In-Line Carbon Filter

[hurricane]

Greetings, i've been thinking lately about in-line carbon filters. Not the standard ones with minimal surface area, but taking a can style filter and making it inline. The purpose of this is two fold. The first is that it can be placed outside the grow tent. The second is that it can run after the fan(blow through, i know not best but my fan has 2 intakes which will make scrubbing the intake side difficult) but still allow me to direct the airflow out of the room the hut is in.

Basically its just taking the DIY carbon scrubber from overgrow, and a attaching 10" to 8" reducer over the main 8" to 6" reducer, and then running solid 10" duct to the top of the filter. After this would use the reducers to get back to 6"(or maybee just 8")

In terms of area for air flow should be good, there are 9Pi sq.in. in a 6" circle, there are also 9Pi sq. in. in a 10"-8" circle. Any reason this wouldn't work? Heres a pic i put together with google sketchup showing what i mean. The carbon would go between the two layers of chicken wire(would prob use 1/2" hardware cloth instead). Large pantyhose wrapped on the hardware cloth to hold the carbon in, all standard for a can filter basically.

Hurricane

 

[Siddartha]

rock on! well worth a try, wish I could be the one, no grow for me for a while, but I'm bookmarking....

 

[Aware]

Looks like a well designed scrubber if ever I've seen one. Only reason I can see for it not working is the off chance you decide not to build it. Give 'er hell and post some pics of product (if not process).

 

[I2KanGrow]

This looks like a very good mod, which may fix what I believe to be a weakness with this type of filter!

The question about this type of filter that's been bothering me for a while now: While building one (without the "thru-mod), the question of whether all of the surface area (the rather expensive carbon) gets used evenly came to mind, it's really been bugging me lately.

Alright, it seems to me, that most of the filtering would take place on the end with the highest positive or negative pressure, whereas the lower-pressure side (in my case, the end cap) would transfer very little air.

Is this what actually happens? Let me show a pic of what I'm trying to say, here:


In this example, my intuition tells me that when air is pushed-in, more air will filter thru near the top, less toward the bottom. The reverse would happen if one draws air thru the other way. Does anyone have any thoughts or knowledge on this - is this really an issue, and if so, would hurricane's modification help solve the problem?

Thanks!!!

 

[Ganja Guerilla]

This looks like a very good mod, which may fix what I believe to be a weakness with this type of filter!

The question about this type of filter that's been bothering me for a while now: While building one (without the "thru-mod), the question of whether all of the surface area (the rather expensive carbon) gets used evenly came to mind, it's really been bugging me lately.

Alright, it seems to me, that most of the filtering would take place on the end with the highest positive or negative pressure, whereas the lower-pressure side (in my case, the end cap) would transfer very little air.

Is this what actually happens? Let me show a pic of what I'm trying to say, here:


In this example, my intuition tells me that when air is pushed-in, more air will filter thru near the top, less toward the bottom. The reverse would happen if one draws air thru the other way. Does anyone have any thoughts or knowledge on this - is this really an issue, and if so, would hurricane's modification help solve the problem?

Thanks!!!

I have wondered that same question about a million times myself, logically it makes sense to me that only a portion of the carbon is being consumed.

 

[hurricane]

Good to see some positive responses. I will probably try and build this next week. Going to make it in three main parts, an inner core(8-6 reducer and inner hardware cloth layer), middle core(10-8 reducer and outer hardware cloth layer), and outer core(10" solid duct and 10-8 reducer, and maybe 8-6 reducer since i don't have any 8" flexi duct).

Will have to be slightly different than the diy from overgrow, but i've got a few ideas. What worries me the most is the outer layer of hardware cloth will have to be inside the 8" part of the 10-8 reducer, and the 8-6 will have to slip over that. Might just require a little creativity, will see. Its so much easier to build things in sketchup, if things run into each other you just resize a touch. Will try to take a few pictures of the assembly process, document it a little.

