Ok, here's another part cooling duct for the Hermera exstruder/hotend assembly. Mine only blows from one direction across the nozzle. Permanoob beat me to the punch on posting this, and his design is great too! I used 40 degrees as my fan mount angle and I have yet to install it onto my printer. (waiting for fan ro arive)
The instructions and inspriration that Permanoob described pretty much are what I used to create my design. My duct mounts wirh two M3 x 8mm socket head cap screws.

I'm using a 40mm x 15 fan.

12/08/19: I updated the model file to center the duct to the hotend and to provide more vertical adjustment of the duct.

12/13/09 Updated model with more accurate fan mount.