hi ben,
the design is only based on my old university course

and is theoritical ..... I did it in 15 min ....... so only ideas .....
I saw one with a cone at the center but fins was not curved ...... if it's yours, yes it has inspired this one
You are right, the channels should be circular in order to start the circular movement as well as increase the surface contact.
The angle of the fins should also be adapted, I was inspired by a fan and a pump, but again, it's a starting point.
As I said, I'm brand new to this

and I'm looking for friend who can help me mill it, I've no milling machine but can find someone.
I will mill it (try

) as soon as I can. I'm in holiday for 1 week and after a redesign with more concrete data (should take 3-4 days to calculate.
I've a friend who has access to thermodynamic simulation software (Catia) and I will ask him to do simulation .......
and of course, yes, I'm ready to collaborate .......

but remember I'm brand new to that