16 replies to this topic

[MarkWill]

Hi,

How does radiator efficiency vary with speed and "angle of attack" in a modern F1 car? For a given inclination, e.g. 45 deg, is there a maximum airspeed, above which there is no increase in efficiency from a standard radiator of a given size? Also, what is preferrable on a modern racing car (not necessarily an F1), two small radiators or one big one with the same cooling capacity?

[Ned]

Markwill, hope you don't mind me tagging on 1 more question here...

Do teams use vortex generators to make the flow turbulent before hitting the radiator tubes? Coz the heat trasnfer coeff for turbulent flow is much higher right?

Ned

[MarkWill]

Aha! No problem tagging on your question - I`m headed a bit in that direction anyway, but lets ee what the answers are first.

[golfball]

Heat rejection scales approximately with mass flow of air to the power 1.5

This isn't affected per se by the angle of inclination of the radiator but the greater the angle, the harder it is to design an inlet duct and the greater the effect of the bodywork behind it. Consider a radiator perpendicular to the flow - the effect of the bodywork around it it small whereas a very angled radiator forms a small angle between it's downstream face and the bodywork which then creates back pressure and reduces flow.

This trade off between back pressure and increased face area is what determines the final solution - the optimum depends therefore on what you want to achieve with the bodywork.

Turbulence is not created in the duct as it will be large scale turbulence. The radiators tend to create turbulence themselves by having jagged finning - this then creates turbulence at a small enough scale to be useful in the gaps between the fins.

[MarkWill]

Is the 1.5 factor a constant, or is there a speed at which the rule changes significatnly? Also, what is better, and ultra-thin radiator, or a radiator with a deeper cross-section? Also, are radiators coated to improve their emmissivity, or are they plain bare aluminium (or whatever the material is)?

[Paolo]

Originally posted by MarkWill
what is better, and ultra-thin radiator, or a radiator with a deeper cross-section?

If you want to save weight, an ultra thin radiator is the way to go : it has a better exchange rate than a deeper one.
About drag, I think there is an optimum depth: of course making a thin radiator requests an increase in frontal area, but a deep radiator with small area will proportionally lose more of it because of the boundary layers forming in the inlets. Also, the flow will lose more energy passing through its lenghtier cells.

[Keith Young]

I am no radiator expert, but i would think as the air gets farther back through the radiator it gets hotter, reducing its cooling ability toward the downstream face of the radiator.

[Paolo]

Originally posted by rough_wood
I am no radiator expert, but i would think as the air gets farther back through the radiator it gets hotter, reducing its cooling ability toward the downstream face of the radiator.

Spot on.
Heat exchamge depends on the temperature differential ; warmer air will take heat at a slower rate. Therefore the downstream sections of a radiator cell are not as efficient as the upstream ones.

[Scoots]

In some radiators the water/oil is turned in the tubes in the radiator to get mor thorough cooling ... don't know if that's used in F1 though.

[RDV]

Scoots- In some radiators the water/oil is turned in the tubes in the radiator to get mor thorough cooling ... don't know if that's used in F1 though.

All oil coolers have this, it ensures that the flow through tubes makes all oil to come in contact with wall... oil is a pretty good heat insulator, and viscosity adds to this problem. Water radiators don't need them..

[perfectelise]

I wonder what sort of contribution direct air-cooling makes with major elements like engine and gearbox. It obviously works well enough for the brakes and electronics.

[Kalle_hopp]

Saw this picture from australia: http://f1total.com/b...aus/fr/z099.jpg

Whats the reason for the "steps" in the radiator ?

[Paolo]

They look more like turning vanes than part of the radiator mesh.
If Ferrari has radiators inclined upwards, they could be used to get the flow normal to them.
Otherwise, beats me.

[golfball]

Originally posted by Kalle_hopp
Saw this picture from australia: http://f1total.com/b...aus/fr/z099.jpg

Whats the reason for the "steps" in the radiator ?

That isn't the radiator - it's a mesh placed in front of it to catch all the crap (leaves, gravel, carrier bags, visor tear-offs). The steps are in it to give it some stiffness.

[Timstr11]

Originally posted by golfball


That isn't the radiator - it's a mesh placed in front of it to catch all the crap (leaves, gravel, carrier bags, visor tear-offs). The steps are in it to give it some stiffness.

But doesn't it impair aerodynamic efficiency and also reduce cooling capacity?

[Kalle_hopp]

There is another picture showing the car ready for action where the mesh seems to be gone: http://f1total.com/b...aus/fr/z019.jpg

And another picture showing McLarens radiator(?): http://f1total.com/b...aus/fr/z045.jpg


Are the radiators built by the teams or bought from a "car-shop" ?

[RDV]

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Originally posted golfball :

That isn't the radiator - it's a mesh placed in front of it to catch all the crap (leaves, gravel, carrier bags, visor tear-offs). The steps are in it to give it some stiffness.
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Also if front (vertical) face gets blocked by crap, the horizontal steps allow air past...

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Originally posted by Timstr11
But doesn't it impair aerodynamic efficiency and also reduce cooling capacity?
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Yes , but better than no air after mid race.....