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no oil cooler

burgundyja

burgundyja

Well Known Member
has anyone thought of just routing the oil line threw one or both of the fuel tanks. i know that you would have to put them on the bottom of the tank. you would also never want to run the tank empty. but i think this would have suficent cooling with all of that surface area. i also think that you would have less drag with no oil cooler fins slowing down the air flow.
 
Why?

Why would you want to do this? Sounds like A LOT of work for something that isn't a problem....oil coolers work great and have limited plumbing. I like the keep it simple mantra.
 
You want to heat up your fuel? I don't think that is a good idea at all. The extra weight and complexity plus the heat being transferred into the fuel just dosn't make sense to me.

JMHO.
 
Well, it's an interesting question.....and if I remember way back to my school days, there are advantages to pre-heated fuels (hey, that's how we do it in the rocket business!), but the weight of the extra oil lines would probably well exceed any theoretical efficiencies, plus I don't know the long-term affect of submerging oil lines in Avgas. (I am sure the interior of the line is fuel proof, but I don't know about the outside.)

I am of the "the less oil line length, the fewer chances for leaks" school of thought BTW....

Paul
 
I think that the heat will disapate from the fuel to the skin into the air. I dont think that the temp of the fuel would rise that much. I think that the wieght of the extra oil lines would be the same as the oil cooler. I do agree that there is more of a chance of a leak. I am just thinking about this and I just was wondering if anyone thought about this.
 
No Oil Cooler

The fact that this is not a common practice...i.e. running oil lines thru the fuel tank....should be indicative of something.

Also, as to the point about by doing this, one would achieve less drag:

You have to have air flowing thru the engine compartment. So it also flows thru the oil cooler which incidently has a whole lot more surface area than a single metal tube routed thru a fuel cell. "If" the amount of HP absorbed by the oil cooler were, say 5 hp then what would be the penalty in cruise speed you would see? It wouldn't be much!

Also, I wonder what the long term effect on Pro Seal would be to add extra heat to it? The last thing you would want is for your fuel tank to start leaking.

A oil cooler mounted on the rear baffle requires short hose runs. If one were to try to use the fuel tank(s) as a heat sink, the weight of the additional hoses would be significant.

Also, what would happen to the efficiency of your fuel tank heat sink when you landed in Phoeinix with your tank nearly empty after a long cross country and you are taxing to the ramp and you're told by Ground to hold at Taxi Way Alpha?

I am not a fan of trying to re-invent the wheel. This is an interesting idea to think about however.

Tom Hunter
 
The one thing that got me, that no one has mentioned, is that you are going to run HOT oil lines through the cabin to get to the wings. :eek:

No thanks for a couple of reasons.
 
N941WR said:
The one thing that got me, that no one has mentioned, is that you are going to run HOT oil lines through the cabin to get to the wings. :eek:
Click to expand...

Of course Bill, you have to realize he's in Minnesota, so maybe that doesn't seem like a problem. Minnesotans have been known to set THEMSELVES on fire to keep warm....:p;)

Paul
 
Take quite a bit of extra oil

You wouldn't be able to drain this oil during a oil change. You would have to run oil lines through the cockpit, not just lines with a restrictor fitting, were talking about lines with some flow to them. There is a possiblity of the line coming leaking in the tank, mixing fuel with oil. Great for a 2 stroke.

Randy
 
:eek:if you really were desperate to heat up your fuel, you'd be better off running a return fuel system and then plumbing the return line via a fuel-oil heat exchanger under the cowling before it returns to the tank - much simpler and lower weight. However...

I think if you did the calcs on surface area etc, you'll find the tanks are a little on the small side and/or the fuel will still be too cool to provide much temperature differential - even if the fuel did reach it's flash point! :eek:

Might be a slightly better idea if you were running Jet-A/diesel though.
 
Oil/Fuel Heat Exchangers

As another data point, many turbine engines employ an oil/fuel heat exchanger. This simply transfers heat from the oil to the fuel. The key point here is that the exchanger is in the engine compartment and is plumbed AFTER the high pressure fuel pump. This eliminates the possibility of vapor lock. Hot fuel (at least jet A) is easier to meter and vaporize, and there is no posibility of ice crystals messing with the fuel metering system (in the airplane I fly at work, the fuel entering the metering system is typically at 85 degrees celsius).

The problem with trying to do this on an RV is that the fuel is much warmer, the oil gets heat transfered to it much faster, the fuel flow versus oil quantity is vastly smaller, and an oil/fuel heat exchanger is probably just as heavy as a oil cooler. When you combine inadequate performance with some very nasty failure modes, its just not worth it.

Pat
 
i am rethinking this now that i am flying.

