A tunnel freezer uses extreme cold temperatures and a high-velocity air flow to quickly cool and freeze food as it moves through the machine on a conveyor belt. This allows for much faster freezing times than other types of freezers, while still ensuring that the food is well-frozen and safe for storage. Tunnel freezers are used to freeze a wide variety of foods, including meats, vegetables, fruits, and other products.
While there are a number of different ways to freeze foods, tunnel freezers are one of the most common and widely-used. The process of cooling and freezing using this type of equipment is relatively simple, and there are a few basic steps that are necessary to ensure that the product is properly frozen.
The first step is to cool the product down to a lower temperature than that of water. This is achieved by introducing air to the freezer, and by adjusting the amount of air that is used. When enough air is introduced, the temperature of the product will drop rapidly. In this way, the food can be quickly cooled and then frozen, which will preserve the nutrients in the food to a large extent.
Another method of lowering the temperature is to use liquid nitrogen. Liquid nitrogen is a chemically inert gas, and as such can be used to freeze food without damaging the proteins within it. This is known as cryogenic freezing, and it is an excellent method for quickly preserving the quality of many types of food.
In order to reduce the freezing time, tunnel freezers are often equipped with special spray nozzles that can spray liquid nitrogen on the food as it is being conveyed through the freezer. This will greatly speed up the freezing process, and can even allow for some foods to be frozen in a matter of minutes instead of hours.
Some tunnel freezers use a combination of air jets and liquid nitrogen sprays to achieve the best results. The jets that are used to cool the food are called impingement jets, and they are capable of cooling the product with a very fast rate of heat transfer, while also reducing the freezing time significantly.
Other tunnel freezers utilize flat belts and a process called vapor stripping. These freezers take advantage of the refrigeration value of converting liquid nitrogen into vapor, which is 86 BTUs per lb. The cold vapor is then blown across the product, and then forced back towards the entrance of the tunnel. This is the most efficient way of using the refrigeration provided by the flat belt tunnel freezer.