Conventional liquid nitrogen containers store samples, mostly in liquid phase;
The liquid phase, simply understood as a way of immersion in liquid nitrogen, has the advantage of being stable at -196°C.
However, not all liquid nitrogen containers are liquid-phase, there are also liquid nitrogen freezers with vapor-phase as the main mode of preserving biological samples by vaporizing liquid nitrogen, which is especially suitable for large-volume preservation of stem cells, bacterial strains, embryos, and so on!
This is achieved by partitioning the liner with the addition of an evaporator!
The main difference between the inner liner design of the liquid nitrogen freezer and the conventional liquid nitrogen container lies in the inner liner to do the partition, separated from the upper and lower parts by a large tray, the upper part of the fixed freezing shelves or other, the lower part of the storage of liquid nitrogen and liquid nitrogen storage area at the bottom of the addition of the evaporator.
When a certain temperature needs to be reached in the upper part, the bottom evaporator works to vaporize the liquid nitrogen into nitrogen gas. The expanded volume of nitrogen, being lighter, travels upwards until it enters the sample storage area, where it maintains the low temperature required for the sample.
Moreover, if the temperature inside the tank is higher than the pre-set value, the intelligent monitoring system of the liquid nitrogen freezer will automatically trigger the evaporator to evaporate the liquid nitrogen at the bottom and supply it to the sample at the top, which has been circulating the vaporized liquid nitrogen to maintain the low temperature and preserve the sample statically for a long time.
These are the vapor phase realizations of cryogenic liquid nitrogen freezers!