Refrigeration Questions and Answers – Refrigerants – Physical Properties

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This set of Refrigeration Multiple Choice Questions & Answers (MCQs) focuses on “Refrigerants – Physical Properties”.

1. What is the temperature till which Freon group refrigerants remain stable?
a) 545°C
b) 535°C
c) 555°C
d) 565°C
View Answer

Answer: b
Explanation: Freon group refrigerants remain stable until the temperature of 535°C. The temperature above this, refrigerants become unstable and by decomposing produce corrosive and poisonous products.
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2. From the following refrigerants, which is one of the most stable refrigerants?
a) Ammonia
b) R – 12
c) Carbon dioxide
d) Sulphur dioxide
View Answer

Answer: d
Explanation: Sulphur dioxide is one of the most stable refrigerants among the given refrigerants. The temperature at which it starts decomposing is 1645°C. The temperature above this, Sulphur dioxide becomes unstable and by decomposing produce corrosive and poisonous products.

3. A refrigerant should show stability and inertness.
a) True
b) False
View Answer

Answer: a
Explanation: To avoid the reaction of metal with the refrigerant, refrigerant should be stable and inert. If not, then the disintegration of refrigerant produces non-condensable gases which increase condenser pressure and vapour lock, which affects the operation.

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4. In the presence of which of the following, Sulphur dioxide becomes corrosive?
a) R – 12
b) Ammonia
c) Water
d) Carbon dioxide
View Answer

Answer: c
Explanation: Sulphur dioxide is non-corrosive with almost every metal, but if the water is present, then it forms sulphuric acid in the presence of water. So, Sulphur dioxide should be used where water is absent.

5. Which of the following is true about refrigerants?
a) Should be corrosive
b) Should not be stable
c) Should have high viscosity
d) Should have low viscosity
View Answer

Answer: d
Explanation: As the pressure drop in the liquid and suction line is smaller, hence for refrigerant to pass through these lines should possess low viscosity for easier operation. Heat transfer through condenser and evaporator is improved by low viscosity.
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6. Which of the following has the least viscosity at a liquid temperature of -15°C and atmospheric pressure?
a) R – 764
b) R – 744
c) R – 717
d) R – 11
View Answer

Answer: c
Explanation: Among the given refrigerants, R – 744, i.e. Carbon dioxide has the least viscosity at given conditions, valued at 0.115 whereas, R – 764, R – 717 and R – 11 have liquid viscosities at given conditions as 0.503, 0.250 and 0.650.

7. Which of the following has the least viscosity at a vapour temperature of -15°C and atmospheric pressure?
a) R – 764
b) R – 744
c) R – 12
d) R – 11
View Answer

Answer: d
Explanation: Among the given refrigerants, R – 11 has the least viscosity at given conditions, valued at 0.0096 whereas, R – 764, R – 744 and R – 12 have liquid viscosities at given conditions as 0.0111, 0.0132 and 0.0114.
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8. What is the criterion to find out leakage of ammonia?
a) Solubility
b) Corrosiveness
c) Colour
d) Odour
View Answer

Answer: d
Explanation: Ammonia is soluble in water and corrosive in nature, but these things have nothing to do with leakage detection. As it is a colourless gas so, the pungent odour of ammonia is the only criterion to find out the leakage in the system.

9. Which of the following has the highest thermal conductivity at a liquid temperature of 40°C?
a) R – 22
b) R – 113
c) R – 12
d) R – 11
View Answer

Answer: d
Explanation: Among the given refrigerants, R – 11 has the highest thermal conductivity at given conditions, valued at 0.1022 whereas, R – 12, R – 22 and R – 113 have thermal conductivities at given conditions as 0.0814, 0.0970 and 0.0971. Higher thermal conductivity is desired from refrigerants for better performance.
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10. Ammonia is used only with iron or steel material equipment.
a) False
b) True
View Answer

Answer: b
Explanation: Ammonia is a colourless and having pungent odour. But due to corrosive property, it reacts with almost all metals and corrode them, but the intensity of corrosion is lesser in iron or steel. Hence, used with only iron or steel.

11. Which of the following has the highest thermal conductivity at the vapour temperature of 30°C?
a) R – 22
b) R – 113
c) R – 12
d) R – 11
View Answer

Answer: a
Explanation: Among the given refrigerants, R – 22 has the highest thermal conductivity at given conditions, valued at 11.784 x 10-3 whereas, R – 11, R – 12 and R – 113 have thermal conductivities at given conditions as 8.318 x 10-3, 9.705 x 10-3 and 7.798 x 10-3. Higher thermal conductivity is desired from refrigerants for better performance.

12. Which of the following has the highest thermal conductivity at the vapour temperature of 0°C?
a) R – 40
b) R – 717
c) R – 744
d) R – 764
View Answer

Answer: b
Explanation: Among the given refrigerants, R – 717 has the highest thermal conductivity at given conditions, valued at 22.182 x 10-3 whereas, R – 40, R – 744 and R – 764 have thermal conductivities at given conditions as 8.492 x 10-3, 14.037 x 10-3 and 8.665 x 10-3. Higher thermal conductivity is desired from refrigerants for better performance.

13. Which of the following has the highest thermal conductivity at a liquid temperature of 20°C?
a) R – 40
b) R – 717
c) R – 744
d) R – 764
View Answer

Answer: b
Explanation: Among the given refrigerants, R – 717 has the highest thermal conductivity at given conditions, valued at 0.5026 whereas, R – 40, R – 744 and R – 764 have thermal conductivities at given conditions as 0.1612, 0.2080 and 0.3466. Higher thermal conductivity is desired from refrigerants for better performance.

14. Which of the following has the highest relative dielectric strength?
a) R – 22
b) R – 40
c) R – 12
d) R – 30
View Answer

Answer: c
Explanation: Among the given refrigerants, R – 12 has the highest relative dielectric strength, valued at 2.41 whereas, R – 22, R – 30 and R – 40 have thermal conductivities at given conditions as 1.31, 1.11 and 1.06. Relative dielectric strength is the ratio of dielectric strength of nitrogen and refrigerant vapour mixture to the dielectric strength of nitrogen at room temperature and atmospheric pressure.

15. ________ is widely used in large industrial plants such as cold storages and ice plants as per the cost basis.
a) R – 40
b) R – 717
c) R – 744
d) R – 764
View Answer

Answer: b
Explanation: R – 717, i.e. Ammonia, is widely used as a per cost basis because it is the cheapest refrigerant. Though cost is not so important in small refrigeration capacity systems, it becomes crucial in large industries and plants. Due to the lowest cost and desirable properties, ammonia is widely used in large plants.

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn | Youtube | Instagram | Facebook | Twitter