F1 radiators, how often are they changed?

[Dipl-Ing.]

Hi guys,
just had a lecture on heat exchangers and this got me thinking of F1 radiators. We were told that a heat exchanger start fouling (which of course reduces efficiency) after 3 hours.
So simple question, does anybody now how often they change radiators?
Because a raceweekend is about 3h for each car so I figured they could manage one weekend without cleaning it. Or do they clean them? how often? Or does fouling even occur? why?/whynot?

thanks in advance, I know there are some clever guys here who should now. But I only mean in F1 not anyother cars or sport.

[mzivtins]

Hi Dipl-Ing.

Great questions, do you mean fouling internally due to fluids or externally due to foreign dodies causing blockages?

Internally i would have thought that due to the fact all liquids are pre-heated externally to the, car would mean the internal operating characteristics would stay very much the same for a longer time than 3hours?

Cheers

[Dipl-Ing.]

I mean fouling internally. and even if the liquids are preheated there is supposedly still some fouling or something else maybe that hinders efficiency. I'm at work so cant upload a graph but we were told that thermal transfer rate starts at x then after t=3,5h reaches it's max at x*1,15 and then falls drasticly to 1/6*x.
so i was thinking 15% is a lot and if you can opperate only in that window you can save 15% of radiator size and help your aero out a lot.

[hardingfv32]

What in the race engine 'world' would cause fouling in three days?

The fluid should be 'almost' pure water, but I am not sure what would cause corrosion.

Brian

[Dipl-Ing.]

I'm sure they wouldnt use pure water, would they?. If you add glycol you will have a much higher heat transfer rate meaning the rads could be smaller. but what I'm getting at is that as the glycol evaporates the heat transfer increases because of the surface roughness, for a period of 3h. and what i thought was if you could get your rads to stay in this lets say sweetspot for a raceweekend, then you could decrease the size of your rads.
Brian certainly no disrespect to you, but I just thought they wouldn't use pure water. but if you are sure then I'll take it as fact.

[hardingfv32]

I believe there is nothing better than pure water and a some agent to increase 'wetting ability of water' for heat transfer. I am not sure what properties we are talking about for 'wetting ability'.

Brian

[Dipl-Ing.]

Ok so I've think I've gotten lost in translation, these things happen if you've been in Germany a while. I dont mean heat tranfer I mean heat capcity of water. heat doesnt need to be transfered if the medium is moving which the coolent in a rad is. To make this more technical the heattransfer of water is 0,6W/mK which compared to lets say copper 420W/mK is nothing. But the heatcapacity of water is 4,2kJ/kgK, so two completly different things, i apolagise for the(my)confusion. And Brian your right, a saline solution has a smaller heatcapacity than pure water. So ofcourse they will use pure water.
thanks for setting me straight.
mods you want to close this?

[Lycoming]

No, synthenic coolants can be slightly better choices, but its probably stipulated in the rules somwhere, in which case they would use de-ionized water.

[mzivtins]

what about weight? does pure water weigh less than the cooling agents? trade off between heat transfer performance and weight would be the only thing they are interested in i would say... keeping the weight down but having to change the rads ever race weekend would, to me anyway, seem like not so much of a problem.

[DaveW]

I believe there is nothing better than pure water and a some agent to increase 'wetting ability of water' for heat transfer. I am not sure what properties we are talking about for 'wetting ability'.

WaterWetter, I believe. The reference is worth a read. Also used as a lubricant in water based damper fluids - it appears to work in that application.

[marcush.]

The story goes on

I have recently read about nanoparticles mixed into the water have shown potential in improving heat transfer.

But realistically ,the thermodynamics in that area of heat transfer is not really
going to net big gains .I think the transfer rate can be improved by 3% or something but in the total chain this will not net any significant gains -compared to say increasing delta T ....
Unfortunatelly the pressure is restricted to 3.5bar and so there is no chance to increas system pressure to make use of this by running the engine hotter.

http://www.google.de/url?sa=t&rct=j&q=n ... Z9Z9Jskdkg

[Sombrero]

I remember this from Ian Marchard (Jordan V-10 Honda).

4000 km for a radiator if all goes well and a lot of maintenance (rubber shred and so on).

[hardingfv32]

What is the issue with heat transfer between the aluminum (or copper) and water? How is this interface made better?

Brian

[marcush.]

we have recently had an excurse towards carbon- or better graphite....I´m currently investigating graphite as a possible means of conducting heat away -say as a heat spreader .Surprisingly enough heat is conducted just as well ás in aluminium with graphite but to add to this:it is very well conducted in plane but quite bad transversially...
Some companies are already substituting copper and aluminium heatsinks/cooling ribs with graphite..I´d say there is potential in it .
graphit foil is readily available:

http://www.sglgroup.com/export/sites/sg ... IT_F_d.pdf

[riff_raff]

What is the issue with heat transfer between the aluminum (or copper) and water? How is this interface made better?
Brian

hardingfv32,

The heat transfer between the coolant boundary flow and radiator tube surface is convective, so you could improve the heat transfer rate at this interface by increasing the relative deltaT, increasing the specific heat of the coolant, increasing the thermal conductivity of the tube material, increasing the mass flow rate of the coolant, increasing the total core surface area available for heat transfer, increasing the temperature rise in the coolant across the core by making the flow more turbulent to promote mixing of the boundary flow, etc.

All other things being equal, a copper core would give better heat transfer than an aluminum core due to copper's higher thermal conductivity. While a copper core could be made more compact for the same heat rejection rate, it would also be much heavier.

One approach being used to make liquid-to-air heat exchangers lighter and more compact is to use a core made from a very dense matrix of very small diameter metal tubes with extremely thin walls. The very small tube ID ensures that most of the coolant flow contacts the tube surface, and the extremely thin tube wall gives efficient heat transfer.

http://www.mezzotech.com/applications.html

riff_raff