As to the issue with more air flowing through the top than the bottom of a standard can filter, i've thought about this as well, and came to the conclusion that i wish airflow modeling software was cheap(or at least downloadable, but its really niche stuff) I can see how there might be differences in air pressure, but how big the effect is is beyond my guessing abilities.

Hurricane

 

[Guest]

Someone named Hurricane not knowing airflow???? lol
If you build it, will you be able to take pictures? Interesting idea.

 

[mikeraach]

To answer I2KanGrow's question, because the fan is blowing the air into the inside of the carbon scrubber, the pressure in that cavity has to be the same. Think of it like a garden hose---when you have the end plugged and water on, the whole hose gets hard because the pressure is equal throughout the length of the hose. Well now your hose (carbon scrubber) has holes all long its side. So what should happen is because there is equal pressure inside the holes, all the air being forced out of the holes should be equal.

I hope I explained it so you guys could follow

 

[la resistance]

To answer I2KanGrow's question, because the fan is blowing the air into the inside of the carbon scrubber, the pressure in that cavity has to be the same. Think of it like a garden hose---when you have the end plugged and water on, the whole hose gets hard because the pressure is equal throughout the length of the hose. Well now your hose (carbon scrubber) has holes all long its side. So what should happen is because there is equal pressure inside the holes, all the air being forced out of the holes should be equal.

I hope I explained it so you guys could follow

yep, I've always had mine set up so the fan is pulling more air than the carbon filter allows in, which creates back pressure within the filter and should create an even flow over all the carbon


edit: the inline filter idea sounds interesting, though. try it!

 

[Ludo]

looks interesting your idea......!!! Think I'll try building one of those jest for my veg-room to elminate the little odor that comes from there......again....great thinking

 

[boroboro]

I2KanGrow,
Just casually looking at my carbon filter, it looks like the central open space is quite wide -- 8 or 10 inches in diameter. I would guess that it's a big enough plenum to equalize out pressures and draw air fairly evenly over the whole surface. If there was a higher pressure or smaller interior volume I would worry more about uneven flow.

 

[TGT]

I believe the carbon is used uniformily. You can see this by looking at the pre-filter of a carbon scrubber after it has been running for a year or so. The pre-filter originally was white, but after use it changes colour from all the dust and impurities in the air. If you look closely at it you can see that the discolouration is uniform. If it was taking in more air at a location it would show by being a darker colour. Out of every carbon scrubber I have used it has always been uniform.

I don't know if the above is 100% correct, but it seems logical. Also, I have always used the in-line carbon scrubbers with the fan sucking the air out of them and not the other way around so I don't know if the effect would be the same.

TGT

 

[BlindDate]

In this example, my intuition tells me that when air is pushed-in, more air will filter thru near the top, less toward the bottom. The reverse would happen if one draws air thru the other way. Does anyone have any thoughts or knowledge on this - is this really an issue, and if so, would hurricane's modification help solve the problem?

To answer I2KanGrow's question, because the fan is blowing the air into the inside of the carbon scrubber, the pressure in that cavity has to be the same. Think of it like a garden hose---when you have the end plugged and water on, the whole hose gets hard because the pressure is equal throughout the length of the hose. Well now your hose (carbon scrubber) has holes all long its side. So what should happen is because there is equal pressure inside the holes, all the air being forced out of the holes should be equal.

You are both wrong: As air enters into the filter it HITS the bottom and it is there where you have the most pressure. The least amount of pressure is at the top. It is the exact opposite of what you thought I2cangrow. The only way to equalize the pressure is to install a set of baffles, but it really does not need to be so precise.

 

[Ludo]

what is a baffle and ahere do I place it???(Blinddate)

 

[flubnutz]

could just take it apart after 6 mos., flip the filter around, reassemble and use that way for the next 6.

don't even have to take apart...just detach out of line, flip, re-splice in. cant do that with a reg. carbon filter. as for evening things out; i figure passage rate thru the filter must vary w. air pressure. that's greatest at bottom as per previous post, so you gotta increase air pressure further up the tube; i'm thinking bernouilli effect, gotta make a venturi at top, flaring out as you go down.