## Ch-1 air refrigeration system

1. One ton refrigeration corresponds to

(a) 50 kcal/min(b) 50 kcal/kr(c) 80 kcal/min(d) 80 kcal/hr(e) 1000 kcal/day.

Ans: a
2. In S.i. unit, one ton of refrigeration is equal to

(a) 210 kJ/min(b) 21 kJ/min(c) 420 kJ/min(d) 840 kJ/min(e) 105 kJ/min.

Ans: a
3. The COP of a domestic refrigerator

(a) is less than 1(b) is more than 1(c) is equal to 1(d) depends upon the make(e) depends upon the weather conditions.

Ans: b

### 4.The coefficient of performance of Heat Pump is always _________ one.

A.Equal to B.Less than C.Greater than D.None of these

Answer: Option C Solution: The coefficient of performance of Heat Pump is always Greater than one.

5.The condition of refrigerant after passing through the condenser in a vapour compression system is

(A) Saturated liquid(B) Wet vapour(C) Dry saturated vapour(D) Superheated vapour

Correct Answer: Option A

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

(A) Compressor(B) Condenser(C) Evaporator(D) Expansion valve

7.The C.O.P. of a Carnot refrigerator in winter will be _________ as compared to C.O.P. in summer.

(A) Same(B) Lower(C) Higher(D) None of these

8.One tonne refrigerating machine means…….

A.One tonne is the total mass of the machine

B.One tonne of refrigerant is used

C.One tonne of water can be converted into ice

D.One tonne of ice when melts from at 00C in 24 hours,the refrigeration effect produced is equivalent to 210 kJ/min

✔ View Answer:- D.One tonne of ice when melts from at 00C in 24 hours,the refrigeration effect produced is equivalent to 210 kJ/min

9.During a refrigeration cycle,heat is rejected by the refrigerant in a…….

B.Condenser   A.Compressor   C.Evaporator   D.Expansion valve

10.One tonne of refrigeration is equal to

A.21/kJ/min   B.210/kJ/min   C.420/kJ/min   C.620/kJ/min

11. Air refrigerator works on……

A. Carnot cycle   B.Rankine cycle   C.Reversed carnot cycle   D.Bell-Coleman cycle   E.Both C and D

12. Air refrigeration cycle is used in…….

A.Commercial refrigerators   B.Domestic refrigerators   C.Air-conditioning   D.Gas liquefaction

13.In air-conditioning of aeroplanes,using air as refrigerant,the cycle is used is…….

A.Reversed carnot cycle   B.Reversed joule cycle   C.Reversed Brayton cycle   D.Reversed Otto cycle

14.The relative coefficient of performance ( C.O.P.)is equal to…….

A.Theoritical C.O.P./Actual C.O.P.   B.Actual C.O.P./Theoritical C.O.P.   C.Theoritical C.O.P. x Actual C.O.P.   D.None of the above

15.One tonne of refrigeration is equal to the refrigeration effect corresponding to melting of 1000 kg of ice ….   A.In one hour   B.In one munite   C.In 24 hours   D.In 12 hours   E.In 10 hours

16.Which type of compressor is used in domestic refrigerator…….

A.Centrifugal   B.Axial   C.Miniature sealed unit   D.Piston type reciprocating

17.Refrigeration of aeroplane uses…….

A.CO2   B.Air   C.Freon-11   D.Freon-22

18. Horsepower per ton of refrigeration is expressed as…….

A.4.75/COP   B.COP/4.75   C.4.75 x COP   D.47.5/COP

## Ch-2 Vapour Compression Cycle

Q1. Which device is used for the expansion of refrigerant in vapour compression refrigeration cycle?
a. throttling valve

b. capillary tube

c. either throttling valve or capillary tube

d. none of the above

ANSWER: c. either throttling valve or capillary tube

Q2. Wet compression is ______.
a. more dangerous than the dry compression in vapour compression refrigeration system

b. less dangerous than the dry compression in vapour compression refrigeration system

c. equally preferable in vapour compression refrigeration system

d. cannot say

ANSWER: a. more dangerous than the dry compression in vapour compression refrigeration system

