Eliminate the need for an intercooler?

[Audiomaker]

Hi all,

My basic understanding is that an intercooler cools the super heated air coming from the intake side of a turbocharger.

It is also my basic understanding that the intake side of a turbocharger becomes super heated by heat conducted from the exhaust side.

In a heat exchanger (air/air or air/water), the exchanger is cooled by atmospheric air temps (meaning the air around us).

So more or less, an exchanger (i.e....intercooler) will not produce air temps lower than the outside air.

So far so good?

Ok...

Well that is the same temperature of air that the intake side of turbo is "inhaling" right? On our bikes, it might even be a bit cooler as the air filters are often on the outside of the bike where intercoolers are getting their air flow from closer to the engine heat.

So, my question is.. if the intake side of the turbo were thermally isolated from the exhaust side, wouldn't the air temperature of the post turbo intake air be at near atmospheric, thereby eliminating the need for an intercooler?

If the answer to this question is "Yes" (which I think it is), then why the heck are they using cast iron, steel and aluminum as the mating parts between the intake housing and the exhaust housing, and also a metal connection between the exhaust wheel and the intake wheel?

Unless I"m looking at the cut away photos of turbochargers wrong, the vast majority of heat transferred to the intake housing comes from the metal connection between the two housings, and by the shaft.

Couldn't one use a non heat conductive material for these parts? There are indeed materials that are rigid, machinable, sturdy, and don't conduct heat. Think of Ebonite frying pan handles... you can put these in the oven at 450 degrees for hours but they are very poor heat conductors.

It just makes sense in my head that if one were going to eliminate heat from the intake air, then the best place to start would be insulating it where the air first becomes heated instead of trying to cool it after the fact.

Thoughts?
Sean

 

[Twobrothersbusa]

You are correct about heat transfer, but that is not the only culprit. You need to look over the compression and expansion of gasses. Turbo's make boost which makes heat.

 

[Boosted Cycle Perf]

No. Anytime you compress air, you create heat. And yes, itercoolers only cool as low as ambient temp, but that's very hard to do on bikes since the innercooler is usually pressed right up aginst the radiator which is also gonna give off heat.

 

[2wicked]

Hi all,

My basic understanding is that an intercooler cools the super heated air coming from the intake side of a turbocharger.

It is also my basic understanding that the intake side of a turbocharger becomes super heated by heat conducted from the exhaust side.

In a heat exchanger (air/air or air/water), the exchanger is cooled by atmospheric air temps (meaning the air around us).

So more or less, an exchanger (i.e....intercooler) will not produce air temps lower than the outside air.

So far so good?

Ok...

Well that is the same temperature of air that the intake side of turbo is "inhaling" right? On our bikes, it might even be a bit cooler as the air filters are often on the outside of the bike where intercoolers are getting their air flow from closer to the engine heat.

So, my question is.. if the intake side of the turbo were thermally isolated from the exhaust side, wouldn't the air temperature of the post turbo intake air be at near atmospheric, thereby eliminating the need for an intercooler?

If the answer to this question is "Yes" (which I think it is), then why the heck are they using cast iron, steel and aluminum as the mating parts between the intake housing and the exhaust housing, and also a metal connection between the exhaust wheel and the intake wheel?

Unless I"m looking at the cut away photos of turbochargers wrong, the vast majority of heat transferred to the intake housing comes from the metal connection between the two housings, and by the shaft.

Couldn't one use a non heat conductive material for these parts? There are indeed materials that are rigid, machinable, sturdy, and don't conduct heat. Think of Ebonite frying pan handles... you can put these in the oven at 450 degrees for hours but they are very poor heat conductors.

It just makes sense in my head that if one were going to eliminate heat from the intake air, then the best place to start would be insulating it where the air first becomes heated instead of trying to cool it after the fact.

Thoughts?
Sean

None of your thoughts or assumptions are correct, the heat comes from compressing the air, not from the turbine side of the turbo, the more you compress the air the hotter the charge air becomes, by your assumptions it would mean superchargers should have no heat higher then ambient in the charge air,
Intercoolers cool the charge air after it has been compressed/heated,

Richard

 

[Audiomaker]

None of your thoughts or assumptions are correct, the heat comes from compressing the air, not from the turbine side of the turbo, the more you compress the air the hotter the charge air becomes, by your assumptions it would mean superchargers should have no heat higher then ambient in the charge air,
Intercoolers cool the charge air after it has been compressed/heated,

Richard

Ok, I thought that was the secondary source of heat with the conductance from the exhaust side being the primary?

