[HN Gopher] The Cuboid: A DIY air purifier that's better than a ...
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The Cuboid: A DIY air purifier that's better than a box-fan
Author : ruph123
Score : 107 points
Date : 2023-06-07 21:08 UTC (1 hours ago)
(HTM) web link (dynomight.net)
(TXT) w3m dump (dynomight.net)
| rainbowzootsuit wrote:
| What this and the box fans seem to miss is that prop fans have
| very little ability to generate static pressure. You will move
| more volume over the static pressure loss of the filters if you
| use a centrifugal type of fan. A little looking on Amazon shows
| those at about 3x the price of the prop boosters for the same
| rated cfm.
|
| If you add even a little bit of duct to extend approximately 3
| duct diameters on the outlet it will make the fan a lot more
| efficient by allowing the airflow to stabilize and lower
| buffeting noise at the outlet. There athere are some of the
| centrifugal fans that include a noise suppressor for more money
| that's basically a short duct that's double walled and perforated
| on the inside.
| londons_explore wrote:
| Having tried both, prop fans seem to beat centrifugal fans for
| the pressure drop across typical filters, and deliver more air
| per watt through a filter.
|
| I suspect the pleated nature of the filter means that the
| static pressure drop isn't all that much. Haven't got a
| manometer to measure it though.
| mrbonner wrote:
| Ok where did they buy 3 HEPa filters for $70?
| mustyoshi wrote:
| He casually mentioned using the same (dirty) filters for the box
| fan run, how much did that skew the results?
| Tyr42 wrote:
| You don't replace the filters every hour do you? It's on e a
| month or once a season for our furnace filters at least.
| chrislan815 wrote:
| bro that's insane
| altairprime wrote:
| There's a simpler construction of this, using tape and the fan or
| filter cardboard packaging, here: https://cleanaircrew.org/box-
| fan-filters/
| csours wrote:
| (2021)
|
| I'm currently dreaming up a ceiling fan replacement that has a
| much lower profile and also cleans the air with a standard
| furnace filter.
| nilstycho wrote:
| Have you seen jefftk's ceiling air purifier?
|
| Post: https://www.jefftk.com/p/ceiling-air-purifier
|
| HN Discussion: https://news.ycombinator.com/item?id=31590773
| csours wrote:
| Haha, yes. I love it.
| kristopolous wrote:
| I'm speaking out of ignorance and not criticism, why not just go
| with a commercial product at that price point?
|
| I can imagine many theoretical reasons like sourcing and
| availability but are there things beyond actual conjecture here
| groos wrote:
| The article didn't mention the static pressure of the fan.
| Typically, for a "suck" type fan, you want higher static pressure
| and there are fans which are designed expressly for this.
| unit_circle wrote:
| Noctua makes some nice, slightly ruggedized 12v high static
| pressure fans.
| plagiarist wrote:
| What would I want to search for to find that? "High static
| pressure fan?"
| ethbr0 wrote:
| https://www.mcmaster.com/products/high-pressure-blowers/
|
| Or don't let the perfect be the enemy of the good -- buy 10x
| box fans for cheaper, because they're manufactured and
| shipped in the millions of units.
|
| If it's not going to catch on fire, why are we worrying about
| the longevity of something that costs $30?
| ilyt wrote:
| ...did you look at what you linked ? They are all 65-75dBA+
| massive blowers...
| Jeff_Brown wrote:
| Why does it work better?
|
| I see that in the test he compares four filters being used
| completely in the cube setup to three being used incompletely on
| a box fan. But that doesn't seem like it can be the entire
| explanation -- particularly given the reduced airflow of the duct
| fan.
| odensc wrote:
| Isn't $100 (the stated cost to make this) the same as a proper
| air purifier like a Levoit Core 300?
| Forbo wrote:
| The Levoit filters are twice as expensive to replace.
| odensc wrote:
| What is that calculation based off of? The article lists the
| 4 filters as $70 (which I'd assume you would replace all at
| once).
|
| The Levoit uses 1 filter "unit", and filters are $55 for a
| 2-pack on Amazon ($27.5/ea), or half that if you trust the
| third-party ones.
|
| Levoit recommends to replace the filters every 6-8 months, so
| you could get 12-16 months of filtration for $55. I can't
| find any calculation in the article for how long the author
| estimates their filters would last.
| binarymax wrote:
| The haphazard assembly of his box fan doesn't look ideal. If
| you're going to do it that way at least get a 20x20 size furnace
| filter and use some duct tape to seal it.
| jacobsenscott wrote:
| If you live in a place with forced air heat you can probably set
| the furnace fan to be on all the time. Install a hepa filter and
| you are good to go.
| turtlebits wrote:
| The only problem is that instead of re-circulating and
| filtering conditioned air, a furnace fan is going to bring in
| external unconditioned air (and is only filtered once).
| ary wrote:
| The design should also fix the worst parts of using a box fan:
| 1. Make less noise. 2. Use less electricity.
|
| Point #1 is not the worst part of a box fan for many people,
| myself included. I have a lot of fond memories from growing up
| where a box fan was running at night due to the outside heat and
| lack of central AC. It made sleeping a much easier and more
| pleasant experience.
| ethbr0 wrote:
| Spend $50 and prepare to have your mind blown.
