2014 intercooling

[aral]

Given the only advantage of waterless coolant is a higher boiling point requiring no pressurisation of the header tank, why are they are running header tanks/accumulators with pressure cap then?

Waterless coolant still needs header tank and pressure caps as it also expands when heated.

[defender90]

Given the only advantage of waterless coolant is a higher boiling point requiring no pressurisation of the header tank, why are they are running header tanks/accumulators with pressure cap then?

Waterless coolant still needs header tank and pressure caps as it also expands when heated.

I can guarantee no teams are running waterless coolants. They have greatly reduced heat transfer properties and as such the coolant in all the engines will be 100% pure deionized water, there is virtually no better coolant. The problems that waterless coolants have been developed to deal with are related to nucleate boiling and corrosion issues. The corrosion issue shouldn't be a problem as the engines don't run far enough, and the nucleate boiling issue can be designed out/dealt with more effectively.

[PhillipM]

It expands, but it doesn't need a pressure cap, that would be the only point of using it.

Still irrelevant, as they're not using it.

[defender90]

As shown here:
https://www.youtube.com/watch?v=uP8SQqIYB3A

[miguelalvesreis]

And if it was only the end substance than matters when it comes to heat transfer then why do cars use water radiators and not air radiators since they would be much lighter. Also why are additives used to help the water cool better. If what you (ringo) said is true then additive or not the same heat transfer for normal cars would take place but that is simply not true, go and read up about thermodynamics.

Additives don't make water cool better. They just change the boiling point and freezing point of the water. They also have anti corrosion and anti scaling properties. For a race car that's going to have all the fluids drained at the end of a race, corrosion is not a problem, engine just has to be flushed out. so water can be used. Freezing isn't a problem either, so glycol is not necessary.

As for you engine question, water takes heat away quicker from the metal of the cylinder walls. The metal is now your limiting factor and not air as in the case of the charged air. The water takes the heat to an area where there is free flow of air to dissipate that heat. If you want to go one better, why not use a metal cooled engine?

What would be even better is metal to air. An air cooled engine like the porsches of old and some of the motor bikes nowadays. Those are more thermally efficient in theory.
But it goes back to the limitation of the location of the engine, can the fins be exposed to cool air? how about the fin design? how much mass of metal is needed to pull heat away from cylinder wall if the air flow is reduced (moving water does this).

As for a good example of an air cooled engine. The porsche 917 CanAm. 1500hp in qualifying. 1,100 in race trim.
https://www.youtube.com/watch?v=JrBwNX6vqSA#t=247 go to 4:07

Don't get me wrong, water cooling gives more control, and gives a nice buffer.But it's what at the ends of the chain that will limit you.

Let's work the example and see what is reveals.
edit: Lycoming illustrates it well/

Is'n this exactly the way a air-water intercooler is supposed to work? One of the assumptions being made is that the surface area will be the same in both systems but, in a air water intercooler, the compressed air is cooled down at the intake manifold, right? Beeing the manifold cooled down by the circulating water, exactly like the cilinder walls, increasing the surface area where the heat transfer occurs?

"Technically, a water/air intercooler has some distinct cooling advantages on road cars. Water has a much higher specific heat value than air. The 'specific heat value' figure shows how much energy a substance can absorb for each degree temp it rises by. A substance good at absorbing energy has a high specific heat value, while one that gets hot quickly has a low specific heat. Something with a high specific heat value can obviously absorb (and then later get rid of) lots of energy - good for cooling down the air." (By Julian Edgar - The Complete Guide to Intercooling)

And from EngineBasics.com:

" air to air intercooler:
...
Pro’s

1. Requires no power to work and therefore is easy to set up.

2. Requires no liquids to work and therefore no chances for leaks .

3. Doesn’t suffer from heat-soak as long as the intercooler is seeing good airflow.

Con’s

1. Efficiency is only as good as the ambient air temperature.

2. Efficiency is only as good as the amount of airflow the intercooler see’s.

3. Cannot be mounted anywhere, since it must be mounted in a location to see airflow.

...

Water to Air Intercooler:
...
Pro’s

1. Really good efficiency, so the size of the intercooler can be smaller.

2. Efficiency can be exaggerated by using ice, or other chemicals to produce normally un-realistic temperatures for short amounts of time.

