Phantoj

The freezing point of the CO2 is less than its boiling point. I can't conceive of any way that letting liquid CO2 out of a container would create the pressure/temperature required for solid CO2.

kc0bbq

Sending a compressed gas into a lower pressure area through a small opening causes it to drop in temperature. That's how they make liquid nitrogen, there isn't any refridgeration method that will do that.

CO2 fire extinguishers make a nice CO2 snow that sublimes right away.

The opposite is also true, which is why things like SCUBA tanks get very hot when filled. Really, really, really hot.

BarracksSi

Is it CO2 snow or is it frost from the surrounding air?

byte_speed

What good is BF without a pissing match?

CO2 can be compressed to the point that it forms a liquid at normal temperatures. At 68°F the pressure in those little CO2 cylinders is 830 psia and the CO2 is a liquid.

Uh, never mind mollusk was right.

jemoryl

At atmospheric pressure CO2 can only exist in two phases: gas and solid; the later is 'dry ice', which goes directly to gas (sublimes) when it warms. If expansion cools the gas enough some solid CO2 might form but I suspect it wouldn't hang around long.

Scorer75

I wonder if I can fill my tires from my SCUBA tanks.

Funky Chops

Im just going to have a stab at this:

Maybe CO2 is easier to compress than normal air. Seeing as normal air is a whole mixture of gases, it might not compress as well as CO2 which is just a single type of molecule.

RoboCheme

jemoryl has it right; the CO2 is stored as a liquid at high pressure. The other issue is that liquid CO2 is a commodity (and by the way there's a shortage of high purity CO2 in the West). It's used for carbonated drinks, beer, etc. It's stored in large tanks (~250 tons) at -17 degrees F and at 220 psig. Since your cartridges are at ambient temperature the pressure in the cartridge is significantly higher. This is similar to the concept of the propane tanks in your BBQ. It's a liquid in the tank under pressure. When you release the pressure by opening the valve, it turns into a gas.

Cliff

Phantoj

This site explains how a CO2 bottle can freeze up with dry ice (scroll down): https://www.teamonslaught.fsnet.co.uk/co2_info.htm

steppinthefunk 

I think it's because CO2 can be compressed into a smaller package.

fprintf

Yes, but who wants to carry SCUBA tanks with them on a ride? They won't fit in my jersey pocket.

RIC0

Carrying a big honkin pump on a bike is gay, CO2 in a pocket is kewl..........

krazygluon

I Highly doubt this bit about more CO2 being exhaled than put into the tire, in fact I'm willing to say, without doing the math this is just plain BS.

I can pump a tire to 120psi in ~20 strokes on my floor pump. if I breathe on each stroke there still wouldn't be that much air exchange. Remember, air is ~18% oxygen, but humans only interchange like 1-2% in each change IIRC.

Edit: if you really want your tires to hold pressure and last longer, go nitrogen.

KiddSisko

And here's my 2 cents worth of input.

kudude

bad argument. floor pump != ****ty frame pump

green814

CO2 is in a liquid state when "stored" in the cylinders. This is the same with paintball tanks, they have liquid CO2, which is ABOUT 1800 psi in the tanks when full. It was stated that in the winter temps the preasure goes UP in the tank, this is not true. It is actually lower. Leaving the windows of a car up, place a CO2 tank inside the car in the middle of the winter. Now do the same in the middle of the summer and it is almost a sure bet the burst disc ( safety disc for to high of preasure ) will blow releasing the tank preasure BEFORE the tank explodes.

When CO2 is released from the "tank", the preasure at which it is stored changes, causing it to become a gas state. While doing this, it release energy in the form of heat, becomin very cold. ( I can't remember the terms for this, but it is exo(something) and endo(something) (if I remember that part right anyway! It is a few years since I had a chemistry class. Maybe one of the "students" can help me!!!!)

As stated, for the same size "tanks", you will have a higher psi in a tube from liquid CO2 "tank" than compressed air (or nitrogen) as even under preasure, compressed air is still AIR.

I was actually checking pumps out today, and I still don't see the benifit of CO2. It may be smaller, and lighter, but you have to replace them every so often. I look at it the same way as my yard waste. I bought some 40g garbage cans ONCE. More money up front, but I still have them after 4 years . Now, where did those $2.00 "yard waste bags" go I put at the curb! (Please understand this comparison in the fact I have a HUGE Maple tree in my front yard. 3 pkg's of bags wouldn't even be enough every fall! )

Chris

kudude

exothermic and endothermic.

has everyone decided on the answer yet, or do we need more responses?

green814

Thank you!

Chris

wcoastbikr

The reason CO2, because it's easier to fill and the CO2 cartridges don't require the same pressure to fill. Keep in mind the CO2 is liquid under pressure, as soon as it is released into your tire, there is more volume than inside the cartridge, and it is also warmer, it changes from a liquid to a gas.

Air takes more space than liquid, so CO2 requires less space when it's a liquid in comparison to compressed air(N2/O2), although N2 and O2 can be liquid, but it requires immense pressure and cold temperatures.

With compressed air (N2/O2) it requires that you have a much higher pressure to fill the same amount of volume, which means that it would require a much more durable, and expensive cartridge. To whoever said they don't use it because of water reasons, is wrong. Compressors for paintball or scuba tanks can filter out water. Also fyi, CO2 in it's liquid state can be corrosive.

gr@sshopper

nope, waterrockets hasn't posted a power curve yet, so I feel the data are inconclusive.