PRESENTATIONON

“BOOT-STRAP AIR COOLING SYSTEM”

REFRIGERATION AND AIR CONDITIONING

SUBMITTED BY:HIMANSHI GUPTA (140120119057)/ ME/A2GUIDED BY:PROF. NIMESH GAJJAR

(2161908)

G A N D H I N A G A R I N S T I T U T E O F T E C H N O L O G Y

BOOT-STRAP AIR 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

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

BOOT-STRAP AIR COOLING SYSTEM

• 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

• 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,

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

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

Thank You