Intercooler Thermodynamic expressions

[daedalusjc]

Hey guys im wondering if someone could shed some physics on this mainly applicable equations.

Lets just assume a theoretical engine setup consisting of pod filter, turbo and intercooler. If the pod filter sees temperatures far higher than ambient from heat soak the resulting charge temperature will be higher after the intercooler rather than the same temperature regardless of the pod filter temperature. Is there a mathematical equation to find the correlation between less dense air(hotter) under pressure (from turbo) and intercooler efficiency?

[Kaido]

The problem you face is you have alot of unknown and you will need to another simplify down the equation or make assumption. The calculation will not be very accurate.

You will have to make an assumption of the temperature of the air hitting the intercooler. There is no simple calculation as there alot of factors which need to be consider, However i will go over my notes later and see if i can find some equations you can use to get a estimate

[daedalusjc]

yeah alot of unknown factors. my initial plan was to run another temperature sensor at the throttle body at a boost level of 1 bar over atmospheric pressure and try and extrapolate results for the given setup over say 20 to 30 runs but my problem is keeping the intercooler at a constant temperature. any equations you have would surely help alot

[daedalusjc]

Its more to work out whether the temperature rise after the intercooler is linear to the input temperature (Say 20c @ Filter = 25c after Intercooler, 25c @ Filter = 30c after Intercooler) or exponential (20c @ filter = 25c after Intercooler, 25c @ Filter = 45c after Intercooler (Input = 4x)). Im assuming its going to be exponential due to extra heat under compression from the turbo

[200MPH]

I've datalogged temperatures on my old turbo car once for a bit of a look see. Temperature sensors for ambient, in pod, after turbo, after intercooler and finally at throttle body.
Found that the temps after intercooler do not rise linearly with pre turbo pod temperature. Also found out that a short stop resulted in large temperature rise in under bonnet pod temperature (obvious) and so sorted out an inlet hose to get pod out in front of intercooler so as to suck cool air into turbo. You'll not be able to calculate accurately without making all sorts of assumptions, as mentioned above. Too many variables. Best thing to do is measure and then you'll know. If you want to do this for some sort of controlled experiment, use engine dyno and put intercooler in water bath with good water flow. That will keep the intercooler efficiency fairly constant and at a high efficiencey at that too. How far do you want to go? You measure all temps and pressures and then you can use thermodynamic calcs to extrapolate accurately from there (up to a point!).

[Lonewolf]

id say it wont be linear or exponential, but a weird curve as intercooler reaches its maximum amount of heatsinking ability.

[180SXTCY]

some good info here:

http://www.bimmerfest.com/forums/showthread.php?t=120057

[daedalusjc]

ah of course it would be almost quadratic. you would reach efficiency saturation on the intercooler at a certain point. duh massive oversight by me. alot of good practical information 200mph cheers. always seem to get straight, informative replies on AL. will do some more tweaking of the temperature compensation maps in ecu and logging. that bimmerfest thread i a great read.

[200MPH]

Found my old data logged temperature traces and some thermographic images of my intercooler. Can't post up pics, so if anyone wants to have a look let me know how to get them to you via email or similar.

[Z2TT]

I don't understand what your trying to say in 1st Post....... basically I get it your asking that if the pod filter is sucking in hotter air.... it will end up being hotter after it gets cooled.... Yes?