In this article you will learn about Aircraft Refrigeration System and its classification.
Definition(Aircraft Refrigeration System)-
It is like refrigeration system we use which is to maintain cooling system and maintain good humidity which is ideal for human that is about 40% to 60%.
There are two types of system is used in aircraft but most of the time Air Refrigeration Cycle is used although it is having different types, which I will share below.
Another type of refrigeration system is used that is Vapour compression refrigeration system.
What is the Meaning of Ground Cooling?
I know may be you have gone through this term couple of times from now that is ground cooling.
Ground cooling means when aircraft is not moving. In this condition simple aircraft refrigeration system works really well.
Classification of Aircraft Refrigeration System-
There are many types of aircraft refrigeration system like Simple aircraft refrigeration, Bootstrap system, Reduced ambient system and Regenerative system but there are many other type of refrigeration system now a day using by aircraft, of course different type of aircraft using different air cooling system.
Simple Aircraft Refrigeration-
This is an open system. In this system low pressure and low temperature is compressed because of ram effect to ram pressure. In this refrigeration system compressed air after cooling in air cooler is passing through a cooling turbine. This system is suitable for ground cooling.
Note- turbine work is not available for the compressor.
Bootstrap System-
In case of bootstrap system, it is having two heat exchangers, the main purpose of Bootstrap refrigerator is to provide extra cooling effect, then main source of air condition unable to provide proper cooling effect. it is not useful for ground cooling.
Reduced Ambient System-
Reduced Ambient System is a type of air cycle refrigeration system used in aircraft that is designed to operate efficiently in hot ambient(surrounding) temperatures.
In this system, the condenser is cooled by a combination of ram air and a water spray, which lowers the refrigerant temperature and increases its efficiency.
This system is commonly used in military and commercial aircraft operating in hot climates, where traditional air cycle systems may not be able to maintain adequate cooling performance.
Note- This refrigeration system is preferred for supersonic aircrafts and rockets.
Regenerative System-
This is one of the modification version of simple aircraft refrigeration system. This system is also good for ground cooling as well as while aircraft is flying.
In this system part of cooling air from from cooling turbine is used for pre-cooling air entering turbine because of this much lower temperature we got at the exit of turbine. In this case also like simple aircraft refrigeration system cooling turbine drives the fan.
MCQ’s with Solution from Aircraft Refrigeration System-
1. (SSC JE 2018) Which of the following is not a primary function of an aircraft refrigeration system?
a) Cooling the cabin air
b) Cooling the electronic components
c) Cooling the engine
d) Cooling the cargo hold
Solution: c) Cooling the engine
Explanation: The primary function of an aircraft refrigeration system is to cool the cabin air, electronic components, and cargo hold to maintain suitable temperature and humidity levels. Cooling the engine is not a primary function of the refrigeration system.
2. (UPSC ESE 2017) Which type of aircraft refrigeration system utilizes engine bleed air for cooling?
a) Vapor cycle system
b) Air cycle system
c) Environmental control system
d) None of the above
Solution: b) Air cycle system
Explanation: The air cycle system in an aircraft utilizes engine bleed air, which is compressed and expanded to provide cooling. It does not use a refrigerant like the vapor cycle system.
3. (GATE 2019) In an aircraft vapor cycle refrigeration system, which component serves as the evaporator?
a) Compressor
b) Condenser
c) Expansion valve
d) Heat exchanger
Solution: d) Heat exchanger
Explanation: In a vapor cycle refrigeration system, the heat exchanger acts as the evaporator where the low-pressure refrigerant absorbs heat from the surroundings and evaporates.
4. (SSC JE 2016) Which classification of aircraft refrigeration system uses a mechanical compressor to compress refrigerant?
a) Air cycle system
b) Vapor cycle system
c) Environmental control system
d) None of the above
Solution: b) Vapor cycle system
Explanation: The vapor cycle system in aircraft refrigeration uses a mechanical compressor to compress the refrigerant before it moves through the condenser, expansion valve, and evaporator.
5. (UPSC ESE 2020) Which component of an aircraft refrigeration system removes heat from the compressed refrigerant?
a) Compressor
b) Condenser
c) Expansion valve
d) Evaporator
Solution: b) Condenser
Explanation: The condenser in an aircraft refrigeration system removes heat from the compressed refrigerant, causing it to liquefy and release the absorbed heat to the surroundings.
6. (GATE 2022) The purpose of the expansion valve in an aircraft refrigeration system is to:
a) Increase the pressure of the refrigerant
b) Decrease the pressure of the refrigerant
c) Regulate the flow of refrigerant
d) Heat the refrigerant
Solution: b) Decrease the pressure of the refrigerant
Explanation: The expansion valve reduces the pressure of the refrigerant, allowing it to expand rapidly, cool down, and absorb heat in the evaporator.
7. (SSC JE 2019) Which of the following refrigerants is commonly used in aircraft vapor cycle systems?
a) R-12
b) R-22
c) R-134a
d) R-410A
Solution: c) R-134a
Explanation: R-134a is a commonly used refrigerant in aircraft vapor cycle systems due to its favorable thermodynamic properties, environmental friendliness, and safety.
