Ed = wrote:

Ok, Paul

Using the K&W = formulas, I=20 calculate that the 14x10 core area would

handle 120HP at 120MPH TAS, you would need = to get to=20 160 MPH to get the mass

flow to handle 160HP. =

Just = scaling your=20 power number on the basis of core area; it comes to about 225hp for my = setup. I designed for 200 hp at 120 mph; so I guess that is = reasonable=20 close correlation. Either we=92re both right, or both wrong=20 J.

Well, = for both=20 your and Paul's sake, I hope we are all correct = {:>).

There = are enough=20 uncertainties just in the differences between different types of = cooler core=20 to make that much difference.

Its = fairly clear=20 that air flow and core area are two of the most significant = factors as=20 together they determine the basic Mass flow possible through the = cooler. =20 If that is not sufficient to carry away the heat you are trying to = reject then=20 all else is moot.

In = K&W there=20 are two coefficients they focus on, Kh the heat = transfer=20 coefficient which is dependent on the characteristics of the core,=20 Kp the pressure drop coefficient - again based on = core=20 characteristics. They end up with a combined coefficient that = rates how=20 well the core transfers heat based on the pressure drop this is = Kv =3D=20 Kh/Kp. These coefficients are dependent on such things = as the=20 openness ratio, the hydraulic diameter of the individual passage in = the core=20 and the thickenss of the core. Both Kh and = Kp=20 are also weakly dependent on the Reynolds number of the air = flow=20 throught the core. I say weakly because they relate to the = inverse=20 fourth power of the Reynolds number or 1/(Re)^(1/4).

=20 Interestingly enough because it is an inverse relationship the heat = transfer=20 is better to the air with lower velocity through the core. Not = quite=20 certain that I fully understand why, except it appears to do with the = shear=20 force and friction between the air flow in the core passage and the = the=20 passage walls. However, while heat is apparently passed from the = core=20 walls to the air better at the lower Reynolds numbers, the downside is = that=20 low Reynold number also means lower air velocity throught the core = which in=20 turn means Low mass flow which is not good for=20 cooling.

So from = the=20 equations in K&W that there is an optimum balance between the heat = transfer due to the lower Reynolds effect and the heat removed due to = higher=20 mass flow through the core. Too much of one and not enough of the = other and=20 your cooling is suboptimal.

FWIW

Ed=20 Anderson