in physics?

Question

Why should the coating of ice be removed from the cooling unit of a refrigerator at frequent intervals?

Answer 1

Because the ice that builds up around the evaporator becomes an insulator. In another words, The freezer is trying to release cold air into the unit, but the ice becomes some type of wall between the freezer and the unit. This makes the freezer use more energy to produce more cold air in order to keep the unit at its right temperature.

Answer 2

The removal of frost (and subsequent ice) from the cooling coil of a refrigerator is necessary to maintain the design air flow through the coil. This removal is called defrosting. The chilling and recirculating of the air inside the cabinet is what cools the refrigerator cabinet and its stock. If there is a frost build-up the air cannot circulate through the coil and the cabinet will not be cooled, it will just make more frost and ice and eventually fail unless safety controls shut it down first. The most convenient and least expensive way to defrost is to just do it automatically on a timed interval. On some units the timing may be adjusted.
The water resulting from the automatic defrost is drained to a pan under the unit and heat evaporates it into the room. On manual defrost units (if they are even still made) this has to all be done by the "custodian of the kitchen" and is very inconvenient and messy.