| ▲ | I Made a Quieter Air Purifier(chillphysicsenjoyer.substack.com) |
| 53 points by crescit_eundo 6 days ago | 28 comments |
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| ▲ | dpark 14 minutes ago | parent | next [-] |
| If these 5 little fans do the job as well as a full size box fan, I have to wonder: 1. Are box fans just really terrible? I would expect the amount of airflow from a box fan to absolutely demolish these little case fans. 2. Does airflow not actually matter that much? Assuming the box fan really does move far more air, that would imply that air filtration is somehow not driven by air flow. Or else the testing methodology is flawed. |
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| ▲ | scosman 3 hours ago | parent | prev | next [-] |
| I had the same insight for in-home air movement. Purpose built inter-room fans from broan/etc are 3x louder and several times more expensive than computer fans at the same CFM. I've been very happy with them. https://scosman.net/blog/using_in_wall_computer_fans_for_hom... |
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| ▲ | ruralfam 2 hours ago | parent | prev | next [-] |
| Appreciate any thoughts you all have re: this post.
For years I have been using Noctua NF-P14 fans to circulate air in house to distribute heat in the winter from our wood stove. E.g. cut holes in the walls, and circulate remote rooms using the fans. Has worked great, and the Noctuas have been rock solid. Recently a daughter moved into a really nice apartment close to a major university/freeway where she will live for the number of years it takes to get a Phd. I got concerned about tire dust. So I am about to start building a really nice air DIY air filter using eight Noctua NF-P14s (about 1000 cfm). XMas present. I really wanted to use merv-13, but got quite worried about air flow restrictions, plus cost to replace (assume monthly). Instead I went with two 12x24 Carter reusable electrostatic merv-8 filters. I use Carter filters on my house blower, and really like them (just washed them... scary how much junk is in household air). Also, I got the 12x24 direct from Carter for a very low price as they were returns. Note: This is NOT a low cost project, but I just got scared re: merv-13 so went with what I know. Anyway, the final product will NOT be like this guy's DIY. I will use my somewhat decent woodworking skills to fashion a good looking standing "lamp like" appliance that should look good in most living rooms. I am thinking of going with knotless cedar as I really like working with cedar, and there are some mills here in NW WA where one can go to get such wood (not a HomeDepot specialty). My question is whether an electrostatic merv-8 filter would do well with tire dust. I am not looking to create "clean room" conditions in the apartment. Just get rid of some of the bad stuff. I am very weak re: understanding filters, mervs, etc. APPRECIATE any insights. Thx, RF |
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| ▲ | tim333 an hour ago | parent | next [-] | | I recently bought one of these. It's pretty quiet (on the low setting) - you quite likely wouldn't hear it near a freeway https://www.amazon.co.uk/gp/aw/d/B071SLZRRV vid of the noise levels https://youtu.be/wOc0TM1ErYA?t=195 | |
| ▲ | bsilvereagle 44 minutes ago | parent | prev [-] | | Check out the plot in the header, and find the particulate size you care the most about: https://www.frdmtoplay.com/nagivating-air-purification/ | | |
| ▲ | ruralfam 16 minutes ago | parent [-] | | Thanks. However note that the site dropped electrostatic filters to simplify things. My understanding is that for non-static-affected particles merv-13 would obviously out perform merv-8 for smaller particles. However the promise of electrostatics is that the materials in the filters create a e-stat field that makes them more efficient re: particles like dust. Certainly the two electrostatic merv-8 filters on my hvac blower capture A LOT of dust (fine particles). Since you clean them in a bathtub by filling the tub and washing the filters thru them, I can attest that there is A LOT of really fine particulates being captured. The lead line for this article pretty much reflects the reason for my post: "The air purifier marketplace is an apt metaphor for how a particle must feel while being trapped in a filter - at every turn there's a new acronym or regulatory agency or purifier type." |
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| ▲ | erwincoumans 3 hours ago | parent | prev | next [-] |
| I wonder if they used silent computer fans? I love the quiet Noctua fans, and replace all noisy fans with them: fans in pc, wifi router, playstation 5, mister fpga, robots, jetson orin etc. |
