2014 intercooling

[langwadt]

The surface area required for surface cooling is probably similar to the total area of conventional finned heat exchangers. One obvious difficulty is transporting and confining the working fluid over the large area required. At the very least it is going to be considerably heavier than the conventional solution - due to greater volume of working fluid and greater mass of the "pressure system" which has only about half of its total surface area exposed to the airstream. In contrast a conventional heat exchanger has most of the metal which confines the working fluid exposed to the airstream.

afair the "predecessor" to the spitfire had surface surface cooling, that wasn't very smart if you get shoot at so the spitfire instead got boxes under the wings with radiators inside afaiu they even provided a bit of thrust

[ringo]

This is actually quite an interesting subject from an academic standpoint. There are many trade-offs to consider with charge air cooling. There is trade between the intake flow and pressure losses produced in the system versus the benefits from increased charge air density and lower charge air temperatures. There are also the aero drag and weight penalties resulting from an air-air heat exchanger installation. If the boost pressure ratios are high, then a liquid-air heat exchanger might work best. However, with the boost levels and compressor efficiencies existing in a current F1 engine, I can't see how the additional complexity and mass of a liquid-air charge air cooler system would make sense.

Liquid to air also makes sense if the desired charge temperature is significantly higher than ambient. I believe this to be the case (as I have stated elsewhere). Honda RA128E was deliberately operated at 80*C to improve combustion and therefore thermal efficiency. Current F1 engines have no need of additional charge density. 3.5 bar boost + intercooling to ambient delivers at least 50% more air than required to burn the allocated fuel.

At 80*C charge temperature a liquid to air system could share the engine cooling system.

80 degrees? are you sure about that?
That looks like the temperature out of the compressor and not after the intercooler.
From my homemade simulator, i'm getting 80 degrees C out the turbo for 11,000rpm and at 15000 that reduces to 51 degrees.
With these engines, the most you may expect is 100 degrees C at lower rpms.
Now for the intercooled temperature that is dependent on what the engineer wants as his outlet temperature. 40 degrees? 30 degrees? who knows, but 80 into the intake manifold is too high.

[gruntguru]

This is actually quite an interesting subject from an academic standpoint. There are many trade-offs to consider with charge air cooling. There is trade between the intake flow and pressure losses produced in the system versus the benefits from increased charge air density and lower charge air temperatures. There are also the aero drag and weight penalties resulting from an air-air heat exchanger installation. If the boost pressure ratios are high, then a liquid-air heat exchanger might work best. However, with the boost levels and compressor efficiencies existing in a current F1 engine, I can't see how the additional complexity and mass of a liquid-air charge air cooler system would make sense.

Liquid to air also makes sense if the desired charge temperature is significantly higher than ambient. I believe this to be the case (as I have stated elsewhere). Honda RA128E was deliberately operated at 80*C to improve combustion and therefore thermal efficiency. Current F1 engines have no need of additional charge density. 3.5 bar boost + intercooling to ambient delivers at least 50% more air than required to burn the allocated fuel.

At 80*C charge temperature a liquid to air system could share the engine cooling system.

80 degrees? are you sure about that?
That looks like the temperature out of the compressor and not after the intercooler.
From my homemade simulator, i'm getting 80 degrees C out the turbo for 11,000rpm and at 15000 that reduces to 51 degrees.
With these engines, the most you may expect is 100 degrees C at lower rpms.
Now for the intercooled temperature that is dependent on what the engineer wants as his outlet temperature. 40 degrees? 30 degrees? who knows, but 80 into the intake manifold is too high.

Re-check your simulator. At 3.5 bar abs boost the compressor discharge temperature will be about 200*C. (assuming compressor efficiency = 80%)
Honda deliberately ran the charge air temperature at 70*C to improve efficiency on the RA168E.

[ringo]

3.5 bar of boost is not what is being used currently. That is a big assumption that you are making.

At 4 bars of boost with the RA167e, intake air temperature was 40 degrees C with the 1000hp layout.

The intake temps were the same for the RA168 at 40 degrees C with the 2.5bar pressures.

Apparently the car had intercooler bypass valves which could control how much air is intercooled. Where you see 80 degrees C is the fuel temperature. The air temp was experimented at 70 degrees C, after the intercooler was bypassed, to obtain best fuel consumption. However the car was fully capable of cooling the air to within 15 degrees C of the ambient temperature.

That high intake temperature was related to the specific fuel that was used, the toluene and the effects temperature had on it's vaporization. In fact there is nothing to suggest that the air coming from the turbo is 200 degrees C.
It wasn't mentioned.
I know, with supporting calculations that the temperatures are not as outrageous as you postulate.

[ringo]

So if you consider that 70 degrees C is the bypassed temperature, which means it's mostly coming straight from the compressor, can you truly say that the turbo temp is 200 degrees C?

