I needed to dry the inside of a small hose that is part of a drinking system for tracking and outdoor sports. The cone shaped extension for a standard PC fan should compress the fans airflow to a small diameter. The top nozzle has the same diameter as the hose and can be directly attached to it.

The desing makes use of the parametric approach of OpenSCAD. In my case, a fan of 70 mm width and height was used. The bottom side of the fan is protected with a grille. Use 4 screws M4 x 30 to assemble the stack of grille, fan and compressor cone.