# Refrigeration Questions and Answers – Boot – Strap Air Cooling System

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

1. In Boot-strap air cooling system how many heat exchangers are there?
a) 1
b) 2
c) 3
d) 0

Explanation: In Boot-strap air cooling system there are two heat exchangers and a cooling turbine driving the secondary compressor instead of the cooling fan.

2. Which of the following is not a process in the T-s diagram of the Boot-strap air cooling system?

a) Isentropic ramming
b) Isentropic compression
c) Cooling of ram air
d) Isothermal expansion

Explanation: T-s diagram of Boot-strap air cooling system consists of Isentropic ramming, Isentropic compression, Cooling of ram air in first heat exchanger, Isentropic compression, cooling of ram air in the second heat exchanger, isentropic expansion and then heating of air.

3. What is the difference between Boot-strap air cooling system and Boot-strap evaporative cooling system?
a) Boot strap evaporative system has an evaporator
b) Boot strap evaporative system has two evaporators
c) Boot-strap evaporator eliminates the need for evaporator
d) Boot-strap evaporator system has three evaporators

Explanation: Boot strap evaporative system has an evaporator between the second heat exchanger and the cooling turbine.
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4. Mass of air per tonne of refrigeration will be _____ in Boot-strap air cooling system than Boot-strap evaporative system.
a) less
b) more
c) equal to
d) can’t say

Explanation: Since the temperature of air leaving the cooling turbine in boot-strap system is lower than the simple boot-strap system, therefore the mass of air per tonne of refrigeration will be more in boot-strap air cooling system.

5. The air cooling system that is used mostly in transport type aircraft is?
a) Boot-strap air cooling system
b) Simple air cooling system
c) Simple evaporative cooling system
d) Regenerative air cooling system

Explanation: Boot-strap air cooling system uses a secondary air compressor along with an after cooler for achieving higher pressures of compression and more cooling effect. The cooling turbine replaces the use of cooling fan as well. Hence the air cooling system that is used mostly in transport type aircraft is Boot-strap air cooling system.

6. A Boot-strap air cooling system is used for a transport aircraft to take 10TR of refrigeration load (Q). The power required for the refrigerating system P is 800 KW. What is its COP?
a) 0.06426
b) 0.04375
c) 0.05435
d) 0.04367

Explanation: COP = $$\frac{210×Q}{P×60}$$
COP = $$\frac{210×10}{800×60}$$
= 0.04375.

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