refrigeration and air conditioning

1. PRESENTATION
ON
“BOOT-STRAP
AIR COOLING SYSTEM”
REFRIGERATION AND AIR CONDITIONING
SUBMITTED BY:
HIMANSHI GUPTA (140120119057)/ ME/A2
GUIDED BY:
PROF. NIMESH GAJJAR
(2161908)
GANDHINAGAR INSTITUTE OF TECHNOLOGY

2. BOOT-STRAPAIR COOLING SYSTEM
 The term Bootstrap as used in Air Cycle Refrigeration
indicates 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 components 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

3. 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

4. BOOT-STRAPAIR COOLING SYSTEM

5. • 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 state 2
• The air from the air cooler is further
compressed from state 4 to state 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
T-s diagram for a boot-strap
air cooling system

6. • If Q tonnes of refrigeration is the cooling load in the cabin, then the
quantity of air required for the refrigeration purpose will be
• Power required for the refrigeration system,
• C.O.P. of the refrigerating system,

7. 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 amounts is tolerable
• The air is light in weight per tonne 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,
fabricate and maintain

8. LIMITATIONS
• The basic system will cool the cabin when the airplane
is on the ground
• The Bootstrap system requires the airplane to be in
flight so that the ram air can cool the heat exchangers
• Since the system does not consist of a separate fan for
driving the air through the heat exchangers, it is not
suitable for ground cooling

9. Thank You 