(ask) Dry Ice for cooling air intake temperature

[ordengineering]

Guys, i know that we could reduce air temperatur by placing the dry ice in the intake manifold.

But I've seen some peeps using dry ice vapor to cooling their intake air temperature.

So the dry ice vapor was sucked into the intake manifold just like carburizing system.

My question is,

1. Dry ice is containing lot of CO2, would it more hurting performance than the benefit that we got from reducing intake air temperature??

2. And how about the sudden impact about the rapid drop temperature inside the combustion chamber, im affraid when the engine works inside their operating temperature then suddenly its drop rapidly by the extreme cold of the dry ice vapor, the internal engine parts would crack.

Any information about "how to" on this system? i mean about the dry ice vapor that goes inside the combustion chamber.

I plan to use it on my drag race Honda N/A motor, that run 15.5:1 compresion ratio.



I know my english was weird, but i believe you guys know my point


Thanks for the share

Regards



Odie Rachmat

 

[curtis74]

without doing the calculations, I would assume that any temperature drop from dry ice would be directly counteracted by the increase in CO2 being ingested.

Using dry ice to cool the intake is something that has been used for years, but putting it in the intake ducting would probably be counterproductive.

I could understand a heatsink in the intake that is cooled by dry ice to get more surface area in contact with the air, but a chunk of sublimating CO2 doesn't sound wise.

 

[Fabrico]

Why shoot a fire extinguisher into your intake? I think I would try regular ice before dry ice.

 

[mcgyvr]

http://www.designengineering.com/products.asp?m=sp&pid=72&gclid=CKuG4eqvgZcCFSGl7QodZn1_ZQ

 

[mcgyvr]

That kit does not inject it into the intake, there is an intake kit with a "bulb" that holds the co2 and cools that air as it passes over the bulb.

 

[evelrod]

Good grief!!! It's 1958 all over again...

If there ever was any one thing that has been "done to death" in drag racing, this is it. Go to the Hot Rod magazine archives from the '50's and you just may find more than you can use.

Dry ice is containing lot of CO2, would it more hurting performance than the benefit that we got from reducing intake air temperature??

Well...DUHHHH!

As to the exterior use of ice.
Ice works to cool the intake manifold to a fair degree. Ice works to cool the incoming fuel for short bursts (cool cans).
Ice works to cool the incoming air to a much lesser degree...huge volume of air in a drag race.
All of this is effective to one degree or another---but--- largely a waste of time and effort.
I know, 'cause I wasted a lot of time on the "next trick setup for go-fasters" when I was drag racing in the 50's.

Bottom line...If it were all THAT effective, you would see it in regular use...and...you do not.

Also, one other point...NHRA banned the use of ice on manifolds as I recall...It's been many years and I do not recall the specifics.

Rod

 

[ordengineering]

Ok, i got the point

Thanks a lot Guys !!

So the CO2 would hurt more than the reduce of Intake Air Temperature.

So i think would place the dry ice outside the inlet path, with a piece of box that sorounding the Intake Pipe, near the velocity stack..

and about the ice banned in NHRA, we dont have that rules for our national drag championship in Indonesia.

 

[mcgyvr]

You should look into water injection with that higher compression ratio on a NA vehical, although technically better for forced induction setups, there will be some benefits.

 

[globi5]

A box filled with dry ice surrounding the intake won't do much, because the surface area is too small in order to cool the fast moving air.

If anything, you would need to add an intercooler before your intake and put that intercooler in a box with dry ice.

 

[patprimmer]

I expect the extra resistance to flow through the intercooler and extra weight might pretty well offset any gains in density.

The cooler charge might allow a higher compression ratio which would yield a power increase so long as the cooling was effective and reliably maintained. Run out of dry ice and you might detonate it into oblivion.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers for professional engineers

 

[globi5]

You can purchase intercoolers with a pressure drop of less than 2%.

Dry ice temperature is -78.5 C. So an absolute temperature drop of over 10% is feasible especially in warmer climates.

Therefore a net-air density and power increase of well over 5% could be achieved.

An intercooler weighs about 5kg. If that dry ice weighs another 5kg and if the car including driver weighs 1000kg, that's 1% extra weight, which is still less than the extra power which could be gained.

But whether that would be worth the extra hassle (including filling up that box with dry ice before each run) is doubtful.

 

[evelrod]

Hmmmmm? I know my math skills have atrophied since I retired (they never were all that hot, anyway)...But...Given that even a mildly tuned "drag" engine can easily suck in ~15 cu.ft./sec. at speed, how does your assumption of a 10% drop in temp. square up?
Just off the top, that would take a mighty big heat exchanger and a 'ton' of dry ice!

