Beckett vs. Needlewheel skimmers

[jnarowe]

<a href=showthread.php?s=&postid=8462589#post8462589 target=_blank>Originally posted</a> by hahnmeister
That does comfirm my suspicion... or at least make it worth looking into more. I know that the longer water is exposed to air, in theory, this should raise the ORP... and raising the ORP should increase the skimmate output. That be a valid reason for the performance of recirculating skimmers being so much greater... possibly. Interesting.

I sort of look at this differently in that because I had to raise the skimmer, the height change reduced the water flow throughput. And with the water flow slower, my ORP has dropped significantly. Based on your statement above it seems like the ORP should have gone up, but it didn't. That seems to be the reverse of your suspicion.

 

[Roland Jacques]

<a href=showthread.php?s=&postid=8462744#post8462744 target=_blank>Originally posted</a> by JC VT


So contact time is not important, IMO. It is the amount of air/water interface present that is actually important, and the rate at which it is turned over. Increasing dwell time may actually increase the amount of air/water interface present, depending on how it is done, but dwell or contact time itself is not a key parameter (IMO).
[/I]

JC VT
we totally agree, on this point. see it was the word contact time that had mess us up. (some contact time is important but just say it minimal)
INTERFACE is what its about.

Now, I would say that the Currents NWs have more interface than becketts.

Especially the new Bubble master skimmer.
NW
smaller size of bubble = more interface
higher air to water ratio 60% plus = more interface
higher air volume = more interface

(the more water you pump into a given amount of air volume your interface goes down along with your air to water ratio.)

This just proves on paper that the "best" NW" works better than the comparable sized beckett.
That still bring us back to what's best for the tank. Now if you had a "best" NW that possessed the same amount of water as the beckett than it would be no debate right?

 

[jnarowe]

"higher air to water ratio 60% plus = more interface"

I find this hard to believe. Is it really possible to get 60% air? I always heard that 13% was the sweet spot.

 

[Roland Jacques]

thats the thing I beleave 13% is max to keep it a fluid state(at a given bubble size). But a lot of skimmers operate well past that.
The BM 250
2500 LPH air
3000 LPH water

the tunze 9000 series skimmer are very simular in ratio

this BM skimmers are really just a neck with no body 7" Id from top to bottom and more or less.

 

[jnarowe]

Sherman was over discussing my skimmer and said that I am getting superb "contact/interface" but that I could reasonably cut about a foot out of my riser because that is where the gunk starts to stick. I thought that was very interesting I have thought since I built it that a 2 foot foam head may have the drawback in that its weight may act to compress the head, and that is why it is so sensitive to feeding the tank. WHen I feed, the head immediately colapses and can take anywhere from 10 minutes to an hour to rebuild.

 

[JC VT]

Now, I would say that the Currents NWs have more interface than becketts.

smaller size of bubble = more interface
higher air to water ratio 60% plus = more interface
higher air volume = more interface

(the more water you pump into a given amount of air volume your interface goes down along with your air to water ratio.)

I don't believe a smaller size bubble has been proven for either side. Rich mentioned earlier that his skimmer neck looked exactly like NoSchwag's skimmer neck (bubbles).

Higher air to water ratio is not proven to give more interface or better skimming. Zephrant mentioned:

"That 1/4" line is on purpose, to partially restrict the air flow as a Beckett makes smaller bubbles when it is held back a little. With years of testing, my opinion is that running 45scfh each is the sweet spot, hence the design."

I also do not run my needlewheel at full bore; I fine tune it with an airvalve.

Higher air volume does not necessarily equate to more interface.

 

[RichConley]

<a href=showthread.php?s=&postid=8458233#post8458233 target=_blank>Originally posted</a> by JC VT
Again though, you're making the assumption that high flow skimmers have equal efficiency rates as low flow ones. The higher the flow, the lower the contact time, and the lower efficiency.

And keeping dirtier water in the skimmer is way more efficient than scrubbing. Higher level of organics paired with the agent to remove them.

I guess this is where we disagree. You think that the water going into your skimmer is significantly dirtier than the water coming out.

