TD (temperature difference)
Short definitionThe difference between room temperature and evaporating temperature. A small TD means high humidity in the room.
The colder the evaporator surface is compared with the room, the more moisture it takes out of the air. With a large TD the room dries out. With a small TD it stays humid.
For products that must not lose water, such as fruit and vegetables, a small TD is chosen with a matching evaporator that has a large surface area. For packaged and frozen products a larger TD is acceptable. That means a smaller and cheaper evaporator.