The dodge 1500 truck rad core is 31 5/8" x 19 3/16" x 1", wouldn't
that give around 600 cubic inches? Or will that be doubled by having 2
of them in the cross counterflow? The newsletter reply below is showing
465 cubic inches for that rad,did I pick the correct rad measurements?
Trying to size a rad to fit the cowl of p-port rx8. Laying down vs
upright on the cool side of cowl.
https://www.radiatorexpress.com/product.asp?part=2001+DODGE+RAM+1500+PICKUP++-+5%2E9+liter+V8+RADIATOR+STOCK+REPLACEMENT%2C+31+X+19+CORE&part_id=218342&aaia_id=1366590
The oil cooler we have is CXRacing with core of 13" x 9" x 2" which
is only 198 cubicinch. I read an old reply from Neil Unger that around
300 cubic inch for 250hp is good for oil cooling?
http://www.cxracing.com/mm5/merchant.mvc?Screen=PROD&Store_Code=CXR&Product_Code=OC-248-30-AN10&Category_Code=OILC
-Matt Boiteau
- Matt
On Sat, Jul 18, 2015 at 4:05 PM, paul lamar
<
rotaryeng@earthlink.net <mailto:rotaryeng@earthlink.net>
<
mailto:rotaryeng@earthlink.net <mailto:rotaryeng@earthlink.net>>> wrote:
Cross counter flow is a more effective heat exchanger.
Here is the sequence for welding the rads to make a cross counter
flow heat exchangers.
Butt tig weld the in and out tanks first by cutting off all tabs on
the rads.
Don't weld the in and out tubes on yet.
They will be marked for position on the tanks while on the
aircraft.
Then the large holes for the tubes will be cut and then the tubes
will be welded over the holes. The tank design will vary
depending on
cool side mounting or bottom mounting. The TTC is a bottom mount.
Most other aircraft use a cool side mount. The 3 rotor allows
longer
rads to be used. Put the diffuser between the rads and the engine.
See my book How to Cool your Wankel for more info.
After the tanks are done (with out the holes and tubes) bolt the
rads together with the wood strips leaving 1/2 to 3/8 of an inch
between in and out tanks.
The idea here they must not touch each other. The wood strips are
heat insulators between the two rads.
Then weld an aluminium strip 1/2" to 3/8" wide at the other end.
Finish by boxing in the other end (the front end).
Weld on them some and let the rads cool some what. They are brazed
together at only 1100 F so it is important to not get them too hot.
Wet rags around the ends of the fins and tubes might help.
Here are a bunch of pictures attached. The JPGs were Dodge Neon
rads
and not the truck rads. The TTC rads will be welded soon.
Apparently when Mercedes owned Chrysler they implemented some up to
date heat exchanger technology. IMHO Chrysler rads are now the best
from an efficiency point of view I have found so far. Honda
also uses
up to date tech but they are more expensive.
Paul Lamar
What about a dual pass rad already done?
http://www.jegs.com/i/Allstar-Performance/049/ALL30048/10002/-1
-Matt Boiteau
It will probably work but you will be paying a weight and drag
penalty.
I don't know how much on the drag penalty. We don't have any
comparison data
on the drag yet. The weight of the core with water will be at least
150% of the cross counter flow Dodge truck rads.
Paul Lamar
For maximum efficiency, you don't want to use the flow pattern
described in
their (Allstar's) text, use the pattern from Paul's book. The
top core (or first core
exposed to cooling air) is the second core the coolant flows
through.
This better utilizes the Delta/T thermal transfer to the
cooling air flow. Read Paul's
book for counter cross flow cooling theory.
C. Smith
Craig, can you send me that Allstar text. I found their web
site but I can't find anything
about that. Apparently they use two rows of one inch tubes .
The Dodge truck rad is one
row of .7 inch tubes.
http://www.allstarperformance.com/instructions.htm
In theory one could cut the All Star rad apart into a top and
bottom for a cross counter flow
reconfiguration. That would give more core volume if two Dodge
truck cores were
not enough core volume . Slightly less efficient however.
The basic idea is you want as large a frontal area you can fit
in the cowling with core
volume of about 500 inches. The Dodge truck core are about 465
cubic
inches and will probably work with 250 HP. We now have about
930 cubic inches
in the time to climb rad which I am guessing will be good for
about 500 HP.
I suspect the time to climb cross counter flow rad is not
enough core volume for 650 HP and
we will have to spray cold water on the assembly.
We used to think we needed 650 cubic inches for 250 HP and that
was before we discovered
the the much improved Kays & London wedge diffuser.
Ian in Perth Oz did some experimenting with a Kays & London S
shape diffuser lying
on it side and was able to reduce the size of the air intake to
10 to 15%
of the core frontal area. That, in theory, reduces the cooling
drag. Ian routinely flies
around the outback.
Ian has built two RV6's powered by rotaries. The first one
crashed when a hose
blew off a rad with out a bead on one of the tubing ports.
Paul Lamar
Do we have any more pictures of Ian in Perth Oz, S shape diffuser
lying on it side ?
-Matt Boiteau
None with the cowl off.
Paul Lamar
The problem with dual and triple pass radiators is that they use the
same air temperature across the entire surface. Coolant flow rate
will be high which is good for turbulent flow unless they use a double
or triple core. The cross counter flow lets the coolant spread out
across the entire surface area in a single row radiator. Then turns
after one pass and returns through the second core. The hot coolant
in the first core is cooled by warm air used to cool the cooler coolant
in the second core. Same "frontal" and surface area as a single radiator
with a two row core but should give a higher delta T. Should provide
better cooling in marginal operating conditions. For space constraints
where the thickness would not pose a problem you could build a three
pass cross counter flow.
Dale Davies
The coldest air goes through the coolest core first. That maximises the
average temperature differences to maximise the efficiency of
the heat exchanger. Heat transfer rate is directly proportional
to average temperature difference. All this is covered in my book How
to Cool
Your Wankel.
Dale please add your new message to the bottom of the forwarded message.
Like this. Make it look like this message.
Paul Lamar
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