Cooling fans

[matt21]

The only thing I can find in the regulations is that moving aerodynamic parts are forbidden.
But does this apply to fans for cooling?

[marcush.]

apart from the little fact that it is forbidden just the following consideration:


the car is moving at an average speed of 200kmh .combine this with an opening of 150x200mm and you see just how much volume is going in there: 1,65 m³/s assuming it´s an open door situation(no preesure drop across the duct)

lets see what a electric fan can move in these conditions :12V/300W EC drive 300mm diameter fan automotive is moving 2800m³/h that´s 0,78 m³/s so you need double that thats 600W 2 300mm diameter fans .....
you usually put the fan behind the radiator to reduce bloackage so the fan is working at higher ambient temps ...reducing the mass flow movement considerably...

600W /13V = 46 amps permanent current draw ....just think of the cabling needed ..

So as there are two openings (one for each Sidepod ) the 600W fans could help you to reduce the inlet opening to half size but you will ineviatbly need to supply those 600W at the Fan drive so you need a much bigger alternator ...

so as ever it is a tradeoff .For a road car it sure makes sense to use the fan (which needs to be big anyways for AC reasons)to support the cooling system and help minimise draggy openings ,but for a Formula 1 car ,a 600W drive with 2 fans is also adding a good 4 kgs of mass to the car not considering the mass you need to add to the alternator..

[mx_tifoso]

Excellent explanation Marcush! It's just what this thread needed.

[riff_raff]

nice marcush.

Yes, in F1, a radiator fan would be considered a moveable aerodynamic device.

And as marcush also noted, at high speeds the fan blades would just get in the way. A well designed liquid/air heat exchanger core and ducting (without an electric fan) should easily produce a net positive effect with regards to drag.

The cooling airflow mass is heated as it passes across the core, its momentum increases, and it provides a thrust reaction as it is ejected from the cooling duct. While the process is not particularly efficient, there is lots of potential energy to work with in the engine oil/coolant system flows. For the electric fan to increase the mass airflow at high speeds, the motor would need to be extremely powerful (and large and heavy).

Think of it this way, the typical F1 heat exchanger is transferring the equivalent of several hundred HP into the passing air mass flow at full speed and WOT. With that much potential energy available to move the requisite cooling air mass across the heat exchanger core, why would one need an additional fan?

On the other hand, a turbine and generator (as opposed to a fan and motor) in the radiator exit duct might make sense (if the rules permitted), since they could extract some useful energy from the cooling system airflow. After all, isn't that essentially what a turbocharger is? A turbine that extracts useful work from the exhaust gas mass flow?

riff_raff

[MIKEY_!]

Not sure how much back pressure that would cause. It would reduce efficiency of the rads at least so unless its doing something else very well then i doubt it would be of use, if its even legal. Good thinking outside the box though.

[marcush.]

one quick and very efficient way to improve the cooling is to increase delta T of Fluid entering the radiator vs ambient temps.

So if you could raise the water temps in the engine that would help an awful lot to rise the cooling system efficiency.One of the reasons why current f1 engines run as hot as they do.

I read about nanofluids containing aluminium and copper particles to enhance heat transfer to and from the fluid.This might or will increase viscositxy -so add drag into the fluid system -so more pumppower may be necessary but it looks like there is potential to it.

[MIKEY_!]

Interesting marcush, good thing we have you around for an informed opinion.

In summary basically there are better ways cool the cars on track than fans. Apart from any issue of legality.

[Rideway]

Even though I agree that fully delegating all the cooling task to a forced air system its pretty difficult, I have seen many cars using fans to help the air convention through the sidepods and therefore through the radiators. Here is the Red Bull:



I have recently seen a "naked" Brawn Gp where the radiator was mounted transversally and with an angle respect to the ground, and it had got fans mounted on the rear side of the radiator. I cant find the pic right now.

[hardingfv32]

This is a demonstration or display car. Look at the quality of the fan mounting system. Also, the ground surface looks like something you might find in a plaza or display room.

Brian

[marcush.]

some figures for a 305mm dc fan -brush type -

http://www.spalautomotive.com/eng/produ ... P70_LL-36A


so at 0 pa backpressure you are well below 3000m³/h that´s 0,83Kg/s and you are covering just a third or even less of the radiator surface as well so it´s not very efficient it´s a fix ,simple as that.

