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hostyle
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Registered: 03/02/13
Posts: 60
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How to achieve 100ft/min laminar flow with a 24
#17909178 - 03/05/13 05:35 PM (11 years, 2 months ago) |
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I'm trying to determine how to achieve laminar flow @ 100 feet per minute using the following filter:
24" x 36" x 6" @ 99.99% at 0.3µm, Airflow: 805cfm @ 0.90” w.g
Here are my calculations so far:
The area for the filter is: 2ft x 3ft = 6ft2
I multiply the required air speed with my filters area: 100 ft/min x 6ft2 = 600ft3/min
My questions are:
#1. Is achieving laminar flow at 100ft/min as simple as finding a blower that will move 600cfm thru this filter at a static pressure of 0.90"(225Pa)?
#2. What does the filter's airflow of 805cfm @ 0.90” w.g mean?
Constructive criticism welcome along with any insights;)
Edited by hostyle (03/05/13 07:28 PM)
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Jeff
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Re: How to achieve 100ft/min laminar flow with a 24" x 36" x 6" HEPA filter ? [Re: hostyle]
#17909693 - 03/05/13 07:17 PM (11 years, 2 months ago) |
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You're close. 36" is 3 foot though not 2.5. You need a fan that will supply over 600 cfm. You can always throttle it back a bit.
-------------------- Myco-tek
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hostyle
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Registered: 03/02/13
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Re: How to achieve 100ft/min laminar flow with a 24" x 36" x 6" HEPA filter ? [Re: Jeff]
#17909790 - 03/05/13 07:32 PM (11 years, 2 months ago) |
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Ah! Thanks for catching that!
So 600cfm it is.
Still wondering about the filters data sheet which says its airflow is 805cfm @ 0.90" w.g. and what that means.
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Jeff
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Re: How to achieve 100ft/min laminar flow with a 24" x 36" x 6" HEPA filter ? [Re: hostyle]
#17909906 - 03/05/13 07:55 PM (11 years, 2 months ago) |
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It is the resistance rating at that given flow. It will increase as the flow increases. The filters usually come with a graphical representation of resistance at different flows.
-------------------- Myco-tek
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t3chnobily
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Re: How to achieve 100ft/min laminar flow with a 24" x 36" x 6" HEPA filter ? [Re: Jeff]
#17910073 - 03/05/13 08:25 PM (11 years, 2 months ago) |
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also add .2 wg for a decent prefilter I believe.
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RogerRabbit
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Re: How to achieve 100ft/min laminar flow with a 24" x 36" x 6" HEPA filter ? [Re: hostyle]
#17912202 - 03/06/13 07:52 AM (11 years, 2 months ago) |
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Quote:
hostyle said:
Still wondering about the filters data sheet which says its airflow is 805cfm @ 0.90" w.g. and what that means.
It means if you produce .9" of static pressure(measured in water gauge ie W.G.) the filter will allow 805 cubic feet per minute to pass through it.
In fact, that +/- 800 cfm is perfect. I prefer 100 to 125 linear feet per minute for the speed of air leaving the filter so if you look for a blower that will deliver 800 cfm @ .9" you'll have the perfect setup after putting on a prefilter. 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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hostyle
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Re: How to achieve 100ft/min laminar flow with a 24" x 36" x 6" HEPA filter ? [Re: RogerRabbit]
#17928626 - 03/09/13 10:34 AM (11 years, 2 months ago) |
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Thank you all for your responses.
Quote:
RogerRabbit said: As a rule of thumb, you can just figure on 1" of static pressure being standard. Some filters are rated .9 and others might be as high as 1.3 or so. In the US, most squirrel cage blowers with a CFM rating have it based on that 1" of static pressure. Because of that, just disregard static pressure and look at cfm.(I can feel anno squirming as I say that...lol). RR
I wish that were true for inline fan's as well because I found a 12" 969cfm inline fan for $260.00, however; it is rated for 969 CFM @ 0.0 S.P.
I've found blower fans rated for 900cfm @ 1"SP on Lo speed but at a cost of $510!!!!
Basically it looks like inline fan's are out and blower fan's are in.