I don't know what the percentage of heat is coming from compressing air, air friction, mechanical friction, or conducted heat from the engine.

While I don't disagree, superchargers indeed have the reputation of producing cooler air by far than turbochargers. The question then would be, by how much?

Of course, if the compression of the air, and air friction are the primary heating source, then there's probably no point to this thread.

On the other hand, if it were 50/50 (random number), then it might be worth considering because even intercoolers aren't removing heat from the air at 100% efficiency.

Put another way.... if an intercooler can reduce the air temp' by 50 degrees and isolating the turbo from exhaust heat could reduce the air temp by 50 degrees, then same difference right?


Sean

 

[GNBRETT]

superchargers indeed have the reputation of producing cooler air by far than turbochargers.

turbos also have the reputation of being more efficient because they use the energy that is otherwise wasted by the exhaust.

 

[Audiomaker]

Talk about confusing.

I copied this directly off of Garrett's website FAQ's


Q. What is intercooler effectiveness and how do I measure it?
A. Effectiveness is defined as the ratio of how many degrees of temperature that were removed from the charge air by the intercooler to the original temperature that is put into the charge air by the turbo. Example: If the turbo compresses the charge air to a temperature of 140° F, but after passing through the intercooler the air is 115° cooler (resulting in a 25° F charge air temperature), the efficiency would be: Effectiveness: 115/140 = 0.82 or 82% efficiency Typically, air-to-air intercoolers for normal street applications range between 60% and 70% efficiency. Often, liquid-to-air intercoolers have effectiveness ratings from 75% to 95%. One common method of improving the cooling of the charge air dramatically in an air-to-water intercooler is the inclusion of ice as a coolant.

What they fail to mention here is what the ambient temperature must be to get a post intercooled charge air temp 7 degrees below freezing!?

I guess you need a lot of boost with Polar Bears chasing you all the time.

Hmmm....

 

[OZBooster]

maybe they mixed up F and C
there is very little conducted heat from the exhaust side
off boost with a hot turbo the intake air is not far from ambiant ,
As a kid had you ever put your finger over the end of a pushbike hand pump and pumped it and burnt your finger as the compressed air released
there is a lot of heat generated by compressing

 

[Audiomaker]

maybe they mixed up F and C
there is very little conducted heat from the exhaust side
off boost with a hot turbo the intake air is not far from ambiant ,
As a kid had you ever put your finger over the end of a pushbike hand pump and pumped it and burnt your finger as the compressed air released
there is a lot of heat generated by compressing

It still doesn't feel right to me that the air compression is responsible for the grand share of heating the air... especially at <30lbs.

I have lots of air powered devices... even air powered turbines spinning at 100k+

I can run 50' of air hose with a constant 100psi going through it (say running a sandblaster) and that hose never gets hot.

An electric yard blower warms the air a little.... not too much, and can be left on for hours without that output air getting hot.

I have a pretty powerful Stihl yard blower attachment that goes at the and of my weedwacker (it's an interchangeable head system), and it puts out massive amounts of air and pretty good pressure, yet doesn't get hot.... in fact, it's made of plastic. (I should put a pressure gauge on that for a test). It takes pressure and flow to move leaves and this thing will move 50X the leaves that the exhaust of my Busa will...without even having any fuel burning.

I have a friend who has a jet engine starter (basically a small jet engine on a trailer that powers a turbine where the output air starts commercial jet engines), and this thing puts out enough flow and pressure that two large men together cannot hold onto the 3" hose without getting pushed over (I was one of them). It warms the air a bit. The brass fitting at the end that attaches to the jet however, will get really hot over time due to friction.

If a turbo can heat ambient air 100* in 8" of travel without that heat coming from the heat of the housing itself, I'd be amazed. Now if the housing itself is a few hundred degrees, it would make more sense.

Now in another topic where I was asking about IAT's, I was being told by a bike builder that an exact formula is hard to reach because (in their example) LSR bikes can have an IAT of 140 at the start, and 250* towards the end.
Why? If the pressure is a constant, then the output temperature should also be a constant...no?

Something is telling me that there's more heat coming from friction and conducted housing temp's than I'm hearing here.

Sean

 

[GNBRETT]

It still doesn't feel right to me that the air compression is responsible for the grand share of heating the air... especially at <30lbs.

it is and always has been. it seems like ur trying to re-invent the wheel in a lot of ur threads when ppl a LOT smarter then you have developed intercoolers to combat heat for DECADES for a reason! its not from conducted housing temps in the metal or whatever you call it. where do u get this stuff from?

ur comparing an electric yard leaf blower to a turbo???? a turbocharger spins at an extremely high speed, some models will approach 160,000 revolutions per minute to provide enough air flow to feed a hungry engine. and thats compressed air from a HOT exhaust! ur starting to sound like a troll....

