787 ECS

[EEngr]

I was surprised to hear (although my source might be wrong) that the 'No bleed' 787 ECS system still uses an air cycle pack. Instead of R-134a or other phase change refrigerants. Once you have dedicated pressurization turbines (electrically driven) and an electrically driven pack compressor, why not go to a refrigerant requiring lower mass flow (smaller, lighter plumbing and heat exchangers)?

Anyone have a link to a 787 ECS system description and/or trade study between the two system types?

[easaman]

Here you are!

787 ECS system description (http://www.boeing.com/commercial/aeromagazine/articles/qtr_4_07/article_02_1.html)

Have fun with it!
easaman

[Station Zero]

The bleed air system on the 787 is the CACs.

The air con system pretty much runs like any other bleed air based pack system. The only thing that does happen is that the electric ram fans (instead of being directly driven by the pack) run on the ground with the packs off to ensure PECS cooling is maintained due to their heat exchangers being located in where they are.

[EEngr]

Here you are!

Thanks. But that shows the ECS (Packs) as 'black boxes'. Nothing about what goes on inside.

The air con system pretty much runs like any other bleed air based pack system.

So, still air cycle machines.