Beckett vs. Needlewheel skimmers

[hahnmeister]

<a href=showthread.php?s=&postid=8465413#post8465413 target=_blank>Originally posted</a> by 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.

No, not at all. reskimming the water is very different than a recirculating skimmer. You are assuming that one equals the other, but that is not the case.

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?

See my last response. You are equating recirculating skimmers with what he said about reskimming the water. If you make this conclusion, then yes, everything I said doesnt make sense. But for the last time, my point about what Randy said was that a recirculating skimmer isnt just about re-skimming the water... its more than that. If you cant get that, then there is no point in arguing with me about it... you are missing that difference.

 

[hahnmeister]

<a href=showthread.php?s=&postid=8465418#post8465418 target=_blank>Originally posted</a> by 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.

No, but I can compare needlewheel pumps that run single-pass to ones that run recirc.

 

[hahnmeister]

"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" -Randy

If this is how he said it, then Randy seems to be contradicting himself. First he says that increasing dwell time may increase the air/water interface, but then that it isnt a key parameter??!?!?!!! WTH?! What does it mean then? Could he be any more of a 'flip-flop' on this? What is the important parameter then, and how does this get affected by the dwell time?

Tell you what, if you can link me to the article/thread that Randy has this in, Im gonna take the battle right to him. There are things that dont add up here, not that he's wrong, but he needs to qualify his statements better.

 

[RichConley]

<a href=showthread.php?s=&postid=8465243#post8465243 target=_blank>Originally posted</a> by 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?

What does that have to do with this conversation?

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.

Again, because we're talking about pulling from the surface, after letting the water striate somewhat. The faster you turn over water, the less striation happens, and the more those protiens sitting at the top get mixed back into the general water collumn, and dont end up in your skimmer.

 

[RichConley]

<a href=showthread.php?s=&postid=8465449#post8465449 target=_blank>Originally posted</a> by JC VT
Food for thought:

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

The tube size doesnt matter, the total surface area of the bubbles does.

So the answer is, whichever one has higher air draw.

 

[Roland Jacques]

hahn, you have to read it yourself in context. he is saying dwell time in itself is not important.
when/if you have a option of more new bubbles instead.

heres a link.
http://reefcentral.com/forums/showthread.php?s=&threadid=961594&perpage=&pagenumber=2

i agree, when we look at the high air flow of say the ER skimmer bubble dwell is not relevant because all the new air being introduced. if 13% is in fact max saturation point of the bubble water mix, and ER is pumping 20% air /water, then bubble dwell is a non issue.

 

[alwest45]

Can someone articulate why the bubbles are getting smaller with less air? There must be some physical law that is being exceeded when the bubbles start to get larger. I understand that Zephrant obtained his sweet spot from lots of testing but is there a way to apply his experience with other skimmers, either becketts or perhaps even other skimmer types?

Why do the bubbles get larger when airflow exceeds a certain limit (no guessing now)?

Al

 

[alwest45]

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.

This is the kind of information I have been searching for. Can you point me at the backup for this. I understand your numbers may not be exact but I am hoping there is some definitive research out there that draws a similar conclusion.

Or is this just something that everybody knows or can be easily figured out just by thinking on it for a bit?

 

[alwest45]

<a href=showthread.php?s=&postid=8467255#post8467255 target=_blank>Originally posted</a> by Roland Jacques
you have to read it yourself in context. he is saying dwell time in itself is not important.
when/if you have a option of more new bubbles instead.

heres a link.
http://reefcentral.com/forums/showthread.php?s=&threadid=961594&perpage=&pagenumber=2

i agree, when we look at the high air flow of say the ER skimmer bubble dwell is not relevant because all the new air being introduced. if 13% is in fact max saturation point of the bubble water mix, and ER is pumping 20% air /water, then bubble dwell is a non issue.

Yikes! When I posted the reference to the Chemistry forum discussion with Randy here I assumed people would go read it before weighing in with their 2 cents. Please, anyone that thinks they have something to contribute go read the Chemistry forum thread first. The excerpts I posted were only intended to whet your appetite and get you to go read the whole thread (it's not that long).

I never intended my excerpts to be an effective substitute for Randy's words. Go read the thread! (link to the thread is right above here)

 

[JC VT]

No, not at all. reskimming the water is very different than a recirculating skimmer. You are assuming that one equals the other, but that is not the case.

