View Full Version : Aircraft A/C

01-04-2002, 08:24 PM
I've read somewhere that the aviation industry uses the "bootstrap" method of air conditioning onboard aircraft - can anyone shed some light on this as it is not something I've come across?

01-04-2002, 09:18 PM
Eh up Franky Boy

The Bootstrap principle is a classic example of "energy cannot be made or destroyed"......all sides being equal, if the energy in one kg/m3 of air with a velocity of x and a total energy of x is used to drive a turbine, or a multi-stage turbine (ala plane air con systems), then the total energy will remain constant but, the make-up will alter.

As the air passes through the turbine, frictional losses will occur, but the main 'change' is the temperature of the fluid...yes, air is classed as a fluid! The air gives up its heat during the process but the total energy of the fluid remains constant.

Frank, I'm no expert on this subject.....but heh, you will understand the principles described above (remember thermofluids with Geoff)- even though it might not be described in text book fashion!

In fact, I think I will go away and investigate further - LOL

Mr Frosty

02-04-2002, 03:06 PM

02-04-2002, 09:14 PM

I understand the pictorial and theoretical cycle but how is this incorporated into the aircraft?

02-04-2002, 09:49 PM
Simple Frank....it bolts on using 250 2" BSF bolts and fits just snugly between the ****pit and the wing section...Hee Hee!

Frosty :D

02-04-2002, 09:53 PM
Heh Frank, see that, they've blanked out the co*k in co*kpit....I ask you.....whats the world coming too!!!!!

See you on the 12th for the muther of all boyz night pi*s ups....had to take out an s there Frank - just in case....don't want to upset anybody!!


02-04-2002, 10:48 PM
LOL, its an automated thing on the forum, nothing to do with the moderators :D

03-04-2002, 08:06 PM

In other words - YOU DON'T HAVE A -UC-IN- CLUE - (edited by me!) do you.

Seems such a simple question really.

Looking forward to the glorious 12th!!

05-04-2002, 03:55 PM
WOW! we cant even say ****pit?? That is a darn shame!
Thanks for the info about the airplane a/c guys! I woulda never thunk it!


24-01-2010, 03:30 PM
Aircraft use what is call an Air cycle system. usully two or three systems per aircraft each is refered to as a "PAC"

Air is bled from the engines or APU. The air is at about 40 PSIG and due to the heat of compression the temp is about 250F The air enters the "PAC" and flows through a primary heat exchanger (air to air) depending on the altitude the air temp is dropped about 100 deg or so the pressure drops by about 2-3 PSIG. The air then enters a centrifugal compressor with about a 2-1 pressure ratio. the pressure rises to about 70 PSI gauge and the temp rises to about 270 F. the air then passes through a secondary heat exchanger dropping the temp again by about 100 deg F. the air then inters a radial inflow turbine that is driving the compressor and also all the fans that force air over the heat exchangers. The air exiting the turbine is controlled to about 35 deg F. The air is supersaturated with moisture and early systems used collessor bags to force condensation, the condensate is piped to spray on the heat exchangers to improve performance. The air temp is trimmed using bypass hot air and the resulting pressure is enough to both heat-cool and pressurize the aircraft.

Each system is about 200,000 BTU

The latest aircraft (B-787) use an electrically driven compressor to provide the initial air. This is due to the fact that it is more expensive (power) to bleed the engines than pull the same amount of electrical power.