Liquid cooling

HomeBuiltAirplanes.com

Help Support HomeBuiltAirplanes.com:

pictsidhe

Well-Known Member
Joined
Jul 15, 2014
Messages
8,812
Location
North Carolina
That was cold.
No, it's a hot tip.

You need surface area to get rid of heat. The thicker the material that is providing that area, the heavier the thing will be. A lot of tubes is going to be bulky, heavy and expensive.

A well implemented and sized modern automotive type radiator is going to be nearly impossible to beat in terms of performance vs weight and drag. A lot of research has been done on this over the last hundred years, you are not going to get close with a hunch.

If you want to look at the science, I'd suggest 'Compact heat exchangers' and 'extended surface heat transfer'.
 

trimtab

Well-Known Member
Joined
Apr 30, 2014
Messages
161
Location
rocky mountains, rocky, usa
It looks like Incropera is to thermodynamics as Shigley, Bruhn, and Hartog are to their respective fields?
Yes...roughly half of undergraduate ME students use the text in the western world.

In short, the problem you describe is a combination of fluids and heat transfer. You will probably find after thrashing around for a very long time trying while to make something very different and better that you realize generations of frustrated engineers have suffered the same fate. And you will end up with something that looks recognizable to something that has been used, and you'll converge on the same approaches and design trades, etc.

I'm not trying to be a debbie downer here. But convective and conductive heat transfer are super important in modern life, pretty expensive in the scheme of things, necessary, and the focus of a lot of people thinking pretty hard about it.

The only things new to heat transfer engineering for most engineers are usually multiphase and radiation problems. And more recently, near field radiation problems. So for a conventional radiator in a plane, train, or automobile, the Nusselt number is really likely the focus of your quest, and the problems associated with determining it.
 

Tiger Tim

Well-Known Member
Joined
Apr 26, 2013
Messages
3,638
Location
Thunder Bay
The air could be slowed down and not have to use heat sinks on the copper since it give up the heat so easily. Pretty much have a tunnel lined with the tubes and the air passes by. Whats everyone think?
It’s a neat thought to have and while I’m not smart enough to intuitively know the nuts and bolts of how heat transfer works I like to look to history for clues on this sort of thing. I figure when it comes to aviation all the easy stuff was figured out by 1945 or so.

What if your copper tunnel was turned inside out and was instead a copper skin on the airplane that radiated off all of the engine heat to the passing air? Turns out it’s been done already, and successfully, on the old Schneider Cup racers. Many of them used almost their entire wing surfaces as radiators and sometimes the fuselage and float surfaces too. It led to some pretty fast airplanes, in fact the fastest going for a while.

Then along comes a fighter like the P-51 (and a bunch of others but the P-51 makes the best example) where it has a traditional radiator buried in the fuselage but with a bit of a twist: a small intake led to a duct that widened up to a pretty large radiator which heated the air before squeezing it out through a tapering exit duct. By adding heat to the air it made a sort of rudimentary ramjet and was said to have actually produced thrust. I don’t think it was much thrust but in the case of the Mustang it’s at least enough to overcome the drag of the duct and radiator, and maybe a bit more.

I don’t know if there’s much to be had beyond that.
 

Sockmonkey

Well-Known Member
Joined
Apr 24, 2014
Messages
2,080
Location
Flint, Mi, USA
WWII came out with a lot of great stuff, but it's important to remember that combat survival was a big factor in which compromises were best.
Can't put a radiator skin in a wing that's likely to get holes shot in it.
 

Tiger Tim

Well-Known Member
Joined
Apr 26, 2013
Messages
3,638
Location
Thunder Bay
WWII came out with a lot of great stuff, but it's important to remember that combat survival was a big factor in which compromises were best.
Can't put a radiator skin in a wing that's likely to get holes shot in it.
True, but AFAIK there’s no armor around the radiator on a Mustang, either. That and nobody raced one with copper cooling jackets wrapped around the wings. Some alternate cooling schemes have been tried since WWII but the fastest ones all seem to run the stock duct and rad.
 

Aesquire

Well-Known Member
Joined
Jul 28, 2014
Messages
2,643
Location
Rochester, NY, USA
The legendary Mustang also got shot down with rifle fire on a too regular basis because of the bottom mounted radiator. Poke one hole and the engine rapidly overheats.

Don't get me wrong. Great plane. But not the best choice for low level strafing of airfields with lots of guys shooting at you. Don't know the numbers but many after action reports tell about losing great pilots to ground fire.

Otoh, the air cooled Thunderbolt routinely returned to England with oil all over the outside of the plane, and entire cylinders shot up, or off. Plenty of pictures of F6F Hellcats parked on carrier decks with big holes and oil the length of the plane.

If you want to draw the conclusion that simpler is more robust, you aren't wrong. But there's a lot of sophistication in the design of the cowling & baffles that direct the cooling air around the cylinders in an air cooled engine, if you want reliability and lower drag. P&W or Lycoming, it's conceptually simpler, but mathematically complex.
 

Vigilant1

Well-Known Member
Lifetime Supporter
Joined
Jan 24, 2011
Messages
5,910
Location
US
There was lots of interest in using the aircraft skin to serve as a heat exchanger back in the 30s. Racers looking for any edge. Some were built. None provided a practical advantage despite the (too obvious) attraction of the idea. Lots of added weight and complexity, and weight increases drag.
This is not new ground.
 

pictsidhe

Well-Known Member
Joined
Jul 15, 2014
Messages
8,812
Location
North Carolina
Leading up to WWII there were experiments with wing surface steam cooling in the UK. It was borderline for cooling and prone to leaks. It was also a very large and vulnerable target for enemy fire. Conventional radiators were a much smaller target and it was also feasible to add some armour so the wing surface cooling was quickly dropped. All British WWII aircraft were designed with knowledge of the Meredith effect, but not to the extreme that the Mustang took it, though I think the Mosquito put more effort in than most. The more compact but higher drag British radiators were a smaller target. It was mostly done for packaging reasons.

