Skimming Principles

[Puffers]

I think that it is this first area, where all of these considerations are taking place, and I wonder if "we" are failing to consider the importance of the "second area", and the "dwell time" that is occuring there.

This was along my train of thought in addition this is where I think the whole turbulence issue comes into play. In many of our current designs the bubbles are moving at a very fast and turbulent rate and seem to finally setting or slow down when they rise up the neck. Perhaps you are right Barryhc in that this area is somewhat self-regulating.

perhaps we should concentrate more on detritus skimmers than protein skimmers (protein skimming would be a secondary effect of the detritus skimmer)? Or is there a better way to get the larger stuff out than oversaturated wet skimming?

I will be adding a large mechanical small micron filter to get a lot of that detritus out. Yes it's a pain to remove the floss every few days but well worth it in the long run.

However what we would like would be a "flosses" filter that captures detritus, large particles and possible proteins. Some thoughts on this are instead of having one skimmer, lets make it more than one. Lets create two or three "different" types of "BB" oriented skimmers.

Could there by any way to use buoyancy inside the body more effective? Once most of the particles are in suspension is there any way to ensure once they get sucked into the body (say skimmer) to force them up/out 99% of the time? Perhaps this is where more current, direction and bursts of air and wet neck design would be more effective.




:bum:

 

[tinygiants]

A skimmer is already pretty good at getting detritus out of the water. If you are wanting to filter it out, I would filter the skimmer output. This way you are giving the skimmer a chance to remove the detritus from the water column (the skimmate cup is not part of the water column).
Any filter will only change the detritus location, but not its presence in the water column. That is why changing the filter floss is so important.

Right now I use my skimmer on unfiltered tank overflow water. The rest of the tank overflow goes to my refugium (unfiltered), UV (unfiltered), and sump (filter sock).

 

[barryhc]

I really only threw out filter floss, because it's becoming a lost "art", and the Mfgs. would rather "sell us razor blades". It's great stuff if you change everyday, and especially if "shortly after feeding". In any case, whether filtering with whatever, the queston becomes "before or after".

I tend to think "not much difference" here, but filter maintanence, might be improved if it was after. Some, far more educated than me, have stated that some protiens have an affinity to "solids", and the presence of solids in the skimmer enhances the removal of these special protiens, I don't know.

On the different "areas" and turbulence, my thinking was that the "second area" is not often discussed, or even acknowledged, and it's height woluld be affected by the vertical location of the "top" of a "recirculation path". It could be 1", 3", 8", whatever. It is just an interesting consideration.

> barryhc :beachbum:

 

[CaptiveReef]

Skimming

Skimming

Barryhc,

I actually joined the "fray" on the first page on a similar point; contact time.

I'm still unconvinced based on my knowledge of fluid flow and chemistry that what we are shooting for is 120 seconds of water dwell time. A fairly straight forward surface chemistry arguement would indicate that what we really need to strive for is 120 seconds of contact between an air bubble and the bulk fluid.

ChemE 120 seconds of dwell time in a skimmer tube would be useless, you are looking to skim the entire tank volume through multiple passes.
120 second dwell time means you are skimming about a gallon an hour,unless you build an 8ft skimmer that at 4inch diameter you stop the flow for 2 mins and let the 5-10 gallons of water in the skimmer tube sit and let it be exposed to the bubbles.That is the only way to get a 120 sec/2 minute dwell time, or a flow rate through the skimmer at an ounce a minute. This is not practical, You need a good flow rate, constant multiple passes will benefit the tank/ system.
Yes your theory will work, but how effective will it be with a fully stocked tank?



CaptiveReef

 

[Whaledriver]

That is why you want a big skimmer, dwell time of 120 seconds. You can engineer all you want but the bubble has to meet the water. There are cheaper ways of getting a big skimmer

http://www.solar-components.com/protskim.HTM

I also like the idea of using a 5 gallon water bottle and making it into a recirculating skimmer. 4 gallon reaction space with a 2 minute contact time gives you a tank rateing of 120 gallons. This could be as effective as almost any skimmer made by the big names. Remember its just foamy water

 

[SDguy]

Just thought I'd show some pics of my DIY skimmer, and some tips I've discovered after 3 years of trying different things with it. It's a CC air fed skimmer, except the air is fed into a recirculating needle wheel sedra 5000, instead of airstones. I used airstones many years ago, and just remembered how annoying it was to replace them quite often.