 

[2wicked]

It still doesn't feel right to me that the air compression is responsible for the grand share of heating the air... especially at <30lbs.

I have lots of air powered devices... even air powered turbines spinning at 100k+

I can run 50' of air hose with a constant 100psi going through it (say running a sandblaster) and that hose never gets hot.

An electric yard blower warms the air a little.... not too much, and can be left on for hours without that output air getting hot.

I have a pretty powerful Stihl yard blower attachment that goes at the and of my weedwacker (it's an interchangeable head system), and it puts out massive amounts of air and pretty good pressure, yet doesn't get hot.... in fact, it's made of plastic. (I should put a pressure gauge on that for a test). It takes pressure and flow to move leaves and this thing will move 50X the leaves that the exhaust of my Busa will...without even having any fuel burning.

I have a friend who has a jet engine starter (basically a small jet engine on a trailer that powers a turbine where the output air starts commercial jet engines), and this thing puts out enough flow and pressure that two large men together cannot hold onto the 3" hose without getting pushed over (I was one of them). It warms the air a bit. The brass fitting at the end that attaches to the jet however, will get really hot over time due to friction.

If a turbo can heat ambient air 100* in 8" of travel without that heat coming from the heat of the housing itself, I'd be amazed. Now if the housing itself is a few hundred degrees, it would make more sense.

Now in another topic where I was asking about IAT's, I was being told by a bike builder that an exact formula is hard to reach because (in their example) LSR bikes can have an IAT of 140 at the start, and 250* towards the end.
Why? If the pressure is a constant, then the output temperature should also be a constant...no?

Something is telling me that there's more heat coming from friction and conducted housing temp's than I'm hearing here.

Sean

In your examples you are only referring the transfer of compressed air, not the actual compressing of air, here is a simple test for you with some logic you might understand, drain your air compressor and then start it up, after has ran for 10 minutes or so, lick or kiss the discharge tube that leaves the compressor head and fills the tank, let me know how that feels,

Richard

 

[m_ridgeway]

Have you ever watched iat's rise, they spike under load for a reason......

 

[2wicked]

Temperature effects and intercoolers
Supercharger CDT vs. Ambient Temperature. Graph shows how a supercharger's CDT varies with air temperature and altitude (absolute pressure).

One disadvantage of supercharging is that compressing the air increases its temperature. When a supercharger is used on an internal combustion engine, the temperature of the fuel/air charge becomes a major limiting factor in engine performance. Extreme temperatures will cause detonation of the fuel-air mixture (spark ignition engines) and damage to the engine. In cars, this can cause a problem when it is a hot day outside, or when an excessive level of boost is reached.


For example, if a supercharged engine is pushing 10 psi (0.69 bar) of boost at sea level (ambient pressure of 14.7 psi (1.01 bar), ambient temperature of 75 °F), the temperature of the air after the supercharger will be 160.5 °F (71.4 °C). This temperature is known as the compressor discharge temperature (CDT) and highlights why a method for cooling the air after the compressor is so important.

In addition to causing possible detonation and damage, hot intake air decreases power in at least one way. At a given pressure, the hotter the air the lower its density, so the mass of intake air is decreased, reducing the efficiency and boost level of the supercharger.

 

[2wicked]

Please see below, I have highlighted a section pertaining to your previous comment about superchargers being more efficient,

Supercharging versus turbocharging
A G-Lader scroll-type supercharger on a Volkswagen Golf Mk1.

Keeping the air that enters the engine cool is an important part of the design of both superchargers and turbochargers. Compressing air increases its temperature, so it is common to use a small radiator called an intercooler between the pump and the engine to reduce the temperature of the air.

There are three main categories of superchargers for automotive use:

Centrifugal turbochargers – driven from exhaust gases.
Centrifugal superchargers – driven directly by the engine via a belt-drive.
Positive displacement pumps – such as the Roots, Twin Screw (Lysholm), and TVS (Eaton) blowers.

Roots blowers tend to be 40–50% efficient at high boost levels. Centrifugal superchargers are 70–85% efficient. Lysholm-style blowers can be nearly as efficient as their centrifugal counterparts over a narrow range of load/speed/boost, for which the system must be specifically designed.

