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shobimono
Why?

Registered: 09/14/04
Posts: 561
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Laminar flow hood blower calculation question
#17917604 - 03/07/13 08:31 AM (11 years, 2 months ago) |
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I'm finally getting around to making a laminar flow hood after ordering a HEPA years ago lol.
The HEPA is 24" x 24" x 6" 99.99% at 0.3µm.
Calcs;
2ft x 2ft = 4ft2
100 ft/min x 4ft2 = 400ft3/min
I have this pressure chat for the HEPA

I'm confused how this chart is used in relationship to the 400ft3/min calculated above?
Should I look for a blower that puts out 400cfm? or does the chart say that I shouldn't use a blower above 350cfm?
Is there a rule of thumb on how large the plenum needs to be?
Will a 2'x2'x2' box (ie 1.5' deep plenum) work?
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Amanita virosa
botanist by day



Registered: 12/04/11
Posts: 2,458
Loc: north kakalacky
Last seen: 10 months, 4 days
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Re: Laminar flow hood blower calculation question [Re: shobimono]
#17917832 - 03/07/13 09:32 AM (11 years, 2 months ago) |
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the plenum should be twice the size of the thickness of the filter, so yours should be a foot deep, slightly bigger is fine. as to the blower, don't torture youself too much about perfectly sizing it... better to oversize the blower for two reasons... one is that as the filter cloggs the resistance increases. therefore if you size the blower exactly to the filter, you will not get the useful life out of your filter. the second is that you can always reduce blower output but you cannot increase it. you can stack filters or cover part of the intake to reduce flow.
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shobimono
Why?

Registered: 09/14/04
Posts: 561
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Re: Laminar flow hood blower calculation question [Re: Amanita virosa]
#17917892 - 03/07/13 09:46 AM (11 years, 2 months ago) |
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Terry M
Stranger in a Strange Land



Registered: 06/18/10
Posts: 1,502
Loc: Rhode Island
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Re: Laminar flow hood blower calculation question [Re: shobimono]
#17918099 - 03/07/13 10:39 AM (11 years, 2 months ago) |
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Either fan type will work, so long as the specs are right. I use an inline fan.
-------------------- Liberté, égalité, humidité.
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RogerRabbit
Bans for Pleasure



Registered: 03/26/03
Posts: 42,214
Loc: Seattle
Last seen: 1 year, 2 months
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Re: Laminar flow hood blower calculation question [Re: Terry M]
#17921290 - 03/07/13 08:17 PM (11 years, 2 months ago) |
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I'd have to guess since the line stopped at 1.2" that's as much static pressure as the filter is rated for. That will give you 350 cubic feet or around 87 fpm and will work OK, especially if you use it in a small, closed room. I prefer a bit more flow, but that's the filter you have. Find a blower that will give you around 400 cfm @ 1.2" W.G. RR
-------------------- Download Let's Grow Mushrooms semper in excretia sumus solim profundum variat "I've never had a failed experiment. I've only discovered 10,000 methods which do not work." Thomas Edison
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shobimono
Why?

Registered: 09/14/04
Posts: 561
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Re: Laminar flow hood blower calculation question [Re: RogerRabbit]
#17923137 - 03/08/13 06:55 AM (11 years, 2 months ago) |
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Thanks I was wondering what that meant when the line ended.
Hm, now I'm wondering if I should even bother with this HEPA or maybe just buy another that will give me more airflow.
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RogerRabbit
Bans for Pleasure



Registered: 03/26/03
Posts: 42,214
Loc: Seattle
Last seen: 1 year, 2 months
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Re: Laminar flow hood blower calculation question [Re: shobimono]
#17923453 - 03/08/13 09:26 AM (11 years, 2 months ago) |
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Check with the manufacturer to see if that was inadvertent. Perhaps you could run at 1.5" or so and get more flow.
If not, that one will still work. RR
-------------------- Download Let's Grow Mushrooms semper in excretia sumus solim profundum variat "I've never had a failed experiment. I've only discovered 10,000 methods which do not work." Thomas Edison
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