| Bill,
Since Charlie hasn't posted any pictures or sketches of his design, I was referencing more what you'll find in auto installations than in a/c. Still the principles are the same, namely that the coolant naturally flows to the bottom and air goes to the top. If it gets low enough, the pump will begin sucking air and will soon loose prime. This will happen much quicker if you're drawing off the upper tank. Of course, if the radiator is located below the engine it will take longer for this to happen than if it is beside the engine because the air pocket will be inside the engine rather than in the radiator. If you have a coolant leak in flight, you'll benefit from more time to get on the ground rather than less.
I don't see where it makes any difference which tank you return the coolant to, but when supplying the pump, any air will risk loss of prime. So, it makes sense to me to draw from the bottom and return to the top. At least that's how I understand it.
In the end its Charlie's decision.
Mark On Mon, Oct 22, 2012 at 11:10 PM, Bill Schertz <wschertz@comcast.net> wrote:
I guess that I don’t understand this (Mark’s) comment. I am assuming that
the radiator is lower than the water pump in any circumstance, since in general
it is either below the engine, or on the side like Tracy’s. The Mazda pump is
very high, and any loss of coolant will cause loss of prime if air gets in the
pump, but whether the outlet of the pump goes to the bottom of the radiator, or
the top, I don’t see the difference. What am I missing?
Bill
Schertz
KIS Cruiser #4045
N343BS
Phase one testing Completed
Sent: Monday, October 22, 2012 6:25 PM
Subject: [FlyRotary] Re: flow path in conventional
radiator
Charlie,
So, with the bottom-up flow what what happens if you get a little low on
coolant? My guess is the pump will start pumping air along with the
coolant, and eventually loose prime altogether and the remaining coolant will
stop flowing, followed shortly by a catastrophic boil-over. This may be
why auto makers favor the top-down flow design. The Mazda's water pump is
already very high up on the engine. I wouldn't want to aggravate this even
more. Also, the cross-flow design doesn't suffer this failure mode,
assuming you draw from the lower hole.
Mark S.
On Mon, Oct 22, 2012 at 2:05 PM, Bill Schertz <wschertz@comcast.net> wrote:
Charlie, I am using two evap cores in parallel, with system pressure
limited to 10 psi on the expansion bottle. When the engine is running, the
pressure measured at the inlet to the cores (exit of the pump) is a function
of RPM and can rise to as much as 20 psi (10 psi over system pressure in the
expansion bottle).
Having the flow enter the bottom of the radiator and out the top, then
going to the inlet of the pump sounds like a good way to avoid problems.
Bill Schertz
KIS Cruiser
#4045
N343BS
Phase one testing Completed
Sent: Monday, October 22, 2012 1:06 PM
Subject: [FlyRotary] Re: flow path in conventional
radiator
Unless there is a serious restriction through the radiator
I can't imagine there would be anything greater then 1 psi over system
pressure caused by pump output. As for the reverse flow, ie, bottom to
top,,, It's called counter flow, and yes it can work. My set up has worked
flawlessly for 500 hours and I use the Moroso swirl / pressure tank and a air
bleed line from the output of the radiator... About 3 minutes into this
video shows my set up..... http://www.youtube.com/watch?v=rCNnEgRkdXc&context=C3e091d3ADOEgsToPDskKmHo69I6bUDuoBHd5YSUfu
Ben Haaswww.haaspowerair.com
To: flyrotary@lancaironline.netDate: Mon, 22 Oct 2012
12:40:11 -0500 From: ceengland7@gmail.comSubject: [FlyRotary] flow path in
conventional radiator I've been doing research on radiators, & my 1st 'experiment' will be a conventionally configured radiator (downflow design) with inlet
& pressure cap on top. In reading about issues with conventional
radiators, a common complaint is pressure venting due to the
water pump + system pressure exceeding the cap's
rating. Crossflow types like the Sirocco are supposed to avoid this because the cap is at the mid-point
in the flow through the rad, which drops some of the pressure
seen by the cap.
Here's my question: Is
there any reason a conventional rad can't be fed from the
bottom, instead of the top? This would achieve
similar effect as the crossflow cap location (all the way to the
end of the flow path) & any air could be vented using the
existing fittings. I'm also considering the removal of the spring loaded seal, & moving the pressure cap
function to a separate swirl can. By doing this, the existing over-pressure port could function as
the air removal port in the top tank of the radiator.
What am I missing?
Thanks,
Charlie
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