This set of Refrigeration Questions & Answers for Exams focuses on “Condensers and Cooling Towers – 2”.
1. What is the pressure side of a refrigerating system in which condenser is used?
a) Low pressure
b) Zero pressure
c) Negative pressure
d) High pressure
View Answer
Explanation: Condenser is used to convert vapor refrigerant discharging from the compressor into liquid refrigerant by rejecting heat. So, it is used on the high-pressure side to do the conversion. At discharge pressure after compression, condensation is carried out.
2. What is the optimum temperature difference in Celsius for the operation of most air-cooled condensers and designed based on this difference?
a) 10
b) 14
c) 20
d) 28
View Answer
Explanation: Heat transfer of condenser depends upon the temperature difference between the condensing medium and vapor refrigerant and affects the heat transfer rate. So, air-cooled condensers are designed for the temperatures difference of 14⁰C for the optimum heat transfer rate and smooth and hassle-free operation.
3. What of the following uses natural convection air-cooled condensers?
a) Domestic refrigerators
b) High capacity room air conditioners
c) High capacity water coolers
d) Industrial air conditioners
View Answer
Explanation: Natural convection phenomenon is used to carry out the operation. Large surface area is required for the proper heat transfer between the mediums. Due to the slow process and able to handle low capacity used just in small-capacity applications like domestic refrigerators.
4. Which of the following is true about shell and coil condensers?
a) water flows in the shell and refrigerant in the coil
b) refrigerant flows in the shell and water in the coil
c) water and refrigerant flow in the coil
d) water and refrigerant flow in the shell
View Answer
Explanation: Shell and coil condensers consists of one or more water coils enclosed in the welded steel shell through which refrigerant flows. So, the refrigerant flows in the shell, and water in the coil is the perfect construction of this type of condenser.
5. What is the material of tubes used for shell and tube condenser in ammonia refrigeration system?
a) Aluminum
b) Brass
c) Steel
d) Copper
View Answer
Explanation: As ammonia is toxic and has the ability to rust the material which comes in the contact. So, in the ammonia refrigeration system, steel tubes are used for shell and tube condensers to avoid the corrosion.
6. What is the condensing medium used in evaporative condensers?
a) air only
b) water only
c) ammonia
d) air and water
View Answer
Explanation: Evaporative condenser uses air and water as a condensing medium. This type of condenser does the combined work of water-cooled condenser and cooling water, and hot vapor is condensed into a liquid refrigerant.
7. What is the value of Heat Rejection Factor if the C.O.P. 4.28?
a) 5.28
b) -3.28
c) 1.233
d) 0.766
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)
HRF = 1 + 1 / 4.28 = 1.233.
8. What is the value of HRF if Work is 10 kW and refrigeration capacity is 40 kW?
a) 1.25
b) 0.25
c) 0.75
d) 1
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)
HRF = 1 + (10 / 40) = 1 + 0.25 = 1.25.
9. Air-cooled condensers operate on lower condensing temperatures than water-cooled condensers.
a) False
b) True
View Answer
Explanation: The main advantage of air-cooled condensers is that they operate at higher condensing temperatures than water-cooled condensers. Due to this high temperature, the compressor has to do more work and might affect C.O.P. in some conditions.
10. The HRF for R – 12 with condensing temperature and evaporator temperature as 40°C and 5°C respectively is 1.5.
a) True
b) False
View Answer
Explanation: HRF depends on C.O.P. as HRF = QC / RE = RE + W / RE = 1 + W / RE = 1 + 1 / C.O.P. and as C.O.P. is affected by condenser and evaporator temperature. So, for the given conditions, the value of the Heat Rejection Factor for R – 12 at condensing temperature and evaporator temperature as 40°C and 5°C respectively is 1.25.
Sanfoundry Global Education & Learning Series – Refrigeration & Air Conditioning.
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