Boot-strap air cooling system

sample presentation

1. PRESENTATION ON “BOOT-STRAP AIR COOLING SYSTEM” SUBMITTED BY: AJEET KUMAR SAINI Mechanical 3 rd year Section :L , T1 GUIDED BY: Assistant Professor Mr. Amit Dhiman 24/02/2018 1 Copyright Ajeet kumar saini

2. Major Concern Some basic concept Simple air cooling system Boot strap air cooling system Working diagram T-S diagram Calculation Advantages Limitation 24/02/2018 Copyright Ajeet kumar saini 2

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. 24/02/2018 3 Copyright Ajeet kumar saini

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) 24/02/2018 4 Copyright Ajeet kumar saini

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. 24/02/2018 5 Copyright Ajeet kumar saini

6. 24/02/2018 Copyright Ajeet kumar saini 6 Simple Refrigeration System Gas turbine Main comp. Combustion chamber Hea t exchanger Cooling fan Ambient air Ram 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. 24/02/2018 Copyright Ajeet kumar saini 7

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 24/02/2018 8 Copyright Ajeet kumar saini

9. 24/02/2018 Copyright Ajeet kumar saini 9 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. 24/02/2018 10 Copyright Ajeet kumar saini

11. 24/02/2018 Copyright Ajeet kumar saini 11 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 ’ T 5 T 5 ’ 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 24/02/2018 12 Copyright Ajeet kumar saini

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 24/02/2018 Copyright Ajeet kumar saini 13

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. 24/02/2018 14 Copyright Ajeet kumar saini

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. 24/02/2018 15 Copyright Ajeet kumar saini

16. THANK YOU FOR WATCHING 24/02/2018 16 Copyright Ajeet kumar saini