For ultimate low drag, wing leading edge cooling may be worth looking at, though it will have a weight penalty. I found an interesting report on heating fuselage sections of scale airliners. It showed that adding boundary layer heat at the beginning of a turbulent section will reduce drag. That will work at any speed, the Meredith effect needs high speed to be worth doing. On a 103, a reasonably implemented Meredith would add about 0.1% thrust...
 

BJC

Well-Known Member
HBA Supporter
Joined
Oct 7, 2013
Messages
12,768
Location
97FL, Florida, USA
IIRC, the P-38 originally used the wing leading edge to (try to) transfer turbocharged air heat to the atmosphere.

There aren’t many subsonic aero things that haven’t been tried.


BJC
 

azevedoflyer

Member
Joined
Feb 4, 2020
Messages
13
Location
247 Blue Mountain Lane - Trion - GA - 30753
I have had an idea for a while. While radiators have been around for quite some time and work they do create a lot of drag. I've seen people making certain contraptions to block air after takeoff to restrict the amount of air and reduce drag. The idea i have is making a copper radiator that doesn't have any fins. It dissipates heat SOOO much better.

The whole science of cooling with a radiator is not to shove as much air as possible but to let enough air through at the correct speed so the air can absorb as much heat as possible before becoming heat soaked. If it goes over to fast it will only pick a little and then you over heat.

Copper is expensive compared to aluminum and that mostly why they use that. Not sure if there would be weight savings. The copper one could be smaller but its a bit more dense. I'd have to run some tests.

What I'm proposing is have a NACA for inlet and an exit hole with a lip that can closed and the lip pushed flush when in flight reducing drag even father.

The air could be slowed down and not have to use heat sinks on the copper since it give up the heat so easily. Pretty much have a tunnel lined with the tubes and the air passes by. Whats everyone think?
Old biplanes and some racers of the "30s used surface radiators to good effect. Modern airliners dump all the waste heat into the fuel and this, in turn, cools via the wing skin. If you are willing to go through the trouble, maybe you can pipe the coolant to tubes brazed to the upper surface of a wing panel.
The heat dissipated might even energize the boundary layer although I would not count with it in the wing design process.
Azevedoflyer
 

Jay Kempf

Curmudgeon in Training (CIT)
Lifetime Supporter
Joined
Apr 13, 2009
Messages
4,260
Location
Warren, VT USA
IIRC, the P-38 originally used the wing leading edge to (try to) transfer turbocharged air heat to the atmosphere.
There aren’t many subsonic aero things that haven’t been tried.
BJC
I think it was a supercharger and the leading edge was used as a charge cooler or intercooler. But yes.... There was a lot of experimentation of where to put various heat exchangers on aero structures. Well documented stuff on drag of various configurations back in the day.
 

BJC

Well-Known Member
HBA Supporter
Joined
Oct 7, 2013
Messages
12,768
Location
97FL, Florida, USA
I think it was a supercharger and the leading edge was used as a charge cooler or intercooler. But yes.... There was a lot of experimentation of where to put various heat exchangers on aero structures. Well documented stuff on drag of various configurations back in the day.
My understanding is that the P-38 used a GE type B turbosupercharger system. That system fed intake air first into the turbocharger (located in the boom, with the shaft vertical), then through the LE intercooler, through the carburetor, then into the engine shaft driven supercharger.

Deuelly, please comment.


BJC
 

Sockmonkey

Well-Known Member
Joined
Apr 24, 2014
Messages
2,080
Location
Flint, Mi, USA
There are some ideas that would have been physically simple to implement, but technologically complex to develop. Essentially anything where you need a complex computer sim, or some bit of information that was only learned in the post-war era.
 

Bill-Higdon

Well-Known Member
Joined
Feb 6, 2011
Messages
1,117
Location
Salem, Oregon, USA
My understanding is that the P-38 used a GE type B turbosupercharger system. That system fed intake air first into the turbocharger (located in the boom, with the shaft vertical), then through the LE intercooler, through the carburetor, then into the engine shaft driven supercharger.

Deuelly, please comment.


BJC
Umm not what I see here
f9b8bbbcd704b51d97188d00e815a3cc--oil-lightning.jpg
 

Sockmonkey

Well-Known Member
Joined
Apr 24, 2014
Messages
2,080
Location
Flint, Mi, USA
One thing I've wondered about is that one you're using an external source of forced induction like a turbo, why didn't they go two-stroke since they wouldn't have had to use crankcase pumping? More power fewer parts.
 

pictsidhe

Well-Known Member
Joined
Jul 15, 2014
Messages
8,812
Location
North Carolina
The P38 was one of the first aircraft to use turbo-supercharging

The name has shrunk over the years. Turbocharger, then just turbo. As usual with reducing complication, reliability has improved greatly. 😁
 

Tiger Tim

Well-Known Member
Joined
Apr 26, 2013
Messages
3,638
Location
Thunder Bay
One thing I've wondered about is that one you're using an external source of forced induction like a turbo, why didn't they go two-stroke since they wouldn't have had to use crankcase pumping? More power fewer parts.
Maybe too much power to stay reliable? Look up the Rolls Royce Crecy, IIRC basically a two-stroke Merlin with the goal of making a 5,000hp Spitfire. The test engines didn’t last particularly long.
 
Top