improving intercooler efficiency

[spereira]

Hi everybody,
Rally cars spray water into the IC surface to increase heat transfer thus further reducing IC outlet temperature. This is true due to the huge latent heat of vaporization envolved. The problem is that once the water bottle is finished, no more spay! an HVAC system uses the same principle but operating in a closed circuit by means of the compressor. What would be the problems of using the AC circuit, if possible of course, to improve intercooler efficiency? Is this a stupid idea ?

 

[spereira]

Hi

for anyone who might be interested check out this link I've found by browsing through the USPTO site:

http://patft.uspto.gov/netacgi/nph-...1=AND&d=ptxt&s1=6347618&OS=6347618&RS=6347618

these guys have designed an AC system to further cool down intake air of an internal combustion engine. In one of the claims they also use an antifreezing to be able to cool dopwn the air to temperatures below freezing point... the question here is that they say the condensed water will also help reduce knocking in the engine, that's right but I've also read that water injection is something that should be avoided in standard vehicles and that it was only used in race cars... so a system that cools the air, not below frezzing but below a point where condensation might happen should have a water drainage somewhere, maybe an expansion bottle in the air piping after the IC, right?

Jiggery, what I meant by increasing pressure drop on the coolant size, thus reducing compressor efficiency I meant it would reduce the overall system efficiency. Isn't the degree of superheating and subcooling on the 2 HE dependent on the pressure drop across the system? And yes, you're right, more tubing means more time available for coolant heating up...
Even considering placing a HE inside the IC (how would you do this?) by changing the flow pattern inside it you'd also be increasing pressure drop, right?
As for the setup, the idea to keep the original air-to-air IC was to help reduce the heat load on the coolant side. 5 or 6 small HE might do the same thing, as you said, but it will all depend on how efficient they are and on the overall pressure drop. it's a question of HE design. but anyway, the idea remains the same.

 

[MRNEL]

I've been looking at reducing the restriction across an intercooler by changing the header tank design/shape and 'radiusing' the tubes on the intercooler core.

The only thing that bothers me is that if I improve the flow would this influence the cooling efficiency of the intercooler? My question is that if you operate the vehicle at a steady state condition [with the same airflow rate as before the modification] with the restriction being lower- if the heat transfer will be affected?

Thank you
Marius Nel

 

[spereira]

hi Mrnel,

I think that you're going to see some change in the HT efficiency by radiusing the core tubes. the problem is that by doing this you're changing core geometry and thus the heat transfer correlations on which its design was based are no longer valid. heat transfer coefficients, hence IC efficiency, is a function of tube geometry an gas velocity. when you change geometry you're changing gas velocity/velocity profile. generally the higher the velocity the higher the are heat transfer coefficients, but, also the higher is the pressure drop across the core. the problem is that it's no so easy to predict the new HT coefficients since correlations change also with geometry. I would try to keep, at least, the same gas velocity in the core tubes to be on the safe side.
regards

 

[mister2]

Re: 'super' cooling

I dont know if it was discussed or not... but the way i had thought about it would be to use the AC system to chill the water/intercooler surface, and then switch it off at WOT, effectively 'storing' the energy when its not needed.

nick

 

[beaverjones]

"The only thing that bothers me is that if I improve the flow would this influence the cooling efficiency of the intercooler?"

yes,but-the less pressure drop,the less energy required to overcome it.

 

[obanion]

Freon when burned at high temps become something like nerve gas? So I guess if we find a pickup truck in Baghdad with a old AC system, I guess we found out WMDs right? j/k

 

[MRNEL]

Thank you Spereira for your answer.

I knew there was something to the heat transfer efficiency but couldn't put me thumb on it. I also came across the following webpage that gives some insight in design :-

http://www.bellintercoolers.com/Pages/tech.asp

Marius

 

[spereira]

Hi guys,

MRNEL, nice info on that link, thks

mister2, I was told some rally cars use the AC to help cooling down the IC core. I think it would work best on a air-to-air IC than on a air-to water IC since in the last case you'd be using the AC to cool the circulating cooling medium and not the charge air directly.

Regards,
Susana