REFLECTOR: High Oil Temps
steve korney
s_korney at hotmail.com
Sun Jun 23 22:09:52 CDT 2013
It will take about 8 square inches of inlet to get enough air to each oil cooler at 150 knots...
Steve
Date: Sun, 23 Jun 2013 21:35:47 -0500
From: michalk at awpi.com
To: reflector at tvbf.org
Subject: Re: REFLECTOR: High Oil Temps
They are the stock coolers, about 4.5"
x 6" face area. The inlet duct is not a real NACA scoop. I
extended the face of the cooler to the skin of the plane. Once I
have enough hours, I will experiment with closing down the aft lip
of the inlet, making a diverging duct.
I've already closed down my armpit scoops a little based upon oil
flows on the fuselage. I have variable armpit scoops, but at the
moment they are only ground adjustable.
On 06/23/2013 09:29 PM, steve korney wrote:
Hey
Brian...how big are the oil coolers and how much inlet scoop
area do you have...?
Steve
> Date: Sun, 23 Jun 2013 17:42:44 -0500
> From: michalk at awpi.com
> To: reflector at tvbf.org
> Subject: REFLECTOR: High Oil Temps
>
> Today I had a very good test flight.
>
> I've been battling high CHT and oil temps, and made the
decision to
> increase my prop pitch for todays flight to bring down
RPM's. That made
> a marked difference in CHT temps, and I could fly without
redlining the
> CHT's.
>
> Now, I still have high oil temps. My oil cooler
arrangement is two oil
> coolers in the nose in parallel. The secondary cooler has
a radiator
> fan attached with a flapper valve that doubles for ground
operations and
> cabin heat. Needless to say, the fan doesn't do a very
good job, and I
> think is the source of my high oil temps.
> For this thought game, assume two identical oil coolers
with equal oil
> flow in parallel. This means that each cooler gets 50% of
the oil.
> Now, assume no cooling air flows through one of the
coolers. The result
> is that half the oil is cooled, and the other half gets
returned at the
> same temperature it began. The result is that I get 50%
of the cooling
> that's available.
>
> What I've done in the meantime is I've capped off my
second cooler. I
> have not flown with this configuration, and will do so
this coming
> weekend. I really do think this will get me within the
temperature
> ranges to get around to some serious flight testing.
>
> Now, the real question:
> Given two identical coolers that flow equal parts oil,
and also have
> equal amounts of airflow, is it better to plumb them in
series or in
> parallel for maximum heat rejection? It seems to me that
parallel is
> like having more frontal cooler area, while in series
would be like
> having a thicker cooler, with the larger frontal area
being the more
> efficient design.
>
> Does anyone have any info on this?
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