4 ms·

The intention of the OP/post might be good, but the comparison (https://dynomight.net/img/cuboid_purifier/boxfan.jpg https://dynomight.net/img/cuboid_purifier/b

by yumraj 3y ago

The intention of the OP/post might be good, but the comparison (https://dynomight.net/img/cuboid_purifier/boxfan.jpg https://dynomight.net/img/cuboid_purifier/boxfan.jpg) makes no sense whatsoever. They have just thrown 3 filters on top of the box fan with lots of gaps on the side. Air will mostly follow the path of lease resistance and not go through the filters. You need a filter that is the same size, 20x20, as the box fan and then the filter(s) will need to be sealed, via duct tape or so, around the fan for it to be effective.

gardnr 3y ago
You are correct from an engineering perspective. From a cheap/GSD perspective the box fan filters are easy to build and provide a measurable result at a low cost. The internet would welcome any new designs you might have. I'm sure OP would be happy to have started a build-off.
- tedivm 3y ago
  Yeah but there are better box fan filters out there. You can do exactly what OP did with his cube and throw a box fan on top of it instead of the duct fan, and with the higher airflow from the box fan combined with the exact same filter setup you'd likely see better results. Most of the box fan filters I've seen these days look like this cuboid fan- as in, they have four filters, a base, and a fan. Many also include some cardboard curved corners to improve airflow and reduce noise. I kind of assumed that's what we were comparing until I saw the image. Like these from another thread: https://cleanaircrew.org/box-fan-filters/ https://cleanaircrew.org/box-fan-filters/
SkyPuncher 3y ago
the open space will build up pressure, to the point that some air will flow through the filters at equal pressures. This is not a perfect device, but it will capture more particulate than nothing.
afterburner 3y ago
Yeah that box fan setup is hilariously bad. He wasn't nearly so careless about air flow with the design he actually liked.
- spion 3y ago
  The box fan is analyzed in a separate article. See https://dynomight.net/2020/12/15/some-real-data-on-a-DIY-box-fan-air-purifier/#:~:text=a%20better%20rate%3A-,Taping,block%20airflow%2C%20you%20slow%20down%20the%20fan.%20This%20could%20be%20counterproductive,- https://dynomight.net/2020/12/15/some-real-data-on-a-DIY-box....
  - afterburner 3y ago
    And the construction is just as shoddy. The gaps where air can bypass the filter are important. Most of the air will bypass the filters because the air will go through the path of least resistance.
    - spion 3y ago
      If you read the article, you'll see some interesting measurements on that topic.
dynm 3y ago
Author here. I've tested the results of taping around the edges, you can see the results here: https://dynomight.net/2020/12/15/some-real-data-on-a-DIY-box-fan-air-purifier/#taping https://dynomight.net/2020/12/15/some-real-data-on-a-DIY-box...
- yumraj 3y ago
  The common way is to use a 20x20 filter, the same size as the box fan. Ideally you want to use a 4” thick filter, so a 20x20x4 filter and then just seal the outside. It provides huge surface area for the filter and the air flow is almost the same as the fan without the filter. I have a setup like that and it can really move air. The filter you have are much thinner. Now, I have no idea why you’re seeing the same results between taped and non-taped, it makes no sense and is indeed surprising. If you time and inclination, you may want to look into a 20x20x4 HEPA filter and try it.

by yumraj 3y ago

gardnr 3y ago

You are correct from an engineering perspective. From a cheap/GSD perspective the box fan filters are easy to build and provide a measurable result at a low cost. The internet would welcome any new designs you might have. I'm sure OP would be happy to have started a build-off.

tedivm 3y ago
Yeah but there are better box fan filters out there. You can do exactly what OP did with his cube and throw a box fan on top of it instead of the duct fan, and with the higher airflow from the box fan combined with the exact same filter setup you'd likely see better results. Most of the box fan filters I've seen these days look like this cuboid fan- as in, they have four filters, a base, and a fan. Many also include some cardboard curved corners to improve airflow and reduce noise. I kind of assumed that's what we were comparing until I saw the image. Like these from another thread: https://cleanaircrew.org/box-fan-filters/ https://cleanaircrew.org/box-fan-filters/

SkyPuncher 3y ago

the open space will build up pressure, to the point that some air will flow through the filters at equal pressures. This is not a perfect device, but it will capture more particulate than nothing.

afterburner 3y ago

Yeah that box fan setup is hilariously bad. He wasn't nearly so careless about air flow with the design he actually liked.

spion 3y ago
The box fan is analyzed in a separate article. See https://dynomight.net/2020/12/15/some-real-data-on-a-DIY-box-fan-air-purifier/#:~:text=a%20better%20rate%3A-,Taping,block%20airflow%2C%20you%20slow%20down%20the%20fan.%20This%20could%20be%20counterproductive,- https://dynomight.net/2020/12/15/some-real-data-on-a-DIY-box....
- afterburner 3y ago
  And the construction is just as shoddy. The gaps where air can bypass the filter are important. Most of the air will bypass the filters because the air will go through the path of least resistance.
  - spion 3y ago
    If you read the article, you'll see some interesting measurements on that topic.

dynm 3y ago

Author here. I've tested the results of taping around the edges, you can see the results here: https://dynomight.net/2020/12/15/some-real-data-on-a-DIY-box-fan-air-purifier/#taping https://dynomight.net/2020/12/15/some-real-data-on-a-DIY-box...

yumraj 3y ago
The common way is to use a 20x20 filter, the same size as the box fan. Ideally you want to use a 4” thick filter, so a 20x20x4 filter and then just seal the outside. It provides huge surface area for the filter and the air flow is almost the same as the fan without the filter. I have a setup like that and it can really move air. The filter you have are much thinner. Now, I have no idea why you’re seeing the same results between taped and non-taped, it makes no sense and is indeed surprising. If you time and inclination, you may want to look into a 20x20x4 HEPA filter and try it.