When refrigerant is fed into the bottom of an evaporator coil, it boils and vapor is produced at the top. This process is called evaporative cooling. The refrigerant is fed into a metering device, also known as a pressure dropper, which creates a pressure drop and causes the refrigerant to boil. As the refrigerant boils, it remains at a constant temperature until it becomes 100% vapor, at which point it begins to pick up additional heat, known as superheating. Click the link below to watch the f