There are many types of
freezers out there, most likely, the type you're familiar with is either the one in your
refrigerator, or the
deep freeze you may have in your basement, but when it comes to commercial
mass production, many businesses use what's called a tunnel freezer. These freezers are either
straight tunnels, or
spiral freezers, straight tunnels are long freezers that run the product in a straight line through the freezer. Spiral freezers are generally larger in volume, but don't take up so much length. The
product runs through the freezer up one
spiral and down another, increasing the time that it is exposed to the cold temperatures, which generally results in a more thoroughly frozen product.
One of the differences between such
commercial freezers and the type that keeps your
burritos cold, is the medium used as a coolant, most commercial freezers use
anhydrous ammonia as a coolant, and require it to be fed in from the outside. This has to do with the fact that ammonia is cheaper to get and is good at carrying away heat.
Note: Tunnel Freezers are considered a
confined space and as such, it would be an extremely bad idea to walk into one while the
conveyor is running (you should probably
lock that out first).