Thanks!
Edited by hostyle (03/09/13 09:59 PM)
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RogerRabbit
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Re: How to achieve 100ft/min laminar flow with a 24" x 36" x 6" HEPA filter ? [Re: hostyle]
#17931437 - 03/09/13 10:00 PM (11 years, 2 months ago) |
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Correct. It needs to have the rated flow at static pressure. If it's rated at zero, it's probably just a fan. You need a blower. Get a furnace blower out of an old trashed unit. You can probably find them free by the dozens at your local landfill. At our landfill, they pile appliances in a separate section and you can dig through the pile any time you want for parts. 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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LD50

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Re: How to achieve 100ft/min laminar flow with a 24" x 36" x 6" HEPA filter ? [Re: RogerRabbit]
#17934981 - 03/10/13 06:11 PM (11 years, 2 months ago) |
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Try ebay as well.... I recently got a dayton blower that moves 1000cfm for 80 dollars shipped to my door. Like RR said there are plenty to be had you simply need to find people selling them cheap.
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hostyle
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Re: How to achieve 100ft/min laminar flow with a 24" x 36" x 6" HEPA filter ? [Re: RogerRabbit]
#17941545 - 03/11/13 11:04 PM (11 years, 2 months ago) |
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This would seem to be the most accessible fan:
1/2 HP 115V, rated for 900cfm @ 1"SP @ Lo speed

Can this monster fan be throttled back enough to make it work?
24" x 36" Filter with an airflow of 805cfm @ 0.90” w.g + A prefilter on the outside of blower = .2" so it will be 1.1" w.g.total
The blower will deliver 900cfm @ 1.1 W.G. or 150 feet per minute.
That seems overly quick, as RR suggested 100 to 125.
Can the intake of the blower be covered with something solid to lower the feet per minute?
How to determine if it's working as intended with the blower covered up, lighter at 2 inches away?
Thank you for your replies.
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Terry M
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Re: How to achieve 100ft/min laminar flow with a 24" x 36" x 6" HEPA filter ? [Re: hostyle]
#17942801 - 03/12/13 07:22 AM (11 years, 2 months ago) |
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Here's a nice picture of laminar flow.

Note the very narrow opening for the guided flow. Low Reynolds number at work!
-------------------- Liberté, égalité, humidité.
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hostyle
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Registered: 03/02/13
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Re: How to achieve 100ft/min laminar flow with a 24" x 36" x 6" HEPA filter ? [Re: Terry M]
#17942879 - 03/12/13 08:08 AM (11 years, 2 months ago) |
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Thank you for your visual contribution Terry M.
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jjhitman
The Harley Guy



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Re: How to achieve 100ft/min laminar flow with a 24" x 36" x 6" HEPA filter ? [Re: hostyle]
#17995347 - 03/22/13 03:01 PM (11 years, 1 month ago) |
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Most of the fan motors that would go into a furnaces can be wired for three speed. Im on the hunt now for a air handler / at least a good squirrel cage. Only problem is, all the used ones are saturated with dust and who knows what. Look up a company called Granger. It maybe granger.com They have every motor imaginable! Their support techs can give you a better idea on what you want or need. I would love to see what you come up with!
Got me thinking. I forgot all about granger! I typed in blower cages, http://m.grainger.com/mobile/search/ecatalog/N-?Ntt=blower+cages&tab=search&Nty=1
-------------------- Put water in a cup, it becomes the cup. Put water in a tea pot, it becomes the tea pot. Water can crash or water can flow. Be water my friend.
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hostyle
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Registered: 03/02/13
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Re: How to achieve 100ft/min laminar flow with a 24" x 36" x 6" HEPA filter ? [Re: jjhitman]
#17995532 - 03/22/13 03:41 PM (11 years, 1 month ago) |
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When I initially started this project I picked a filter size and was trying to match the blower to it.
Used blowers are saturated with dust and dirt but can be easily cleaned with pressurized air. I dismantled mine and pressure washed it after watching a video on youtube.
If you've got money to burn purchase one new, matched exactly to your filter size.
