- Thread starter
- #81
It can't be both.
In this thread, there is no surface cooling on the He 100.
We can ask him when he stops by on this forum
He 100 in service, but with caveats
- Thread starter tomo pauk
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In this thread, there is no surface cooling on the He 100.
We can ask him when he stops by on this forum
Shortround6
Major General
I could be wrong but "high temperature cooling" means that the cooing system is going be operating at a higher temperature than the boiling point of water. Wither that is 15% or 20% or more is subject to question. Turns out you can't go too high or some of the load gets transferred to the oil system.
The whole trick to "evaporative" cooling is the huge amount of energy needed to move boiling point water (100 C) to 101C degree steam. and then when you move the steam to evaporative area the amount of energy that is released when the steam becomes hot water.
The "high temperature cooling" doesn't do this. Just about the same amount of heat energy is used to raise the cooling fluid from 98 C to 99C and then to 100C and so on, roughly the same amount of energy to go from 114 to 115. The high temperature does allow for a smaller radiator because you have greater difference in temp between the cooling fluid and the air.
Pressurizing an "evaporative" cooling system doesn't get you anything and it makes things even more difficult. Steam at 101 C needs 1600 times the volume of water at 100C.
Trying to design a system that won't spring leaks all over the place is extremely difficult.
The whole trick to "evaporative" cooling is the huge amount of energy needed to move boiling point water (100 C) to 101C degree steam. and then when you move the steam to evaporative area the amount of energy that is released when the steam becomes hot water.
The "high temperature cooling" doesn't do this. Just about the same amount of heat energy is used to raise the cooling fluid from 98 C to 99C and then to 100C and so on, roughly the same amount of energy to go from 114 to 115. The high temperature does allow for a smaller radiator because you have greater difference in temp between the cooling fluid and the air.
Pressurizing an "evaporative" cooling system doesn't get you anything and it makes things even more difficult. Steam at 101 C needs 1600 times the volume of water at 100C.
Trying to design a system that won't spring leaks all over the place is extremely difficult.
Howard Gibson
Senior Airman
The Rolls Royce Merlin pressurised its coolant so that it could run at 130C. The DB601 lacked this capability or at least, not to 130C. This was a sore point for Willy Messerschmitt, who wanted smaller radiators on his aircraft.
BarnOwlLover
Staff Sergeant
From what I read on Wikipedia about the development of the Jumo 211/213 (Wikipedia, so take it as you will), the DB 601 did have a pressurized cooling system--a sore point with Junkers over the original 211 design. However, if the Merlin was capable of running up to 130C without issues, I'd have to say that it was likely that the 601 might not have been able to do 130C, at least without difficulty or engine/cooling problems.
Big advantage in aircraft is that pressurized cooling keep the pressure and boiling point of water constant, especially at high altitudes (less dense air, less cooling effect, lower the coolant's boiling point).
Big advantage in aircraft is that pressurized cooling keep the pressure and boiling point of water constant, especially at high altitudes (less dense air, less cooling effect, lower the coolant's boiling point).
GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
Each engine manufacturer will have their own specific design in regards to how the engine's cooling system will operate.
The design of the coolant flow through the heads, the placement of the water pump(s), inlets, outlets, and so on is unique to each manufacturer and even then, to each engine series.
The design of the coolant flow through the heads, the placement of the water pump(s), inlets, outlets, and so on is unique to each manufacturer and even then, to each engine series.
- Thread starter
- #86
Good call for people to be vary with what Wikipedia says.
Jumo 211 was with pressurized cooling system from day one - the 'closed, pressurized cooling system'* that allowed for sea-level max of 95°C was on the 211s before the F (includes the G and H that actually pre-dated the F).
The 211F introduced the 'over-pressure cooling system'*, that upped the max temp at sea level to 115°C, and at 10000 m up to 85°C.
* per 'Flugmotoren und Strahltriebwerke', pg. 86
We can note that Merlin II was rated for 120°C, per manual for the Spitfire I.
Very high pressures on the radiator require strong construction, without skimping on quality of material for the radiator itself and of the adjoining pieces. Junkers circumvented the issue by the time Ju 213 arrived via 'low-pressure' radiator cooling both oil and high-pressure coolant circuits via the heat exchanger.
Also later the intercooler circuit was cooled by the heat exchanger on the 213E.
Agreed. While it did yield planes like the He 178, it also yielded the He 100 and He 177.
Indeed, he basically focused on drag to the exclusion of everything else.
It is kind of ridiculous that this managed to slip past me...
It's surprising that they didn't consider that. It seemed that some manufacturers such as Focke-Wulf did factor in ruggedness moreso than others.
Wait, I thought the whole point of a coolant is to absorb heat? Wouldn't that be kind of self-defeating?
While this might reflect an ignorance for WW2 engine design: I'm curious when the US, UK, and Germans started to switch over to Glycol (or a mix of Water/Glycol) systems from water?
