There may be situations when, even though we are using a microfin tube, the capacity decreases compared to the use of smooth tubes.
This reason is due to the pipe side pressure drops.
In fact, if there are some Kelvin of pressure drops, the end-of-evaporation temperature decreases.
See the chart below:
From point 1 to 2, we have the ideal evaporation (at constant pressure).
But if there is a pressure drop of 2K or more, the evaporation temperature is represented by the trend from 1 to 2 ', thus causing a lower end-of-evaporation temperature than the beginning.
And this causes, therefore, a decrease in capacity.