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When does a small liquid nitrogen container only store liquid nitrogen need to be replenished?

2024-01-22 10:37:25

There are two ways to use liquid nitrogen containers: liquid nitrogen only and liquid nitrogen + sample;

But whether you store only liquid nitrogen or liquid nitrogen + samples, the problem of adding liquid nitrogen is inevitable, but the reference for replenishing the liquid is different.

When storing samples, use the sample as a reference because it is necessary to ensure that the liquid nitrogen completely covers the sample and is not affected by temperature fluctuations.

Small liquid nitrogen containers that only contain liquid nitrogen do not need to store samples, and there is no need to consider unsafe issues caused by temperature fluctuations. They only store liquids and use liquid nitrogen for low-temperature experiments, or ice cream, spot moles, etc. What is it? When is the right time to add liquid nitrogen?

When the amount of liquid nitrogen is 1/3 of the total capacity of the small liquid nitrogen container!

Liquid nitrogen is evaporating all the time, and the vacuum structure of a small liquid nitrogen container can only be reduced. As the amount of liquid nitrogen decreases, the temperature in the tank without liquid nitrogen coverage will gradually rise. The smaller the amount of liquid nitrogen, the greater the temperature increase. Fast, because this low temperature is difficult to help maintain the temperature of the upper liquid nitrogen-free zone.

If you do not replenish the liquid nitrogen when it is only 1/3 of the total volume of the tank, the remaining liquid nitrogen will only evaporate faster and the temperature in the container will inevitably rise. Wait until the liquid nitrogen has completely evaporated before replenishing the liquid. At this time, the temperature inside the container is close to normal temperature. When new liquid nitrogen is injected, it is not pre-cooled and the evaporation rate is fast (because the temperature of the jar itself is high and there is heat exchange), which can easily be mistaken for the jar not being insulated. . Pre-cooling is more troublesome and needs to stand for several hours before use.

Therefore, if it is a small liquid nitrogen container that only contains liquid nitrogen, it is recommended to add liquid nitrogen when the total capacity is only 1/3!

When does a small liquid nitrogen container only store liquid nitrogen need to be replenished