Aren’t all the fans that are being marketed for our grow tents/rooms mixed-flow (hybrid) designs?
Yes, and thank you for doing so.
I toyed briefly with the idea of designing a DIY filter, but realized that many competent engineers have explored this problem already and everyone’s settled on the design we know. I’m not apt to do better.
I will, however, use the method @Growdoc described to make an ordinary filter refillable.
Here’s the latest version of my filter spreadsheet. Inspired by the lighting thread that @Low created, I decided to expand it to include all sizes.
Aqua denotes the filter(s) that offer the lowest cost/CFM in each size category. Yellow denotes close seconds.
Cost/CFM tends to increase with the thickness of the carbon layer, so the “best value” filters presumably don’t last as long or filter as well.
Finally, just for fun, I fit a simple predictive equation to the data. A straight line fit works fairly well (R2 = 0.97), but those familiar with regression can see from the residuals that there’s a 2nd-order effect that isn’t accounted for.
