REFLECTOR: High Oil Temps

Brian Michalk michalk at awpi.com
Mon Jun 24 12:57:51 CDT 2013


What would happen if you just vented into the engine compartment?

On 6/24/2013 9:52 AM, Brent Bourgeois wrote:
> I did lots of measuring in flight and found inlet area is not nearly 
> as important as exit area. Most have way to much inlet and the largest 
> portion of the air never makes it through the cooler. I was never 
> successful cramming more air in the cooler and achieved  real good 
> results sucking it out. ( that's for cylinder cooling also) A ramp or 
> lip in front of the exit can be used to actually make the air behind 
> the cooler much lower pressure than in front. My coolers are good for 
> about 15 degrees each. The best thing I did was to move the oil lines 
> each to their own duct and add a 1 inch hole inlet and a 1.5 x3 
> reverse ramp on the duct exit 6 inches before the firewall. There is 
> more cooling available in those 2 long aluminum lines than most coolers.
> Cool the oil and the CHT problem will take care of it self.
> Call if I can help
> 985-785 eight two nine 9
> Brent
> N61VB
>
>
> ------------------------------------------------------------------------
> *From:* steve korney <s_korney at hotmail.com>
> *To:* Reflector Reflector <reflector at tvbf.org>
> *Sent:* Sunday, June 23, 2013 10:09 PM
> *Subject:* Re: REFLECTOR: High Oil Temps
>
> 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 <mailto:michalk at awpi.com>
>     > To: reflector at tvbf.org <mailto: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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