Pressure or velocity for better cooling?

[DaveKillens]

The "surface" radiators on the Bluebird did not have air passing through them, but rather along the surface. So as the picture displays, there are actually four radiators on the Bluebird, a pair each side, mounted back to back. For the Bluebird, each radiator was composed of hundreds of tubes, tightly packed side-by-side to become the actual surface. No fins, no air channels, just a lot of tubes.

[Carlos]

I would say surface radiators work by CONVECTION. Yes I would. I firmly stand by convection. Wait, wait ... with the air rushing past ... I'll call it Forced Convection. Hmmm - milk and cookies are having their way with me. I'm off for a nap. But I'll dream of the Bluebird and the BT46. Yes I will. Not about Gordon Murray. Definitely not. Maybe that new Spainish Miss racing F2. I'd sure like to see how she pilots the parabolica Monza. Probably really have her way with it. Trail braking. Definite good trail braking.
http://en.wikipedia.org/wiki/Convection

[xpensive]

Jeez, I heard about armchair-enthusiasts, but wikipedia-engineers?

But DK, given that the surface-coolers consists of multiple tubing and not much else, how do you figure that was arranged on the Brabham car, those pad-looking things must be connected somehow?

[DaveKillens]

By plumbing

[xpensive]

Just by the look of the cooling-elements, I'm certain there is a little more to it then simple tubing and plumbing.
http://www.forix.com/8w/6thgear/brabham-bt46.jpg

[rjsa]

It has to be heavy water running in flexible titanium tubing.

[riff_raff]

The drawback of that surface radiator is that it probably has too little surface area to be effective. The reason a conventional radiator core has all of those zig-zag fins between the tubes is to increase the surface area involved in the heat transfer. The only way you can reject enough heat thru the small surface area of that surface radiator is to significantly increase the temperature difference (deltaT) between the coolant and the ambient airflow. Super high-temp/high-pressure cooling circuits (like steam cooling) have been tried in the past, mainly to reduce the size and drag of the heat exchangers. But the 2009 F1 reg's limit coolant system pressures to about 55 psig and forbid using latent heat effects for cooling.

steam cooled engine: http://en.wikipedia.org/wiki/Rolls-Royce_Goshawk

If you look at the close-up photo of a radiator core posted by Belatti, you'll also note that the fins have tiny louvers. And, if you could see inside the tubes, you'd find that they have "turbulators" inside that cause the coolant to swirl around. The purpose of the louvers and turbulators is to effect mixing between the fluid core flows and the boundary layers. This makes the heat transfer more effective since heat transfer only occurs between the very thin fluid boundary layers and the metal surfaces.

Automotive radiators may look like simple devices, but in reality they are very high-performance, highly engineered components.

Free reading: http://books.google.com/books?id=G52EfF ... lt#PPP1,M1

[xpensive]

Regarding the BT46 "surface-cooling", it was all part of a bigger plan.
With the advent of Lotus 78 1977, Murray quickly realized that groud-effect was the way to go, but for 1978 he would be stuck with the massive Alfa Romeo engine, which was not suitable for a venturi-underbody, besides it required extensive cooling.
The BT46 was therefore designed around the concept of a giant fan in the back to suck air through the enclosed engine-bay and rear-mounted oil- and water radiators.
In the process, the fan created an underpressure under the car, which was said just to be a bi-product of the cooling, but was of course the true objective.

In order to make the cooling-argument more plausible, as well as create a smoke-screen to cover what they were realy up to, the surface-cooling hoax was presented, but was in reality just the fan-car without the fan. If you look carefully, those "cooling-pads" are just attached to the surface of the original aluminium-tub, there's no complex plumbing behind them.

http://www.forix.com/8w/6thgear/brabham-bt46.jpg

Murray was an engineer, he would have had very little difficulty to verify what riff_raff and others explained above.

Imagine being an F1 designer in them days, must have been a blast.

[DaveKillens]

Interesting theory, but the timeline does not agree. The BT46 was designed for the 1978 season, and the surface radiator concept was trialed in pre-season testing. The concept was a failure, and Murray then went to mounting the radiators on the nose. That configuration was used until the BT46B was unveiled for the 8th race of the season, the Swedish GP. Of course, after winning that race, the potential furor caused Bernie to withdraw the fan car.
Additionally, the plumbing for the surface radiators was under the bodywork.

[xpensive]

Only, there is no bodywork under those "surface-coolers", only the aluminiumtub, which contains the rubber-bellow tanks on each. Bet those pads were just styrofoam.

Timeline agrees fine, the fan-car was simply not ready before the race in Sweden, why the nose-radiator version had to make-do. The "surface-cooler" was as said before, just a diversion.

[DaveKillens]

The BT46 was tested with those surface radiators. There had to be some mechanism for dissipating the heat, and I just can't see them using styrofoam pads.

[xpensive]

That's just it DK, there has never been any pics or credible reports of the surface-car ever driven in anger. Look again at those pads, do they seem serious to you?

[Carlos]

Did men really walk on the moon?

Credible reports? Pictures?

Only if you look for them. Goggle gives a dozen references. They only mention "surface radiators" Sounds like we need a third XFiles movie

[xpensive]

Right, and they all show the same pic of the BT46 "surface-cooled" mock-up, which never ran seriously.
While all along the fan-cooled car was the true objective, a project of serious proportions.

[riff_raff]

Surface cooling can be made to work. It's just a matter of getting the difference in temperature great enough between the ambient airflow and the coolant. Here's a 2000hp aircraft engine that used surface cooling: http://www.collectair.com/images/s6.jpg

As far back as I can remember, the regulations always stipulated where the radiator ducts could discharge. With a car utilizing an underwing/diffuser arrangement for downforce, any engineer would quickly deduce that dumping the hot and energetic cooling airflow into the low-pressure zone in the diffuser would both reduce cooling drag and make the diffuser much more effective. That's why it has long been outlawed.

What you need to remember is that the energy content of the hot air coming out of the radiator is roughly equivalent to about 50% of the power produced at the crankshaft. It's huge. A few years back, most F1 chassis also dumped the exhaust flow into the diffuser for the same reason. It's not done any more because the exhaust flow at full throttle created lots of extra downforce, but when the driver backed off of the throttle going into a corner, the sudden loss of downforce upset the aero-balance of the car too much.