Need advice from heat exchanger experts 2

[turbomotor]

I have been trying to confirm the definition of effectiveness for an air-to-air intercooler installed between a turbocharger compressor discharge and an engine intake manifold. I looked around the internet and found a number of answers (some contradictory - no surprise), and I finally went to a Turbo-by-Garrett web site.

https://www.turbobygarrett.com/turbobygarrett/intercooler-effectiveness

I thought these guys were the experts, but I am puzzled by what is said because it does not seem right to me. Any advice? Are these guys correct?

1. They use the word effectiveness and efficiency interchangeably for a heat exchanger. This does not agree with what I think I learned in thermodynamics class many years ago. Have the definitions loosened to the point were it is OK to consider effectiveness and efficiency as the same thing?

2. In the linked explanation, the effectiveness is defined as a ratio between the delta T (hot side) across the intercooler against the compressor discharge temperature. (in degrees F, not absolute temperature). I remember heat exchanger effectiveness (hot side) as being the ratio between delta T (hot side - that is, the hot air being cooled) against the difference between the hot side temperature going into the heat exchanger and the cold side sink temperature. Or maybe something like Eff = (Tin (charge air hot side) - Tout (charge air cooled side)) / (Tin (charge air hot side) - Tcold (cooling air inlet side)).

Any advice or comments from those professionals who work in this field would be appreciate. Thanks.

 

[VEBill]

How would one define "efficiency" for an air-to-air intercooler? The mind boggles. ;-)

Disclaimer - not my area, but I know a bit of Physics.

 

[SomptingGuy]

Effectiveness is actual temperature drop divided by theoretical maximum drop. That FAQ is confusing. They need to spell out that the numerator and denominator are both deltas.

 

[EdStainless]

Part of the ambiguity is that in an air-to-sir intercooler you don't control the air flow nor do you care about the cooling air outlet temp.
With water cooled intercooler HX performance matters because your water is more dear.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[gruntguru]

The linked explanation is just plain wrong. Garrett must employ rev-heads to write some of the stuff on that site.

je suis charlie

 

[Hoxton]

Garrett have obviously been taken over by the "Yee-hah!" Branch of engineering last seen in the "Dukes of Hazzard"

I particularly liked the part about the inclusion of ice as a coolant. Pumping ice will be an engineering challenge!

 

[RodRico]

"Effectiveness" is subjective and can be assigned to any characteristic. From the wording of the FAQ, I take it they are using efficiency as the measure of effectiveness, so I see no contradiction. The comment about ice refers to the practice, common among street racers, of pulling intake air or radiator inlet air through a container of ice. If the ice is in a container in the trunk (the approach I see most often on TV), the efficiency of the intercooler is actually reduced because the delta temperature between intake charge and the air passing through the intercooler is reduced. Conversely, if the inlet air to the intercooler passes through ice, then the efficiency of the intercooler is improved due to an increase in delta temperature.

 

[DMBocci]

I'm a turbocharger design engineer and also design heat exchangers for a known Garrett competitor. I use effectiveness when describing heat exchangers because to me, from thermodynamics, efficiency implies that some work is being done in the process. With a heat exchanger, unless you are using the waste heat to drive another process or mechanism.. there's no work done and hence no efficiency calculation.
Taking thermo 2 in college cleared this up.

This is what I use to describe heat exchangers when matching them to customers applications:
Effectiveness=(hot in - hot out)/(hot in - cold in{ambient or cooling medium, if water})<--same as your stated equation.

Eff = (Tin (charge air hot side) - Tout (charge air cooled side)) / (Tin (charge air hot side) - Tcold (cooling air inlet side))


And yeah.. whoever is writing some of those tid-bits for the Garrett website doesn't have as much knowledge as they should and whoever is reviewing it doesn't know the difference.

 

[MacGyverS2000]

Perhaps the word you're looking for is, efficacy, not efficiency...

Dan - Owner

http://www.Hi-TecDesigns.com

 

[turbomotor]

If anyone is still interested in this topic, I just read a well written white paper on the subject. See the attached link to the Vortech Supercharger web site (automotive performance aftermarket).

http://legacy.vortechsuperchargers.com/pdf/papers/cooler_paper.pdf

 

[CWB1]

I've been in various related roles (turbo matching, cooler design, combustion development, etc) on both research and product development teams at several engine OEMs and more often than not the terms have been used interchangeably as Garrett describes (albeit poorly worded). Occasionally someone will draw a distinction between the two to distinguish between idealized (lab) data and reality, but that's rather rather even among the pinky-up crowd.