After passing through the expansion valve, the refrigerant is admitted to the evaporator in liquid form. As the pressure in the evaporator is low, the refrigerant evaporates at a low temperature. On the outside of the evaporator there is a fluid flow to be cooled (water, ethylene glycol solution, air, etc.).
As the temperature of this fluid is higher than that of the refrigerant, it evaporates.
After all the refrigerant has evaporated, it will suffer an increase in temperature called overheating.