3. Can be mounted anywhere along the charge piping route.

Con’s

1. Requires a lot of other accessories to work.

2. Because it is more complex, it naturally causes more opportunity for problems, like leaks.

3. Can become heat soaked when used for long periods of hard driving and become terribly in-efficient."

So, main advantages seem to be packaging and temperature control (via water flow control). The extra weight and proneness to heat-soak seem to be the main issues.

[aral]

It expands, but it doesn't need a pressure cap, that would be the only point of using it.

Still irrelevant, as they're not using it.

Have it your own way, but I know different! Two teams which I have a connection with, are using it!

[turbof1]

I moved 4 pages of intercooling discussion from the w05 car topic to here. Bump to get topic back on top

[ringo]

Worked example:

Heat transfet rate of the intercooling system can be respresented simply with this equation:

Q = U A dT.

U is the total heat transfer coefficient of the process
A is the heat exchange areas between the flows involved.
dT is the temperature diference between the flows ie the charge air and the air in the sidepod.

Now the process can be represented by a thermal circuit with each medium posing as resistance to heat flow.

For the air to air:

T0 ------/\/\air/\/\-------------/\/\metal/\/\----------------/\/\/air\/\/\----------T1


for water air:

T0-------/\/\air/\/\/\--------/\/\metal/\/\---------/\/\water/\/\--------/\/\metal/\/\------/\/\air/\/\----T1



those zig zag things are resistors.

now the total resistance R, would be R = 1/ [(1/r1) + (1/r2) + ....(1/rn)], we call it U in thermo,

for moving fluids, resistance is the convective heat transfer coefficient in W/m2.K
for solids it's the conductive heat transfer coefficient in W/m.K

for air: it's very complicated since it's moving and it's at a certain temperature, but let's use one value as provided by the link. in reality Reynolds number and other things come into play.

so lets use 25 for the outside air. I will use 39 for the compressed air.
for the water use 100.

conductive coefficient for aluminum is 205 W/m.K, thickness of of 0.5 mm is used for the radiators.


so air to air system

U = 1 / (1/39) + (0.0005/205) + (1/25) = 15.23 W/m2.K

for the water to air: U = 1 / (1/39) + (0.0005/205) + (1/100) + (0.0005/205)+ (1/25) = 13.22 W/m2.K

Already we see that air to air has the advantage thermally. It will flow more heat energy for the same area and temperature difference.

[ringo]

The story doesn't end there however,

I haven't included the mass flow of air or the mass flow of water, or the total mass of water.

The outside air is treated like it's temperature cannot change, as a reservoir, because of it's expanse.

To a lesser extent if you have a large amount of water, it will take a lot of energy from the charge air before it changes temperature. This can be used to advantage in the water to air system.
The water will eventually heat up to the same temperature as the charge air and will have to give off the heat to the bigger reservoir, the atmosphere if it is to continue to draw heat from the charge air.


Also the next consideration is heat exchange surface area. From the above example we see that one system will need 15.23/13.22 = 15% more surface area for the same heat rate.

Now saying that, the one reservation i have for water to air and why it's possibly used is that even though the total system is 15% larger. It has the flexibility to be split into two.

...
edit: i removed another calculation because the water will not be the same temperature as the outside air, there will be a temperature gradient. And more than likely the water intercooler can be smaller than air to air, but it's radiator will still be considerably sized to the air to air.

[Cold Fussion]

Haven't not gone through the calculations I can't say for sure, but the convection coefficient of 100 you used for water is surely a little low?

[basti313]

Haven't not gone through the calculations

You don't have to. Just look at the main equation, it tells you everything:
now the total resistance R, would be R = 1/ [(1/r1) + (1/r2) + ....(1/rn)], we call it U in thermo,

Every resistor you add will raise your total resistance. It can not be easier and it can not be more true.

Now look at the picture Ringo painted for us:
For the air to air:

T0 ------/\/\air/\/\-------------/\/\metal/\/\----------------/\/\/air\/\/\----------T1


for water air:

T0-------/\/\air/\/\/\--------/\/\metal/\/\---------/\/\water/\/\--------/\/\metal/\/\------/\/\air/\/\----T1


Easy: More resistors means more resistivity.

I can't say for sure, but the convection coefficient of 100 you used for water is surely a little low?

