This set of Refrigeration Question Paper focuses on “Domestic Electrolux and Lithium Bromide Refrigeration System – 2”.
1. What is the key difference between a simple VAR and Electrolux refrigerator?
a) Absorber
b) Liquid pump
c) Working mechanism
d) Generator
View Answer
Explanation: Simple VAR uses a generator to do work as well as a pump to pressurize the liquid to the generator. So, total work done is the summation of work done by a pump and generator. Refrigeration effect is the heat absorbed in the evaporator. But as in the case of Electrolux refrigerator pump is not present. It is the VAR system with no liquid pump; hence, it is the key difference between Simple VAR and Electrolux refrigerator.
2. What is the other name for Electrolux refrigerator?
a) Single-fluid absorption system
b) Two-fluid absorption system
c) Three-fluid absorption system
d) Four-fluid absorption system
View Answer
Explanation: Electrolux refrigerator uses Ammonia, Hydrogen, and Water to carry out the desired effect. As three fluids are used for the operation, Electrolux refrigerator is also called a Three-fluid absorption system.
3. Which of the following is valid for one of the processes in the Electrolux refrigerator?
a) Ammonia evaporates in hydrogen
b) Hydrogen evaporates in ammonia
c) Water evaporates in hydrogen
d) Ammonia evaporates in water
View Answer
Explanation: According to Dalton’s principle, the hydrogen entering the evaporator allows the liquid ammonia to evaporate at low pressure and temperature. Evaporated ammonia absorbs latent heat and produces refrigeration effect.
4. What are the fluids used in the Electrolux refrigerator?
a) Hydrogen, Water
b) Hydrogen, Water, Lithium
c) Hydrogen, Water, Bromide
d) Hydrogen, Water, Ammonia
View Answer
Explanation: Electrolux refrigerator uses Ammonia, Hydrogen, and Water to carry out the desired effect. As three fluids are used for the operation, Electrolux refrigerator is also called a Three-fluid absorption system.
5. What is the purpose of using Hydrogen in Electrolux refrigerator?
a) To increase the vapour pressure of ammonia
b) To increase the rate of evaporation
c) To decrease the rate of evaporation
d) To get evaporated by using ammonia
View Answer
Explanation: Hydrogen is light, non-corrosive, and insoluble in water. Hydrogen being light, used for increasing the rate of evaporation. As lighter the gas, faster is the evaporation process. Hence hydrogen is used on the low-pressure side of the system to allow faster evaporation of ammonia.
6. What is the role of water in the Electrolux refrigerator?
a) Solvent
b) Evaporation rate enhancer
c) Evaporation rate reducer
d) Refrigerant
View Answer
Explanation: Water is used as a solvent in Electrolux refrigerator due to the nature of readily absorbing the refrigerant i.e., ammonia.
7. What is the value of C.O.P. in the Electrolux refrigerator?
a) QG / QE
b) QE / QG
c) QG / QC
d) QC / QE
View Answer
Explanation: As VAR uses the generator to do work as well as pump to pressurize the liquid to the generator. So, total work done is the summation of work done by a pump and generator. Refrigeration effect is the heat absorbed in the evaporator. But in the case of Electrolux refrigerator, a liquid pump is not used so QP = 0.
So, C.O.P. = Refrigeration effect / Total work done
= Heat absorbed in the evaporator / Work done by pump + Heat supplied in the generator
QE = Heat absorbed in the evaporator and QG = Heat supplied in the generator
C.O.P. = QE / QG
8. Which refrigerants are used in Electrolux and Li-Br water refrigeration system?
a) Ammonia and Lithium
b) Water and Water
c) Water and Bromide
d) Ammonia and Water
View Answer
Explanation: In the Electrolux refrigerator, ammonia is used as a refrigerant, and in the case of Li-Br water system water is used as a refrigerant due to their desirable properties to produce refrigeration effect.
9. In Li-Br water system, Water is used as an absorber and Li-Br solution as a refrigerant.
a) False
b) True
View Answer
Explanation: In Li-Br water system, water is used as a refrigerant and Li-Br solution as an absorber due to its strong affinity for water vapour.
10. Which of the following nature of Li-Br solution leads to the usage of inhibitors?
a) Toxic
b) Corrosive
c) Strong affinity for water vapour
d) Low boiling point
View Answer
Explanation: Due to the corrosive nature of Li-Br solution, inhibitors are added to protect the metal parts. Often used corrosion inhibitor is Lithium chromate.
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