This is an improved fan duct combining a few different designs, while also optimizing the air channels by removing many of the obstructions. However, I have not printed this, and am not confident that it can be printed without soluble supports. I will update if I find a way to reliably print it.
Still need to add an airflow gate for printing with temp sensitive filaments.
You will also need to print with ABS as PLA will melt and deform.