Yes. Maybe the post should have stopped right after the formula that tells us "More resistors means more resistivity."
100 is far too low for water, but also far too low for moving air. At 250km/h you already have 100W/m2.K for the cooling air on a flat plate...a well made radiator should exceed this easily.
With the water we have the problem, that we do not have any idea of the speed of the water. This is regulated at below 3.5Bar (rules for engine cooling) and as you want small tubes, this means that the amount of the moving water is limited at a not very high value. That gives us hardly very high values for the U there...

Water to Air Intercooler:
...
Pro’s

1. Really good efficiency, so the size of the intercooler can be smaller.

2. Efficiency can be exaggerated by using ice, or other chemicals to produce normally un-realistic temperatures for short amounts of time.

3. Can be mounted anywhere along the charge piping route.

Con’s

1. Requires a lot of other accessories to work.

2. Because it is more complex, it naturally causes more opportunity for problems, like leaks.

3. Can become heat soaked when used for long periods of hard driving and become terribly in-efficient."

So, main advantages seem to be packaging and temperature control (via water flow control). The extra weight and proneness to heat-soak seem to be the main issues.

Now let us come to F1 reality:
We have a car driven at 60% full throttle.
So the last point "Can become heat soaked when used for long periods of hard driving and become terribly in-efficient." will spoil everything. Both relevant pro's are only right if the water temperature is low and can stay low for a longer timescale. But we are talking about nearly steady state, the temperature will be in a very narrow temperature band for the whole race.

[mpower]

Thermal conductivity of air is very poor, about a factor 24 worse then water and about 8500 X worse then aluminium conductivity.

air 0.024 W/(m.K)
water 0.58 W/(m.K)
aluminium 205 W/(m.K)
copper 401 W/(m.K)

[theloniousmonk]

Haven't not gone through the calculations

You don't have to. Just look at the main equation, it tells you everything:
now the total resistance R, would be R = 1/ [(1/r1) + (1/r2) + ....(1/rn)], we call it U in thermo,

Every resistor you add will raise your total resistance. It can not be easier and it can not be more true.

Now look at the picture Ringo painted for us:
For the air to air:

T0 ------/\/\air/\/\-------------/\/\metal/\/\----------------/\/\/air\/\/\----------T1


for water air:

T0-------/\/\air/\/\/\--------/\/\metal/\/\---------/\/\water/\/\--------/\/\metal/\/\------/\/\air/\/\----T1

While thats true, what about things like heatpipes used in cooling for computers. Heatpipes can multiple interfaces in which they move from one substance to another eg. CPU>Heatspreader>Copper base>Heatpipe>Water>Heatpipe>Aluminium Fins>Air. Yet that design of heatsink is far more effective at removing heat for a given surface area than a machined/cast heatsink made from a block of aluminium or copper. The heat capacity is much higher, and there's no pumps or such involved.

[mrluke]

The benefit of air to water is that you can use a smaller "charge cooler" as it is being cooled by cold water with a high SHC rather than warm air. The charge cooler is a resistor on the intake pipework system, lower resistance here will help your engine efficiency.

In addition it allows you to minimize intake pipework which will help with packaging and minimize heat soak post cooler.

The challenge is to keep the water cool enough to work efficiently as a cooling fluid. You also have a few extra bits of kit to fit within the sidepods.

Obviously if you cannot keep the water cool then you are quickly going to run into problems. The biggest challenge to this will not be on long straights but rather places like Monaco where you are using lots of boost and low speed or tracks with particularly high ambient tracks.

Once you get up to high speed your airflow should be more than enough to cool down your cooling fluid.

[basti313]

Yet that design of heatsink is far more effective at removing heat for a given surface area than a machined/cast heatsink made from a block of aluminium or copper.

No, it is not. A heatpipe system can only be as effective as the "machined/cast heatsink made from a block of aluminium or copper" on the hot side of the heatpipe.
It can be more effective if you can place a lager heat sink on the hot side than you are able to place without the heatpipe.
This is the same in a F1 car: You always end up with a normal aluminium/air interface and all the heat must run through that interface. You can not make it smaller just cause there is water on the other side of the aluminium. The energy IS THE SAME!

The benefit of air to water is that you can use a smaller "charge cooler" as it is being cooled by cold water with a high SHC rather than warm air.

How can the water be cooler than the radiator in the sidepod?

I somehow get the impression, that some people think the water cooling or heatpipe cooling is like a perpetual motion machine...I put a water cooler/heatpipe on a bottle of beer and what I get is ice cold beer...