Skimming Principles

[Pyrrhus]

how large of a tank is this skimmer being designed for?

[tinygiants]

My tank that I am designing for is a 90 G with a 20 G Refugium and a 100 G sump. It is lightly stocked now (5 fish, 4 shrimp, cleaner crew and average collection of soft and stony corals).

[duhfactor]

Dale,
Have you had a chance to read this thread?

http://reefcentral.com/forums/showth...&pagenumber=17

I found it very informational....I question now if the skimmer design I talked about is really necessary..?

Thanks,

D

[tinygiants]

Are you asking about the Thread at ReefFrontiers? Yes that is where I got this info to start with. That thread does not take into account the 120 second air bubble. It assumes that water contact of 120 seconds is the same.

[ChemE]

Damon,

I think you will get more protein removal from skimmers in series as opposed to in parallel. Only one way to know for sure though.

I think that the bubbles' time in the neck would count towards the 120 seconds the more I think about it. The only drawback to using this residence time in addition to the time spent in the reaction chamber is that bubbles can pop in the neck whereas they can't in the reaction chamber. So some fraction of our bubbles won't make it to the 120 second mark and will release their proteins. These proteins may or may not be captured by bubbles further down the neck and even if they are, the clock will start over at 0 for those proteins. If we use a gentle recycle loop to get 120 seconds in the reaction chamber we do away will this concern.

I was considering a spiral within a tube to try to increase bubble dwell time; along the lines of your slanted tube idea. Keep up the excellent disscusion, I'm enjoying it greatly.

Chris

[coreygoforth]

good luck

[duhfactor]

Chris, this is a pathetic diagram of the concept of inclined tubes for an inclined skimmer. Obviously, it isn't to scale, nor does it represent any of the sizing principles we've talked about in this thread, it is simply a conceptual idea trying to help us visual learners......I wish I had a program that I could use to really draw this thing. I found some extra 4.5 inch acrylic tubing left over from building my calcium reactor (which has worked great). That size is very easy to use standard plumbing connectors, elbows, etc, and could be made into this reactor.....Anybody think it's worth trying to build it? We would have to implement all the parameters in Escobals design, and maybe we could see about sizing it for Dales tank. I would love to try it so Dale could have a little more info. Heck, I could even use it for a while and see if it works any better than my kent skimmer (works average) Unfortunately I just sold my home, and my packed 75 gal reef is over at my brother in-laws house while I'm trying to build a new house...Arghhhhh. I suppose it could still be done... but slowly. Any thoughts?



Damon

[duhfactor]

Tiny Giants,
The thread I posted the link for was more or less how to fine tune your skimmer to maximize it's skimmate production with standard designs. Anthony has a fair bit of experience with different skimmers, and gives his thoughts on the best designs and how to mod them. I found many things I can do to improve skimmate production in my system....learned a lot. I'm not sure if it will be helpful for you.....may be old info.....

D

[crazzyreefer]

Its about time people think outside the box! commercial models are copied and altered, rarely completely redesigned.

I'm in the process of producing a large scale skimmer, some of your posts have sealed the ideas firmly, I do like the tunze Idea, but they are expensive because they are variable speed, are you suggesting them because they use less energy?

I have 6 of the largest sieo coming in. As soon as the seio 2600 comes in ill test out your theories, I'm envisioning a large cylinder base with air stones in the center and the seio to cause a circular path that the water and air can mix, but would this create a vortex in the center of the chamber, and if so would this be beneficial? would all the air ruin the pump and make it surge? I like the idea of vertical rungs, but I need to think about cleaning, I received the air stones from MoJoREEF awhile back and a large sweetwater pump to power them, and the only part of the puzzle is the cleaning, a Wet neck skimmer from what I have observed keeps the bubbles from bursting and the neck cleaner, but over time the efficiency decreases with the organics collecting on the neck. constant maintenance is not the answer, but self cleaning would be, I have a source for Large Pyrex tubes, They run cleaner just like a glass tank, but sizes over 6.5 inches are special orders, 10-12 inch size has a 80 piece minimum, and they run 200.00 each... so it will have to be acrylic... any thoughts on a cleaning system? although this thread is manly theories, practice is a slight be more messy... I have been following this thread for some time now, it will have its place in the archives!

[crazzyreefer]

[crazzyreefer]

first testing failure, the spinning water in a round container didn't work with or without the air. using a modified mag18, A large 24" container, filled with 10" of sea water. Results: the water motion was spinning but not fast enough to keep the bubbles in the current for any longer than a few seconds, next problem was air going through the pump was extremely loud and produce a weaker flow. Back to the drawing board... Ok so if we are trying to keep the bubbles and water together cant we just make a skimmer out of flex hose? fed with the water from the bottom and a air stone, have the two travel together for 120 seconds minumum until they reach the bubble chamber where they separate? Drawings to follow....

[crazzyreefer]

This should work better, but the distance is still an unknown factor, the water/air mixure would travel togeather, but would the bubbles join as they rise up the race track?

http://reefcentral.com/gallery/showp...p?photo=141796

[crazzyreefer]

Last post contained the wrong image

http://reefcentral.com/gallery/data/...9skimmer_3.gif

[Pyrrhus]

reverse the water flow and i think you have something.