Q3. How is the condensation process in vapour compression refrigeration cycle carried out?
a. at constant volume

b. at constant pressure

c. at constant enthalpy

d. all of the above

ANSWER: b. at constant pressure

Q4. What is flash gas fraction?
a. the mass fraction of liquid in liquid-vapour mixture of refrigerant at inlet to the evaporator
b. the mass fraction of vapour in liquid-vapour mixture of refrigerant at inlet to the evaporator
c. the mass of vapour actually compressed to the mass of vapour should have compressed ideally
d. none of the above

ANSWER: b. the mass fraction of vapour in liquid-vapour mixture of refrigerant at inlet to the evaporator

Q5. In evaporation process of vapour compression refrigeration system
a. heat is rejected from refrigerant to surroundings

b. heat is rejected from surroundings to refrigerant

c. only pressure change takes place

d. none of the above

ANSWER: b. heat is rejected from surroundings to refrigerant

Q6. The heat required to melt 1 tonne of ice in 12 hours is equivalent to
a. one tonne of refrigeration

b. two tonne of refrigeration

c. half tonne of refrigeration

d. four tonne of refrigeration

ANSWER: b. two tonne of refrigeration

Q8. What is the main reason behind subcooling of liquid refrigerant at the condenser outlet in vapour compression refrigeration system?
a. to increase the refrigerating effect

b. to reduce the mass of vapour formed during expansion process

c. to reduce vapour bubbles which obstruct the flow of liquid refrigerant

d. all of the above

ANSWER: d. all of the above

Q9. What is the result of superheating of vapour at the evaporator outlet?
a. no liquid droplets will travel to the compressor

b. the compressor discharge temperature increases

c. both a. and b.

d. none of the above

ANSWER: c. both a. and b.

Q10. Which expansion device is capable of regulating the flow of refrigerant according to the load on the evaporator?

a. capillary tube

b. throttle valve

c. both a. and b.

d. none of the above

ANSWER: b. throttle valve

Q12. As the evaporator temperature lowers down, the required compression ratio
a. becomes lower for a given condensation temperature

b. becomes higher for a given condensation temperature

c. becomes steady for a given condensation temperature

d. cannot say

ANSWER: b. becomes higher for a given condensation temperature

Q13. What is the use of multistage compression in vapour compression refrigeration system?
a. to increase volumetric efficiency of of compressor

b. to allow the system to operate between higher pressures

c. to reduce risk of damage to refrigerant

d. all of the above

ANSWER: d. all of the above

Q14. What is used as an intercooler in multistage compression of vapour compression refrigeration system?
a. water

b. air

c. refrigerant itself

d. none of the above

ANSWER: c. refrigerant itself

Q15. Which of the following statement is true for a condenser?

a) it can be air-cooled or water-cooled

b) small self-contained units use water-cooled condenser

c) large installations use air-cooled condenser

Answer: a Explanation: We use air-cooled condenser for small self-contained units and water-cooled condenser for large installations.

Q16.For an expansion device, which of the following is true?

a) it increases the pressure of refrigerant b) it regulates the flow of refrigerant to evaporator c) both of the mentioned d) none of the mentioned

Q17. Which of the following is a type of expansion device?

a) capillary tubes b) throttle valves c) both of the mentioned d) none of the mentioned

Q18. Throttle valves are used in ____

a) small units b) larger units c) both of the mentioned d) none of the mentioned

Q19.The clearance volumetric efficiency is equal to a) 1 + C + C(p2/p1)^(1/n)

b) 1 – C – C(p2/p1)^(1/n)

c) 1 – C + C(p2/p1)^(1/n)

d) 1 + C – C(p2/p1)^(1/n)

Q20.Why is multistage compression with intercooling adopted?

a) using a single stage with high pressure ratio decreases volumetric efficiency

b) high pressure ratio with dry compression gives high compressor discharge temperature

c) the refrigerant is damaged

d) all of the mentioned

View AnswerAnswer: d Explanation: Because of these reasons we have to use multistage compression with intercooling.

