What is the difference between liquid helium and liquid nitrogen? The minimum temperature difference is large!

Helium, liquid helium

In the field of low-temperature technology, liquid helium and liquid nitrogen are the most widely used coolants and refrigerants. These two liquid phase gases have one thing in common, which is low-temperature refrigeration. Looking at the low-temperature use of these two gases, there may seem to be many similarities, but in reality, there are many differences.

The minimum temperature difference between liquid helium and liquid nitrogen is significant

Since they are both low-temperature artifacts, we naturally need to talk about the lowest temperature they can reach first. Helium can reach temperatures close to absolute zero, which means its lowest temperature can reach -273.15 ℃. Although liquid nitrogen has good low-temperature performance, its lowest temperature is only -196.56 ℃! Obviously, compared to liquid helium, it is really 'less explosive'!

However, due to different customer needs, liquid helium and liquid nitrogen emit light and heat in different usage environments, providing effective services for many fields.

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The chemical properties of liquid helium and liquid nitrogen are very different

Why are we discussing chemical properties here? Because they are not raw materials for product manufacturing, but only serve as cooling fluids, it is their responsibility to cool rather than 'cause trouble'.

The best thing to do about "finding trouble" is liquid helium! We all know that helium is the least active element and hardly combines with any other element. That is to say, liquid helium, as a refrigerant, will not react with the cooling target, changing any of its characteristics, and therefore will not cause additional losses. But liquid nitrogen is different, its properties are much more active than liquid helium, so liquid nitrogen is a common laboratory ultra-low temperature cooling method, and the cooling liquid widely used in some quantum physics laboratories is actually liquid helium.

When it comes to the activity of coolant, there is a gas that must be mentioned, and that is liquid hydrogen. In theory, it can be used as a cooling liquid and its performance may be better than liquid nitrogen. After all, liquid hydrogen can lower the temperature to -252.8 ℃, which is very close to the level of liquid helium. However, it should be noted that whether it is liquid nitrogen or liquid helium, the evaporation products are inactive gases, especially helium, which is an inert gas that hardly reacts with any substance.

And the liquid hydrogen evaporates into hydrogen gas, which is a highly explosive and dangerous gas.

The price difference between liquid helium and liquid nitrogen is significant. Overall, many people may think that liquid helium is subjectively much better than liquid nitrogen, but we should not ignore their price difference!

Helium, as a rare gas, has a high acquisition cost. 95% of helium in the domestic market relies on imports, so its price is comparable to gold. Nitrogen is different because the gas with the highest content in the air is nitrogen, which is easy to obtain and has a larger quantity, so its price is several times different from helium. In short, liquid helium and liquid nitrogen have different minimum temperatures, properties, and price differences when purchased according to needs, but demand is the biggest reference for selection.