oc tei 4. -30 == 1400 = 20 .30 kJ/(kg K) - 00
Transcribed Image Text:Licensed for single user. © 2009 ASHRAE, Inc. 100 20 150 200 250 300 350 400 450 500 550 R-134a 600 20 1050 -- 1000 (1,1,1,2-tetrafluoroethane) 10 Reference state: 900 600 p= 500 kg/ma -800 700 - h = 200.0 kJ/kg, s= 1.00 kJ/(kg K) for saturated liquid at 0°C 8 400 10 6 300 8 200 6 c.p. 150 4 100 2 80 60 60 2 1 40 0.8 40 30 0.6 30 4 1 0.8 20 20 0.4 0.6 15 10 0.4 10 0.2 8.0 +T=-10°C 6.0 0.2 -20 4 0.1 4.0 0.08 -30 3.0 0.1 0.06 2.0 0.08 -40 0.04 1.5 0.06 50 1.0 0.04 0.02 20 0.80 0.60 0.02 0.01 100 0.40 150 200 250 300 350 400 0.01 600 Properties computed with: NIST REFPROP 450 500 550 ENTHALPY, KJ/kg version 7.0 Based on formulation of Tillner-Roth and Baehr (1994) Fig. 8 Pressure-Enthalpy Diagram for Refrigerant 134a INT | 1100 1200 1250 .091 = 1 IN T E. 001 F110 08 F0L T I 09- -50 1450 E 0,00- =1 Oc tei 4. -30 == 1400 = 20 .30 kJ/(kg K) - 00
The cold storage room is maintained at T; = -70 °C by two stage vapor-compression refrigeration unit. In the low temperature cycle, R170 (ethane) is used as the working fluid. In the high temperature cycle, R134a is used as the working fluid. After selecting reasonable pressures for all heat exchangers, calculate evaporator capacity, COP of the system, and compressor powers. Show refrigeration cycles on P-h diagrams i Draw the T-s diagrams of R134a and R170 cycles as well. Draw schematic of refrigeration system with its components. ULI Notes 1) Isentropic efficiency of compressors are 0.75. 2) Refrigerants leave the condensers as saturated liquid and exit from the evaporators as saturated vapor. 3) When determining the cooling requirement, only the wall conduction load will be taken into account. (consider 5 walls, neglect heat loss through the floor) 4) The inner and outer walls are normally covered with steel sheets, but their conduction resistance can be neglected due to high heat conductivity constant k of steel. See the Lecture Note titled “Refrigeration" regarding two stage vapor-compression refrigeration cycles. Cold Storage 5 cm thick polyurethane foam insulation material is used for all storage walls. Kurethane = 0.035 W/m.°C 2m T = -70 °C h; = 10 W/m?.°C T, = 25 °C ho = 10 W/m?.°C %3D 1 m 1 m Heat loss through the floor is neglected.
Transcribed Image Text:The cold storage room is maintained at T; = -70 °C by two stage vapor-compression refrigeration unit. In the low temperature cycle, R170 (ethane) is used as the working fluid. In the high temperature cycle, R134a is used as the working fluid. After selecting reasonable pressures for all heat exchangers, calculate evaporator capacity, COP of the system, and compressor powers. Show refrigeration cycles on P-h diagrams i Draw the T-s diagrams of R134a and R170 cycles as well. Draw schematic of refrigeration system with its components. ULI Notes 1) Isentropic efficiency of compressors are 0.75. 2) Refrigerants leave the condensers as saturated liquid and exit from the evaporators as saturated vapor. 3) When determining the cooling requirement, only the wall conduction load will be taken into account. (consider 5 walls, neglect heat loss through the floor) 4) The inner and outer walls are normally covered with steel sheets, but their conduction resistance can be neglected due to high heat conductivity constant k of steel. See the Lecture Note titled “Refrigeration" regarding two stage vapor-compression refrigeration cycles. Cold Storage 5 cm thick polyurethane foam insulation material is used for all storage walls. Kurethane = 0.035 W/m.°C 2m T = -70 °C h; = 10 W/m?.°C T, = 25 °C ho = 10 W/m?.°C %3D 1 m 1 m Heat loss through the floor is neglected.
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