My oil temps are a little high. Maybe I could run a small line with a valve and just turn it on when the oil gets hot. I have a oil cooler as the main unit. Then I could put a temp sensor on the fuel tank and if the fuel gets to hot shut the valve. Also with the 8 the lines would have a very short run. In the cabin. I could fire sleeve them.
 
Heated leather seats?

Why fire sleeve? Heated leather seats are nice. Put the heat to good use there in the far North instead of lighting the clothes on fire;)
 
As illogical as this idea might sound, it is actually done in some jets--except they're called 'fuel heaters.' I'm thinking about the Gulfstream aircraft where at higher altitudes the fuel can actually get cold enough to gel. So, in the G-V for example, engine oil is routed through heat exchangers in the wings to keep the fuel temp above 0 degrees C. Not a problem for the RVs, though. :)
 
Really don't do it!

I suspect (although it would be fun to do some heat load calcs) the oil cooler dissipates a LOT of heat...lets say 10hp for fun..Now think of a 10HP heater heating 1/3rd of a tank of fuel...I think you can see your fuel would get mighty hot in short order!

Remember, the fuel then has to dissipate its heat to air at say 100F....your fuel could get very warm indeed, especially considering you will evenutally lose a lot of the surface area of the tank cus there will be air between the fuel and the tank.

Gasoline is NOT like kerosene, it has a much higher vapour pressure and will likely flash to vapour at the slightest provocation on a warm day...Really I think a 0.357magnum would be a quicker way to achieve what your likely to end up doing!!!

VL crashes airplanes..it happens its real, don't do it!!

OK..I will now do some calcs when I'm back home from my business trip.

Frank
 
No Oil Cooler

frankh said:
Hot fuel on a warm day....Your asking for vapour lock...Don't do it.
Click to expand...

Using the fuel tanks for an oil cooler sounds like "A lot a sugar for a dime" to me!

However, you could always run the fuel through the (unused) oil cooler to help keep it cool and avoid vapour lock! :)>) :eek:..................... and the beat goes on!
 
The lines in the fuel tank would have to be aluminum or similar to conduct heat away from the oil.....not rubber.

Then you have to keep TBD fuel over the lines to prevent problems...forget about running the tanks low. Thus you lose range.

Thinking outside the box is good. I just don't see this being a viable concept.
 
frankh said:
I suspect (although it would be fun to do some heat load calcs) the oil cooler dissipates a LOT of heat...lets say 10hp for fun..Now think of a 10HP heater heating 1/3rd of a tank of fuel...I think you can see your fuel would get mighty hot in short order!

Remember, the fuel then has to dissipate its heat to air at say 100F....your fuel could get very warm indeed, especially considering you will evenutally lose a lot of the surface area of the tank cus there will be air between the fuel and the tank.

Gasoline is NOT like kerosene, it has a much higher vapour pressure and will likely flash to vapour at the slightest provocation on a warm day...Really I think a 0.357magnum would be a quicker way to achieve what your likely to end up doing!!!

VL crashes airplanes..it happens its real, don't do it!!

OK..I will now do some calcs when I'm back home from my business trip.

Frank
Click to expand...

don't forget though that during flight you would be shedding heat through the tank skins exposed to outside air. this would decrease as the fuel level is reduced to an extent, there would be some gas movement within the tank due to heating and cooling to compensate somewhat.
 
Here's one airplane that uses fuel to cool...

... the radar system. The E-3 has fuel tank heat exchangers that run liquid coolant all the way from the radar system into the wing tanks. We never had a problem with fuel freezing when the radar was up.

boeing-e-3-sentry.jpg


If I remember right, the coolant was Sulphur Hexaflouride, Sf6, not oil.
 
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oil water exchanger

What about a oil water exchanger. I could run 1/4 hard lines down the leading edge and have deice :) the hot water could also be used it get heat in the back of the 8. A small tank for taxi.
 
Sorry if this strays off subject a tad, but atleast two VariEZ builders managed to successfully delete the traditional oil cooler. One is Bill James on his 0-235 powered VariEZ.. He custom built a fiberglass deep oil pan and installed a series of aluminum bent tubes into the pan, basically trying to cool the oil, by air, directly from the pan itself. Explained below:

http://v2.ez.org/feature/F0502-1/F0502-1.htm

The other is Klaus Savier on his multiple world record setting 0-200 powered VariEZ. He says he skipped ANY formal oil cooling completely, claiming that his engine cools so efficiently that his oil system requires no extra help. Granted, his plane is no weekend warrior, but he has done everything from long distance high altitude efficiency runs to running 251mph average lap speeds at Reno going neck and neck with John Harmon's Rocket 3 in 2004-2005.

http://www.aopa.org/


just some food for thought....

George
 
The O-235 powered Piper Colt didn't use an oil cooler either. I don't think the factory made any mods to the pan.
 
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