13. A food storage locker requires a refrigeration system of 2500 kJ/min capacity at an evaporator temperature of – 10°C and a condenser temperature of 30°C. The refrigerant used is Freon-12 and sub-cooled by 5°C before entering the expansion valve and vapour is superheated by 6°C before leaving the evaporator coil. The compression of refrigerant is reversible adiabatic. The refrigeration compressor is two-cylinder single- acting with stroke equal to 1.3 times the bore and operates at 975 r.p.m. Determine (using thermodynamic tables of properties for Freon-12): (i) Refrigerating effect per kg. (i) Mass of refrigerant to be circulated per minute. (iii) Theoretical piston displacement per minute. (iv) Theoretical power required to run the compressor, in kW. (v) Heat removed through the condenser per minute. (vi) Theoretical bore and stroke of compressor. Properties of Freon-12 Specific volume of Saturation Absolute Enthalpy Entropy temp. pressure Liquid kJ/ kg Vapour kJ/ kg Liquid kJ/kg K vароur Vapour m I kg kJ/ kg K - 10°C 2.19 0.0767 26.9 183.2 0.1080 0.7020 30°C 7.45 0.0235 64.6 199.6 0.2399 0.6854 Take : Liquid specific heat = 1.235 kJ/kg K Vapour specific heat = 0.735 kJ/kg K. [Ans. (i) 129.17 kJ/kg (ii) 19.355 kg/min (iii) 1.518 m³/min (iv) 7.2 kW (v) 2931 kJ/min (vi) 91 mm, 118 mm]
13. A food storage locker requires a refrigeration system of 2500 kJ/min capacity at an evaporator temperature of – 10°C and a condenser temperature of 30°C. The refrigerant used is Freon-12 and sub-cooled by 5°C before entering the expansion valve and vapour is superheated by 6°C before leaving the evaporator coil. The compression of refrigerant is reversible adiabatic. The refrigeration compressor is two-cylinder single- acting with stroke equal to 1.3 times the bore and operates at 975 r.p.m. Determine (using thermodynamic tables of properties for Freon-12): (i) Refrigerating effect per kg. (i) Mass of refrigerant to be circulated per minute. (iii) Theoretical piston displacement per minute. (iv) Theoretical power required to run the compressor, in kW. (v) Heat removed through the condenser per minute. (vi) Theoretical bore and stroke of compressor. Properties of Freon-12 Specific volume of Saturation Absolute Enthalpy Entropy temp. pressure Liquid kJ/ kg Vapour kJ/ kg Liquid kJ/kg K vароur Vapour m I kg kJ/ kg K - 10°C 2.19 0.0767 26.9 183.2 0.1080 0.7020 30°C 7.45 0.0235 64.6 199.6 0.2399 0.6854 Take : Liquid specific heat = 1.235 kJ/kg K Vapour specific heat = 0.735 kJ/kg K. [Ans. (i) 129.17 kJ/kg (ii) 19.355 kg/min (iii) 1.518 m³/min (iv) 7.2 kW (v) 2931 kJ/min (vi) 91 mm, 118 mm]
Elements Of Electromagnetics
7th Edition
ISBN:9780190698614
Author:Sadiku, Matthew N. O.
Publisher:Sadiku, Matthew N. O.
ChapterMA: Math Assessment
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Problem 1.1MA
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![13. A food storage locker requires a refrigeration system of 2500 kJ/min capacity at an evaporator temperature
of – 10°C and a condenser temperature of 30°C. The refrigerant used is Freon-12 and sub-cooled by 5°C
before entering the expansion valve and vapour is superheated by 6°C before leaving the evaporator coil.
The compression of refrigerant is reversible adiabatic. The refrigeration compressor is two-cylinder single-
acting with stroke equal to 1.3 times the bore and operates at 975 r.p.m. Determine (using thermodynamic
tables of properties for Freon-12):
(i) Refrigerating effect per kg.
(ii) Mass of refrigerant to be circulated per minute.
(iii) Theoretical piston displacement per minute.
(iv) Theoretical power required to run the compressor, in kW.
(v) Heat removed through the condenser per minute.
(vi) Theoretical bore and stroke of compressor.
Properties of Freon-12
Saturation
Absolute
Enthalpy
Entropy
Specific
volume of
temp.
pressure
Liquid
kJ/kg
Vapour
kJ/kg
°C
vapour
Liquid
Vapour
m2 I kg
kJlkg K
kJ/ kg K
- 10°C
2.19
0.0767
26.9
183.2
0.1080
0.7020
30°C
7.45
0.0235
64.6
199.6
0.2399
0.6854
Take : Liquid specific heat = 1.235 kJ/kg K
Vapour specific heat = 0.735 kJ/kg K.
[Ans. (i) 129.17 kJ/kg (ii) 19.355 kg/min (iii) 1.518 m³/min (iv) 7.2 kW
(v) 2931 kJ/min (vi) 91 mm, 118 mm]](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2Ffdfdab83-fc69-428b-b946-08a8ad0ea819%2Fc586dfd1-da12-49b7-a4b5-b6be8641b5a5%2Fednra45_processed.jpeg&w=3840&q=75)
Transcribed Image Text:13. A food storage locker requires a refrigeration system of 2500 kJ/min capacity at an evaporator temperature
of – 10°C and a condenser temperature of 30°C. The refrigerant used is Freon-12 and sub-cooled by 5°C
before entering the expansion valve and vapour is superheated by 6°C before leaving the evaporator coil.
The compression of refrigerant is reversible adiabatic. The refrigeration compressor is two-cylinder single-
acting with stroke equal to 1.3 times the bore and operates at 975 r.p.m. Determine (using thermodynamic
tables of properties for Freon-12):
(i) Refrigerating effect per kg.
(ii) Mass of refrigerant to be circulated per minute.
(iii) Theoretical piston displacement per minute.
(iv) Theoretical power required to run the compressor, in kW.
(v) Heat removed through the condenser per minute.
(vi) Theoretical bore and stroke of compressor.
Properties of Freon-12
Saturation
Absolute
Enthalpy
Entropy
Specific
volume of
temp.
pressure
Liquid
kJ/kg
Vapour
kJ/kg
°C
vapour
Liquid
Vapour
m2 I kg
kJlkg K
kJ/ kg K
- 10°C
2.19
0.0767
26.9
183.2
0.1080
0.7020
30°C
7.45
0.0235
64.6
199.6
0.2399
0.6854
Take : Liquid specific heat = 1.235 kJ/kg K
Vapour specific heat = 0.735 kJ/kg K.
[Ans. (i) 129.17 kJ/kg (ii) 19.355 kg/min (iii) 1.518 m³/min (iv) 7.2 kW
(v) 2931 kJ/min (vi) 91 mm, 118 mm]
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