Frans,
I have a one off custom FWF that uses the stock engine mount, water rad
iator and oil cooler (located one behind the other which in many aspects
is close to what you have done). I had a very similar experience to yo
urs in that I conducted my first flight in January when temps were mild
and as summer approached I ran into major cooling issues just as you des
cribed. I do not believe dropping the oil cooler will do anything for y
ou if your design is like mine in that it is properly sealed around the
inlet of the water radiator. Because my water radiator and oil cooler a
re in line I have sealed the space between them on the top. The sides a
nd bottom are sealed around the sides of the cowling. I will try and po
st a picture of this. Anyway, what Rob states below about heat transfer
is spot on. You need to look at it as a system. In addition the oil a
nd water dog house which measures 2.375" x 7.375" at the inlet, my init
ial design had two very small round openings (2" diameter) in a location
close to the stock cowling.
Like Kevin I am able to climb out at high power settings (usually 31" MP
) to the high teens without issue so long as I don't go slower than 90 K
IAS. This limits the nose high attitude. Any slower and I will start t
o overheat. BTW I live in Las Vegas, NV and we have been know to have a
warm day every now and then. Yesterday we hit 108 deg F.
This is what I did to solve my cooling problem which was pretty straight
forward: I enlarged the 2" diameter holes to create a horizontal teardr
op. The extra air flowing over the top of the engine was sufficient to
keep it cool both on the ground and during climb. I also use Evans cool
ing which did increase my temps by about 10 degrees C over 50/50 water &
antifreeze but provides a higher boiling point. I was initially tempte
d to lower the oil cooler, however, this would have been a major modific
ation with my design, so that was out and it was doubtful from a system
perspective if this would have really helped. It is another matter if I
had the stock Europa cowling since there is a large gap at the bottom o
f the cowl and lowering the oil cooler fills this space preventing the a
ir from bypassing around the radiator and oil cooler. I didn't have thi
s issue with my design as noted above. So, two options were left, incre
ase the size of the oil cooler and radiator, or open up the round holes
to provide more flow over and around the engine. The latter was the eas
iest to option and worked out well for me. My guess though is that a la
rger radiator and oil cooler, retaining my original 2" holes would resul
t is the least drag option. Keep in mind I am near red line during clim
b usually around 125 deg C. on oil temp which leads CHT. I hope the ab
ove is helpful.
Good luck.
Erich Trombley
N28ET Classic Mono 914
From: "Rob Housman" <europa@hyperion-ef.com>
Subject: RE: Europa-List: Cooling issues, once again!
While it is true that "heat transfer is directly proportional to tempera
ture
difference" that does not tell the whole story. First, remember that th
e
relevant temperature difference is the difference between the temperatur
e of
the fluid on the inside and the air on the outside, and even with pre-he
ated
air the second radiator could have the same delta T as the first radiato
r.
I'll grant you that there is probably a difference, however.
Also relevant, and non-trivial, are the area of the heat transfer surfac
e,
the flow rate of the liquids inside the heat exchangers (radiators, in
common aircraft and automotive parlance), the flow rate of the air outsi
de
these heat exchangers, the heat transfer coefficients for each of the fl
uids
involved, the heat transfer coefficients of the materials from which the
radiators are made, the effect of any scale or similar deposits on the h
eat
transfer surfaces (both inside and outside), Reynolds numbers for the
flowing fluids (a function of flow rates and fluid properties), and the
physical properties the radiators and of the coolant and oil flowing wit
hin
the heat exchangers.
Having said all of that, there is no doubt that "re-using" the cooling a
ir
will affect heat transfer within the radiator using pre-heated air, and
this
is undoubtedly why Europa recommend placing one below the other.
Best regards,
Rob Housman
Irvine, CA
Europa XS Tri-Gear
A070
Airframe complete
From: owner-europa-list-server@matronics.com
[mailto:owner-europa-list-server@matronics.com] On Behalf Of Robert Borg
er
Sent: Saturday, June 05, 2010 11:02 AM
Subject: Re: Europa-List: Cooling issues, once again!
Paul,
I don't see how it can. Simple thermodynamics is against it. Heat tran
sfer
is directly proportional to temperature difference. Both radiators are
at
about the same temperature. Once the air has been heated by the first
radiator its ability to accept heat from the second has been greatly red
uced
if not eliminated.
And this is assuming that the area below the radiators has been sealed s
o
that the air goes through the radiators and not under them, doing no goo
d at
all.
Check six,
Bob Borger
http://www.europaowners.org/N914XL
Europa XS, Short Wing, Intercooled Rotax 914
rlborger@mac.com
Cel: 817-992-1117
On Jun 5, 2010, at 11:43 AM, Paul McAllister wrote:
Hi All,
I am curious to know if there are any examples of standard XS cooling se
t
up's that do not have the oil radiator lowered that work fine.
Thanks, Paul
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