Radiator Angle

[Caito]

Hello guys, I have a doubt about radiator angles, maybe you can help me out.

We normally see race cars with big radiators angled. I ussually get the answer that they're angled to lower the COG.

The answer seems quite logical. What I don't understand is, given that the air that will go through the radiator is limited by the hole size(say the "sidepod" hole) why don't, instead of putting a big radiator angled, put a small radiator straight up?


Thank you!

bye bye


Caito.-

[Holm86]

AFAIK they dont mount the radiators at this angle because of the CoG.

They do it because they want a bigger area to dissipate heat and that is more effective than a smaller radiator that is vertically mounted.

And it is not only the size of the airintake that determine how much air can pass through the sidepod. The exit has just as much to say. If not even more.

[bettonracing]

A small radiator sitting straight up has less surface area for thermal transfer than a large radiator at an angle.

A large radiator sitting straight up will have higher frontal area (& therefore higher net drag), as well as a higher CoG.

Regards,

H. Kurt Betton

[GTRdesign]

The desired effect is to increase the pressure difference through the core by increasing the pressure on the radiator face. By angling the core, the effective cross sectional area the air travels through is dramatically increased, thus slowing the air stream, and effectively increasing the pressure on the face.

As for inlet/outlet size, a "stream tube" develops ahead of the intake, and pretty much adjusts it's own size to meet the duct's requirements. The outlet duct, and the area to which it exhausts are far more critical.

[marcush.]

where is the difference in terms of CoG height for an angled vs an upright radiator. You imply that an angled rad has lower sidepods?

[xpensive]

where is the difference in terms of CoG height for an angled vs an upright radiator. You imply that an angled rad has lower sidepods?

Sinus the angle comes to mind?

The desired effect is to increase the pressure difference through the core by increasing the pressure on the radiator face. By angling the core, the effective cross sectional area the air travels through is dramatically increased, thus slowing the air stream, and effectively increasing the pressure on the face.
...

What you really want is to maximize the air-speed through the radiator in order to increase the forced convection between air and core, but it's always a balance with the xposed area as well as aerodynamic drag.

[marcush.]

where is the difference in terms of CoG height for an angled vs an upright radiator. You imply that an angled rad has lower sidepods?

Sinus the angle comes to mind?

The desired effect is to increase the pressure difference through the core by increasing the pressure on the radiator face. By angling the core, the effective cross sectional area the air travels through is dramatically increased, thus slowing the air stream, and effectively increasing the pressure on the face.
...

What you really want is to maximize the air-speed through the radiator in order to increase the forced convection between air and core, but it's always a balance with the xposed area as well as aerodynamic drag.

err.. maximise yes but you slow down the air stream by having a divergent radiator inlet.(small inlet converging towards a big radiator surface)TheAngled
rads also make the air hit the radiator core at an angle,maybe this is also not the best of ideas...so you need a slower moving air to make the bend...and looking at Renaults rads the other option with almost upright rads does work as well ....so maybe it is not really as sophisticated thinking as we believe it is.

[Mystery Steve]

Having the radiators angled could also make the flow through the fins more turbulent and could help increase the convective efficiency. Without numbers it's all just a guessing game regarding specifics. In reality there is a balance point between drag and cooling capability. Each team just has to decide how much cooling they need and how much drag they're willing to pay to get it. While the angled radiator certainly lowers the center of gravity (water is heavy and those are big radiators), I would suspect the biggest reasons are to reduce drag on the body and do create the diverging duct in the most compact way possible (as marcush said).

[xpensive]

Let's try and get this straight marcush, but first of all I have to straighten your post out, sorry about that;

Err.. maximise yes but you slow down the air stream by having a divergent radiator inlet, a small inlet converging towards a big radiator surface. The angled rads also make the air hit the radiator core at an angle, maybe this is also not the best of ideas...so you need a slower moving air to make the bend...and looking at Renaults rads the other option with almost upright rads does work as well....so maybe it is not really as sophisticated thinking as we believe it is.

Now, in the old days, when I was young and handsome, the radiators were always angled horizontally, if you can follow,
but now radiators seem to be installed in a standup fashion, at a shallow vertical angle, which doesn't do much for the CoG?

Furthermore, the RBR radiator is looong, with a passage area that looks like at least four or five times more than the sidepod opening, which would indicate that they are deliberately slowing the air down. The price to pay for a wider core perhaps?

[marcush.]

Renault worksteam and RBR follow completely different philosophies and it seems to work for both ...but both not scoring in the drag field...
It seem to be like:different ways to skin the cat again...RBR going for x-times pass and long cooling paths for the water +maximisesd radiator core surface licked by air at less than optimum angles,whereas Renault uses a an almost upright radiator ,maybe single pass(!) so very short cooling path plus a small but surface area wich is hit at right angles by the air...

[xpensive]

I once saw a picture of RBRs radiator, where I got this strange impression that their rad's core was all horizontally arranged and stremlined tubes, without lammellas, which would indicate some aerodynamical thinking behind it, Newey's work perhaps?

[madtown77]

I once saw a picture of RBRs radiator, where I got this strange impression that their rad's core was all horizontally arranged and stremlined tubes, without lammellas, which would indicate some aerodynamical thinking behind it, Newey's work perhaps?

Strange concept since you generally need turbulence in the airflow passing through the radiator for it to work efficiently along with all that extra surface area.

[Caito]

I revive this post.

Last semester I learnt about heatsinks, coolers, etc. I can draw some conclusions from there. These are normally used for electronics, but the same concepts(forced convection) still applies.


When you force convection there's a great increase in cooling but to a point. At the beginning you get a really big increase, and there's a point when there's no marginal win in augmenting the airspeed.

I believe this happens in formula 1. If air goes too fast, it can't cool so they widen the sidepod, reduce airspeed and hence put bigger radiator. As for the thickness, it would increase cooling but also drag.





I leave one question pending. Last year I saw the FIA GT in Potrero de los Funes and I noticed all teams had the radiator mounted horizontally. This(I believe) decreases CoG and increases downforce(if the air ends going up, the car must go down).

Why is it that lots of gt, tourism cars have radiators horizontally and most formula cars doesnt?

Bye bye!

[marekk]

There is more to that than just aerodynamic drag.
Using bigger radiator, you can have lower coolant speed for a given heat transfer, and significantly reduce power needed to drive the water pump.