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Using liquid nitrogen or liquid CO2 for cooling

frazierk

Member
I would like to switch to chillers for all cooling needs (cold traps, gas injection temperature, column jackets, condensing coil/heatexchangers/etc) . However that's a huge cost up front so I will upgrade slowly over time. Until then I want to get away from dry ice/alcohol mixtures, as that gets expensive over time. It seems to me that using liquid nitrogen or liquid CO2 would be the most cost effective method of cooling at this point.

Before I pick some up though I have a few questions:

Is the use of either of these liquids both effective and efficient for all cooling needs? Which do they work for and which do they not?

How can the temperature of the liquids be controlled? Liquid nitrogen boils at -321F. How would I use it to get my gas to around -30F?
 
How can the temperature of the liquids be controlled? Liquid nitrogen boils at -321F. How would I use it to get my gas to around -30F?

While liquid nitrogen boils at -321*F, you aren't actually going to get anywhere close to that right away because of the thermal mass at a way higher temp that is already present in the system (thermal enthalpy)

As for your second question, I think the DIY way to do it would be a temperature probe set up with a PID controller and a solenoid hooked to your LN2/CO2 tank. May also require some sort of needle valve to throttle the amount that comes out at once.
 

Gray Wolf

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I would like to switch to chillers for all cooling needs (cold traps, gas injection temperature, column jackets, condensing coil/heatexchangers/etc) . However that's a huge cost up front so I will upgrade slowly over time. Until then I want to get away from dry ice/alcohol mixtures, as that gets expensive over time. It seems to me that using liquid nitrogen or liquid CO2 would be the most cost effective method of cooling at this point.

Before I pick some up though I have a few questions:

Is the use of either of these liquids both effective and efficient for all cooling needs? Which do they work for and which do they not?

How can the temperature of the liquids be controlled? Liquid nitrogen boils at -321F. How would I use it to get my gas to around -30F?

LN2 works well for subzeroing LPG prior to injection, but wouldn't be the best choice for cooling pump discharge.

We used a counterflow exchanger and injected liquid N2 in one end of the jacket and discharged N2 vapor out the other.

We control the temperature with an orifice on the discharge end of the jacket, and by the rate of flow of the LPG passing through the center heat exchanger tube.
 

frazierk

Member
Are there any counterflow heat exchangers on the market that can handle such cold temperatures, or would I need to have one custom made? Everything I have found so far is used with water for homebrewing and doesn't seem like it would hold up.

If it does need to be made custom, how do you calculate how thick the steel needs to be, how long of a coil is needed, and what diameter is needed for the tubing/jacket?
 

Gray Wolf

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I had to have ours custom built by Albina Tubing in Tualatin, OR.

I used 304SS 1/2" inner tube and 3/4" outer. ASME requires a .049 minimum wall thickness for 1/2" tubing in LPG service, and the brewing industry counterflow exchangers only had .035 wall.

I suggest 20' lengths for counter flow exchanger, because that is how long the sticks are and it it too hard ($) to insert the inner tube in a coil, using a coil. You can always use more than one exchanger.

I used Swagelok 3/4 X 1/2 X 1/2 Tees on the ends, and through drilled out the 1/2" tube socket, so the 1/2" tube passed right through it.

The 20' exchangers were adequate for the Haskel pump discharge cooling using a Temco Fisher Merlin 150 -15C chiller, and for LPG injection using LN2.
 

Old Gold

Active member
GW: What do you normally set PRV at when using LN2? I'm sure this varies with temperature selection; but the lower the jacket pressure, the better.

We are transitioning towards using nitrogen for cooling finally.
 

Gray Wolf

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GW: What do you normally set PRV at when using LN2? I'm sure this varies with temperature selection; but the lower the jacket pressure, the better.

We are transitioning towards using nitrogen for cooling finally.

We don't use a PRV at those temperatures, but use an orifice at the hex discharge instead. We open the Dewar supply valve wide open and control the flow by how big the discharge orifice is.

You can use a simple orifice or Swagelok valve for that application, but you won't be able to operate the valve after the first few seconds of flow, so have to adjust it fast.

The valve can never be closed completely, because if the Dewar valve is also closed, any liquid in the lines converting to gas will rupture the lines.
 

Old Gold

Active member
Really? So if you constantly vent off at, say, 1 psi.....you're telling me the vessel walls will implode? My initial reaction was to not use a PRV, but I've also heard of others doing so, so they must have gotten lucky. But I also know that liquid CO2 cooling requires often higher pressures in jackets than the internal vessel holds (bizzybee systems). I figured it mostly came down to wall thickness/vessel shapes.
 

Gray Wolf

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Really? So if you constantly vent off at, say, 1 psi.....you're telling me the vessel walls will implode? My initial reaction was to not use a PRV, but I've also heard of others doing so, so they must have gotten lucky. But I also know that liquid CO2 cooling requires often higher pressures in jackets than the internal vessel holds (bizzybee systems). I figured it mostly came down to wall thickness/vessel shapes.

We used a 150 psi PRV for CO2, but none for LN2.

Not sure what you mean by imploding?
 

Old Gold

Active member
We used a 150 psi PRV for CO2, but none for LN2.

Not sure what you mean by imploding?

I mean the jacket pressure causing the interior vessel to implode.

High pressure outside of the cylinder + low pressure inside the cylinder = a much weaker cylinder.

