Damit Tracy, don't get me started thinking about this = :-) Has=20 anyone tried using one of these for oil yet? Certainly = the=20 pressure should be OK. Arrrrrgh...

Rusty (not flying again soon, but certainly before = Tracy's=20 RV-8 <g>)

I am using one for an oil cooler, mounted up in the nose = cowl. I=20 have not yet flown, but cooled great on ground run ups. Never went = over=20 180 in the pan even when water temp went to = 230.

Lonnie

Sorry to stir the pot Rusty! But, Glad to = hear the evap=20 core is working well on the ground for oil cooling = Lonnie. The=20 main reason I want to use one is for the more efficient use of=20 the dynamic pressure available at flight speeds. = The=20 stock coolers work well but I think they require more CFM to = do the=20 job. Minimizing cooling drag (as many of you are = tired=20 of hearing me preach : ) is largely a mater of minimizing CFM used = to do=20 the job.

When I get the time, I want to correlate the = excellent data=20 that Ed has been sharing with how I think cooling drag=20 works. Some of it is = counterintuitive. =20 For example, minimizing aircraft cooling drag can often = mean increasing the turbulence = (drag) through the=20 heat exchanger.

Tracy Crook

I'll be=20 interested to hear your theories, Tracy. For one thing it = appears=20 that once you trip the boundary layer into turbulent flow, you = have=20 encountered 75-80% of the drag you are going to encounter. = Adding=20 more inches after that point does little to increase drag = further. =20 Drag is proportional to frontal area as we all know, so that would = also=20 support the thicker (rather than larger) is better for cooling (in = our=20 application where we do have higher dynamic pressure to work for=20 us).

Also my=20 calculations indicates that the evaporator core has much less drag = than=20 one might think based on its thickness. Most heat exchangers of = the type=20 used as radiators have a openness ratio of around .70 - 75 while = my=20 measures and calculations shows the GM cores has an openness ratio = of=20 around 0.81 further indicating less air = resistance.

If you think=20 about it, it makes sense there would not be much resistance to air = flow in=20 the core as it has a puny electric motor in the car to force = air=20 through it, so it is undoubtedly designed not to have much air=20 resistance.

So I wanna'=20 hear your story

Ed=20 = Anderson