This set of Refrigeration Multiple Choice Questions & Answers (MCQs) focuses on “Condensers and Cooling Towers – 1”.
1. What is the purpose of using a condenser?
a) To absorb heat
b) To reject heat
c) To convert liquid refrigerant to vapor refrigerant
d) To convert solid refrigerant to vapor refrigerant
View Answer
Explanation: Condenser is used to convert vapor refrigerant discharging from the compressor into liquid refrigerant by rejecting or removing heat and attaining the saturated liquid line for the refrigerant.
2. Which of the following is not the criterion for the selection of the condenser?
a) The capacity of the condenser
b) Type of refrigerant used
c) Type of cooling medium available
d) Type of compressor and evaporator used
View Answer
Explanation: For the selection of the condenser, there is no effect of the type of compressor and evaporator used in the system. The capacity, type of refrigerant used, and type of cooling medium available play a crucial role in the selection.
3. What is the expression for the load on the condenser?
a) QC = RE + W
b) QC = RE – W
c) QC = RE x W
d) QC = RE / W
View Answer
Explanation: The load on the condenser, i.e., QC is the summation of refrigeration capacity and work done by the compressor. Hence, it is given by
QC = RE + W
Where, QC = Load on the condenser, RE = Refrigeration capacity & W = Work done by the compressor.
4. What is the expression for the heat rejection factor?
a) HRF = W / RE
b) HRF = RE / W
c) HRF = QC / RE
d) HRF = RE / QC
View Answer
Explanation: Heat rejection factor is the load on the condenser per unit refrigeration capacity. So, it can be represented as,
HRF = QC / RE, Where, QC = Load on the condenser & RE = Refrigeration capacity.
5. What is the expression for the heat rejection factor in terms of C.O.P.?
a) 1 + C.O.P.
b) 1 – C.O.P.
c) 1 – 1 / C.O.P.
d) 1 + 1 / C.O.P.
View Answer
Explanation: Heat rejection factor is the load on the condenser per unit refrigeration capacity. So, it can be represented as,
HRF = QC / RE, Where, QC = Load on the condenser & RE = Refrigeration capacity
And as we know, the load on the condenser, i.e., QC is the summation of refrigeration capacity and work done by the compressor.
QC = RE + W
Hence, HRF = QC / RE = RE + W / RE = 1 + W / RE = 1 + 1 / C.O.P. (as C.O.P. = RE / W).
6. Which of the following does not affect the refrigeration capacity of the condenser?
a) Material
b) Amount of contact
c) Temperature difference
d) Type of refrigerant
View Answer
Explanation: Condenser capacity is not affected by the type of refrigerant. Material is affected due to the ability of different material to reject heat differs and affect the capacity. By varying the amount of contact, rate of flow of condensing medium is varied and hence affects the capacity. Heat transfer of condenser depends upon the temperature difference between condensing medium and vapour refrigerant and affects the heat transfer rate. So, the type of refrigerant used has nothing to do with the condenser capacity.
7. Materials form deposits inside the condenser water tubes is called _______
a) water rusting
b) water corrosion
c) water fouling
d) water failing
View Answer
Explanation: The water contains a certain amount of minerals and foreign materials when used in water-cooled condensers. These minerals depend upon the source. These materials start to form deposit inside the condenser water tubes is called water fouling.
8. Which of the following is not the effect of water fouling?
a) Increase in heat transfer rate
b) Tube insulation
c) Reduction in heat transfer rate
d) Restrict water flow
View Answer
Explanation: The water contains a certain amount of minerals and foreign materials when used in water-cooled condensers. These minerals depend upon the source. These materials start to form deposits inside the condenser water tubes is called water fouling. These deposits insulate the tube, reduce the heat transfer rate, and restrict the water flow but do not increase the heat transfer rate at any condition.
9. What is the fouling factor?
a) Heat transfer coefficient
b) 1 / Heat transfer coefficient
c) \(\sqrt{Heat \,transfer \,coefficient}\)
d) 1 / (Heat transfer coefficient)2
View Answer
Explanation: The water contains a certain amount of minerals and foreign materials when used in water-cooled condensers. These minerals depend upon the source. These materials start to form deposit inside the condenser water tubes is called water fouling. These deposits insulate the tube, reduce the heat transfer rate, and restrict the water flow but do not increase the heat transfer rate at any condition. So, the fouling factor is the reciprocal of the heat transfer coefficient for the material of scale. Ex: For copper tubes and R – 12 its is valued at 0.000095 m2 s K/J.
10. The initial cost of the air-cooled condenser is high.
a) False
b) True
View Answer
Explanation: As the name suggests, the air-cooled condenser is the one in which the removal of heat is carried out by air. As the construction of this type of condenser is very simple, just tubing and different type of fins; hence, the initial cost is less, and even maintenance cost is less.
Sanfoundry Global Education & Learning Series – Refrigeration & Air Conditioning.
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