[crazzyreefer]

I thought the water flow has to flow with the air, and as the air rises, it will carry the water upward, if they were reversed wouldn't they just create back pressure? so how would I figure the runs needed to keep the water/air mixure?

[tinygiants]

If the water is flowing counter current to the air, it slows the air travel down. Have the air enter the bottom and the water enter the top. The air will migrate up, and the water will flow down.

[duhfactor]

crazzy reefer,
I like the idea, I think the counter current design still has value as well primarily because many believe that the "bombardment rate" is as valuable potentially as the air dwell time. The inclination of the plates in your diagram, or the angle of rise would potentially need to be tuned to achieve the speed of air bubble flow upward. The tough part is how to know what angle to set the plates to allow a 120sec. bubble dwell time as the bubbles raise, given a certain amount of water flow downward. I'm sure someone really smart could mathmatically get it very close...but may be trial and error for the rest of us. I'd love to see you try it out.

D

[crazzyreefer]

I'm hoping I dont end up with a giant wet dry... But I see said the blind man... I'm using a sweetwater sl22 it produces 3cfm at 2 PSI and it will be diffused by two micro fine 12X1.5 air stones, I'm going to space the plates 3/4 of a inch apart, if they run flat or ? if the run at an angle. I still am concerned that the machine will just belch out the air because of the bubbles joining to make air pockets.

[barryhc]

Crazyreefer, you are unabashedly fearless! The results are beginning to look promising. A small angle of say, 2 to 5 deg. on each plate in the "stack", would eliminate potential air pockets so long as you keep the base more level than that. I think you may need much more angle than that, otherwise, the air and water are likely to seperate, unless the design remains "non-counter-current".

You may want to construct, with two opposite ends of the "box", left open for 2/3 of the height, and then close them with panels that slide verticaly, in channels, so they can be removed for cleaning.

Some minor leakage would occur, but would be of no consequence other than requiring the skimmer to be located in the sump. Dirty skimmers can cause a lot of headaches.

Keep it up, > barryhc

[crazzyreefer]

I produced this in excel, only change values in Yellow! I noticed a important fact as I was entering the data, counter current skimmers models work only slightly better suspending the bubble in the air column, bubble rise was was taken form the published works Here http://www.seas.ucla.edu/stenstro/NewBubble.pdf

and was applied to the spread sheet, you will notice that as you change values you will need to modify pump GPH to obtain the 13% saturation of air and water. I believe this to be accurate, please let me know if there is an error and ill correct it.

also not I believe, counter current skimmers with large pumps do more than break up the air, but each time the bubble passes through the pump you have to start from Zero in the calculations of bubble rise time/bubble Dwell time, due to the pump stripping off the bonded organics, object therefor is to make a gentle counter current skimmer to increase the dwell time of co-current and add travel distance of bubble rise.

[crazzyreefer]

Version 1.1

[crazzyreefer]

Dammon1 the skimmer in the drawing needs to have 13 feet of tubes and a 10 gph pump, running counter current, and a air pump that delivers 0.5 cfm. through a vary fine diffuser
This is a vary workable model!

[duhfactor]

crazzyreefer,
What diameter pipe with those numbers?

thanks,
Damon

[tinygiants]

Bubbles are ellipsoidal in shape, motion is irregular, and velocity is independent of
bubble diameter (approx. 28 - 30 cm/sec) for bubbles having radii up to 0.75 cm. For
larger bubbles their velocity tends to increase to 35 - 40 cm/sec, but they are not stable
and tend to subdivide into smaller bubbles.

I will admit that the math in the formulas is beyond my skills, but I believe that the rate of rise is 28 to 30 cm/s. Did I miss a conversion needed for our bubbles?

As I played with the numbers some things did not seem right. When I increased the flow rate to 120 gallons the cocurrent dwell time was still 134 ( nothing else changed). In a cocurrent design, that would be pushing the bubbles to the surface. That number seemed high in a cocurrent set up. The counter current number is only 8 seconds longer.

Is that the right math?

Thanks,
Dale

[crazzyreefer]

you stated 4.5, not sure if that was inside or outside dia. but its of no consequence to dwell time. due to bubbles travel up, and tube size only affects your air to water ratio.... but I re-looked at your skimmer with a mod, I can reduce the tube to a few feet...or inches! hear me out... take a skimmer, at the base use a large pump as a vacuum, a variable speed motor would help....a few inches above it, place the air stone, the bubbles will rise, so adjust the pump to suck the water out from the bottom almost as fast, but not too fast to suck in the bubbles... the bubbles will be on a treadmill of sorts until they reach the top, you can literally shorten the tube to only a few inches, and still have dwell time of 120+ seconds and have nearly a saturation point of 12-13%, and the skimmer can be made in any size including HOB, It dawned on me as I was trying to figure out how to make a more practical and affordable model... then I thought about convection, like an oven.... so I temporally named this a convection skimmer... I know convection is only used in heat... well anyone have a better name?