The tunnel freezer is a cryogenic freezing system prevalent in the food industry. It uses liquid nitrogen (LN2) or carbon dioxide to cool products from hot or room temperature at one end of the freezer, to a solidly frozen state at the other end. Most of these systems utilize a conveyor belt to transport the product along the length of the freezer, and the LN2 or CO2 is sprayed across the surface of the conveyor in order to rapidly chill or freeze the products.

IQF Cryogenic Tunnel Freezer

A tunnel freezer is the ideal solution to quickly freeze a wide variety of fresh or frozen foods without the risks associated with thermal shock, dehydration, or yield loss. Our IQF tunnel freezers are designed and built to meet the specific water content, weight, shape, and fragility specifications of your product and can be customized for your production requirements.

Compared to the other cold-storage solutions available, the advantages of a tunnel freezer are clear: it can quickly and thoroughly cool, or even freeze, a large volume of products, it can protect the quality of the product and its packaging against harmful microorganisms, it can reduce spoilage by preventing product dehydration, and it requires lower operating costs than mechanical systems.

Most tunnel freezers use either nitrogen or carbon dioxide as the cooling cryogen, with the choice of which one to use often based on the product being cooled. Liquid nitrogen works very similarly to carbon dioxide in a tunnel freezer: the liquid is sprayed onto the product and then blows the extremely cold vapor back over the product in order to make maximum use of the refrigeration potential that exists from the conversion of liquid to vapor (Latent Heat of vaporization, at about 86 BTUs per lb.).

However, flat belt tunnels are able to take advantage of the refrigeration that comes from the sublimation of dry ice. When piped to the tunnel as a high pressure liquid, CO2 expands into a mixture of gas and tiny, dry ice solid particles (known as “dry ice snow”) when it enters the freezer’s injection orifices. The cold vapor from this condensation instantly hits the food products being transported through the tunnel and a refrigeration effect occurs based on the latent heat of sublimation (246 BTUs per lb. of solid CO2).

Compared to the nitrogen tunnels, the refrigeration from CO2 is much more rapid and does not depend on the conversion to a vapor phase. Therefore, a flat-belt CO2 tunnel will look very similar to a conventional LN2 tunnel. However, in the same way that a carbon dioxide tunnel will spray the cold vapor directly onto the product, a new generation of insulated flat-belt freezers will also be able to circulate the cold vapor around the product to make full use of its refrigeration potential. This allows the system to achieve the same low refrigeration costs as a traditional nitrogen tunnel, but with more energy efficiency.

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