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| ▲ | ruralfam 10 minutes ago | parent [-] | | I use a bank of eight Noctuas to vent from the rooom with our wood stove to the main hall. Then use more units with two sets of Noctuas ganged to move from the hall to various remote rooms. Been using them for more years than I can remember. Silent, never failed yet. It has been great vs. using house fans (my initial approach). BTW: Our local thrift store has a huge amount of various DC power supplies from donations. I sift thru them to find the right volts/amp combo needed for the ganged units, and generally spend about a dollar per supply. HTH, RF. |
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| ▲ | tyre 2 hours ago | parent | prev | next [-] |
| My favorite DIY air purifier setup is buying this Conway, myself: https://www.amazon.com/dp/B01728NLRG Quiet, efficient, works super well |
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| ▲ | notatoad an hour ago | parent [-] | | yeah, i get why people were doing the DIY air purifier thing during covid when air purifiers were hard to come by, and the box fan version at least has cost-effectiveness going for it. but 5x arctic cooling PC fans is ~$100. the commercial versions are easily available, more effective, no more expensive, and don't look like a box of furnace filters taped together. |
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| ▲ | xnx 2 hours ago | parent | prev | next [-] |
| Are those 200mm fans? |
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| ▲ | jsheard 2 hours ago | parent [-] | | They're from Arctic Cooling, so 140mm at most. They don't make anything bigger than that. |
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| ▲ | runariot 5 days ago | parent | prev | next [-] |
| Why do computer fans blow air inside? |
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| ▲ | chr-s 3 hours ago | parent | next [-] | | You want to suck air through the filters rather than blow into them. For one, this keeps the fans cleaner but also it's more efficient, reducing turbulence inside the box. https://old.reddit.com/r/crboxes/ is a good resource if you're looking to make your own. There's been a general shift from large box fans to PC fans because their performance/noise ratio is better. | |
| ▲ | pixl97 3 hours ago | parent | prev | next [-] | | Your question isn't very clear... Is it why do they use computer fans? (My guess is that is what they had). Or is it why do you blow instead of suck? | |
| ▲ | brtv 3 hours ago | parent | prev [-] | | I think this done to create a slight overpressure which helps keep the dust out. |
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| ▲ | calvinmorrison 3 hours ago | parent | prev [-] |
| Corsi-Rosenthal... they taped some filters to a fan, something the poor folk have been doing forever and academia acts like they invented fire. It's caveman technology with a fancy name. embarassing |
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| ▲ | pkd 2 hours ago | parent [-] | | It didn't really come out of academia in that way. It was an innovation borne out of necessity during Covid. I don't think I've seen anybody using a box design for it. If you have a source, I'll be happy to be corrected. Regardless technology is often named after people who made it popular, especially when original inventors are unknown or too diffuse. | | |
| ▲ | tguvot 2 hours ago | parent [-] | | not that much of innovation. i build one like this back in 2018 during california fires. used it mostly in garage for filtering air when i work on "things". decommissioned it last week. i guess i am not the only one who came up with this idea prior to covid as this is pretty obvious | | |
| ▲ | tehjoker 2 hours ago | parent [-] | | i did think the 4-sided design using the cardboard box as a base was very efficient. one of the contributions here was Corsi and Rosenthal did this in a lab and reported particulate counts, flow rates, and energy usage. So there was some kind of intellectual contribution to broaden adoption by giving it more of an imprimatur of quality other refinements were using a shroud to prevent back flow | | |
| ▲ | tguvot 2 hours ago | parent [-] | | back in 2018, during fires, when air filters were unobtanium, on bayarea subreddits (and probably here) were floating a lot of posts of DIY filter made from box fan + hvac filters. plenty of people also posted particulate count reduction charts. you don't need a lab to figure out that replacing 1" filter with 4" filter and even better arranging multiple filters in a box will improve flow rates and filtration (especially for box fans that not really designed for static pressure) corsi&rosental work, imho, is equivalent to lab work reporting that you can move more water through 10" pipe than through 1" pipe. | | |
| ▲ | tehjoker an hour ago | parent [-] | | I can see that argument, but I think what they contributed was that there's something approaching a cost-optimal design. they reported that the 4-sided design with box fan had higher CADR than many if not all commercially available filters though it often used more power and was louder, so the filtration per dollar was very good | | |
| ▲ | tguvot an hour ago | parent [-] | | p100 masks will have optimal filtration on HEPA level per dollar. | | |
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