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  #1  
Old 06-10-2004, 09:41 AM
JohnA JohnA is offline
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Default Nitrous oxide vs Water injection - which one cools best?

...Or more accurately, which one has the highest latent heat of evaporation?

I'm talking to a NOS guru and he insists that nitrous would far outdo WI as far as charge cooling is concerned. (gas is cooled down to -128F blah blah...)

But is this true, if we also take in-cylinder cooling into account?

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  #2  
Old 06-10-2004, 05:00 PM
hotrod hotrod is offline
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Default apples and oranges

Its an apples and oranges comparison.

If your spraying them on the outside of the intercooler, the N20 is "capable" of cooling more, but the economics are out of the ball park unless your just using it for a single drag race pass. I think guys have used up an entire bottle of N20 in a 2 - 3 1/4 mile passes.

If your using it as an internal coolant, spraying into the intake tract you also have to muck around with the fuel to keep from going lean with the N20 due to its oxygen content. With the WI you can simply up the injection rate without needing to worry about melting a piston.

Larry
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  #3  
Old 07-10-2004, 09:00 AM
JohnA JohnA is offline
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Default Re: apples and oranges

Quote:
Originally Posted by hotrod
Its an apples and oranges comparison.
...which is another way of saying you don't know the latent heat of evaporation for nitrous oxide :wink:

I never said it's a fair comparison, just curious to know IF the same mass of liquid NOS made it to the chamber, how would its cooling effect compare to that of water (which is about 4 times higher than that of petrol)
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  #4  
Old 07-10-2004, 10:08 AM
SaabTuner SaabTuner is offline
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Default

"...which is another way of saying you don't know the latent heat of evaporation for nitrous oxide"

Latent heat? Always thought it was a compressed gas, not a liquid.

Nitrous oxide cools off the intake gasses better than WI ... however it HEATS UP combustion.

Cars which run Nitrous oxide often require special super high octane fuel because of the increased tendancy to detonate. You may have heard of the term "nitrous fuel". Nitrous Oxide hugely increases cyllinder temperatures and pressures. The cooling effect can sometimes compensate for this, but only to a point.

Nitrous Oxide cannot be thought of as an anti-detonant like WI.

Adrian~
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  #5  
Old 07-10-2004, 01:42 PM
JohnA JohnA is offline
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Default

Quote:
Originally Posted by SaabTuner
..Latent heat? Always thought it was a compressed gas, not a liquid.
Any gas could be seen as a liquid and vice versa, depending on their pressure/temp combo.

Nitrous oxide in liquid form will turn into gas if let out of the bottle and expands/heats a bit. At that stage it will absorb a lot of heat as it changes state from liquid to gas.
That is what I need to know, how many kCalories will it absorb per mass unit.
I searched all over the internet, but nothing. I suspect that it's about 1/3 of that of water (similar to ethanol), but I'm not 100% certain.

I know it's a silly comparison, because nitrous will also cool the intake charge in ways water cannot. But we're talking in-cylinder cooling here, and latent heat of evaporation is the game. :wink:

This guy sells both W.I. and Nitrous systems, and believes that even a tiny shot of NOS renders WI totally redundant.
I just want to see if he is correct.
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  #6  
Old 07-10-2004, 03:14 PM
hotrod hotrod is offline
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Default Gas properties

Quote:
"...which is another way of saying you don't know the latent heat of evaporation for nitrous oxide"

No it means I didn't bother looking it up because the combustion effects would totally negate it.

Its about 1/6th the latent heat of vaporization of water. But if you used any where near enough to get the same cooling level the oxygen release in the cylinder would probably make your pistons catch fire literally.

The info is widely available in MSDS sheets.

Nitrous Oxide
Molecular Weight

* Molecular weight : 44.013 g/mol

Solid phase

* Melting point : -91 ?C
* Latent heat of fusion (1,013 bar, at triple point) : 148.53 kJ/kg

Liquid phase

* Liquid density (1.013 bar at boiling point) : 1222.8 kg/m3
* Liquid/gas equivalent (1.013 bar and 15 ?C (59 ?F)) : 662 vol/vol
* Boiling point (1.013 bar) : -88.5 ?C
* Latent heat of vaporization (1.013 bar at boiling point) : 376.14 kJ/kg
* Vapor pressure (at 20 ?C or 68 ?F) : 58.5 bar

Critical point

* Critical temperature : 36.4 ?C
* Critical pressure : 72.45 bar

Gaseous phase

* Gas density (1.013 bar at boiling point) : 3.16 kg/m3
* Gas density (1.013 bar and 15 ?C (59 ?F)) : 1.872 kg/m3
* Compressibility Factor (Z) (1.013 bar and 15 ?C (59 ?F)) : 0.9939
* Specific gravity (air = 1) (1.013 bar and 21 ?C (70 ?F)) : 1.53
* Specific volume (1.013 bar and 21 ?C (70 ?F)) : 0.543 m3/kg
* Heat capacity at constant pressure (Cp) (1.013 bar and 15 ?C (59 ?F)) : 0.038 kJ/(mol.K)
* Heat capacity at constant volume (Cv) (1.013 bar and 15 ?C (59 ?F)) : 0.029 kJ/(mol.K)
* Ratio of specific heats (Gamma:Cp/Cv) (1.013 bar and 15 ?C (59 ?F)) : 1.302256
* Viscosity (1.013 bar and 0 &degC (32 ?F)) : 0.000136 Poise
* Thermal conductivity (1.013 bar and 0 &degC (32 ?F)) : 14.57 mW/(m.K)

