The document presents a presentation on a boot-strap air cooling system by Ajeet Kumar Saini. It discusses the basic concepts of refrigeration, simple air cooling systems, and boot-strap air cooling systems. The boot-strap system uses two compressors and two heat exchangers to raise the pressure and cool air that is then expanded through a turbine to provide cabin cooling. Diagrams of the system and calculations of required air mass and power are included. Advantages are that air is freely available and disadvantages are that ram air is needed for heat exchange, limiting its use to aircraft in flight.

1. PRESENTATION
ON
“BOOT-STRAP AIR COOLING
SYSTEM”
SUBMITTED BY:
AJEET KUMAR SAINI
Mechanical 3rd year
Section :L , T1
GUIDED BY:
Assistant Professor Mr. Amit Dhiman
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2. Major Concern
Some basic concept
Simple air cooling system
Boot strap air cooling system
 Working diagram
 T-S diagram
 Calculation
 Advantages
 Limitation
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3. SOME BASIC CONCEPT
 REFRIGERATION:
 The term refrigeration may be defined as the process of removing
heat from a substance under controlled conditions.
 It also include the process of reducing heat & maintaining the
temperature of a body below the general temperature of its
surrounding.
 UNIT OF REFRIGERATION:
 Capacity of refrigeration unit is generally defined in ton of
refrigeration. A ton of refrigeration is defined as the quantity of heat
to be removed in order to form one ton (1000kg) of ice at 0c in
24hrs, from liquid water at oc. This is equivalent to 3.5kj/s(3.5kw)
210kj/min.
 REFRIGERANT:
 The refrigerant is a heat carrying medium which during their cycle
in a refrigeration system absorbs heat from a low temperature
system & delivers it to a higher temperature system.
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4. TYPE OF REFRIGERANTS
Primary refrigerants:
 These are the liquids that change from a liquid to a gas
after absorbing heat.(eg. Trichlorofloromethane-
Cl3F2C, Dichlorofloromethane-Cl2F2C, Propylene,
Ammonia etc.)
Secondary refrigerants:
 These are the liquids which acts only as heat carriers
(eg. Brine and Water)
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5. Principle of Refrigeration
 The refrigeration cycle is also known as vapour
compression cycle. The cycle operates at two pressures
high and low, to produces a continuous cooling effect.
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Simple Refrigeration System
Gas turbine
Main comp.
Combustion chamber
Heat exchanger
Cooling fan
Ambient airRam air

7. Explanation of Simple air cooling system
 Ambient air gets rammed before the main compressor.
The air required for refrigeration system is then bled
off from this compressor.
 It is then sent to the heat exchanger where this high
pressure and high temperature air is cooled using ram
air.
 Air is further cooled in the cooling turbine due to its
expansion. The turbine work drives the cooling fan
which draws ram air through the heat exchanger.
 The cooled air from turbine is then sent to the aircraft
cabin.
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8. BOOT-STRAP AIR COOLING
SYSTEM
 The term Bootstrap as used in Air Cycle Refrigeration
indicate a system in which the pressure of the working
fluid is raised in two levels by using two compressors,
before the working fluid which is air, expands in the
turbine section.
 The main component of this system are:
• Two heat exchangers(air cooler and after cooler)
• A secondary compressor, which is driven by the turbine of the
cooling system.
 Application:
• This system is suitable for high speed aircraft, where in the
velocity of the aircraft provides the necessary airflow for the
heat exchangers
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BOOT STRAP AIR COOLING SYSTEM
Copyright Ajeet kumar saini
Gas turbine
Main comp.
First heat
exchanger
Second heat
exchanger
Combustion
chamber
Ambient air
Exit
jet
Exit
jet
Secondary comp. Cooling
turbine
C
Ram air

10. WORKING
 The air bled from the main compressor is first cooled
by the ram air in the first heat exchanger.
 The air is then compressed to a higher pressure and
temperature in the compressor of the cooling turbine.
 A substantial amount of heat of compression is
removed in the secondary heat exchanger and the air is
cooled further as it expands through the turbine
section of the cooling turbine.
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S
1
2 2’
3
3’
4
5
5’
6
7
7’
8
Ambient pressure
Ideal ram pressure
Actual ram pressure
Cabin pressure
Main comp. pressure
Secondary comp. pressure
T7
T7’
T8
T1
T2=T2’
T4
T6
T3
T3’
T5
T5’
T
Cooling in first heat exchanger
Isentropic expansion in
cooling turbine
Cooling in second heat exchanger
Isentropic comp. in 2 comp.

12. EXPLANATION OF T-S DIAGRAM
• Ambient air state 1 is pressurized to state 2 due to the ram
effect
• This air is further compressed to state 3 in the main
compressor
• The air is then cooled to state 4 in the air cooler
• The heat rejected in the air cooler is absorbed by the ram
air at state2
• The air from the air cooler is further compressed from
state 4 to 5 in the secondary compressor
• It is then cooled to state 6 in the after cooler, expanded to
cabin pressure in the cooling turbine and is supplied to
the cabin at a low temperature T7
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13. CALCULATION
 If Q tonnes of refrigeration is the cooling load in the cabin, then
the quantity of air required for the refrigeration purpose will be:
Ma= 210Q/cp(T8-T7’)kg/min
• Power required for the refrigeration system:
P=ma.cp(T3’-T2’)/60 KW
• C.O.P. of the refrigeration system,
=210Q/CP(T3’-T2’) OR 210Q/P60
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14. ADVANTAGES
 The air is easily available and there is no cost of the
refrigerant.
 The air is non-toxic and non-inflammable.
 The leakage of air in small amount is tolerable.
 The air is light in weight per ton of refrigeration.
 The chilled air is directly used for cooling, there by
eliminating the cost of separate evaporator.
 The pressure in the whole system is quite low,
therefore the piping, ducting etc. are quite simple to
design, fabricated and maintain.
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15. LIMITATION
 The basic system will cool the cabin when the airplane
is on the ground.
 The Bootstrap system requires the airplane to be in the
flight so that the ram air can cool the heat exchangers.
 Since the system does not consist of a separate fan for
the driving the air through the heat exchanger, it is not
suitable for ground cooling.
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16. THANK YOU
FOR
WATCHING
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