Extreme cooling design?

[dakels]

I am not a CPU cooling expert nor a physics expert, I just want to know why certain things aren't done or aren't feasible. Now bear with me cuz I am quite ignorant on the subject but it's just a concept that popped in my head while waiting for a printout

A highly pressurized cold substance like liquid LN2 or CO2, under high pressure will remain cold won't it? As the substance heats up it will try to expand but without room for expansion it will stay condensed and cold?

Now if you had a cooling block with LN2 piping through it, fully insulated, maybe ceramic or ceramic covered metal, only your point of CPU contact, the top of the core would need a conductive surface. Since it's under very high pressure would the LN2 or CO2 heat up or heat up considerably? What about using a convection circulation design that circulates the LN2 across the conductive area that meets the CPU core. The shape I have in mind is like a funnel. (hard to explain what I mean without a diagram) I'm thinking of a hurricane model where as hot air (or LN2 or CO2 in this case) will push up the center, reach the top and come back down the sides as cooler. A natural convection moving the inner super cooling fluid around. It could also be quite small in this manner as well and be self sufficient requiring no power and no added cooling liquids or recharging.

I realize it's pretty simple so I am probably missing some fundamental rule of physics here regarding the transfer of heat energy but I was just curious. Come to think of it... I think my idea is not that far off from radiator cooling/heating methods... So why can't you fill the pipes so to speak with LN2 or CO2? I Imagine it would require a construction that could withstand enourmous pressure, but if it's made to be self contained, then I don't see how hard that would be for a small amount of liquid.

Please edumacate me as to why this is not feasible. And you'll probably tell me to read up on thermodynamics and peltier cooling and bla bla bla right?

 

[Lynx516]

What you are talking about is phase change cooling. This uses the principal that when somethign expands it cools and hence absorbs any sourrounding heat. So in these systems you use a compressor to compress the refrigerent then it goes through some capillary tubing to create a pressure differential and on the other side you have an evaporator where the refrigerant boils hence cooling the surrounings. The Reason LN2 is not used is that it requires alot of energy to condence it. What you seem to be missing is that you need to loose the heat to get it to condence again. The boiling is what cools the surface not realy the liquid itself because the liquid will go straight to gas at the temperatures of a CPU core

Hope this explains your post

 

[dakels]

Thanks, I kinda figured that. For heat to dissapate off the liquid it must do something like evaporate to release that energy. So this system would have to use a condenser eh?

But then why does a container of presurized liquid gas stay cold? Like a canister of CO2. The canister is stting in a room thats 200 or whatever degrees hotter then it is yet remains cold. Or is it not transferring and releasing energy? is that why? whereas something that actively cools something like a processor would need to transfer and release that energy through something like evaporation?

 

[f95toli]

The liquid in the tube is not cold. The C02 is cooled down when you let it out of the tube because you allow it to expand.
The temperature of a gas is propotional to 1/volume, that is, if you double to volume you decrease the temperature to half of the orignal value. This is known as the gas-law: pressure*volume=(the amount of gas)*temperature (or pV=nRT for short, R is a constant equal to 8.31).

 

[dakels]

So in an inanimate state, it is not cold, but as it expands it is it releasing it's own energy thus a cooling effect? IS it pulling in energy as well? I guess so if that is heat absorbtion right? If LN2 gets on your hand for instance, your hand will freeze because the LN2 is pulling the heat energy away so it could expand?

So I guess this is the principle behind the condenser. The cooling liquid expands to release heat, then the condenser uses it's own energy to condense the gas back into a liquid state to go all over again? I guess I just learned some basics in refrigeration

 

[Peter]

You guys are talking about how standard kitchen refrigerators work. Plenty literature about that ...

 

[dakels]

They knew that, I didnt until now. They just helped me realize that my "light bulb moment" is basically what I use to cool my beer.

 

[Smilin]

Don't knock yourself. You also invented the heat pipe here too.

 

[dakels]

Originally posted by: Smilin
Don't knock yourself. You also invented the heat pipe here too.

w00t!!! too bad I'm not smart enough to think of it first
some brains + no education = poor








btw what's a heat pipe? lol

 

[Howard]

Originally posted by: dakels
Thanks, I kinda figured that. For heat to dissapate off the liquid it must do something like evaporate to release that energy. So this system would have to use a condenser eh?

But then why does a container of presurized liquid gas stay cold? Like a canister of CO2. The canister is stting in a room thats 200 or whatever degrees hotter then it is yet remains cold. Or is it not transferring and releasing energy? is that why? whereas something that actively cools something like a processor would need to transfer and release that energy through something like evaporation?

