Me 109 F vs Spitfire coolant radiator installations

[Siegfried]

Speaking of radiators
How Bf 109F&G actual radiators would compare, from drug point of view, to an installation similar to Fw 190D9 ? On planned later version of Me 410 Messerschmitt was planning to replace the under wing radiators with annular radiators. If that choise had advantages could have been appleid to 109 as well?
Fw 190 V18 used an under belly fairing to house the intercooler and turbo supercharger air intake. Would be possible to use a smaller version of the fairing to house the coolant and oil radiators like p 51, g55 , re 2005 did instead of an annular radiator? I know it would be more expensive to produce but would cause less drug?

It's interesting to note that the Me 209-II was also to use this type of installation. It must have had much to recommend it. I suspect it was capable of generating substantial ram thrust.

 

[riacrato]

I think the main selling point was that you could just bolt on and off an entire powerplant in the field with little effort. You also keep ducting to a minimum, saving weight. Hard to tell how it compares in the drag department but iirc vsaero models of the Fw 190 D showed that plane to to be a bit better than the spitfire so the annular radiator can't be all that bad. BUT the way it works, I expect it to be less and less favourable as it opens. I also doubt it utilizes the meredith effect well. On the plus again it does not offer an additional weak spot from behind or below. The only really vulnerable angle is form the front where any bullet would hit the engine otherwise anyways.

 

[wuzak]

This report shows Napier claims less cooling drag for an annular radiator than for a radial, or for chin and leading edge radiators.

http://pdingle214687.home.comcast.n...iles/Napier_Flight_Test_Developments_1946.pdf


The core is oriented differently than this used by Germany during WW2, and used a sliding ring rather than gills.

 

[cimmex]

very similar to the air flow at the oil cooler arrangement of the Fw190A series
cimmex

 

[Siegfried]

This report shows Napier claims less cooling drag for an annular radiator than for a radial, or for chin and leading edge radiators.

http://pdingle214687.home.comcast.n...iles/Napier_Flight_Test_Developments_1946.pdf


The core is oriented differently than this used by Germany during WW2, and used a sliding ring rather than gills.

What they are saying is that the increased frontal area allows less pressure loss through the radiator than in wing or chin type raditors and this, overall, produces less drag than a smaller frontal area radiator that must be both long and dense to transfer sufficient heat. They are also claiming more energy recovery than a chin type radiator.

 

[spicmart]

This report shows Napier claims less cooling drag for an annular radiator than for a radial, or for chin and leading edge radiators.

http://pdingle214687.home.comcast.n...iles/Napier_Flight_Test_Developments_1946.pdf


The core is oriented differently than this used by Germany during WW2, and used a sliding ring rather than gills.

It seems they found the same or similar cooling system as that of the Republic XF-12 Rainbow. Wonder why the Germans would not go with this solution whereas the flaps they were using increased drag when they had to open up..

 

[Juha]

I do not know speed, but open position sure reduce performance of climb of IX... http://www.spitfireperformance.com/jl165climb.gif

Thanks, Tante Ju!
Unfortunately I don't have more accurate info on the effects of the radiator flaps of 109G on climb than that their opening reduced climb markedly, as they wrote in the FAF test report.

Juha

 

[wuzak]

It seems they found the same or similar cooling system as that of the Republic XF-12 Rainbow. Wonder why the Germans would not go with this solution whereas the flaps they were using increased drag when they had to open up..

Fw190As didn't use flaps either.

 

[Juha]

Thanks for the info, Hop!

Juha

 

[Juha]

I think the main selling point was that you could just bolt on and off an entire powerplant in the field with little effort. You also keep ducting to a minimum, saving weight...

That is also my understanding.

IIRC correctly, I don't have now time to check that, Meredith proposed 2 or 3 ways to improve Spitfire's radiator and one of them was annular radiator a la 190D,

Juha

 

[Siegfried]

It seems they found the same or similar cooling system as that of the Republic XF-12 Rainbow. Wonder why the Germans would not go with this solution whereas the flaps they were using increased drag when they had to open up..

I doubt this is the case, the cowl flaps probably wouldn't have more drag or disturbance to the airflow than the air spilling out of a flush sleave. Furthermore there is no suction drag behined these cowl flaps and as there is heated and expanded air ejecting out one would instead expect to find some thrust. At high speed the cowls would tend to be closed. Think of it this way, it would be harder to keep the cowl flaps closed, I think they would be trying to open themselves.

There seem to be precious few photograhs of Dora's in flight.

 

[wuzak]

What they are saying is that the increased frontal area allows less pressure loss through the radiator than in wing or chin type raditors and this, overall, produces less drag than a smaller frontal area radiator that must be both long and dense to transfer sufficient heat. They are also claiming more energy recovery than a chin type radiator.

