REFLECTOR: High Oil Temps

[steve korney]

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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