Q21.The intercooler pressure is given by a) p1*p2 b) sqrt(p1*p2) c) (p1*p2)/(p1+p2) d) (p1+p2)/2 View AnswerAnswer: b Explanation: Here p1 is the evaporator pressure and p2 is the condenser pressure.
Q22.The most widely used refrigerants are

a) freon

b) genetron

c) arcton

d) all of the mentioned

Q23.1. During a refrigeration cycle, heat is rejected by the refrigerant in a

• Compressor
• Condenser
• Evaporator
• Expansion valve

2. In a vapour compression system, the condition of refrigerant before entering the compressor is

• Saturated liquid
• Wet vapour
• Dry saturated liquid
• Superheated vapour

3. The highest temperature during the cycle, in a vapour compression system, occurs after

• Compression
• Condensation
• Expansion
• Evaporation

4. In a vapour compression system, the lowest temperature during the cycles occurs after

• Compression
• Condensation
• Expansion
• Evaporation

5. The sub-cooling in a refrigeration cycle

• Does not alter C.O.P
• Increases C.O.P
• Decreases C.O.P

6. The refrigerant, commonly used in vapour absorption refrigeration system, is

• Sulphur dioxide
• Ammonia
• Freon
• Aqua-ammonia

7. In ammonia-hydrogen refrigerator

• Ammonia is absorbed in hydrogen
• Ammonia is absorbed in water
• Ammonia evaporates in hydrogen
• Hydrogen evaporates in ammonia

8. Which of the following refrigerants has the lowest boiling point?

• Ammonia
• Carbon dioxide
• Sulphur dioxide
• Freon-12

9. Which of the following refrigerant is highly toxic and flammable?

• Ammonia
• Carbon dioxide
• Sulphur dioxide
• Freon-12

Q24. The purpose of installing a flash chamber in the refrigeration circuit is to (A) improve overall heat transfer coefficient (B) reduce pressure losses through the evaporator (C) reduce the size of the evaporator by avoiding vapours going to the evaporator (D) all of the above Answer (D)
Q25.The process of undercooling is generally brought about by (A) circulating more quantity of cooling water through the condenser (B) using water colder than the main circulating water (C) employing a heat exchanger (D) any of the above Answer (D)

## Ch-3 Vapour Absorption Cycle

Q1. The mechanical work required to run vapour absorption system
a. is more than the mechanical work required to run vapour compression system

b. is less than the mechanical work required to run vapour compression system

c. is similar to the mechanical work required to run vapour compression system

d. cannot say

ANSWER: b. is less than the mechanical work required to run vapour compression system

Q2. The compressor in the vapour compression system id replaced by
a. an absorber

b. a generator

c. an absorber-generator

d. none of the above

Q3. What is the condition of refrigerant at the exit of evaporator in aqua-ammonia absorption system?
a. low pressure ammonia vapour

b. high pressure ammonia vapour

c. low pressure strong vapour mixture of ammonia and water

d. high pressure strong vapour mixture of ammonia and water

Q4. What is the process carried out in generator of vapour absorption refrigeration cycle?
a. weak solution of ammonia in water is heated

b. strong solution of ammonia in water is heated

c. only water is heated and heat is given to the ammonia to form its vapour

d. none of the above

Q5. In absorber of aqua-ammonia absorption refrigeration system
a. strong solution is taken in and weak solution is given out

b. weak solution is taken in and strong solution is given out

c. the ammonia vapour from strong solution is taken out and made it a weak solution

d. none of the above
View Answer / Hide Answer ANSWER: b. weak solution is taken in and strong solution is given out

Q6. What is the purpose of analyser-rectifire in aqua-ammonia absorption system?
a. to absorb ammonia into the water

b. to remove water vapour out from ammonia after generator

c. to exchange heat between weak solution and strong solution

d. none of the above

Q7. What is an advantage using analyser-rectifier in aqua-ammonia absorption system?
a. it makes ammonia-water solution strong

b. it prevents expansion valve from blocking due to ice formation

c. both a. and b.

d. none of the above

ANSWER: b. it prevents expansion valve from blocking due to ice formation

Q8. For a same pressure the saturation temperature of ammonia is
a. higher than the saturation temperature of water

b. lower than the saturation temperature of water

c. same as the saturation temperature of water

d. none of the above

Q9. Which type of energy is required to expend in vapour absorption refrigeration system?

d. none of the above

Q10. The vapour absorption refrigeration system is
a. more noisy than the vapour compression refrigeration system

b. more silent than the vapour compression refrigeration system

c. equally noisy as the vapour compression refrigeration system

d. it depends upon plant capacity