Tracy wrote>>

The 'fix' I tried (and plan to try again) was to use the

wet wing fuel tanks as radiators (almost zero weight gain ).  This of

course

requires that the fuel itself be used as the heat transfer medium

Marc wrote>

Tracy,
This sounds like the turbine engine fuel/oil heat exchanger. A smallish
unit mounted alongside the turbine that contains the subject exchanger,
which preheats the kerosine and cools the oil.

Marc Wiese

Mark wrote>

Not really what Tracy proposed. The Fuel/oil heat exchanger is dumping
engine oil heat into the fuel, but the fuel is not exchanging this heat to
the air as Tracy proposes, rather just relies on the the huge flow rate (A
GE90 usually exceeds 10 tons/hour fuel flow during take off) and dumps this
heat with the fuel into the combustion chamber.

As others have pointed out, Tracy's plan sounds like airliners submerged
hydraulic system heat exchangers. Using this to add the extra cooling
capacity for the hot day climbs sounds good. How do you intend to regulate
this so you are not increasing the vapor lock risk with nearly empty tanks?
(Although looking at normal flight profiles - whenever you need power, you
normally have either lots of fuel, and /or lots of airflow over the wings).

What is the worst case?

Long taxi to a parking place at Oshkosh after a long x-country - no safety
concern here?
Missed approach on hot day at high altitude airfield after long X-xountry -
will this be an IFR RV-8?

Tracy, have you tried putting preheated or cooled fuel in you RV-4 and
getting some data on heat rejection rates? Would be interesting to know how
much heat you can reject per gallon of fuel in your tank configuration per
minute.

Do you intend using the stock RV cowl? When you add the weight and
complexity of oil lines to the tank plus the heat exchanger, it would seem
easier to just use a larger radiator. The RV-8 cowl can't be that lmited in
volume.

Mark Wrathall.

 
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