This set of Thermodynamics Multiple Choice Questions & Answers (MCQs) focuses on “Vapor Compression Refrigeration Cycle-2”.
1. 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
d) all of the mentioned
View Answer
Explanation: We use air-cooled condenser for small self-contained units and water-cooled condenser for large installations.
2. 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
View Answer
Explanation: The expansion device reduces the pressure of refrigerant.
3. 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
View Answer
Explanation: These are the two types of expansion devices.
4. Throttle valves are used in ____
a) small units
b) larger units
c) both of the mentioned
d) none of the mentioned
View Answer
Explanation: They regulate the flow of refrigerant according to load on evaporator.
5. Capillary tubes are used in ____
a) small units
b) larger units
c) both of the mentioned
d) none of the mentioned
View Answer
Explanation: In their case, id size and length are fixed, the evaporator pressure also gets fixed.
6. Types of compressor include
a) reciprocating
b) centrifugal
c) rotary
d) all of the mentioned
View Answer
Explanation: These are the three types of compressor.
7. When volume flow rate of refrigerant is large, which compressor is used?
a) reciprocating
b) centrifugal
c) rotary
d) all of the mentioned
View Answer
Explanation: For plants with higher capacities, centrifugal compressors are used.
8. Which of the following statement is true?
a) rotary compressors are mostly used for small units
b) reciprocating compressors are employed in plants with capacity up to 100 tonnes
c) both of the mentioned
d) none of the mentioned
View Answer
Explanation: This is the difference in reciprocating and rotary compressors.
9. In reciprocating compressors, actual volume of gas drawn in cylinder is ____ the volume displaced by piston.
a) less than
b) more than
c) equal to
d) none of the mentioned
View Answer
Explanation: The reason being, leakage, clearance and throttling effects.
10. 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)
View Answer
Explanation: Here C is the clearance and p1,p2 are pressures.
11. Plate evaporator is a common type of evaporator.
a) true
b) false
View Answer
Explanation: In a plate evaporator, a coil is brazed on to a plate.
12. 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 Answer
Explanation: Because of these reasons we have to use multistage compression with intercooling.
13. The intercooler pressure is given by
a) p1*p2
b) sqrt(p1*p2)
c) (p1*p2)/(p1+p2)
d) (p1+p2)/2
View Answer
Explanation: Here p1 is the evaporator pressure and p2 is the condenser pressure.
14. The most widely used refrigerants are
a) freon
b) genetron
c) arcton
d) all of the mentioned
View Answer
Explanation: These are a group of halogenated hydrocarbons.
15. Why is ammonia used in food refrigeration?
a) high COP
b) low cost
c) lower energy cost
d) all of the mentioned
View Answer
Explanation: Also ammonia can be detected easily in case of a leak.
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