We know that Dao temperature of the critical boundary of nitrogen is – 147℃, and the critical pressure return force at critical temperature is 3.4mpa. According to thermodynamic knowledge, nitrogen cannot be liquefied above the critical temperature. However, when searching for nitrogen tanks, it was found that the working pressure of nitrogen tanks on the market was not higher than 3.4mpa, but far lower than 3.4mpa.
The temperature is lower than the critical temperature. Generally, the temperature in the liquid nitrogen tank is about 190 below zero, and the pressure is generally about 0.3-0.8. This is a low-pressure tank. There are also high pressure tanks, which can reach 2,88 MPa
Liquid nitrogen tank, also known as Dewar tank, is a low-temperature adiabatic cylinder, which has a very heat preservation effect, but it can also absorb heat and increase pressure. After all, it will not be absolutely insulated.
When the pressure increases to the maximum design pressure of the tank, a safety valve in the tank will automatically open to discharge the high-temperature gas from the gasified part until the pressure is reduced to the design pressure of the tank, and the safety valve will automatically close.
The design temperature of liquid nitrogen storage tank is – 196 ℃, and there are two kinds of conventional pressure, one is 0.8MPa, the other is 1.6Mpa. These two kinds of design pressure are based on the needs of use. Under pressure, when the temperature reaches – 196℃, nitrogen will become a dark blue liquid, namely liquid nitrogen. Liquid nitrogen can be stored under pressure or without pressure. The temperature difference from the air separation is not big, but the temperature will be higher and higher and the density of liquid nitrogen will be smaller as time goes on
Post time: Nov-13-2020