It's not like I did not try all this stuff 'back in the day'!!! So did everyone else, it was the hot setup in 1958...That, in itself, should say something about how effective it was/wasn't. The idea died and righteous death...! Why not do like Jag did for a while, use the AC to cool the fuel...Another "great idea" that went nowhere fast.

Rod

 

[globi5]

Assuming your run takes 20 seconds you burn about 11 kg of air (at 15cufeet per second).

To cool 11 kg of air by 40 C, you need about 360 kJ which is less than the latent heat of sublimation of one kg of dry ice.

Even at an efficiency of less than 15%, 5kg of dry ice is therefore enough per run.

Latent heat of sublimation of dry ice: 572 kJ/kg
Specific heat of air: 0.813 kJ/kg/K
15cuft per second = 0.425 m^3/s



Why it's hardly being done? I don't think less than 10% of power gain is worth the costs of a proper intercooler including container for dry ice and constantly filling this container with dry ice. For instance, nitrous oxide produces much more additional power per $.

Besides dry ice intercoolers do exist (although on supercharged drag race cars, where the benefit is much higher):

http://www.pwr.com.au/photo_drag.html

 

[curtis74]

Let's also not forget.... how will you get fuel to evaporate at such cold temps? Might be overkill.

Carb - no way.
EFI - maybe, but still too cold for practical max power.

 

[drwebb]

Perhaps the 'technical information' supplied for the above referenced product is illuminating to this discussion:

"Do yourself justice and get yourself one.........it is a must have product"

 

[globi5]

Assuming the absolute temperature drop is 10%, then at 25C outside air temperature the intake air temperature would be -5C.

Most gasoline powered cars can operate at well below -30C outside air temperatures.

 

[PedroCG]

Hi guys, im new here XD and this is my first post.

globi5, 5kg of dry ice would be enough to cool the air, but would they be abble to cool the air in 20 seconds, the system would need to be very efficient since the area would be small and the temperature difference is only 100 ish ºC.

I thing expanding gaseous CO2 from a pressure bottle in some sort of heat exanger would make a more efficient system.

I guess NOS is forbiten other wise all this conversation is... dumb

 

[globi5]

I said and calculated an efficiency of 15%.
15% efficiency is generally not considered high.

The point of using an intercooler as opposed to a simple pipe is because of its large area.

http://www.pwr.com.au/coolers_atoi.html

The temperature difference is around 100 degree C, but the temperature drop required is only 30 degree C.

A temperature drop of 30% at an efficiency of 15% is easily achievable.

A pressurized bottle including controls is heavier than 5 kg and still requires that intercooler. More importantly: In order for it to be effective, you need a very large volume flow of CO2 gas, which might cause other issues...

 

[PedroCG]

Well i've done some heat transfer math and i give up... it can be done easily, i just dont know how easy one can fit a 1 meter long system on a car... and make it weigth less than 5kg... and make the losses in the piping be smaller than the gains in density.
I assumed a 0,25Kg/s mass flow (air needed to burn the amount of gasoline needed to produce 300Hp with 30% efficiency, bit on the high side), smooth pipes, constant wall temperature of -73,15ºC (one less thing to interpolate) (i'm not sure u could keep the temperature that low...), i also assumed that the air would split evenly by the number of tubes. The formula i used to calculate Nusselt's number is for L/d > 60 witch did not verify... dont think that makes much diference.
The system i designed may not be the most efficient one but i thing its enough to show how difficult would be to build an efficient one, unless i got the math wrong in that case i apologisse...
Check the link below.

 

[globi5]

In order to reduce the pressure loss and heat transfer, the intercooler should be short and fat rather than long and narrow.
Increasing the cross-section reduces the air velocity, which not only reduces the pressure loss but also increases the time of air-exposure in the intercooler. And reducing the length of intercooler further reduces the pressure loss.

In order to increase the surface area, reduce the overall size, reduce the length of the system, and reduce the empty space around the pipes, the pipes need to have a narrow rectangular shape rather than a round shape.

With 10 rectangular pipes and a cross-section of 200mm x 6mm each, the cross-section is almost doubled and even at a fifth of the length (200mm) the surface area is quadrupled (and this at double the exposure time per m2). The cross-section from the example above is the same as a pipe with a diameter of 125mm, which is still significantly larger than an intake pipe of a typical 4-cyl engine.

Since the intercooler is not pressurized, the aluminum sheets making the rectangular pipes can be thin. At 0.5 mm sheet thickness you're at around 5kg.

But as I said: I don't think it's worth the effort.