Miscellaneous

* Solubility in water (1.013 bar and 5 ?C (41 ?F)) : 1.14 vol/vol

Larry
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  #7  
Old 07-10-2004, 09:59 PM
JohnA JohnA is offline
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Default Re: Gas properties

Thank you Larry
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  #8  
Old 24-10-2004, 06:53 PM
Richard L Richard L is offline
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Default Re: Nitrous oxide vs Water injection - which one cools best?

Quote:
Originally Posted by JohnA
...Or more accurately, which one has the highest latent heat of evaporation?

I'm talking to a NOS guru and he insists that nitrous would far outdo WI as far as charge cooling is concerned. (gas is cooled down to -128F blah blah...)

But is this true, if we also take in-cylinder cooling into account?

Cheers
One other thing you have to take into account when comparing the two:

The nitrous oxide will only absorb heat during the expansion phase - ie at the point of evaporation. Any further cooling effect will only be in gasous state (no latent heat of evaporation), it will be very similar to blowing cold air into a cluster of hot gas, the effect will be proporational to the ratio of the two gases.

Water on the other hand, is injected in liquid form. Cooling is taking place during the entire journey into the engine until it comes out of the exhaust.

In my opinion, without any mathematical proof, just a hunch - water will cool more than nitrous per unit mass - can't wait for the next post to tell me the contrary.

There are a great deal of mis-information out there when pushing a product for the innocent Joe public. As JohnA mentioned... charge cooling is concerned. (gas is cooled down to -128F blah blah...) ...

The fact the figure of -128F is mention, the human brain will aurtomatically conclude that nitrous is a better intercooling coolant than water.

There are two types of nitrous injection system on the market:

1) The traditional (USA) type delivers and meters the gas at the point of injection, ie the restrictor is placed at the inlet runners - an eight cylinder engine has eight jets with inbuild restrictor. This type will give good cooling effect as the liquid nitrous enters the inlet tract is still partially liquid, evaporation is taking place there - the rule of latent heat of evaporation applies.

2) The second type (I am not qualify to judge which is better), has only one restrictor, the quantity of nitrous is metered there and then split into eight un-restricted delivery tubes and fed into the individual runners of each cylinder. This is the very point of my concern about the cooling effect this type of nitrous system. Need to calculate before comparing WI and NI.

Conclusion: since the state change of the second system is remote from the runners, there are no cooling effect by evaporation (excellent cooling properties), only by mixing (not so good, in fact it is pretty poor). So IMO, if the phase change (expansion) is remote from the point of delivery, the cooling is worse than water injection.

I hope there will be more inputs from others and hope that we can leave no stone un-turned on this site - just the bare truth and not just taken for granted that -128F is better.

Thank hodrod for giving some basic properties of the two liquids.
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  #9  
Old 27-10-2004, 05:32 PM
JohnA JohnA is offline
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I am expanding the 'NOS' page of my site lately, so I am delving into information that I didn't have before.

I suspect that the much-hyped cooling effects of nitrous may not be as dramatic as some people want to believe.

I, too, thought that there will be cool gas squirting out of a bottle, even if it is not pushing liquid. What the heck, conventional wisdom, eh?
Well, this is actually incorrect: I had a friend position a bottle in a way that the pickup tube inside was only picking gas (they do this all the time these NOS folks!)
Guess what? the gas coming out was room temp. Not super-cool, not even cool-ish. Room temp. I (reluctantly) put my hand and there was no cooling whatsoever. The bottle was mostly full, by the way.

So the cooling advantage applies only when liquid is delivered in the manifold (not as often as most people think)
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  #10  
Old 02-11-2004, 08:09 PM
Richard L Richard L is offline
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Default

There are a great deal of people out there buying things under the influence of marketing hype, even they have doubt at the back of their mind that it is "just to good to be true", they still buy because it won't do any harm.

Trader that relies on hypes or slagging -off their competitor's product in order to gain market share will eventually be challenged. When the truth comes out, it really hurts. But in majoyity of the time, they have such thick and slippery skin, everything seemed to slide off. They know that there is always the chance of - "one being born each day"

If every trader just stick to their own product without making reference to others, the tuning world will be a much better place to be in.

I remembered last year you have posted a link to a site where they claimed that the Aquamist pump produced too much pressure and caused puddling and hence getting bad results, compared to a washer-pump based WI system.
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