Cold air circulating liquid nitrogen freezing, using liquid nitrogen to cool the circulating cold air and using air as refrigerant to freeze food, can reduce the initial investment and do not need so many refrigeration equipment.

Detailed liquid nitrogen refrigeration equipment can be divided into: liquid nitrogen cabinet refrigeration equipment, immersion refrigeration equipment, tunnel refrigeration equipment, rotary refrigeration equipment and so on.

There are three freezing zones in the process of liquid nitrogen spray freezing: precooling zone, freezing zone and temperature equalization zone. Liquid nitrogen (usually stored in a liquid nitrogen tank) exchanges heat with food through atomization through a nozzle, and the liquid nitrogen at-196℃ absorbs heat and evaporates into nitrogen, which is used for precooling new food, so that both latent heat and sensible heat of liquid nitrogen are utilized, and the cold energy of liquid nitrogen is fully utilized.