I'm not assuming that at all. I understand clearly that recirc skimmers can "recirculate" little to almost all of the skimmer volume.

No, but I can compare needlewheel pumps that run single-pass to ones that run recirc.

What's the title of this thread?

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

So the answer is no, he doesn't see the benefit to reskimming the water. So we're clear now, on the fact that reskimming the water at the expense of turnover is bad right? That all that hoo doo, scary, stubborn protein stuff is not that important?

 

[JC VT]

What does that have to do with this conversation?

That your conclusions that you drew from your calculations are irrelevant.

Again, because we're talking about pulling from the surface, after letting the water striate somewhat. The faster you turn over water, the less striation happens, and the more those protiens sitting at the top get mixed back into the general water collumn, and dont end up in your skimmer.

I've asked earlier and the question was completely dodged. How are you getting this striation? If you're talking about proteins orienting themselves at the air/water interface, I understand that. But how are you getting these gradients in a tank with any sort of decent flow?

 

[JC VT]

<a href=showthread.php?s=&postid=8466168#post8466168 target=_blank>Originally posted</a> by RichConley
The tube size doesnt matter, the total surface area of the bubbles does.

So the answer is, whichever one has higher air draw.

:lol: :lol:

Since we're talking about skimmers, lets go ahead and imagine that both are filled with bubbles. Same air draw (Hahn's Aquamedic skimmers). Which one has more surface area? The 2 ft tube or 3 ft tube? And don't wiggle out of it with "depends on the size of the bubbles".

 

[twon8]

but it does depend on the size of the bubbles

 

[Zephrant]

Easy enough- Two tubes, the same diameter with the same air-input, but one has a water level that is 2' and one is 3'. The one with 3' of water will have 50% more air in at any given moment in time than the one with 2' of water in it.

IF we assume that the backpressure to the pump is not significant, bubble size is identical, etc...

However, those kinds of assumptions may not be valid in practice.

 

[JC VT]

IF we assume that the backpressure to the pump is not significant, bubble size is identical, etc...

Yes, but backpressure on a beckett can be mitigated by putting the beckett on a riser, right?

And I think this just doesn't apply to becketts. I'm sure there will be other factors; that if you double the height of the rxn chamber, that you will not get 2x the interface area.

My point was to challenge people into understanding what I believe is Randy's point:

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).

This would explain why a ASM G4x has a higher rating an ASM G4. And why an MR-3 would out perform an MR-2. Why Hahn's AM tall skimmer would outperform the shorty. People extending the height (within reason), are, according to Randy, not seeing increased skimmer performance only due to bubble dwell, but because there is more interface area. Randy is not contradicting himself in the least.

 

[cerreta]

Wholly Crap!!! that's it! I have had enough! Another damn thread about skimmers. I'm going skimmerless!

 

[hahnmeister]

I like Zeph's idea, but he has the materials to pull off a test better than anyone else.

I was thinking this for a test...

Two skimmers, side by side in a sump. One is recirc, the other single pass. Both same size bodies, both same pump. See what happens.

 

[sherm71tank]

<a href=showthread.php?s=&postid=8415375#post8415375 target=_blank>Originally posted</a> by kimoyo
Sherm71tank - have you measured the pump with a watt meter or is 125W just the pumps rating?

Sorry it took so long. On the Kill A Watt it is drawing 112 watts.

 

[RichConley]

<a href=showthread.php?s=&postid=8469001#post8469001 target=_blank>Originally posted</a> by JC VT
What does that have to do with this conversation?

That your conclusions that you drew from your calculations are irrelevant.

Again, because we're talking about pulling from the surface, after letting the water striate somewhat. The faster you turn over water, the less striation happens, and the more those protiens sitting at the top get mixed back into the general water collumn, and dont end up in your skimmer.

I've asked earlier and the question was completely dodged. How are you getting this striation? If you're talking about proteins orienting themselves at the air/water interface, I understand that. But how are you getting these gradients in a tank with any sort of decent flow?

Again, how does dumping skimmate back into the tank have anything to do with talking about skimmer performent.

 

[JC VT]

Because it's highly concentrated. Your calculations are correct, but your conclusion is not. It is not 0.001% cleaner every time through.