Practice these basic questions on the subject of Refrigeration and Air Conditioning. Test your understanding on the subject and prepare well for GATE Mechanical and UPSC ESE Mechanical engineering exams.

Q1. Pick up the wrong statement. A refrigerant should have

1. Low specific heat of liquid
2. High boiling point
3. High latent heat of vaporization
4. Higher critical temperature
5. Low specific volume of vapour.

Q2. A statement ice point temperature corresponds to the temperature of

1. Water at 00c
2. Ice at – 40c
3. Solid and dry ice
4. Mixture of ice, water and vapour under equilibrium conditions under NTP conditions
5. Mixture of ice and water under equilibrium conditions.

Q3. Which of the following cycles uses air as the refrigerant.

1. Ericsson
2. Stirling
3. Carnot
4. Bell – coleman
5. None of the above.

Q4. The relative coefficient of performance is

1. Actual COP/theoretical COP
2. theoretical COP/actual COP
3. actual COP * theoretical COP
4. 1-actual COP * theoretical COP
5. 1-actual COP/theoretical COP.

Q5. Clapeyron equation is a relation between

1. Temperature, pressure and enthalpy
2. Specific and enthalpy
3. Temperature, pressure and specific volume
4. Temperature, pressure, specific volume and enthalpy.

Q6.Claperon equation is applicable for region at

1. Saturation point of vapour
2. Saturation point of liquid
3. Sublimation temperature
4. Triple point
5. Critical point.

Q7.One ton of refrigeration is equal to the refrigeration effect corresponding to melting of 1000kg of ice

1. In 1 hour
2. In 1 mintue
3. In 24 hour
4. In 12 hours
5. In 10hours.

Q8. One ton refrigeration corresponds to

1. 50 kcal/min
2. 50 kcal/kr
3. 80 kcal/min
4. 80 kcal/hr
5. 1000 kcal/day

Q9. In SI unit, one ton of refrigeration is equal to

1. 210 kJ/min
2. 21 kJ/min
3. 420 kJ/min
4. 840 kJ/min
5. 105 kJ/min

Q10. The vapour compression refrigerator employs the following cycle

1. Rankine
2. Carnot
3. Reversed Rankine
4. Brayton
5. Reversed Carnot

Q11. The moisture in a refrigerator is removed by

1. Evaporator
2. Safety relief valve
3. Dehumidifier
4. Dries
5. Expansion valve

Q12. The condensing pressure due to the presence of non – condensable gases, as compared to that actually required condensing temperature without non – condensable gases,

1. Will be higher
2. Will  be lower
3. Will remain unaffected
4. May be higher or lower depending upon the nature of non – condensable gases
5. Unpredictable

Q13. Critical pressure of a liquid is the pressure

1. Above which liquid will remain liquid
2. Above which liquid becomes gas
3. Above which liquid becomes vapour
4. Above liquid becomes solid
5. At which all the three phases exit together.

Q14. Critical temperature is the temperature above which

1. A gas will never liquefy
2. A gas will immediately liquify
3. Water will evaporate
4. Water will never evaporate
5. None of the above.

Q15. The refrigerant for a refrigerator should have

1. High sensible heat
2. High total heat
3. High latent heat
4. Low latent heat
5. Low sensible heat.

Q16. The COP of a domestic refrigerator

1. Is less than 1
2. Is more than 1
3. Is equal to 1
4. Depends upon the make
5. Depends upon the weather conditions.

Q17. Horse power per ton of refrigeration is expressed as

1. 4.75/COP
2. COP/4.75
3. 4.75 * COP
4. 47.5/COP
5. None of the above.

Q18. Refrigeration in aeroplanes usually employs the following refrigerant

1. CO2
2. Freon - 11
3. Freon – 22
4. Air
5. None of the abov

Q19. Air refrigeration operates on

1. Carnot cycle
2. Reversed Carnot cycle
3. Rankine cycle
4. Erricson cycle
5. Baryton cycle.

Q20. For better COP of refrigerator, the pressure range corresponding to temperature in evaporator and condenser must be

1. Small
2. High
3. Equal
4. Anything
5. Under some conditions small and under some conditions high.

Q21. Highest temperature encounted in refrigeration cycle should be

1. Never critical temperature encountered in refrigerant
2. Above critical temperature
3. At critical temperature
4. Much below critical temperature
5. Could be anywhere.

Q22. If T1 and T2 be the highest and lowest absolute temperatures encountered in a heat pump operating on a reversed Carnot cycle, then its COP is equal to

1. T1 - T2 / T1
2. T1 - T2 / T2
3. T2 / T1 - T2
4. T1 / T1 - T2

Q23. Efficiency of a Carnot engine is given as 80%. If the cycle direction be reversed, what will be the value of COP of reversed Carnot cycle

1. 1.25
2. 0.8
3. 0.5
4. 0.25
5. None of the above

Q24. In a refrigeration cycle, the flow of refrigerant is controlled by

1. Compressor
2. Condenser
3. Evaporator
4. Expansion valve
5. All of the above

Q25. Where does the lowest temperature occur in a vapour compression cycle?

1. Compressor
2. Condenser
3. Evaporator
4. Expansion valve

11. Drier 13.option 3 14.option 3 15. High latent heat 16. Cop greater than 1

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6. Option1, situation point f vapour 7. 24 hrs, 8.50 kcal/hr 9.210kj/min 10. Reversed carnot

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