REFLECTOR:Cooling a canard

[Chuck Jensen]

John, your right about that.  My engine operates at a temp way lower than
190F and I get thirsty several times a day.  

There is one other dynamic at play here, related to moisture evaporation,
that I'm unsure of the impact (if any).  Clearly, water has a higher vapor
pressure than oil, so it'll evaporate off more readily.  However, in the
engine, any condensation that collects in the crankcase is going to be
covered by a thick blanket of oil which may reduce/prevent evaporation.
Nonetheless, by long experience in aircraft ops, it seems that any engine
oil temps in the +190F range is effective at driving off unwanted moisture
and that temps of +212F is not required.

The only other advantage of running higher oil temps is it implies a hotter
engine.  Some basic physics taught us a hotter engine is more efficient (up
to the point that you start melting components).  In addition, the high temp
implies less cooling and less associated drag.  By my calculations, if you
run the oil at 212F instead of 190F, considering the improved engine
efficiency and reduced cooling drag, your overall operations will be 0.0197%
more efficient.  Of course, the speed gain of 0.101 mph from the increased
energy conversion efficiency will require you to recalculate the timing of
your descent so you don't overshoot the airport.  Caution: Your calculations
may vary.

Chuck Jensen
Diversified Technologies
2680 Westcott Blvd
Knoxville, TN  37931
Phn:     865-539-9000 x25
Cell:     865-406-9001
Fax:     865-539-9001
cjensen@dts9000.com


-----Original Message-----
From: reflector-admin@tvbf.org [mailto:reflector-admin@tvbf.org]On Behalf Of
John Dibble
Sent: Monday, September 15, 2003 9:18 AM
To: reflector@tvbf.org
Subject: Re: REFLECTOR:Cooling a canard


Actually any water will evaporate at temperatures much lower than 190 F,
much like a
wet towel dries in the air.

John Dibble

Chuck Jensen wrote:

> Well, Larry, the definite answer to that is "maybe."  I assume the 212F is
> referenced because we want any accumulated condensation to boil off.
>
> Fair enough but I suspect its not that simple.  First, as we go up in
> altitude, the boiling point for water drops (I'm too lazy to look it up
but
> it probably drops to around 190F at a few thousand feet.  So, during climb
> out, when the oil is the hottest (and condensation from setting on the
ramp
> the greatest) you are heating the oil to its highest temp while lowering
the
> boiling point of water with altitude.  All good stuff.
>
> Of course, if the condensate has dissolved minerals and other "junk" in
it,
> that will raise the boiling point as well the positive pressure in the
> crankcase.
>
> What does all that mean?  I don't, know but probably not much.  At least,
> I've not heard of anyone draining water out of the crankcase every time
they
> change oil (have they?).  If that is the case, it seems that 190+F with an
> occasional excursion above 200F seems to be adequate to flash off the
> moisture in the oil.
>
> Must go.  My head is hurting from all that thinking.
>
> Chuck Jensen
> Diversified Technologies
> 2680 Westcott Blvd
> Knoxville, TN  37931
> Phn:     865-539-9000 x25
> Cell:     865-406-9001
> Fax:     865-539-9001
> cjensen@dts9000.com


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