[gruntguru]

Bypassed charge was mixed with cooled charge to maintain 70*C. (sorry about the 80*C confusion with fuel temp)

3.5 bar abs is the number quoted by Renault. What do you say the boost is?

If boost was 3 bar abs (2 bar gauge, 29 psi). . . .

T2=T1*(P2/P1)^((k-1)/k) for isentropic compression.
= 293*(3)^((1.4-1)/1.4)
= 401*K (128*C) ie temp rise of 108*C

At 70% isentropic efficiency, temp rise will be 108/0.7 = 183*C so T2 = 203*C (About the same as 3.5 bar 80% eff which I posted above)

[dren]

Would there be any benefit to heating the fuel, since it looks like the charge cooler of the Mercedes is in or near the fuel cell? With the fuel regulations, could they formulate a fuel that would benefit from being heated and act as a better coolant?

[matt21]

Would there be any benefit to heating the fuel, since it looks like the charge cooler of the Mercedes is in or near the fuel cell? With the fuel regulations, could they formulate a fuel that would benefit from being heated and act as a better coolant?

Fuel heating was used in the 80ies as the fuels were hard to atomize, as they consisted mainly from toulene.
Normally you want to inject the fuel at the lowest possible temperature in order to use the latent heat to increase efficency.
And with todays fuel, you shouldn´t have the atomization problem.

[dren]

The latent heat is more for knock resistance, right, therefore higher efficiency since higher CRs can be utilized? Are there high octane fuels with significantly higher vaporization points compared to the "normal" stuff? I figured the heat energy sucked out of the engine for vaporization was purely for the state change, and not much on the temp rise of the fuel. So the fuel could still be used to cool, possibly? The chemical side of things I don't have much of a clue on...

[ringo]

Bypassed charge was mixed with cooled charge to maintain 70*C. (sorry about the 80*C confusion with fuel temp)

3.5 bar abs is the number quoted by Renault. What do you say the boost is?

If boost was 3 bar abs (2 bar gauge, 29 psi). . . .

T2=T1*(P2/P1)^((k-1)/k) for isentropic compression.
= 293*(3)^((1.4-1)/1.4)
= 401*K (128*C) ie temp rise of 108*C

At 70% isentropic efficiency, temp rise will be 108/0.7 = 183*C so T2 = 203*C (About the same as 3.5 bar 80% eff which I posted above)

At 3.5 bar absolute with 82% compressor efficiency, boost pressure is 120 degrees C. My intake temperature is 15 degrees C which is standard for engine tests.

Your efficiency of the compressor is just grossly bad. Why do you apply the isentropic efficiency of 70% directly to the temperature?

[gruntguru]

Applying efficiency direct to the delta T is a reasonable approximation of the effect of isentropic efficiency <100% at low presssure ratios. An 82% efficient compressor will need 1/0.82 x isentropic power. (About 22% greater shaft power). All of this additional energy goes into heating the charge.

At 3.5 bar abs boost 15*C inlet and 100% compressor efficiency:

T2 = (273 + 15) x 3.5 ^ ((1.4 - 1)/1.4)
= 412*K (= 139*C) ie much hotter than your 120*C. At 82% efficiency the charge will be hotter still.

[ringo]

You are not using the theory correctly. Compressor efficiency is treated different from turbine efficiency. For the compressor, you multiply the efficiency to the enthalpy change for the turbine you divide by the efficiency.
A more efficient compressor requires less shaft work, a more efficient turbine delivers more shaft work.

200 degrees C air would actually generate steam in the water cooled bearing cartridge; depending on the water pressure.

Another question to ask yourself is are you expecting the intecooler to drop over 100 degrees C? try doing a simple calculation and see if you can get down 200 degrees to 40 degrees in an intercooler that can fit in an F1 sidepod.

[gruntguru]

Yes. A more efficient compressor requires less work. So an 82% efficient compressor requires 1/0.82 x the work for a 100% compressor eg if a 100% isentropic compressor requires 100kW, a compressor with 82% isentropic efficiency requires 100/0.82 = 122 kW.

and No - I am not using the theory incorrectly. Check my calcs here http://www.engineering-4e.com/calc4.htm

200*C - 40*C in an intercooler? Yep - happens all the time

[mrluke]

Sorry but i am struggling to believe that people put 200 deg c air through plastic / silicone pipework pre intercooler and theres plenty running over 2bar boost (3 bar abs).

[lks]

Sorry but i am struggling to believe that people put 200 deg c air through plastic / silicone pipework pre intercooler and theres plenty running over 2bar boost (3 bar abs).

Where is the problem with silicone, most heavy tuned road cars / quarter mile cars are using steel or alu. piping with silicone joiners.
I don't recall ever seeing plastic piping pre. intercooler.
Silicone is very heat resistance. High temp cables are normaly made from silicone insulation.

Even on OEM road cars i am not aware that u see plastic before after the intercooler, but i am also not aware of that high boost pressure on OEM cars.