|
| https://www.amazon.com/Adaptive-Sound-Technologies-LectroFan...
| xen2xen1 wrote:
| I both need the noise and the air (I sleep warm), but I had
| what had to be a 1950s version of this when I was a teenager
| , which was just a small enclosed fan that had a top you
| could regulate to change the sound. Still miss it sometimes.
| salad-tycoon wrote:
| Yep. Bought one at one of the donation stores for $2. Made
| in USA, must be about double my age, and still works great.
| Amazed that a little fan like that can just keep spinning
| for that long.
|
| Hooked it up to a wifi power switch. Old meets new.
| ipsum2 wrote:
| You can also make this with a box fan, construct a box with 4
| filters of roughly the same size as the fan, the bottom of the
| box can be cardboard. Did this back in 2019 and it works great,
| though I ended up switching to a Coway a few years later because
| of the noise.
| londons_explore wrote:
| Related question:
|
| As filters age, they change colour. Mine start white and turn
| dark grey when old.
|
| However, I noticed that even the outlet side got darker. That
| made me wonder if a 'blocked' filter was actually allowing more
| small particulates through (for example perhaps because all the
| surface area that a bit of PM2.5 could electrolytically stick to
| has already been stuck to).
|
| Does this sound plausible? Anyone got test results for small
| particulates of different materials and how the filter performs
| as it ages?
| flaburgan wrote:
| Can we fix one of these filter at the back of my PC? Would that
| actually work?
| dsr_ wrote:
| In order to prevent dust buildup inside the PC? Yes.
|
| In order to meaningfully clean the room's air? Not on one PC,
| with any reasonable number of fans.
| ilyt wrote:
| Some big radiator + unreasonably sized fans PC+filter build
| would be _interesting_ at the very least
| tedunangst wrote:
| > If you take the top pick from the Wirecutter and read user
| reviews carefully, you'll see that roughly one person a week
| reporting that their unit exploded.
|
| I mean, if you read colander reviews on Amazon, you'll find
| people who somehow lost a hand to it.
| themerone wrote:
| I love the reviews and comments where you really hope the
| person left it on the wrong product page, such as the person
| asking how big reppelent helps with babies teething.
| astockwell wrote:
| This is almost exactly the design used by BlueAir purifiers
| https://www.blueair.com/us/blue-family.html
|
| Can recommend.
| breput wrote:
| The Corsi-Rosenthal box[0] design using a standard box fan and
| furnace filters has been tested and verified to be very effective
| (and cheap):
|
| [0] https://cleanaircrew.org/box-fan-filters/
| skeaker wrote:
| How does this stack up in terms of noise versus the one in the
| OP?
| [deleted]
| breput wrote:
| It's constructed using a regular 3 speed box fan, so it isn't
| going to be significantly louder than that and possibly
| quieter depending on how it is shrouded and insulated.
| fellowniusmonk wrote:
| I have a few box fans filters and one cuboid fan, it's not
| actually the cuboid though, I used a circular hepa filter
| with the inline duct booster fan.
|
| I leave the fan duct fan running on low (right at the
| midpoint of the speed dial so technically medium I guess)
| 24/7 in my kitchen out of eye site because it's so quiet.
|
| So, in my experience, much quieter, quiet enough that people
| don't notice it running all the time. I have the dial in
| reach though so I can crank it all the way if something burns
| on the stove, clears the air out shockingly fast.
|
| I got some sound proof panels and crappily bungee corded them
| around the fan and it didn't have a noticeable effect. I
| think if I put more effort into the sound baffles it would
| reduce the sound, but the whole setup without baffles is
| quiet enough I haven't bothered.
| binarymax wrote:
| Indeed, linked in that article is this which I built yesterday
| and works very very well.
|
| https://www.texairfilters.com/a-variation-on-the-box-fan-wit...
|
| -EDIT- I should also mention that you don't need 5 filters for
| this (MERV 13 is expensive), you can use 4 and a piece of
| cardboard for the 6th side that is touching the ground.
| duxup wrote:
| I just built one in preparation for a home remodel. I want to
| try to clean out any excess dust while we're living through a
| remodel.
|
| Or even all the excess dust kicked up from a digging out old
| things we didn't know he still had...
| DeRock wrote:
| I see this all the time, why use multiple 1" thick filters to
| build a box, when you could just use 1x 4" filter. They are
| pleated, and the surface area should be equivalent. I
| documented my setup here before:
| https://news.ycombinator.com/item?id=28395232
| postpawl wrote:
| Can confirm this works great. I wish there were more options
| for higher quality 20x20 box fans though. I've had Lasko fans
| that got loud after a few months, and I assume that's a
| bearing going bad.
| bsilvereagle wrote:
| Note that the OP uses ASHRAE's definition of CADR (nominally
| airflow rate * removal efficiency) and not AHAM's more
| complicated definition which accounts for contamination rate.
|
| Some details about AHAM's CADR calculation are here:
| https://frdmtoplay.com/nagivating-air-purification/
| [deleted]
| carabiner wrote:
| BTW in Seattle we have learned to stock up on these fans, filters
| in the winter, because they regularly sell out in stores when
| it's smoke season.
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(page generated 2023-06-07 23:00 UTC)