I agree with captivereef. I am skimming my tank with multiple passes. I think the key is to make each of those passes as efficient as possible, but within reason. The most important thing I discovered is to have the tank overflow water be fed directly into the skimmer. So my tank water flows into a large PVC pipe, connected directly to the intake of the skimmer feed pump (mag 5). My sump return pump is also a mag 5, so essentially all the surface water skimmed from the tank goes directly into the skimmer.

For a while I had the flow through the skimmer turned down very low, and this worked well, but it wasn't practical to try to get my sump return pump equal. With tank suface water therefore not all entering the skimmer, I was getting surface gunk (the technical term for it, I believe ) in the sump. Then I tried opening up the flow to the skimmer all the way. What I found was that bubble/contact time in the skimmer actually increased, because the flow would pull the bubbles down somewhat in the skimmer. I could tell by seeing how long it takes for bubble to get to the top of the skimmer when I first turn the air on.

Things I would change if I had to do it again:

1. Use larger than 4" pipe for the body, and put the riser tube on the inside (just for looks). Add another sedra if necessary.

2. Mount the sedra higher up. At it's current height, the water pressure from the column is too much, and it requires airpumps to inject air into the venturi.

Anyways, here are some pics, it's not pretty, but works well:

 

[Randy Holmes-Farley]

I don't provide any engineering discussion of skimmer design, but I do discuss the chemical mechanisms involved in skimming in this old article:

Protein Skimming: How It Works
http://web.archive.org/web/20010309054900/http://home.mweb.co.za/jv/jv79/reef/skimmers2.html

 

[CaptiveReef]

Excellent article!!!!!!!!!!!!!!!!!!

Excellent article!!!!!!!!!!!!!!!!!!

Randy excellent article!!!! this really explains the skimmer's function, and how important it is to have a skimmer.
The article gives everybody an idea of what collects in an enclosed system.



CaptiveReef

 

[jacmyoung]

I don't know if anyone had experimented with injecting colder air into the skimmer? Since solubility decreases at lower temperature, wouldn't that increase the skimmer efficiency by precipitating more pollutants out of water? Of course cold air bubbles can expand in warm water that may defeat the purpose.

But an experiment in that maybe interesting to see. There is plenty of cold air in the winter, and in the summer the air intake maybe connected to the house AC system, who knows it maybe enough to get ride of the chiller?

 

[barryhc]

Somebody has been thinking, what will come next?

Maybe a "better mousetrap"!

> barryhc :beachbum:

 

[Puffers]

Since solubility decreases at lower temperature, wouldn't that increase the skimmer efficiency by precipitating more pollutants out of water?

I don't see how it could being that there is less soluble stuff on the surface of the bubbles. I may be missing the boat here but IME the hotter my tank temp gets the more foam I get. So if solubility does increase at a higher temperature, wouldn't it be better to raise the water temp or "bubble temp"?

It also might depend on which soluble items are being taken out at the different temps. Perhaps using the cold air will take out more "desirable" soluble than at a higher temp

 

[barryhc]

So, "insolubes" may skim better at a lower temperature, and "solubles" at a higher temperature. OK, fine.

You've just about beat it to death here, and even exceptionaly good theory suffers from "chaos" ( as in "Chaos theory" ). :hammer:

What came first, "the chicken or the egg"? "God, or Darwin"?

Theory in general, only gets you "half way". Imperical data through observation" finishes up", for a new "round" of theorization.

I'm the most theoretical and logical "SOB" that you will ever meet ( or "discuss with" ), check out the "Plenums and wasting" thread for an example.

Practicality "rules", it's a "Question of Balance".

Make a summary of your theories and observations. Incorporate some adjuastability into your design as you finalize it, allowing for further theorizing and observation, based on available adjustments that you design into the prototype.

Yeah, it's "longwinded" and whatever else you prefer, but, this is where you are at.

Go for it, and enjoy the "Journey"!!!!!

> barryhc :beachbum:

 

[Randy Holmes-Farley]

Like other materials such as inorganic salts, there is not a strict trend toward higher or lower solubility of proteins as temperature is raised. They can go either direction.