From memory, since I haven't read it in a while, it says that the annular radiator allows for much better expansion ratios between inlet, radiator face, and also for the converging duct than for the leading edge radiator.

 

[wuzak]

I doubt this is the case, the cowl flaps probably wouldn't have more drag or disturbance to the airflow than the air spilling out of a flush sleave. Furthermore there is no suction drag behined these cowl flaps and as there is heated and expanded air ejecting out one would instead expect to find some thrust. At high speed the cowls would tend to be closed. Think of it this way, it would be harder to keep the cowl flaps closed, I think they would be trying to open themselves.

There seem to be precious few photograhs of Dora's in flight.

I'm sure that at speed the closing force is greater than the opening force of teh cooling air. Remember that even when closed there is a gap for teh air to escape.

The jet thrust of the sliding ring system would not be disimilar to the cowl flaps, if different at all. But it would reduce the drag measurably, if not significantly.

A sliding door could have been used for the Mustang's radiator exit instead of a flap, if so desired. Flaps in that situation are easier. The cowl flaps on radial engine/annular radiator installations required many actuators, or flexible drive systems. A sliding ring woul dbe simpler to operate.

 

[Siegfried]

I'm sure that at speed the closing force is greater than the opening force of teh cooling air. Remember that even when closed there is a gap for teh air to escape.

The jet thrust of the sliding ring system would not be disimilar to the cowl flaps, if different at all. But it would reduce the drag measurably, if not significantly.

A sliding door could have been used for the Mustang's radiator exit instead of a flap, if so desired. Flaps in that situation are easier. The cowl flaps on radial engine/annular radiator installations required many actuators, or flexible drive systems. A sliding ring woul dbe simpler to operate.

I still don't think cowl flaps would produce any drag. Consider that if the cowl flaps were just free hinged they would be open anyway as the dynamic pressure 'ram effect' from air entering the nose would push it open as it sought a way out. The pressure on either side of the cowl flap would be equal. There would be some tension on the hinge but that would be from skin friction drag and relatively small. If there was no free hinged cowl flap the air would simply spill out of the anular slot in much the same streamline or flow pattern.

The air however has been heated by the radiator, by forcing the cowl flaps closed the heated air is accelerated effectively turning the cowl flaps into nozzles.

The drag comes from the intake, not the cowl flaps. I don't see them changing the airflow much at all.

However opening the cowl flap beyond its 'free floating angle' would create suction behined the flap, this would cause drag but also reduce backpressure, effetively it would suck more cooling flow through the engine.

 

[wuzak]

I still don't think cowl flaps would produce any drag. Consider that if the cowl flaps were just free hinged they would be open anyway as the dynamic pressure 'ram effect' from air entering the nose would push it open as it sought a way out. The pressure on either side of the cowl flap would be equal. There would be some tension on the hinge but that would be from skin friction drag and relatively small. If there was no free hinged cowl flap the air would simply spill out of the anular slot in much the same streamline or flow pattern.

The air however has been heated by the radiator, by forcing the cowl flaps closed the heated air is accelerated effectively turning the cowl flaps into nozzles.

The drag comes from the intake, not the cowl flaps. I don't see them changing the airflow much at all.

However opening the cowl flap beyond its 'free floating angle' would create suction behined the flap, this would cause drag but also reduce backpressure, effetively it would suck more cooling flow through the engine.

Suction on the underside of the flaps would tend to try to close them too.

Also, usually in radial engined aircraft it was desireable to close the cowl flaps for takeoff - because of drag.

 

[Juha]

Also IIRC in some radial engined twins with only marginal one engine capacity opening the cowl flaps of the running engine resulted loss of altitude, IMHO a clear indication of drag rise.

Juha

 

[Siegfried]

Also IIRC in some radial engined twins with only marginal one engine capacity opening the cowl flaps of the running engine resulted loss of altitude, IMHO a clear indication of drag rise.

Juha

There are likely to be more than two settings.

Open would be to maxiumise cooling especially at low speeds and high power levels, partially closed to maximise jet thrust

 

[Denniss]

But copper is a better at heat transfer than aluminum, just check any radiator website.

No, it's not better than aluminum if heat is to be transferred to air, as experience from today's CPU cooling shows.
There were some pure copper coolers that transferred heat from CPU into the heatsink rather quick but with all sorts of problems to transfer it further into the cooling air. It required lots of very thin cooling fins (large surface area) to ensure proper heat transfer to cooling air. Aluminum was not that capable to transfer heat from CPU to heatsink but did not require such a large surface area to transfer heat to cooling air. That's the primary reason most of today's CPU coolers are a hybrid copper/alu construction - copper for fast transfer into the heatsink unit with alu for the surface areas and heatsink->air transfers.