What I did was got my blower used for $80.00 from a HVAC company. I think I called about 7 different company's and just waited for someone to call back with what I'd need.
By looking at the data sheets I could find for my blower, and the helpful folks here I've been able to determine that my blower's 1/2 is strong enough for a 24 x 24 filter.
If it's too strong I can just partially cover the blowers intake to reduce the CFM's till I get it just right.
So if you don't care how big the filter is and don't want to shell out huge amounts of coin, I would suggest getting a used furnace blower, figuring out it's output and then purchasing a new filter to fit the blower.
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jjhitman
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Re: How to achieve 100ft/min laminar flow with a 24" x 36" x 6" HEPA filter ? [Re: hostyle]
#17995740 - 03/22/13 04:37 PM (11 years, 1 month ago) |
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At the moment I just have a plane old square box fan with filters taped to both sides. Its ghetto ane i hate it. The number one goal for me right now is to find a good, cheap, big hepa filter or possibly a electrostatic filter. Do you have any recommendations on a good cheap filter? Im really digging some of these smaller multispeed blowers on graingers web site I just seen.
-------------------- Put water in a cup, it becomes the cup. Put water in a tea pot, it becomes the tea pot. Water can crash or water can flow. Be water my friend.
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hostyle
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Registered: 03/02/13
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Re: How to achieve 100ft/min laminar flow with a 24" x 36" x 6" HEPA filter ? [Re: jjhitman]
#17996729 - 03/22/13 08:33 PM (11 years, 1 month ago) |
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Depends really.
I picked 24 x 24 x 6 filter because it matched my blower, luckily for me =====>(Smaller the filter face size the smaller the price)
If you live near a fair sized city I'd recommend checking with local filtration or Ventilation companies. If you buy a filter from them you can usually pick up the filter and save yourself $80.00 on shipping. I'd suggest figuring out what you need first though, before you call them.
The fan you have with two filters on it.... sounds ghetto for rizzle.
Definately source out a blower first imho.
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jjhitman
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Re: How to achieve 100ft/min laminar flow with a 24" x 36" x 6" HEPA filter ? [Re: hostyle]
#18000643 - 03/23/13 07:12 PM (11 years, 1 month ago) |
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How many hours are these filters rated? I just dont know if it would continuously filters good untill the end of its life? Could I get a year or two out of it?
-------------------- Put water in a cup, it becomes the cup. Put water in a tea pot, it becomes the tea pot. Water can crash or water can flow. Be water my friend.
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RogerRabbit
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Re: How to achieve 100ft/min laminar flow with a 24" x 36" x 6" HEPA filter ? [Re: jjhitman]
#18001550 - 03/23/13 11:13 PM (11 years, 1 month ago) |
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I still have the original filter in my flowhood from over ten years ago and I run it several hours daily.
The key is to get a good prefilter. Look for the finest weave furnace filter you can get and change it anytime the flow starts to drop, or at least twice a year anyway. 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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jjhitman
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Re: How to achieve 100ft/min laminar flow with a 24" x 36" x 6" HEPA filter ? [Re: RogerRabbit]
#18001647 - 03/23/13 11:42 PM (11 years, 1 month ago) |
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10-4! Ive did hvac for the last 15 years or so and had a journeymans license at one point.. Ive installed a lot of different air moving equipment. But nothing hepa with this many cfms. The only flow hoods I installed where above friers. Not sure if my hvac supply houses carries hepa fiters (with out them ordering them) johnstones, swh, 2j's, carrier, furgisons are some of the hvac supply houses I have around here. But hell.. if I can get 10 years + out of one im not going to worrie about buying the cheapest one.
-------------------- Put water in a cup, it becomes the cup. Put water in a tea pot, it becomes the tea pot. Water can crash or water can flow. Be water my friend.
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RogerRabbit
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Re: How to achieve 100ft/min laminar flow with a 24" x 36" x 6" HEPA filter ? [Re: jjhitman]
#18002314 - 03/24/13 06:26 AM (11 years, 1 month ago) |
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The cheapest will never be the best. Buy a flow hood filter for performance and success in mycology, not for cost. 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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