Hi, Amindzo

Not so simple as a calculation ... nor to realize.

In fact, you try to realize a full climate control unit !!!

I think the easy way is

A) for entering air

- Measure temp and Humidity

B) for Target conditions

- calculate the Dewpoint temp for those conditions

C) Heat ( or cool ... depends on entering air ) your air to the calculated dewpoint temp

D) saturate it with sprinkled water @ ~ the dewpoint temp (- only if needed ! )

E) Heat it to your required temp; the humidity will be very close to what you look for ... no ???

Alain