I thought the tendency for bubbles to form was specific to the He 177?
Also why did the RLM impose restrictions on cobalt, nickle, and chromium?
Actually it did predominantly use surface-cooling; it just had a radiator to deal with low-speed flight.
From what it would appear the Merlin was designed for 120-130˚C and the V-1710 was built for 125˚C so that still is a bit on the low side, but a considerable improvement from 95˚C. (I have no idea what temperatures were used for the DB601).
And that would have been an issue of cost, war economy, and a bit of a learning curve?
So they used one cooler to cover both oil and engine cooling?
I didn't factor in the outside air-pressure, but it definitely makes sense.
So the engine's basic design dictates what the manufacturer can do? Is there normally collaboration between both?
- Thread starter
- #88
That is indeed your prerogative.
Supply of that (and a lot of other things) was low and was getting lower as the war progressed.
Yes.
No, you're entitled to your own opinions, not your own facts. So it formed in all installations, but was worse on others?
Was this an issue early on (1936-1942)?
So, the learning curve for high pressure radiators was that steep?
GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
Yes and yes - the aircraft engineer decides that a certain engine will be incorporated into their design and the engine manufacturer provides data to the aircraft manufacturer so that the aircraft will be able to function properly.
Weights and measures, mounting points, plus projected oil consumption, projected operating temperatures and pressures, etc.
The cooling system design is up to the aircraft manufacturer, who has the engine operating data in hand, to find a way to keep that engine operating within spec.
Surprising that Daimler didn't look into ways to jack up the pressure on their cooling systems.
The "bubbles" were aeration of the oil that was a problem, particularly on the DB 601, 603 and 605. This was a complicated issue that is, strangely, also quite well understood. However, Daimler-Benz were slow to resolve the problem which often manifested itself as destructive main bearing failure, particularly on the DB 605A in the Bf 109 G.
I have quite a bit of the detail of this and I hope to publish details of the saga in the future. In the meantime, you can find an impressive account of the problems from the German side, in Calum Douglas' exceptional book, The Secret Horsepower Race, which every person interested in WW2 Aviation should have!
Eng
Shortround6
Major General
Think about your cars cooling system.
Those of us that are old enough can remember local radiator shops even in not big towns.
Now think about a airplane whose radiator is operating at even 20,000ft were the out side pressure is 1/2 what it is at sea level. The radiator goes (if you are using a 7-8lb) pressure cap of resisting about a 50% great load at sea level to a load of 100% at 20,000ft.
Now fly higher, stick the radiator close to a vibrating 1000hp engine, and now perform a few High G maneuvers.
Kind of amazing they stood up as well as the did
ThomasP
Senior Master Sergeant
I do not know if this factors into the conversation (it is a little broken up and confusing ) since the OP was about the He100 - but the Merlin used 120°C max for the early models that used pressurized pure ethylene-glycol (ie Merlin II/III/IV/VIII etc), as tomo pauk mentioned up-thread. When they switched to pressurized water/ethylene-glycol mix in the next generation models (ie Merlin XII/XX/45 etc) the coolant temps were raised to 125°C for 30/60 minutes (early/late) at Climb rating and 135°C for 15/5 minutes for Combat rating(s), which is inline what Zipper730 said - this is also what is listed for the 2-stage series (ie Merlin 60/70) in the manuals I have.
I have read that at some point in some installations the Merlin 2-stage coolant system psi limit was increased over the earlier models, but I have not run across any details.
) since the OP was about the He100 - but the Merlin used 120°C max for the early models that used pressurized pure ethylene-glycol (ie Merlin II/III/IV/VIII etc), as tomo pauk mentioned up-thread. When they switched to pressurized water/ethylene-glycol mix in the next generation models (ie Merlin XII/XX/45 etc) the coolant temps were raised to 125°C for 30/60 minutes (early/late) at Climb rating and 135°C for 15/5 minutes for Combat rating(s), which is inline what Zipper730 said - this is also what is listed for the 2-stage series (ie Merlin 60/70) in the manuals I have.I have read that at some point in some installations the Merlin 2-stage coolant system psi limit was increased over the earlier models, but I have not run across any details.
GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
The only aircraft that reached combat status that is closest to the He100, would be the KI-61 - so how did the Japanese solve the cooling system needs with the Ha40 (license built DB601A)?
- Thread starter
- #96
Ki-61 used the 'normal' cooling system, not that different as what the Italian ww2 fighters powered by V12 engines used.
Deleted member 68059
Staff Sergeant
- 1,058
- Dec 28, 2015
Ugh, all garbage on wikipedia, I`ve edited a couple of engine entries but much of what remains is junk from writers who dont understand the engines or dont understand research.
Deleted member 68059
Staff Sergeant
- 1,058
- Dec 28, 2015
Only a couple.
Daimler-Benz DB 600 - Wikipedia
