Cryogenic (LN2) gas vs liquid for cooling 
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*For cooling, would you recommend using gas over liquid or vice-versa? What is the temperature differential between gas and liquid? 


In other words, at standard volumes and pressures from a gas discharge vs standard flows and pressure from the liquid dispenser side of the 180L tank, 


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*what kind of temperature differences can we expect? 


I would expect the minimum achievable temp with a gas only system to be a lot higher than if we were feeding liquid directly to the setup, however I would also expect that using gas will help preserve the tank longer. Looking into Nitrogen phase diagrams now. I'm guessing that both gas and liquid are delivered at $22 PSI$.
 A: At my workplaces (your mileage may vary), LN2 is so cheap and easily accessible, that it really doesn't matter. It's simply easier to dump a few liters of it wherever it's needed and not worry. In fact, that was the even general approach to handling LN2 back during my diploma studies in a lab where cryogens were generally in short supply.
However there are benefits to using a cryogen in gaseous form. The heat of vaporization of N2 is 5.56 kJ/mol. Its heat capacity is 29.1 J/(mol K). If you're cooling down something from room temperature, you can initially pull out some extra 29.1*(300-77)=6.5 kJ/mol of cooling power. Of course, that's no reason not to evaporate the cold LN2 against the object to be cooled, before using the vapors to cool it further.
One really starts to feel the difference when dealing with LHe though. It's beyond the scope of the OP, but the heat of vaporization of LHe is tiny. Tiny, as in, liquid helium cannot cool down anything. It serves to stabilize the low temperature of something, that's already cold and contained in a nicely insulated dewar/cryostat. It's the heat capacity of the gas that does the trick.
In that same lab I mentioned, we would very slowly fill a bath cryostat with LHe, making sure, that there was absolutely minimal overpressure of vaporized helium, so as to utilize its heat capacity as a gas to the fullest. Allow the pressure to rise, and the cold helium gas with all its cooling potential would escape into the recovery lines.
