# Refrigeration Questions and Answers – Simple Air Cooling System

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This set of Refrigeration Multiple Choice Questions & Answers (MCQs) focuses on “Simple Air Cooling System”.

1. Which one of the following is not a component of a simple air cooling system?
a) Main compressor
b) Cooling fan
c) Heat exchanger
d) Generator

Explanation: The main components of simple air cooling system are the main compressor driven by the gas turbine, a cooling fan, heat exchanger and a cooling turbine.

2. For a simple air cooling system which one of the following is not a process of the cycle in T-S diagram?

a) Ramming process
b) Compression process
c) Heating process
d) Refrigeration process

Explanation: A simple air cooling system has 5 processes in T-S diagram namely ramming process, compression process, expansion process, refrigeration processes and cooling process.

3. The COP of simple air cooling system is given by?
T6 = Inside temperature of cabin
T5′ = Exit temperature of cooling turbine
T3′ = Temperature at the exit of compressor
T2′ = Stagnation temperature
a) COP = $$\frac{(T_6 – T_{5′})}{(T_3′ – T_{2′})}$$
b) COP = $$\frac{(T_6 + T_{5′})}{(T_3′ – T_{2′})}$$
c) COP = $$\frac{(T_6 + T_{5′})}{(T_3′ + T_{2′})}$$
d) COP = $$\frac{(T_6 – T_{5′})}{(T_3′ + T_{2′})}$$

Explanation: COP = Refrigeration effect produced i.e. (T6 – T5′) divided by Work done i.e. (T3′ – T2′).
Hence COP = $$\frac{(T_6 – T_{5′})}{(T_3′ – T_{2′})}$$.

4. The simple air cooling system is good for _____ flight speed.
a) low
b) high
c) moderate
d) any

Explanation: The simple air cooling system is good for low flight speed so as fan can maintain airflow over the air cooler, which is difficult for it while at high speeds.

5. What is the main difference between simple air cooling system and simple air evaporative cooling system?
a) Simple air evaporative cooling system has an evaporator
b) Simple air evaporative cooling system has two evaporators
c) Simple air evaporative cooling system has an extra compressor
d) Simple air evaporative cooling system has three evaporators

Explanation: The difference between the simple air cooling system and simple air evaporative cooling system is that it has an evaporator between the heat exchanger and the cooling turbine.

6. If cooling of 45 minutes or less is required, it may be advantageous to use evaporative cooling system.
a) True
b) False

Explanation: The evaporative cooling system provides an additional cooling effect through evaporation of refrigerants such as water etc. Hence if cooling of 45 minutes or less is required, it may be advantageous to use evaporative cooling system.

7. A simple evaporative air refrigeration system is used for an airplane to take 20 TR of refrigeration load (Q). The power required for the refrigerating system P is 746 KW. What is its COP?
a) 0.086
b) 0.094
c) 0.079
d) 0.099

Explanation: COP = $$\frac{(210×Q)}{(P×60)}$$
COP = $$\frac{(210×20)}{(746×60)}$$
= 0.094.