1. Liquid refrigerant tends to vaporize as pressure imposed upon it is reduced. (It is already known that water boils at a lower temperature at high altitudes where the atmospheric pressure is lower.) This is what happens to the refrigerant as it is drawn into evaporator coil of a refrigeration unit and the reason the evaporator feels cold.
2. Vapor refrigerant tends to return to its liquid state (condensate) as pressure imposed upon it is increased. (This is what happens as refrigerant is forced into the condenser of unit.)
3. Vaporizing refrigerant absorbs heat from its immediate surrounding environment. (This is what happens in the evaporator.)
4. When vapor refrigerant gives up a certain amount of heat, it changes back to its liquid state. (This is what happens as hot refrigerant vapor is forced into the condenser coil and that is why the condenser feels warm.)