Positive-displacement superchargers may absorb as much as a third of the total crankshaft power of the engine, and, in many applications, are less efficient than turbochargers. In applications for which engine response and power are more important than any other consideration, such as top-fuel dragsters and vehicles used in tractor pulling competitions, positive-displacement superchargers are very common.

The thermal efficiency, or fraction of the fuel/air energy that is converted to output power, is less with a mechanically driven supercharger than with a turbocharger, because turbochargers are using energy from the exhaust gases that would normally be wasted. For this reason, both the economy and the power of a turbocharged engine are usually better than with superchargers.

Turbochargers suffer (to a greater or lesser extent) from so-called turbo-spool (turbo lag; more correctly, boost lag), in which initial acceleration from low RPM is limited by the lack of sufficient exhaust gas mass flow (pressure). Once engine RPM is sufficient to start the turbine spinning, there is a rapid increase in power, as higher turbo boost causes more exhaust gas production, which spins the turbo yet faster, leading to a belated "surge" of acceleration. This makes the maintenance of smoothly increasing RPM far harder with turbochargers than with engine-driven superchargers, which apply boost in direct proportion to the engine RPM. The main advantage of an engine with a mechanically driven supercharger is better throttle response, as well as the ability to reach full-boost pressure instantaneously. With the latest turbocharging technology and direct gasoline injection, throttle response on turbocharged cars is nearly as good as with mechanically powered superchargers, but the existing lag time is still considered a major drawback, especially considering that the vast majority of mechanically driven superchargers are now driven off clutched pulleys, much like an air compressor.

Turbocharging has been more popular than superchargers among auto manufacturers owing to better power and efficiency. For instance Mercedes-Benz and Mercedes-AMG previously had supercharged "Kompressor" offerings in the early 2000s such as the C230K, C32 AMG, and S55 AMG, but they have abandoned that technology in favor of turbocharged engines released around 2010 such as the C250 and S63 AMG biturbo. However, Audi did introduce its 3.0 TFSI supercharged V6 in 2009 for its A6, S4, and Q7, while Jaguar has its supercharged V8 as a performance option in the XJ and XF.

 

[kromdom]

my head hurts......but learning a lot
P.S. I do know/understand enough WHY the EATON s/c in my truck is nicknamed HEATon

 

[edsx10]

And that?

Comprex Pressure Wave Supercharger - Sport Compact Car Magazine

 

[Audiomaker]

Lot's of great information. I'm reading and re-reading.

For the record, I'm not arguing, I'm trying to gain an understanding on a personal level. That is different than simply storing known facts in one's brain.

GNBRETT, if trying to understand something makes me a troll, then I'm a troll. I don't go through life thinking that I'm smarter just because I can quote facts someone "a LOT" smarter than me actually understands.


Ok, well this is a very interesting discussion to me. I was looking around on the net and found this at Pro-charger's site:

This is for an engine driven supercharger.

This does show a 71* increase in charge air temp due to the Constant Gas Law by itself @ 8psi.

However, it also shows a 24* increase due to the housing itself, and even more due to engine compartment heat.

I wish I could find this graph for a turbocharger.

In this example, it looks like 70* of heat is due to air compression, and 40+ additional is due to friction and transferred heat.

On an exhaust driven supercharger (ie..turbocharger), I would expect the numbers to be a little different.... especially in the transferred heat area?

If a turbocharger is getting (pick a random number) 40* in temp rise from environmental factors (ie...sharing a shaft from the hot side, and being physically mounted to the hot side via a conductive material), then isn't that number significant?

Sean

 

[edsx10]

Comprex Pressure Wave Supercharger - Sport Compact Car Magazine

 

[edsx10]

Influences the amount of air? (liters per minute)

 

[Audiomaker]

More info...

In [URL="

Video[/URL], the person has hooked up a temp sensor pre/post intercooler.

It appears that the Post turbo temp is sitting around 45* Celsius (113F) off boost and rises to 109* Celcius (228F) at full boost. The ambient air temp in this video is reported as 15* Celsius (59F) and the IAT pre-turbo at 16* Celsius (61F).


So off boost (1 atm/bar), the turbocharger is creating by itself over 50 degrees F in rise without compressing air? Is that not going to be a factor in overall efficiency? Dunno.

If anyone was paying attention, in my first post on this thread, I was wondering about how much heat getting to the intake air could be avoided by using non-thermally conductive materials at the mating points of the cool and hot side of the turbocharger, and I'm still wondering that?

Now I'm starting to get a grasp on the percentages that different elements induce heat into the air, and with that, I can see that there is no avoiding the Constant Gas Law, but still... 50 degrees at 1atm is quite a lot isn't it?

Sean