Question on Bleed air
Since there are some smart people who frequent this section of the website I have a question that I have yet to be answered. The question is regarding bleed air.
Obviously through the process of compression, air drawn in the intake of a turbine engine is heated as it's volume is reduced. In the Blackhawk helicopter, we don't have air cycle machines and the air is used for cabin heat and engine/engine inlet anti-ice. The air for cabin heat is mixed with outside air before it is released into the cabin. All our manuals state that the air is warm because it is compressed. Obviously, within a second of entering our nonpressurized cabin, it is no longer compressed. Simple adiabatic heating and cooling would render the air the same temperature that it was prior to entering the engine inlet. I know that friction is also at play in this heating, but my question is: Is the net increase in temperature of air released in the cabin of a Blackhawk (unpressurized) simply due to the friction of the air in the compressor section or is there some other force at play as well?
Anyone care to take a crack at it??
Thanks in advance