Yes, I did consider tilting the front end down Vs up but what I remember is there becomes an interference with the 90 degree 1.5 inch hose connections into the radiator as they get up against the engine and mount ... it looks better from the "French curve" diffuser aspect ... the drawing isn't to scale either so there is also a limit to the down-tilt before the cowling gets really ugly.
Jeff

-----Original Message-----
From: Jeff Whaley
Sent: July-31-18 8:35 AM
To: 'Rotary motors in aircraft'
Subject: RE: Using Fluidyne oil coolers as Primary Radiator

Charlie I agree with your analysis as interpreted from the drawing sent ... however it's not a surface doubling it's actually 210 total sq inches placed in a Vee (105 each half) Vs 247 total sq in placed in a slanted position. Yes in application there should be flow dividers to prevent all the air piling up at the back 3RD of VEE - I have done that leaf blower experiment with a couple of heater cores ... For the slanted single core it is also difficult to get air through the front half, combined with the fact that an engine/oil pan is parked on top.

I will elaborate more: the air flow through the Vee has to make one "S" bend to pass through the cooler and exit the cowling, whereas with a slanted-up single radiator the air has to make one "S" bend to pass through the core and another "S" bend to make its way around the firewall and exit under the airframe, so from an airflow perspective the Vee is more efficient - as I see it.

A concern is the flow rate through the two types of cores - I don't know the difference between a radiator core Vs an oil cooler core from the perspective of internal construction.  Are 0.75 inch lines large enough to flow enough coolant? There reason for consideration is the oil coolers are of the appropriate size and shape with AN fittings incorporated - though they each cost as much as one big radiator.

Jeff



1st, let me say, 'I don't know'. :-)

Having said that....

If you're doubling the face area vs a single cooler perpendicular to the duct, then it will probably cool a bit better, but nowhere near twice as good. If you're feeding that configuration from a straight duct, my money would be on most of the flow being through the last third of each cooler. It looks like basically a two sided wedge, and I can say from experience that a wedge diffuser will do what I described, unless the downstream end is pinched down so it almost touches the face of the cooler. Perhaps a flow divider (more or less a diamond shape) to supply the pinch effect would balance the flow.

It's easy enough to see the effect. Get a couple of junk coolers (anything would do to test, as long as they're the same cooler). Mount them in a cardboard duct using (wait for it...) duct tape, and feed it air using your leaf blower. Tie a thread (yard works better; it's lighter for it's cross section) to a thin stick, and move it around the exit faces. You'll quickly see where the air is moving through the cores (and where it's not).

Charlie