A fan would help the silica gel pick up water from the filament as long as it’s not saturated at the box RH% but a proper dryer would help a lot. Because of the slow liberation of water from filament at room temperature even in a closed up box, even if the silica gel has more water capacity at the box RH, “drying” will be slow.
Have a look at some of the dryer threads here but IMO, most reasonable cost dryers don’t work well unless you are in a dry environment with the lid propped open. They can even add water on humid days. It’s a long story. I answered because I’ve been deep in desiccants and dryers trying to get things sorted because on some prints I’ve been seeing some humidity effects.
Anyway, what the low cost dryers need is a source of dry air that pushes the moist air out. I’ve got what I hope will be a very functional design almost finished. To give it away (it’s documented in another thread) it’s just an aquarium pump and desiccant that supplies dry air to whatever filament dryer people have. I built a test stand to get a better handle on what was important and what wasn’t so now comes the actual device.
Results are promising and it delivers <=10% RH air to the dryer. I say <=10% because the hygrometers can’t display below 10%. Even 10% is a win but it’s likely much lower. What I’m doing in the next version is going to a simplified and optimized design with the larger pump mentioned in the thread. Apologies if it’s of no interest but I was drying filament while it was raining outside and the doors and a window were open - a spool of “dry” filament lost over a gram of water weight.
https://forum.bambulab.com/t/filament-drying-preliminary-results/