I dont. I think theyre both essentially clean, and the skimmer is working to get out a small amount out. My skimmer pulls maybe 8-10 ounces of skimmate out a day(like a coffee mug full). It gets about 300gph fed through it. Thats 7200 gallons per day that go through my skimmer.

10 ounces out of 7200 gph. 1 gallon is 128 ounces. Thats 921600 ounces a day. Thats 0.001085% of what goes through my skimmer actually getting pulled out. That means, on each pass, the water coming out of the skimmer is 0.001085% cleaner than it was going in.


I dont see getting water thats .001% dirtier into the skimmer being all that important. I think its important that my skimmer gets everything thats in its body, out of the water.

 

[Roland Jacques]

well you'll just have to check for yourself about the bubbles size. I know if you put a real big pressure pump on a bekect the bubbles do get a lot smaller. but from you average beckett it is not even close.


"Higher air to water ratio is not proven to give more interface or better skimming. Zephrant mentioned:"

He did not say that. Read your own quote.
(If the bubble size is the same) the higher ratio of air to water will increase interface contact. that is a FACT.
And It is a Very BASIC FACT at That.


That quote,
"That 1/4" line is on purpose, to partially restrict the air flow as a Beckett makes smaller bubbles when it is held back a little. With years of testing, my opinion is that running 45scfh each is the sweet spot, hence the design."

he restricts air is to achieve What? smaller bubbles. Why? for better interface contact. It is better to have smaller bubbles than more air in a lot if not most cases, and I totally agree with that. That is because sometimes you cant have both and you have to choose one or the other.

Again, If the bubble size are the same, and all else is the same, yes more air does equate to more interface contact, this is the Basic facts of skimming. No one can dispute these FACTS


(now mathematically they is a point where more air less water will start to decrease interface but that's going to be a lot higher than 100% to 100% ratio or 1 to 1)

you may not no it or agree but I've found that when I restrict the air a little to my NW skimmers I get better performance. the reason is because the bubbles get smaller. even though my eyes cant see the bubble size differences a photo sometimes can.

http://www.putfile.com/pic.php?img=3787039

 

[twon8]

<a href=showthread.php?s=&postid=8462489#post8462489 target=_blank>Originally posted</a> by spazz
twon8 can you tell me a little about how your cooling your system currently. i may be able to help. you might not have to spend a ton of money replacing that skimmer if its working for you. if you dont have very many fans blowing across the top of the water that in itself would help to keep the tank cool. just a thought.

i have quite a few fans blowing across the water, and into the canopy; im going to stick it out for a bit, but once summer rolls back around im afraid the heat will get to me.

 

[JC VT]

Again, If the bubble size are the same, and all else is the same, yes more air does equate to more interface contact, this is the Basic facts of skimming. No one can dispute these FACTS

If.

Where did I say they were equal? Didn't I say that bubble size hasn't been proven for either side? What application does this have to beckett vs needlewheel, and what argument are you trying to support?


you may not no it or agree but I've found that when I restrict the air a little to my NW skimmers I get better performance.

Yes I do know it and yes I do agree. Please read my post more carefully before making assumptions:

I also do not run my needlewheel at full bore; I fine tune it with an airvalve.

 

[Charlie Davidson]

Anthony, My tank went up a few Deg's this week.. best I can figgure----out side temps are lower-- A/c isn't pulling humidity out like it was..
Last night, I even added a fan to my slump. never had this problem before..
Get rid of the skimmer? Hey, why not just pick up a mag 18.. (if you feel thats the prob. OR
You want my G4X? I have it doing 900 lph.. (deltec dude ) I can buy me another play toy!! (or a bubblemaster)

 

[hahnmeister]

Smaller bubbles meaning more interface area is a matter of math. The surface area of a shpere is 4*pi*radius squared. The Volume is 4/3*pi*radius cubed. We can set these two equal to each other with respect to radius to get a ratio, but perhaps an easier way to illustrate the point is by using some examples. Lets say you have one bubble that is 1 cubic inch of air. Lets say you have two bubbles that combined have 1 cubic inch of air. Well, that means that the single larger bubble has a radius of about 0.62035, and two smaller bubbles would have a radius each of 0.49237. So the surface area of that one larger bubble is about 4.835 cubic inches, and the surface area of the two smaller ones of equal volume have a combined surface area of 6.092 cubic inches. So by taking the same volume of air, yet halving the bubble size, you are gaining about 21% more surface area for proteins to bind to. If you were to reduce bubble size even more... the percentage would go up from there.

