In the freezer industry, tunnel freezers are a common type of cryogenic cooling system that is used to cool food products very quickly. These long, cryogenic tunnels use liquid nitrogen (LN2) or carbon dioxide to freeze products from hot or room temperature at one end of the machine to a frozen state at the other end.
Tunnel freezers have a number of advantages over other types of freezing systems. They have higher heat transfer rates than other freezers, which results in a faster freezing process that minimizes dehydration. Additionally, tunnel freezers can be adapted to a variety of different product sizes and shapes, making them very flexible machines that can handle a wide range of food products.
A tunnel freezer uses a conveyor belt to move the product through the cooling tunnel. The product is positioned in front of a cold air blower that directs the air flow over the product. The cold air blower has multiple fans that blow cold air through a filter that is designed to capture and recycle the nitrogen gas vapor from the product surface. This cold air vapor is then blown back over the product in order to maximize the refrigeration potential.
Many of the same benefits are associated with this type of tunnel freezer that are seen in LN2 immersion tunnels. The main difference between the two is that immersion tunnels use liquid nitrogen, while flat belt LN2 tunnels utilize a combination of liquid and vapor nitrogen. Unlike the liquid nitrogen that is sprayed directly on the product, vapor nitrogen contains more BTU’s than the liquid does. Therefore, it is necessary to make sure that the refrigeration value of vapor nitrogen is used efficiently. CSE designs nitrogen freezers with this in mind, so that the available refrigeration from both the liquid and vapor is used to its fullest potential.
Both types of tunnel freezers have a few advantages over each other, but the choice between them is usually based on what the customer needs and the type of product being frozen. For instance, some companies prefer the taste of carbon dioxide, while others believe that it has better color retention qualities in certain meat products. It is important to have a discussion with your gas supplier about what the options are for supplying your tunnel freezer, and make sure that you understand how your choice will impact your overall gas usage costs.
If you have any questions regarding tunnel freezers, please contact us at Demaco. Our team has extensive experience connecting all types of tunnel freezers to a storage dewar of the required cryogenic liquid, and we can help you to choose the right solution for your facility.