I figured a PRV set for LN2 might slow it's flow down and perhaps make it a more efficient in cooling. But it may not be necessary at all as you stated.
 

Gray Wolf

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I mean the jacket pressure causing the interior vessel to implode.

High pressure outside of the cylinder + low pressure inside the cylinder = a much weaker cylinder.

I figured a PRV set for LN2 might slow it's flow down and perhaps make it a more efficient in cooling. But it may not be necessary at all as you stated.
Roger that!

Looks like collapse pressure on Schedule 5 is around 315 psi.
http://www.tubeweb.com/Non-Ferrous-Tube/theoretical-bursting-collapsing-pressures-for-pipes.html

Here is a flow through an n diameter orfice at X pressure link: http://www.engineersedge.com/fluid_flow/discharge-air-orifice.htm
 

dybert

Active member
Roger that!

Looks like collapse pressure on Schedule 5 is around 315 psi.
https://www.tubeweb.com/Non-Ferrous-Tube/theoretical-bursting-collapsing-pressures-for-pipes.html

Here is a flow through an n diameter orfice at X pressure link: https://www.engineersedge.com/fluid_flow/discharge-air-orifice.htm

I personally know a "reputable" extractor company that uses co2 cooling jackets, and he has confirmed that clients have indeed imploded vessels. We have run the same system with pressure up to 200ish and haven't had a problem but have heard some weird noises and definitely am not comfortable with it.
 

Gray Wolf

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I personally know a "reputable" extractor company that uses co2 cooling jackets, and he has confirmed that clients have indeed imploded vessels. We have run the same system with pressure up to 200ish and haven't had a problem but have heard some weird noises and definitely am not comfortable with it.
One thing to consider when looking at pressure ratings, is that they are based on some temperature, typically ambient, but not specified on the chart I shared.

Carbon steel looses most of its ductility at those temperatures, so a 300 series austenitic stainless is typically used, but even they don't retain full properties at subzero to cryogenic temperatures.

If the 315 psi crush is a good number, the 200 psi ya'lls reputable associate is using is probably closer to collapse than 63% load would suggest.

I built my first columns out of 304SS Schedule 10 pipe, which has a collapse of 845 psi, and might be an option for someone wanting to push pressure with CO2 or LN2.

CO2 presents less of a delta T issue at the PRV than LN2. We successfully used a relatively cheap one on our DIY SCFE CO2 experiments.

Hardly anything cheaper regulating flow at a given pressure than a fixed orifice, with less to go wrong, go wrong, go wrong...........
 

Rickys bong

Member
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Another point to remember when pressurizing a jacket is that tube implode pressures are lower than burst pressures due to the tube being in compression.

When pressurized from the inside out, everything is in tension and the tube shape can be less than perfectly round.
Tube implode pressure charts assume a near perfectly round tube. Any distortion due to welding and it may implode at a much lower pressure.

I use two relief valves for CO2, one set to the pressure we're working at an another for safety set 30psi higher.

You need at least 60psi to keep the CO2 liquid. But when the valves open the pressure can drop quickly forming dry ice so 75 psi works well.

You can regulate the temp somewhat by setting the blowoff pressure. Higher pressures give higher temperature.
For instance, at 84psi CO2 boils at -56. At 130psi CO2 boils at -40
Some relief valves don't like low temps so a heat band to keep it warm helps if the valve sticks open. Larger prvs seem to have less sticking issues.

Peace

RB
 

thcnology

Member
I had to have ours custom built by Albina Tubing in Tualatin, OR.

I used 304SS 1/2" inner tube and 3/4" outer. ASME requires a .049 minimum wall thickness for 1/2" tubing in LPG service, and the brewing industry counterflow exchangers only had .035 wall.

I suggest 20' lengths for counter flow exchanger, because that is how long the sticks are and it it too hard ($) to insert the inner tube in a coil, using a coil. You can always use more than one exchanger.

I used Swagelok 3/4 X 1/2 X 1/2 Tees on the ends, and through drilled out the 1/2" tube socket, so the 1/2" tube passed right through it.

The 20' exchangers were adequate for the Haskel pump discharge cooling using a Temco Fisher Merlin 150 -15C chiller, and for LPG injection using LN2.

GW..where did you find this? "ASME requires a .049 minimum wall thickness for 1/2" tubing in LPG service, and the brewing industry counterflow exchangers only had .035 wall." For example if I wanted smaller tubes instead of 1/2"...where can I find that? Thx
 

Gray Wolf

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GW..where did you find this? "ASME requires a .049 minimum wall thickness for 1/2" tubing in LPG service, and the brewing industry counterflow exchangers only had .035 wall." For example if I wanted smaller tubes instead of 1/2"...where can I find that? Thx

Cheer tiz
 

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Sriley28

Member
Hey guys,

I’m looking at using LN2 to cool my double jacketed tank with cooling coil. Still learning what I need to do this properly and safely. GW what size orifice do you have on your exhaust end? Also what psi is your dewar?
 

Gray Wolf

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As I recall, about .34" and 200 psi. We re-drilled a couple of times.

You can use a 3/8" ball valve rather than an orifice on the exhaust side, you just can't adjust them once they get cold, and if you close it completely, you risk a line rupture when the liquid converts to gas.
 

Sriley28

Member
Sounds like just leaving a 3/8’s valvue open is pretty close to what you had. Did you leave it on the entire time you doing the run? How much would you go through in say a coupe hours time?
 

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