Intercooler setups

[mic*]

I should probly let dead dogs lie but i just thought of something;

Some pool heaters are done with hoses in the sun. And as you say Mick, the overall length of hose is the most influential factor on how much heating it'll achieve. But what im saying is that they use main lines, and run MANY laterals to achieve the same heat exchange with less pressure loss (smaller pump needed). The pressure loss is reduced, because the VELOCITY through each hose is lower, and pressure loss rises exponetially with velocity....

Anyway.

[jonra23]

Been fun though.

[mic*]

indeed...

Just about pipe size again. From everything i can find, you would need a very small pipe to be causing velocities associated with high loss. Basically if you air is moving at a speed where it can be considered INCOMPRESSIBLE (>102ms-1 - Thanx Skip) its too fast and pressure loss will start becoming high! Although the density used was about 1/2 what it should be, Skip calculated 43ms-1. If you double this to 86ms-1, you are still under the threshold where loss starts to rise significantly. (From a 56mm ID pipe with ~1bar boost on a 2.0L.) So the rule of compressor outlet size or slightly greater shouldnt lead you astray.

Larger than necessary pipe work also means greater than necessary volume of air to fill before response is felt.

I have also heard a "rule of thumb" that every bit of pressure loss in the intake pipework, results in twice the backpressure increase in the exhaust manifold. Thats probly why i focus on the IC loss being minimal, as much as its ability to cool.

It can cool al it likes but nearly all power gain can be negated by the pressure loss if its not addressed well. This applies to all bends and joins just as much.

[Skip]

Skip, you may say rubbish, but as a GENERAL TREND, im sorry its true!!!! The factors you speak of are more to do with END TANK DESIGN. And turbulators - refer back to the graph i posted for how this affects internal area.

You posted two intercoolers and claimed one is more efficient due to more charge air face, I simply said it's not as easy as that, everyone one else keeps going off on a tangent so why can't I?

[Skip]

EXACTLY!

And the BOOST affects the density as per what i said! The temp rise is the density loss!

How the hell can there be twice as much pressure and only a small percentage more mass. More molecules = more mass. Its fundamental physics.

The density you are using is based on STANDARDISED VALUES of atmospheric air, heated to certain temps at certain altitudes so on and soforth.

To take another angle, if a compressor was IDEAL (100% efficiency) the density would be equal to the STANDARD VALUE (1.23kg/m^3) X the pressure ratio. Because it heats the air, the STANDARD VALUE for air density gets lower as the air gets hotter, which you have pointed out. This results in a lower density than if the air had not been heated to acheive the given pressure ratio.

And Skip, go back and edit, coz you distinctly said <102ms-1 = compressible. Which is right, but 43.66ms-1 isnt >102ms-1 so it NOT INcompressible...

Ive read that 5 times and still unsure what you are trying to say. The density of the air increases as it is compressed and decreases as the resulting compression heats it up, as a guess I estimates the resulting compression would heat the air to 90 degrees C. If I now go to my steam tables for dry air at 1atm at a temperature of 102 degrees C the density is 0.9413 kg/m^3. Now multiply that by the pressure ratio of 11 psi:

(14.7+11/14.7)x0.9413 = 1.65 kg/m^3 supprisingly close to what came out before, care to attempt to tell me once again why this is wrong???

As for the mach number thing, I see the mistake now and have corrected.

[Skip]

indeed...

Just about pipe size again. From everything i can find, you would need a very small pipe to be causing velocities associated with high loss. Basically if you air is moving at a speed where it can be considered INCOMPRESSIBLE (>102ms-1 - Thanx Skip) its too fast and pressure loss will start becoming high! Although the density used was about 1/2 what it should be, Skip calculated 43ms-1. If you double this to 86ms-1, you are still under the threshold where loss starts to rise significantly. (From a 56mm ID pipe with ~1bar boost on a 2.0L.) So the rule of compressor outlet size or slightly greater shouldnt lead you astray.

AAARRRGGGHHH! Dude you are trying to say the density would be doubled, I have proved twice this is not the case, temperature has a much greater effect on the air density than you realise. If you are doubling the air velocity into the engine you are trying to say it's VE is 2, this is not heard off for a turbocharged ULP automotive engine, I believe it would not get much higher than 1, can someone please find this out?

The pressure is not related to the air speed, the pressure is static, the engine can only consume and push out so much!

[mic*]

No thats spot on Skip.

All i said was your first calc didnt allow for boost. You second post was correct too. I shouldna posted the way i did coz i see that it kinda suggests a conflicting point (other than your talking 11psi, im talking 14.7, and the thread starter said 12...). Sorry mate.

All it was about is saying that the compressor efficiency value taken from reading the map's at your parameters takes the guess work out of the denisty loss.

Its is a ratio of pressure ratio : density ratio.
If they were 1:1 then its 100%
If its 1:0.8 then its 80% efficient...

If you multiply the pressure ratio desired by the stated effciency at this pressure, you get the actual density ratio to ATM - 1.23kg/m^3.

Then you use your table to predict the outlet temp...

[mic*]

AAARRRGGGHHH! Dude you are trying to say the density would be doubled, I have proved twice this is not the case, temperature has a much greater effect on the air density than you realise. If you are doubling the air velocity into the engine you are trying to say it's VE is 2, this is not heard off for a turbocharged ULP automotive engine, I believe it would not get much higher than 1, can someone please find this out?

The pressure is not related to the air speed, the pressure is static, the engine can only consume and push out so much!

Dont get knotted. I know density would not double in real world scenario, but doubling it makes it a massive overestimate. Its just examplifying that pipe size is not a big limiting factor!

Geez mate, instead of trying to show you can pull a formula and work it out, try explaining it a bit more for those dont so well...

Not get much higher than 1 what? 100% VE? VE is a function of cams and revs & design. You GENERALLY allow for VE when calculating a Lmin-1 flow rate of your engine at ATM redline BEFORE turbo sizing. Then based on this max flow figure, you size a turbo. Basically assuming that the increase in pressure doesnt affect VE...

Eg. 2.0L four stroke with 7000rpm redline and 85% VE
= 1.0 X 7000 X .85
= 5950Lmin-1

Therefore a compressor flowing ~12000Lmin-1 would achieve ~1 bar...

[Skip]

Hehe okay

The air speed will remain the same, there is just more if it going in as it is now more dense, the air is not travelling any faster through the pipework or intercooler or whatever, it's speed is dependent on engine revolution not boost pressure, it's that simple. I agree VE may not be the correct term to describe this, was probably wrong term on my behalf.

The air being of greater density (compressed) will though effect the Reynold's number by increasing it and therefore the pressure loss will also increase