Adding a fan to the Sunlu FilaDryer S1 makes a big difference in the performance of the dryer. Without it the filament does not achieve an overall temperature. When I set the temperature to 50C the center of the spool barely reached 35C even after 6 hours. With the fan, the center of the filament spool was up to 45C in a little over an hour and up to 50C within 2 hours of starting. It then maintain a good even 50C for the rest of the drying time. This bracket will hold a standard 40x20mm fan. It doesn't require much air flow so get a very slow fan or one with a speed control.
Repost by @MidLifeHiker from Thingiverse