REFLECTOR: High Oil Temps

[Brent Bourgeois]

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
>> 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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