Quote:
Originally Posted by Bicycle Bob
I was fascinated to discover that turboshaft helicopters are heated by air that is bled off from the compressor ahead of the combustion zone. The heat of compression is wasted, but the effect of the combined inefficiencies even that far along are sufficient to produce nice warm air. This is a lighhtweight and technically simple solution to cabin heat, not necessarily, or even likely, an efficient one.
|
If you've flown in a commercial jet or turbuprop aircraft you've experienced pressurization with bleed air. It's passed through an air-to-air heat exchanger to alter the high temperature. Bleed air is used to deice the wing leading edges, pressurize fuel tanks, and other jobs that can be done with pneumatics.
The Boeing 787 is the first commercial aircraft to do away with bleed air to improve compressor efficiency. It removes a heavy, complex and leak-prone duct system to be replaced by new compact, lightweight, high-efficiency HVAC/pressurization systems originally developed for the Space Shuttle.