This set of Refrigeration Multiple Choice Questions & Answers (MCQs) focuses on “Refrigerants – Thermodynamic Properties”.
1. Among the following refrigerants, which is having the lowest freezing point?
a) R – 21
b) R – 11
c) R – 12
d) R – 22
View Answer
Explanation: Freezing temperature is a crucial property to carry out refrigeration. Among the given refrigerants, R – 22 is having the lowest freezing point, valued at -160°C. R – 11, R – 12 and R – 21 having freezing points as -111°C, -157.5°C and -135°C respectively.
2. What is the boiling point of Ammonia at atmospheric pressure?
a) -10.5°C
b) -30°C
c) -33.3°C
d) -77.7°C
View Answer
Explanation: Ammonia has a boiling point at -33.3°C. This low boiling point makes Ammonia possible to get refrigeration below 0°C even at atmospheric pressure.
3. R – 717 is the refrigerant number of which of the following refrigerant?
a) Ammonia
b) Water
c) Carbon dioxide
d) Sulphur dioxide
View Answer
Explanation: R – 717 is the refrigerant number of Ammonia. Whereas, refrigerant number of Water, Carbon dioxide, and Sulphur dioxide is R – 118, R – 744 and R – 764 respectively.
4. What is the boiling point of Carbon dioxide at atmospheric pressure?
a) -20.5°C
b) -73.6°C
c) -50°C
d) -68°C
View Answer
Explanation: Carbon dioxide has a boiling point at -73.6°C at given conditions. Carbon dioxide is having the lowest boiling point among all the refrigerants which are commonly used due to high capacity o refrigeration.
5. What is the freezing point of R – 12 at atmospheric pressure?
a) -86.6°C
b) -73.6°C
c) -157.5°C
d) -160°C
View Answer
Explanation: R – 12 is having a boiling point at -157.5°C at given conditions. R – 12 is having the second-lowest freezing point after R – 22, which is valued at -160°C.
6. What is the refrigerant number of Water?
a) R – 717
b) R – 744
c) R – 118
d) R – 100
View Answer
Explanation: Water is having refrigerant number as R – 118. Whereas, R – 717, 744, 100 corresponds to Ammonia, Carbon dioxide, and ethyl chloride.
7. Among the following refrigerants, which is having the lowest boiling point?
a) Ammonia
b) R – 12
c) Carbon dioxide
d) Sulphur dioxide
View Answer
Explanation: Boiling point temperature is a crucial property to carry out refrigeration. Among the given refrigerants, Carbon dioxide is having the lowest boiling point, valued at –73.6°C. Ammonia, R -12 and Sulphur dioxide are having boiling points as -33.3°C, -29°C and -10°C respectively.
8. Among the following refrigerants, which is having the lowest C.O.P for refrigeration system working under the temperature limits of -15°C and 30°C as evaporator and condenser temperature respectively?
a) Ammonia
b) R – 12
c) R – 30
d) Carbon dioxide
View Answer
Explanation: Coefficient of performance is the ratio of refrigeration produced and work done to get that refrigeration effect. C.O.P. is a crucial entity. The more the C.O.P., more the refrigeration effect is produced, and lower temperatures can be achieved. Among the given options, Carbon dioxide is having least C.O.P. for given temperatures conditions, which is valued at 2.56. Whereas, Ammonia, R – 12 and R – 30 is having C.O.P. as 4.76, 4.70 and 4.90 respectively.
9. R – 11 is having the highest C.O.P for refrigeration system working under the temperature limits of -15°C and 30°C as evaporator and condenser temperature respectively.
a) False
b) True
View Answer
Explanation: Coefficient of performance is the ratio of refrigeration produced and work done to get that refrigeration effect. C.O.P. is a crucial entity. The more the C.O.P., more the refrigeration effect is produced, and lower temperatures can be achieved. For a Carnot cycle, C.O.P. under given conditions is 5.74 and R – 11 posses 5.09 C.O.P. very close to the ideal cycle.
10. A refrigerant should have a low latent heat of vaporization at the evaporator temperature.
a) True
b) False
View Answer
Explanation: A refrigerant should have a high latent heat of vaporization at the evaporator temperature. More the latent heat of vaporization more is the capacity of refrigerant to absorb heat in the evaporator. So, Higher the value of latent heat of vaporization, higher is the refrigeration effect produced.
Sanfoundry Global Education & Learning Series – Refrigeration & Air Conditioning.
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