Also, add to this the lesser bouyancy that a smaller bubble has. A larger bubble rises faster than a smaller one, so in effect, the smaller volume bubble is also going to have a longer dwell time.

Combine this with a counter-current design, and you might have bubbles small enough and stagnating enough to give you well beyond that 120 second ideal of dwell time.

 

[JC VT]

10 oz of concentrated waste. If you left that 10 oz in your tank, how much nitrate and phosphate would you get? If you poured your skimmate back into your tank, how much dirtier do you think your tank would be?

If tank water is not that much dirtier, then why did hahnmeister's cousin double his skimmate when fed directly from the tank? Why do others report that skimmer production is improved when fed from the tank? Either that small percentage you calculated is significant (I don't believe so), or something else is at play here.

 

[JC VT]

Also, add to this the lesser bouyancy that a smaller bubble has. A larger bubble rises faster than a smaller one, so in effect, the smaller volume bubble is also going to have a longer dwell time.

Combine this with a counter-current design, and you might have bubbles small enough and stagnating enough to give you well beyond that 120 second ideal of dwell time.

<a href=showthread.php?s=&postid=8462744#post8462744 target=_blank>Originally posted</a> by JC VT
Randy's quote:

I also think maximizing dwell time is misleading and may be wrong, depending on how it is thought of. If you have the same total surface area of bubbles in contact with the water inside the skimmer, the replacing those bubbles with fresh clean surfaces may actually give better skimming action than leaving the original bubbles in place longer.

...

So contact time is not important, IMO. It is the amount of air/water interface present that is actually important, and the rate at which it is turned over. Increasing dwell time may actually increase the amount of air/water interface present, depending on how it is done, but dwell or contact time itself is not a key parameter (IMO).

 

[hahnmeister]

<a href=showthread.php?s=&postid=8462742#post8462742 target=_blank>Originally posted</a> by JC VT
NOTE: He said he sees no benefit to re-skimming the water. That does not mean he sees no benefit to a recirculating skimmer.

So now we've gone from scrubbing everything out by reskimming to no benefit to reskimming? We can atleast agree that reskimming water at the expense of turnover is not a good option, right?

If running recirc means I can get the same air throughput on a skimmer that is 6-12" taller... why not?!?!

You mean like adding an extension onto a beckett skimmer? Why must it be a recirc?

You are taking what I say to the extreme here. First, he does see benefit to re-skimming the water, as there are still many organics yet to be removed. He only sees no benefit to re-skimming it IN COMPARISON to just re-skimming it the next time the skimmer gets to it.

The foundation of that argument assumes that if one pass gived you 5% removal, then a second pass gives you 10% removal. I agree, and that is really all that Randy's comment means. It doesnt take into account any of the other things presented here. If you insist, I can go ask Randy in his own forum to clarify, because if he does insist that there is nothing more to it, I will 'pitty the fool'. Sure, what he said: that makes sense, but it doesnt say anything directly about recirculating skimmers, only about recirc. But the main argument for recirc skimmers is that the 2x exposure time results on not 10%, but more like 15% due to other factors(just example numbers, I dont have specifics.... just the idea). The design advantages of a recirculating needlewheel allow for much more air, countercurrent flow, etc.

So no, I do not agree that reskimming water at the expense of turnover is not a good option. Lower turnover for skimmers has many advantages.

