The only difference between a refrigerator and a freezer is temperature. The refrigerant moves through the freezer at a faster pace to maintain that core temperature of 0 degrees Fahrenehit (-18 degrees Celsius). For a fridge, the vapor travels a bit slower, because a fridge needs to be set only at about 32 degrees Fahrenheit (0 degrees Celsius).
Types of Freezers
In your home, you probably have a refrigerator/freezer combination unit. Whether you have a side-by-side fridge/freezer appliance, the kind with the freezer on top, or one with the freezer on the bottom, the differences are few. Each freezer is a single unit, so they all use the same machinery described earlier in the pursuit of vapor compression. About the only difference is energy efficiency. The bottom-mount uses the least amount of power [source: Hakim and Turiel]. Why? If the compressor is on the bottom, doesn't have to push vapor very far. On the side-by-side or top-freezer styles, the compressor has to force refrigerant through a tube to reach the freezer compartment.
Another kind of freezer is the standalone, also called a "deep freeze" or "sub-zero," although the latter is a trademarked name for a specific brand of freezer. They, too, operate on the basic principles of vapor-compression.
Have you ever worked in a restaurant and had to retrieve food from a large, walk-in commercial freezer? Again, these use vapor-compression; the only major benefit for this kind of unit is that many of them have reinforced aluminum floors which can hold up to 600 pounds (about 270 kilograms) of weight per square foot -- a very valuable concept in a high-volume restaurant (but which would be completely unnecessary for a family of four).
Whatever kind of freezer you use, be sure to keep the temperature low and consistent. Otherwise, you'll get a buildup of a freezer's worst enemy: frost. On the next page, we'll take a look at how frost occurs and what you can do to prevent it.