The cold storage room is maintained at T, -70 C by two stage vapor-compression refrigeration unit. In the empcrature evcle. R170 (ethane) is used as the working fluid. In the high temperature cycle, R134a is used

Elements Of Electromagnetics
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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 uploaded with
the midterm exam question sheet. Draw the T-s diagrams of R134a and R170 cycles as well. Draw schematic
of refrigeration system with its components.
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.
KÜLT
3) When detemining 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.
Kan 0.035 w/m.C
2m
T-70°C
h-10 W/m2C
T 25°C
h10 W/mC
1m
1m
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 uploaded with the midterm exam question sheet. Draw the T-s diagrams of R134a and R170 cycles as well. Draw schematic of refrigeration system with its components. 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. KÜLT 3) When detemining 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. Kan 0.035 w/m.C 2m T-70°C h-10 W/m2C T 25°C h10 W/mC 1m 1m Heat loss through the floor is neglected.
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