The gas is not cold. It is at room temperature.

 

[Howard]

Originally posted by: dakels

Originally posted by: Smilin
Don't knock yourself. You also invented the heat pipe here too.

w00t!!! too bad I'm not smart enough to think of it first
some brains + no education = poor


btw what's a heat pipe? lol

A closed hollow pipe with a substance inside which evaporates when heat is absorbed. It condenses on a cooler interior surface, thereby increasing the thermal conductivity manyfold.

 

[Howard]

Originally posted by: dakels
So in an inanimate state, it is not cold, but as it expands it is it releasing it's own energy thus a cooling effect? IS it pulling in energy as well? I guess so if that is heat absorbtion right? If LN2 gets on your hand for instance, your hand will freeze because the LN2 is pulling the heat energy away so it could expand?

So I guess this is the principle behind the condenser. The cooling liquid expands to release heat, then the condenser uses it's own energy to condense the gas back into a liquid state to go all over again? I guess I just learned some basics in refrigeration

If liquid nitrogen gets on your hand, your hand will not freeze. In fact you will not feel much of anything.

 

[dakels]

Originally posted by: Howard

Originally posted by: dakels
So in an inanimate state, it is not cold, but as it expands it is it releasing it's own energy thus a cooling effect? IS it pulling in energy as well? I guess so if that is heat absorbtion right? If LN2 gets on your hand for instance, your hand will freeze because the LN2 is pulling the heat energy away so it could expand?

So I guess this is the principle behind the condenser. The cooling liquid expands to release heat, then the condenser uses it's own energy to condense the gas back into a liquid state to go all over again? I guess I just learned some basics in refrigeration

If liquid nitrogen gets on your hand, your hand will not freeze. In fact you will not feel much of anything.

well that depends on how much I think. I know in fairly small amount sit will evaporate so fast it won't freeze anything. I have done it. It boils right off your skin. Now in large amounts though like gallon+ I think there would be enough to freeze you. Still not the point of my example though

 

[Cogman]

I watch a guy poor about a liter of LN2 over a class mates hand. She said it felt a little cold, but not freezing. Now If she had cuped her hand I dont know what would have happend. Ive also had some LN2 Frozen Marshmellows, and Tootsierolls (robotics lab at the INEEL, I still wonder what the LN2 had to do with anything...)

 

[Howard]

Originally posted by: Cogman
I watch a guy poor about a liter of LN2 over a class mates hand. She said it felt a little cold, but not freezing. Now If she had cuped her hand I dont know what would have happend. Ive also had some LN2 Frozen Marshmellows, and Tootsierolls (robotics lab at the INEEL, I still wonder what the LN2 had to do with anything...)

If you cupped your hand, nothing would happen. The expanding N2 would just force its way out.

 

[f95toli]

IF you cup your hand when someone poures liquid nitrogen over your hand you WILL get hurt, Ive learned wht LN2 can do the hard way since if I use the stuff every day. If some LN2 gets "stuck" under something (under a ring, watch) you will get a wound that looks more like a burnmark than frostbite.
LN2 behaves more or less like water on hot plote, small amounts will vaporize but if you use enoughh of it you will start cooling things down, rapidly.

 

[Shalmanese]

One has to wonder how exactly people find out stuff like "If you cup your hands and pour liquid nitrogen in them, nothing happens". Then they discover the Darwin Awards and it all becomes clear.

 

[Jeff7]

Originally posted by: Shalmanese
One has to wonder how exactly people find out stuff like "If you cup your hands and pour liquid nitrogen in them, nothing happens". Then they discover the Darwin Awards and it all becomes clear.

I hear it tastes sort of like Pepsi too.


:Q

 

[Cogman]

Originally posted by: Shalmanese
One has to wonder how exactly people find out stuff like "If you cup your hands and pour liquid nitrogen in them, nothing happens". Then they discover the Darwin Awards and it all becomes clear.

really, its not hard to find that out, even without getting hurt one can imagine that unless the LN2 can escape it will freeze the surrounding area in order to obtain a balance of sorts. now, what I wonder is who was the first to poor LN2 over their hands to see what would happen.

 

[dakels]

Originally posted by: Cogman

Originally posted by: Shalmanese
One has to wonder how exactly people find out stuff like "If you cup your hands and pour liquid nitrogen in them, nothing happens". Then they discover the Darwin Awards and it all becomes clear.

really, its not hard to find that out, even without getting hurt one can imagine that unless the LN2 can escape it will freeze the surrounding area in order to obtain a balance of sorts. now, what I wonder is who was the first to poor LN2 over their hands to see what would happen.

anyone smart enough to pour it on a lab rat first lol