8. (UPSC ESE 2018) The purpose of the environmental control system in an aircraft is to:
a) Maintain cabin temperature and pressure
b) Control the aircraft’s external environment
c) Provide power to the aircraft systems
d) Monitor the aircraft’s refrigeration system
Solution: a) Maintain cabin temperature and pressure
Explanation: The environmental control system in an aircraft is responsible for maintaining comfortable cabin conditions, including temperature, humidity, and pressurization.
9. (GATE 2021) Which of the following is not a component of an aircraft refrigeration system?
a) Compressor
b) Heat exchanger
c) Expansion valve
d) Fuel pump
Solution: d) Fuel pump
Explanation: The fuel pump is not a component of the aircraft refrigeration system. The compressor, heat exchanger, and expansion valve are essential parts of the refrigeration system.
10. (SSC JE 2020) Which type of aircraft refrigeration system is more efficient in terms of cooling capacity?
a) Air cycle system
b) Vapor cycle system
c) Environmental control system
d) All have similar cooling capacities
Solution: b) Vapor cycle system
Explanation: The vapor cycle system is more efficient in terms of cooling capacity compared to the air cycle system. The vapor cycle system uses a refrigerant to absorb and release heat, providing effective cooling.
11. (UPSC ESE 2022) Which component of an aircraft refrigeration system controls the flow and direction of refrigerant?
a) Compressor
b) Condenser
c) Expansion valve
d) Evaporator
Solution: c) Expansion valve
Explanation: The expansion valve in an aircraft refrigeration system controls the flow and direction of refrigerant by regulating its pressure and allowing it to expand into the evaporator.
12. (GATE 2017) Which type of refrigeration system is commonly used in small aircraft with limited cooling requirements?
a) Air cycle system
b) Vapor cycle system
c) Environmental control system
d) Hybrid refrigeration system
Solution: a) Air cycle system
Explanation: Air cycle systems are often used in small aircraft with limited cooling requirements due to their simplicity, lower weight, and lower cost compared to vapor cycle systems.
13. (SSC JE 2021) In an aircraft vapor cycle refrigeration system, which component removes moisture from the air entering the cabin?
a) Compressor
b) Condenser
c) Expansion valve
d) Air separator
Solution: d) Air separator
Explanation: The air separator is a component in an aircraft vapor cycle refrigeration system that removes moisture from the air entering the cabin, ensuring a dry and comfortable environment.
14. (UPSC ESE 2019) Which type of refrigeration system requires an external power source to operate?
a) Air cycle system
b) Vapor cycle system
c) Environmental control system
d) None of the above
Solution: c) Environmental control system
Explanation: The environmental control system in an aircraft requires an external power source to operate, as it performs various functions beyond refrigeration, such as pressurization and air conditioning.
15. (GATE 2020) Which classification of aircraft refrigeration system utilizes a combination of both air and vapor cycles?
a) Hybrid refrigeration system
b) Dual-cycle refrigeration system
c) Multi-cycle refrigeration system
d) Composite refrigeration system
Solution: a) Hybrid refrigeration system
Explanation: A hybrid refrigeration system combines elements of both air and vapor cycles to optimize cooling efficiency and meet specific requirements of the aircraft.
16. (SSC JE 2022) Which component in an aircraft vapor cycle refrigeration system removes heat from the compressed refrigerant?
a) Compressor
b) Condenser
c) Expansion valve
d) Evaporator
Solution: b) Condenser
Explanation: The condenser in an aircraft vapor cycle refrigeration system removes heat from the compressed refrigerant, causing it to condense into a liquid state and release heat to the surroundings.
17. (UPSC ESE 2021) Which of the following refrigerants is commonly used in air cycle systems?
a) R-12
b) R-22
c) R-134a
d) Air (No refrigerant is used)
Solution: d) Air (No refrigerant is used)
Explanation: Air cycle systems utilize ambient air as the working fluid and do not require any specific refrigerant.
18. (GATE 2018) The purpose of the compressor in an aircraft refrigeration system is to:
a) Increase the temperature of the refrigerant
b) Decrease the temperature of the refrigerant
c) Increase the pressure of the refrigerant
d) Decrease the pressure of the refrigerant
Solution: c) Increase the pressure of the refrigerant
Explanation: The compressor in an aircraft refrigeration system compresses the refrigerant, increasing its pressure and temperature before it enters the condenser.
19. (SSC JE 2017) Which component in an aircraft refrigeration system transfers heat from the cabin air to the refrigerant?
a) Compressor
b) Condenser
c) Expansion valve
d) Evaporator
Solution: d) Evaporator
Explanation: The evaporator in an aircraft refrigeration system absorbs heat from the cabin air, transferring it to the refrigerant, which then evaporates.
20. (UPSC ESE 2023) Which type of refrigeration system provides cooling for the aircraft’s electronic components?
a) Air cycle system
b) Vapor cycle system
c) Environmental control system
d) Hybrid refrigeration system
Solution: a) Air cycle system
Explanation: Air cycle systems in aircraft can provide cooling for the aircraft’s electronic components by circulating cooled air through the electronic compartments.