This set of Refrigeration Multiple Choice Questions & Answers (MCQs) focuses on “Mechanism of Simple VCR System”.
1. A vapor compression refrigeration system is an improved type of air refrigeration system in which a suitable working substance, termed as refrigerant is used.
Explanation: A vapor compression refrigeration system is an improved type of air refrigeration system in which a suitable working substance, termed as refrigerant is used. Refrigerants such as ammonia, CO2 and Sulphur dioxide etc. are used as refrigerants in a vapor compression refrigeration system.
2. The vapor compression refrigeration system is similar to a ________
a) latent heat pump
b) latent heat engine
Explanation: The vapor compression refrigeration system is a latent heat pump, as it pumps its latent heat from the brine and delivers it to the cooler.
3. The first vapor compression refrigeration system was developed by ________
a) L. G. Hamilton
b) Jacob Perkins
c) Stephen Rossi
d) Lenard Sandwik
Explanation: The first vapor compression refrigeration system was developed in 1834 by Jacob Perkins using hand operations.
4. The COP of vapor compression refrigeration compared to simple air refrigeration system is ________
d) can’t say
Explanation: COP of vapor compression refrigeration compared to simple air refrigeration system is high due to the use of refrigerant and as it can be employed over large range of temperatures.
5. Which of the following is not an advantage of vapor compression refrigeration system over air refrigeration system?
a) Smaller size for a given capacity of refrigeration
b) It has less running cost
c) It can be employed over wide range of temperature
d) There is no problem of leakage in vapor compression refrigeration system
Explanation: In vapor compression refrigeration system the prevention of leakage of the refrigerant is a major problem. The advantages of it are smaller size for a given capacity of refrigeration, it has less running cost and it can be employed over wide range of temperature.
6. The low pressure and temperature vapor refrigerant enters the ______ of the vapor compression system.
Explanation: In the compressor the low pressure and temperature vapor refrigerant from the evaporator is drawn through the suction valve, where it is compressed to high pressure and temperature.
7. The high pressure and temperature vapor refrigerant enters the ______ of the vapor compression system.
Explanation: In the condenser the high pressure and temperature vapor refrigerant from the compressor is condensed, during which the refrigerant gives up its latent heat.
8. In any compression refrigeration system there are how many pressure conditions?
Explanation: In any compression refrigeration system there are 2 pressure conditions, namely high pressure and low pressure side.
9. Which of the following is not an advantage of vapor compression cycle over reversed Carnot cycle?
a) It’ COP and refrigeration effect can’t be increased
b) Use of expansion valve reduces the size and cost of plant
c) It is a practical cycle on which plant can be built
d) Wet compression of Carnot cycle is avoided
Explanation: It’ COP and refrigeration effect can be increased by use of superheated vapor at entry of compressor. The advantages are use of expansion valve reduces the size and cost of plant, it is a practical cycle on which plant can be built and wet compression of Carnot cycle is avoided.
10. The pipe line emanating from compressor up to the condenser is called ________
a) suction line
b) pipe line
c) liquid line
d) delivery line
Explanation: The pipe line emanating from compressor up to the condenser is called delivery line or discharge line or hot gas line. Whereas suction line is the low pressure vapor line from the exit end evaporator leading to the compressor suction side and liquid line carries the liquid from receiver to the control valve.
11. The coefficient of performance of a vapour compression refrigeration system is quite high as compared to the air refrigeration system.
Explanation: VCRS uses a refrigerant having specific properties. The most important properties include heat absorbing and rejecting capacities. Due to the occurrence of phase change of refrigerant in the Vapor compression refrigeration system and high-temperature range applicability, it has higher COP. VCRS used in applications like refrigerators for domestic and industrial applications.
12. In a refrigeration cycle, in which of the following heat absorption takes place?
c) Expansion valve
Explanation: Evaporator helps to raise the temperature of the refrigerant and convert that liquid form into gaseous form. For that, it absorbs heat energy from the items placed in the system. Utilizing that heat to make the phase change.
13. After which process during the VCR cycle, the highest temperature is achieved?
Explanation: The compression process is used to increase the pressure. So, according to Gay-Lussac’s law,
P ∝ T
As the highest pressure obtained after compression, the temperature obtained is also the highest.
14. The expansion valve in a refrigerator does not control the flow of refrigerant.
Explanation: Expansion valve acts as a diffuser, where pressure reduction is carried out using an orifice. By controlling the flow of refrigerant flowing through an orifice, the desired pressure drops obtained.
15. In a domestic vapour compression refrigerator, which of the following refrigerants commonly used?
Explanation: FREON is a trading name for several gases called refrigerants. Commonly used refrigerants are hydrofluorocarbons and hydrocarbons. Though ammonia and dichlorodifluoromethane have the same boiling point, it is not toxic like ammonia. Hence, it is safe to use Freon than ammonia.
Sanfoundry Global Education & Learning Series – Refrigeration & Air Conditioning.
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