It just delays the time before the whole thing goes up in smoke a bit further as the demo cars have to wait longer than they are designed for (pitstops are a few seconds and grid is less than 1 minute ...the real test maybe is a start from pitlane when the car has to wait for an awful ong time at the traffic light at pit exit .

there is no fan in Formula 1 cars definitely ...it´s not allowed and not feasible.

just look at the fan shroud this is a universal catalogue part not even specified for the temps it will see. this type of fan does 80, maybe 90°C for a short time ....and the engines of today run ALOT hotter than this ....so rest assured this is a service part for the democar.... it would NEVER go on a automotive appication .
the EC -counterpart with integrated electronics will run happily at 120°C for extended time (hours) but at 130°C even these are calling quits ...If anyone would specify fan assmblies for this application ...it would clearly be separate electronics to make it survive in this environment .Not available on the market as far as I know.
suffice to say ,you would not mounbt the fan as close to the radiator ,as the blockage caused by the motor and proximity of the fan blades to the rad is not helping efficiency either...

[Rideway]

I dont think that the temperature would be a problem as there are some polyamids that stand very high temperatures (even up to 300ºC).

But ass you said before, and i fully agreed with that, its difficult/impossible for a fan to move the air mass flow needed to cool down the system without needing huge amounts of electricity, not possible for this application.

[xpensive]

apart from the little fact that it is forbidden just the following consideration:


the car is moving at an average speed of 200kmh .combine this with an opening of 150x200mm and you see just how much volume is going in there: 1,65 m³/s assuming it´s an open door situation(no preesure drop across the duct)

lets see what a electric fan can move in these conditions :12V/300W EC drive 300mm diameter fan automotive is moving 2800m³/h that´s 0,78 m³/s so you need double that thats 600W 2 300mm diameter fans .....
you usually put the fan behind the radiator to reduce bloackage so the fan is working at higher ambient temps ...reducing the mass flow movement considerably...

600W /13V = 46 amps permanent current draw ....just think of the cabling needed ..

So as there are two openings (one for each Sidepod ) the 600W fans could help you to reduce the inlet opening to half size but you will ineviatbly need to supply those 600W at the Fan drive so you need a much bigger alternator ...

There's also the pressure drop over the passage through the duct and radiator to consider, if you try to move 1.65 m^3 with a measly 600 W, you can only handle 360 Pa (0.0036 Bar), while as a comparison the dynamic pressure at 200 km/h is 1850 Pa.

[marcush.]

I dont think that the temperature would be a problem as there are some polyamids that stand very high temperatures (even up to 300ºC).

But ass you said before, and i fully agreed with that, its difficult/impossible for a fan to move the air mass flow needed to cool down the system without needing huge amounts of electricity, not possible for this application.

sorry ,I was a bit unclear there ..

the problem is the brush system and windings inside the drive .For the EC fan it´s also the electronic components (capacitors for example) ..these are not specified for the downstream airtemps of a F1 car.(as the drive has its own waste temperature to add as well).

PA 66 GF30 are specified at around 260°C melting temps so that should not be the big problem even though one should not forget the exhaust radiated heat when the thing is glowing...this can lead to a few surprises.

[riff_raff]

one quick and very efficient way to improve the cooling is to increase delta T of Fluid entering the radiator vs ambient temps.

So if you could raise the water temps in the engine that would help an awful lot to rise the cooling system efficiency.One of the reasons why current f1 engines run as hot as they do.

Good points.

Besides increasing the coolant side temps, you could also increase the heat transfer rate by using a core material with higher thermal conductivity, like copper. But even though the copper core would be about 1/2 the size of an aluminum core, it would be over 3 times as heavy. The ideal core material would be beryllium, if you could afford the horrifying cost. The beryllium core would have about the same thermal conductivity as the aluminum core, but would weigh about 1/3 less.

You could also increase the temperature rise in the air mass flow across the core by using a thicker core. The thicker core would need less frontal area, and thus smaller duct cross sections, so it should have a lower drag penalty. But it would likely be heavier. Since most current F1 heat exchangers tend to be thin with large frontal area, one can logically assume that weight is more important than drag for this application. However, if you've ever seen a heat exchanger on a high speed aircraft, they tend to have very thick cores and small frontal areas.

Here's a quick read on the "Meredith Effect", which is about the net thrust gain that can be produced from a heat exchanger installation:

http://www.hq.nasa.gov/pao/History/SP-445/ch5-5.htm

Regards,
riff_raff

[marcush.]

I think the biggest potential would be to change current cooling from a pure fluid heat transfer to something based on vapourisation and condensing the fluid .
The Heat transfer would be a LOT bigger and I think the power needed to move the fluid will also be considerably lower ..So you would gain in two areas =potential for reduced radiator surface + smaller water pump.
I would think the temperature spread across the engine could be better as well.

So the question is : is it legal ? Or could you say its fluid cooling and the system is due to its bad design vapouring the cooling fluid?


I wonder how much potential there is in optimising heat transfer from water via the aluminium to the air when Air is such a bad heat conductor .
So you may be able to get perfect heat transfer from the engine to the fluid and to the radiator tubes ...but the BIG loss is when the aluminium of the rad has to
be fed to the ambient air ....?