Here's a recent article showing one particular set of proteins become less soluble as temperature is raised:

Whey proteins solubility as function of temperature and pH. Pelegrine, D. H. G.; Gasparetto, C. A. Department of Food Engineering, Food Engineering Faculty/UNICAMP, Campinas, Brazil. LWT--Food Science and Technology (2004), Volume Date 2005, 38(1), 77-80.

Abstract

An integrated study was conducted on the effects of temp. and pH on the soly. of whey proteins. The soly. was detd. exptl. in the range of 40-60Ã"šÃ‚°C for temp. and 3.5-7.8 for pH. The results showed that, both temp. and pH influenced in the protein soly., and these properties had great interaction. Besides, for whey proteins, the soly. values were min. at the pH value of 4.5, which is the isoelec. point of whey proteins, for all temp. values. It was also obsd. that at pH 4.5, the soly. decreased as the temp. increased, which indicated that the protein denaturation occurred. This behavior was also noticed in the neutrality (pH=6.8).

 

[jacmyoung]

I don't see how it could being that there is less soluble stuff on the surface of the bubbles. I may be missing the boat here but IME the hotter my tank temp gets the more foam I get. So if solubility does increase at a higher temperature, wouldn't it be better to raise the water temp or "bubble temp"?

It also might depend on which soluble items are being taken out at the different temps. Perhaps using the cold air will take out more "desirable" soluble than at a higher temp

Well then have you experimented with locally heating the water in the skimmer to increase the skmimmer efficiency or do you also find this question laughable? Not a difficult thing to try. Had I have a small enough heater to fit in my skmmer chamber I woudl have experimented already. By simply move the heater from after the skimmer to right before the skimmer, maybe enough to observe any change in foam generation.

It is quite obvious most oils desolve better in hot water than cold water. You can skimm a lot of oils by simply cool the water and allow oil to separate from water and float on the surface. Of course that requires extreme temperature change which may not be practical in reef setting.

 

[barryhc]

A "whole lot more" has been considered in this thread, already, than is considered in most "commercial designs".

This thread has been pursuing "functionality and effeciency" of operation, whereas "commercial designs", primarily pursue "effeciency of sale and profit".

You are "way ahead" here already.

> barryhc

 

[jacmyoung]

Puffers had already stated that he observed more foam in hotter water, why is then a bad question to ask if by raising the skimmer temperature he might be able to skim more oils?

Why not try to do the experiment above yourself first, then come back with data to debuke my theory, I thought that was what an engineer supposed to do? At least Puffers offered his own observation first, what did you offer so far?

 

[barryhc]

Puffers had already stated that he observed more foam in hotter water, why is then a bad question to ask if by raising the skimmer temperature he might be able to skim more oils?

Why not try to do the experiment above yourself first, then come back with data to debuke my theory, I thought that was what an engineer supposed to do?

You were correct to begin with, and so was Puffers, albeit a bit confused, as he stated.

I am not rebuking a theory, including yours, and if you spent more time considering the information offered, you might obtain some insight as to how to proceed.

You are suffering from "lack of consideration", and if you think about this long enough, you might understand this statement.

Try it just once, and see how it turns out.

> barryhc :strooper:

 

[jacmyoung]

...I am not rebuking a theory, including yours, and if you spent more time considering the information offered, you might obtain some insight as to how to proceed...
> barryhc :strooper:

Are you implying that such experiment had already been done and proved to be a fantasy? If so why couldn't you just say it in plain English to save us the time?

 

[barryhc]

Why not try to do the experiment above yourself first, then come back with data to debuke my theory, I thought that was what an engineer supposed to do? At least Puffers offered his own observation first, what did you offer so far?

I have many irons "in the fire" and I do not currently have time for this experiment.

I do not "debuke" theories, I contribute to them.

What I did so far, was to read this thread from the beginning, and I have been involved in this thread from the beginning. That is one of many things that I offer.

You have not. You continue to suffer from a lack of consideration.

I rarely imply anything. I never said anything whatsoever relative to your post. You need to take a "chill-pill" and try some of that consideration ( i.e. rereading ) of that information that has been offered.

Have a good day. > barryhc

 

[barryhc]

You were correct to begin with, and so was Puffers, albeit a bit confused, as he stated.

> barryhc :strooper:

What do you not understand, about "YOU WERE CORRECT TO BEGIN WITH" !!!!!!!!!!!!!!!!!!!

Are you "AWAKE"?

> BARRYHC :strooper: