All the grainy photos or bad sketches I've seen show a rotating circular disk that somehow picks up heat from exhaust gases and transfers it to the compressed air before combustion -- all kinds of seals that don't work, etc.
Why not just use a counter flow heat exchanger?
Bret Cahill
The disk is made like the core of a catalytic converter, without the catalyst. Gas flows through many channels in parallel and exchanges heat with the solid material, which is physically transported between hot and cold gas channels.
The leak paths across the face of the disk are relatively long, so the 'seals' can be just small clearances.
-Mike-
I haven't seen any with rotating equipment. Do you have an example? Is it maybe due to the distinction in english between 'recuperator' (involving heat storage) and 'regenerator' (operating continuously)?
They use any word to mean anything.
Bret Cahill
BretCahill said the following on 12/15/2004 8:15 PM:
You're viewing a rotary heat exchanger or maybe a Ljungstrum air preheater:
I will venture to guess that these types of HEX's are preferred for utility plants for the following reasons:
- pressure drop is almost nothing. This decreases the power requirements for fans that are about the size of a small house. - heat transfer efficiency is inherently higher than tubular HEX's. This results in smaller overall size (and cost). - simpler design and maintenance resulting in lower costs. - Who cares if a little cold air leaks into the flue gas? This cools down the flue gas and reduces the power requirements of the induced-draft fan.
Lance
*****Lance said the following on 12/16/2004 8:02 AM:
I feel stupid. Soon as I hit SEND, I see your question is specific to small gas turbines. Maybe some of the reasons for big boilers apply to gas turbines too.
Lance
*****
Same thing except the feed air is compressed in GT which makes leakage much more of a problem, even ignoring economies of scale.
Steam turbines provided the initial analytical framework for the turbines in gas turbines. I'm guessing steam power is where they got the regenerator idea too.
Funny how much people need to operate from something that is already established, even if it isn't the best way to do something -- kind of like judges not wanting to establish a new precedent.
I get stuck in my ways myself sometimes.
Bret Cahill
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