No-frost refrigerator evaporator is a heat exchanger. It’s an aluminum or copper tube like a car radiator.
The refrigerant that flows in the tube uses the little omount of heat around the tube to boil. That leaves the area around the evaporator cool.
Refrigerant-flow in the system is a continuous process called the refrigeration cycle. The continuous refrigerant cycle in the evaporator leaves the tube’s surrounding (refrigerator compartments) cooler and cooler. That’s how a refrigeration system obtains cold temperature in refrigerators