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"no matter which leg of the coolant system
you pick up the heat from the oil cooler, you raise the temp of the coolant
loop by the amount of additional heat; so the rejection temp of the rad is
higher either way."
Not so fast! Here's my take on it.
Yes, the total heat rejection of the rad has to end up being the same. BUT with the cold side oil cooler, to keep the engine coolant inlet temperature (and temperature of the engine block) the same requires a 33% larger rad (compared to what we needed a separate air to oil cooler). Actually, the rad has to be even bigger than this because we have to have the rad outlet temp even lower to compensate for the rise in coolant temp due to temp rise of oil cooler. That means the median temp of the rad is lower and therefore less efficient.
If you cool the oil on the hot side of the coolant circuit, the inlet temp of the rad is now higher than in the cold side scheme and the required rad size and/or the airflow through the rad size increase is smaller due to the higher delta T between air and rad. This results in less cooling drag.
That's my story & I'm stick'n to it : )
Tracy
On Sun, Dec 19, 2010 at 12:13 PM, Al Gietzen <ALVentures@cox.net> wrote:
For
maximum cooling of the oil from an oil/water HX (heat exchanger) you’ll
want to plumb the oil from engine out to the cooler; and plumb the cooler
between the radiator and the engine return. And I’m not quite sure
about Tracy’s point because no matter which leg of the coolant system
you pick up the heat from the oil cooler, you raise the temp of the coolant
loop by the amount of additional heat; so the rejection temp of the rad is
higher either way. The assumption is, of course, that you have sufficient
capacity to keep the coolant exiting the engine below boiling for extended high
power.
On
my Velocity 20B installation I have a primary radiator in the cowl, and a
secondary in the wing root; plumbed in parallel. The wing root rad has an
in-line 170F thermostat, and generally only comes on line during extended climb.
No thermostat in the engine that would restrict flow and add a potential failure
mode.
I
have an oil/air cooler and an oil/coolant HX, also plumbed in parallel. The
oil/coolant HX is plumbed to the exit of the primary rad. The oil temp
runs about 20F higher than the coolant (measured at oil return and coolant
out). I could probably reduce that difference by restricting flow to the
oil/air cooler forcing more through the oil/coolant HX; but I’m quite
happy with the way things work.
Over
200 hours and lovin’ my rotary more all the time.
Al G
----- Forwarded Message ----
From:
"CozyGirrrl@aol.com" <CozyGirrrl@aol.com>
To: keltro@att.net
Sent: Mon, December
13, 2010 4:05:31 PM
Subject: Re: Fw: [FlyRotary] Re:
Fw: Water temps
Thanks Tracy for the adjustment in
my thinking. I don't want to target temps unrealistically.
Where
does that leave us with our pick up and return points for the oil/water cooling
system? If the oil were being cooled with water only and we wanted the best
possible chance at that, wouldn't we want to feed it the cooler water from the
high pressure side of the pump prior to entering the block?
Whatever
space we would use for an oil/air cooler takes away from potential coolant
radiator space. Putting the two side by side becomes less efficient spacewise
for both due to losses for structure etc. If it is not possible to cool the oil
adequately with water alone then we'll need to back up a little and make other
layout plans. I remember Richter's Cozy III with three P-51 scoops, it got the
job done but was like dragging a parachute in drag.
Kelly,
to your comment below, while I am sure we'd have no problem putting adequate
heat into the oil, I am very concerned about keeping any more than just enough
out of it. Much easier going one way then the other =)
In a
message dated 12/13/2010 2:49:02 P.M. Central Standard Time, keltro@att.net writes:
My own opinion is that after warm up and in flight the oil temp leaving the
engine before the
coolers
(air or water to oil) will almost always be well above
160-180 F..............If it is not this
high
then the oil to water cooler will actually help warm it to a more
efficient temp.........IMHO
Somebody correct me if this is a fallacy !!.......................<:)
Kelly Troyer
"DYKE DELTA
JD2" (Eventually)
"13B ROTARY"_
Engine
"RWS"_RD1C/EC2/EM2
"MISTRAL"_Backplate/Oil Manifold
"TURBONETICS"_TO4E50
Turbo
From: "CozyGirrrl@aol.com" <CozyGirrrl@aol.com>
To: keltro@att.net
Sent: Mon, December 13, 2010 12:52:06 PM
Subject: Re: Fw: [FlyRotary] Re:
Fw: Water temps
This is
where I get confused:
-ideal
water temp = 160*~180*F
If we
are cooling oil with water that is at best hotter than the ideal temp of the
oil, then are we not adding heat to it rather than removing it?
If we
are trying to cool oil, why would we feed the highest temp water to the
oil/water cooler rather than the coolest temp water by tapping into the pump
housing where it enters the block?
Based
on feedback, the water entering the block may be as low as 150*~160*F, would
this be cool enough to do an adequate job of cooling the oil?
Also,
which model of Mocal is being used?
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