And for your second question... a recirculating skimmer conserves the pressure of the skimmer height. It means that rather than drawing from a body of water that is 12" lower, or maybe more (maybe 36" lower), and having that back-pressure to work with in addition to drawing in air, the pump has less work to do, or it can suck in more air. Combine this with the idea that a recirc can have a much larger pump as well, you end up with more air. Even if you dont run a larger pump, its still more air because they pump has an easier time drawing in air because there is less head pressure on the pump. OR, if more air is not desired due to turbulence reasons, as Barr pointed out, the skimmer could be taller. Elimiinating the back-pressure on the pump would allow you to mount the pump on a skimmer that is 6" taller? 12" taller? Etc. The same skimmer body running as a single pass skimmer, then converted to recirculating has about 2x the lpm going through it. As Barr pointed out, more is not always a good thing, but it seems that every skimmer mfg, if given the choice, is no where near hitting that point because they all increase the air throughput significantly when going from single pass to recirc, with little to no concern for too much turbulence. OR, in the case of the Aqua Medics, they dont increase diameter but rather height for their performance gain.

If dwell time, countercurrent operation, etc... all these things werent so important, then how would you explain the T5000 shorty being only rated for a 200g tank, and a T5000 twin being rated for 1500g? They pull about the same air (the T5000 twin does have two pumps, but the amount of air that they can each draw in with 6' of skimmer on them is halved... so the throughput in each skimmer is about the same, about 21 scfh.

 

[hahnmeister]

quote:
--------------------------------------------------------------------------------
Originally posted by JC VT
Randy's quote:

I also think maximizing dwell time is misleading and may be wrong, depending on how it is thought of. If you have the same total surface area of bubbles in contact with the water inside the skimmer, the replacing those bubbles with fresh clean surfaces may actually give better skimming action than leaving the original bubbles in place longer.

...

So contact time is not important, IMO. It is the amount of air/water interface present that is actually important, and the rate at which it is turned over. Increasing dwell time may actually increase the amount of air/water interface present, depending on how it is done, but dwell or contact time itself is not a key parameter (IMO).

--------------------------------------------------------------------------------


Okay, this is a direct contradiction with all the large waste management skimmers out there, as well as what most mfg's and other authors/researchers agree with. Randy provides no proof of this, merely speculation. If this idea of his was true, then explain how the T5000 Twin can have such a higher output than the T5000 shorty... same air throughput on both, same body diameter, etc... just the Twin is taller?

 

[JC VT]

Hahn, you just completely contradicted yourself.

You said:

NOTE: He said he sees no benefit to re-skimming the water. That does not mean he sees no benefit to a recirculating skimmer.

Then you said:

First, he does see benefit to re-skimming the water, as there are still many organics yet to be removed. He only sees no benefit to re-skimming it IN COMPARISON to just re-skimming it the next time the skimmer gets to it.

So which is it? Does he or doesn't he see the benefit to re-skimming the water?

 

[JC VT]

Combine this with the idea that a recirc can have a much larger pump as well, you end up with more air. Even if you dont run a larger pump, its still more air because they pump has an easier time drawing in air because there is less head pressure on the pump. OR, if more air is not desired due to turbulence reasons, as Barr pointed out, the skimmer could be taller.

You cannot possibly be comparing the pumps used on a beckett and a pump used on a needlewheel.

 

[JC VT]

If dwell time, countercurrent operation, etc... all these things werent so important, then how would you explain the T5000 shorty being only rated for a 200g tank, and a T5000 twin being rated for 1500g? They pull about the same air (the T5000 twin does have two pumps, but the amount of air that they can each draw in with 6' of skimmer on them is halved... so the throughput in each skimmer is about the same, about 21 scfh.


Randy's quote:

It is the amount of air/water interface present that is actually important, and the rate at which it is turned over. Increasing dwell time may actually increase the amount of air/water interface present, depending on how it is done , but dwell or contact time itself is not a key parameter (IMO).

:lol:

 

[JC VT]

It is the amount of air/water interface present that is actually important, and the rate at which it is turned over. Increasing dwell time may actually increase the amount of air/water interface present, depending on how it is done , but dwell or contact time itself is not a key parameter (IMO).

Food for thought:

Which holds more air/water interface: a 2 ft tube or a 3 ft tube of the same diameter?