|
|
I think the "Flat Plate" type radiator comes closer to what the majority of us are using including the evaporator cores than you might think. The tube and fin type like some of the auto transmission and oil coolers use are a different beast. A lot of the cheaper tube and find type are simply one long serpentine tube with fins attached which is bound to cause the DeltaT factor to suffer. Some of the better one have multiple tubes between two side tanks.
My GM cores has about 14 channels approx 1/8" thick that channel coolant between the two side tanks. These look more like plates to me - than tubes. The louver fins on the GM core are suppose to be the best practical fin configuration for heat transfer. So I think the heat transfer is undoubtedly better and suspect the drag is also higher than the finless flat plate type.
So while its beyond my capability to prove it, I think there is more correlation between the Naca study on thick cores and our cores than you might first think. Besides, there graphs of data shows extrapolation of cores only 4" thick, which puts it closer than the 9-16" mentioned in the text. So the only major difference I see is ours have fins and the one's in their stuff did not. Would this enhance or degrade the effects they measured?
I think our cores would have enhanced heat transfer and increase core drag compared to the study - but, I readily admit just speculation on my part.
Ed
----- Original Message ----- From: "Ron Springer" <ron2369@sbcglobal.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Sunday, November 25, 2007 2:42 AM
Subject: [FlyRotary] Re: what are they
I am just a radiator novice, but all radiators that I
have any experience with have had straight passages
from front to back between fins. When that is the
case, most books and reports use flat plate drag
equations to determine the skin friction and heat
transfer as a first cut. Now if a flat plate radiator
is a radiator where flat plate drag equations can be
used, then I guess I haven't seen a radiator that
isn't one.
Actually, I take that back. The A/C condenser on my
car has taken so many rock hits that the leading edge
of many of the fins are badly bent. I guess some new
equations will be needed!
Ron
--- Ed Klepeis <techwelding@comcast.net> wrote:
Dear Tracy
I'm with you what are these special flat
plate rads. I have built many systems but haven't
come across these flat plate rads. I will stand
corrected if someone comes up with something. I
think what everyone is talking about is a flat plate
cooler that is put in the bottom tank on rads to
cool trans fluid. I think fluidyne is using them as
oil to water oil coolers. I looked into that but
didn't like the sealing system they used around the
oil inlet/outlet good enough for cars but not safe
for aircraft. If anyone has anything to add to this
I would be happy to hear about it.
Regards
Ed Klepeis
--
Homepage: http://www.flyrotary.com/
Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.html
|
|