Tiny Might skimmer rockin'

[BeanAnimal]

Hey, what ever happened to the 'idea' that the venturis that came with the pumps were the best possible design for the intake?!?! Lol.

Um hahn, I never said that. I said that joe blows washer and tee was not as good as an engineered shape. I said that DIY EDUCTORS (a bit different in overall design with regards to intake and the type of fluid being educted [READ NOT AIR] were likely not as efficient as a properly engineered design. Again a very very simple concept and another thread that you turned into a nightmare of vectors and velocities and angled dangles... Please don't take swipes unless you wish to recieve them.

I would assume that the maximum mixture was already achieved with the pump and venturi... and even if not, a simple valve on the water intake would hemp maximize air intake while minimizing water intake (in a non-forced air system).

You know that they say about assuming... You can't be sure that the air intake is anywhere near the maximum air/water ration that the pump can handle. The pump is not a fixed displacement unit. Yes the air intake will vary depending on the pumps performance, but it will also vary on the performance of the venturi, their curves likely don't match. So to assume they do is a a large step in the wrong direction.

Choking the water flow will help to determine what is going on, but it still may not give you the full picture (for the reasons I already stated). However, it may help you get more air to water before the pump yells uncle. (what we want anway). You just won't know if it "all" the pump can do unless you clean up the intake path and play around with different air injection points and pressures.

This is all just in reference to the venturi on the intake of course... but aside from tampering with the pump's impeller design

which is something we have already done!

, boring out shrouds, enlarging inlets/outlets

again, already done!

the intake venturi/valve setup is what is going to determine the maximum intake mixture of water or air (what else possibl y is there?).

Of course, nobody said any different.

In another thread I was told I was wrong for suggesting ...

No idea what your talking about there.

Im not disagreeing with you Bean, but even if some MFG hasnt achieved maximum performance/tweaking for a venturi intake, with these DIY skimmers, I would assume that there would be a valve on the air and the water intakes before the venturi

Why would you assume that? Valves cost money and glueing them in place costs more. They just make products that work well enough to get out the door. If needed they do a little to make them better than the next guys. Not many manufacturers do more than needed to generate sales, it's called leaving money on the table. Being the best only means being marginally better than the next best!

... what more could you ask for assuming that the venturi is as 'fluiddynamic' as needed? Im just going with the idea that water is the independent variable (you can have less or more flow of air and still have the same amount of water with just the venturi.. of course more air means less water

I have no idea what you are trying to say. However don't be so sure that "MORE AIR MEANS LESS WATER" there is a bit more to it than that. Again these are not FIXED DISPLACEMENT devices. The input dynamics certainly have an effect on the overall throughput, as does the output path. Remember these pumps operate on the bernoulli principle (one of your favorite things )

throughput), and air is the dependent variable (you cant turn down the water throughput and expect to get more suction of air).

Nobody said that was the case... but still trying to follow along with your reasoning here.

Going by this, I can see what you are saying... perhaps the venturis and intakes arent 'tweaked' 100%, but assuming that they have been

Uhh ohh! another assumption! You can take one look at the design and see that they have not been tweaked (or anything near tweaked) AGAIN they simply work well enough to sell skimmers! Note those photos that showed the new eheim BTW did you notice the BIG LONG venturi on that little pump? It does appear that they did some tweaking on that.

, and for what we are trying to achieve here, we could assume that the only way we are going to get more air sucked in is with more water passing through that intake (increasing velocity, lowering pressure, etc... ).

Well for starters:
1) we are using forced air
2) we could easily try more refined venturis (more air for the same amount of flow past them)
3) we can try changing the flow paths and position of the air intake

you cant create more suction in the venturi if you decrease the water volume/velocity assuming everything else it at its max

Again... nobody said this was the case. Also, why in the world would you assume everthing is at it's max when it is very obviois that it is not.

On a side note... I tried that whole 'multiple small inlets' vs. 'large gulp of air...it makes no difference... ...There might be some sort of relationship here, but it doesnt seem to be significant enough to notice.

well at least you tried without assuming But this does not really have anything to do with the bigger issue of maximizing the amount of air that a given pump can handle, it was only an idea to aid in the delivery of pressurized air.

Another thing to keep in mind... remember Deltec suggests turning back many of their eheim 1260 powered skimmers by 20-30%. Restricting the air intake increases performance in this case. Trying to get more air into some of skimmers might be overkill in the same respect.

Of course that is a very reasonable assertation. Either an excess of air OR an excess of FLOW (or both) could hurt the performance of a skimmer.

Im all for tinkering, but two OR3700s on my 8x8x48" tall skimmer is looking like its all I need. When I tried injecting more air, the turbulence went up.

But that does not mean that it could not be handled either. It just means that in the current configuration that your design can not handle that much flow without turbulance. Rember the 13% ceiling that Escobal calculated and others confirmed (or vice versa). Put another way, if you skimmer cant do 13% and do it well (without turbulance or whatever) then it is not an optimum design. Will it skim YOUR tank? Well if so, then it will be fine, if not... then it is time to redesign.

 

[hahnmeister]

I dont know about the 13%, but I know that Im using about 2x the suggested input compared to what aquamedic uses on their stock Turboflotor...

No problems with the 'assumptions' and all, Im just saying that I would hope that a person had tweaked the intake and all before trying to tweak anything else... thats all.

I wasnt aiming that comment about 'what ever happened to the idea that stock venturis were the best thing ever'... it was in another thread.... I suggested that using certain types of valves (with the air intake right after the valve itself) would be better than a stock venturi because you could manipulate the restriction for the best mix... stock venturis dont/cant take into account the height of the skimmer or back pressure placed on the pump (single pass or recirc).... being able to tweak the intake has always been a good thing... No argument there. Im using a ball valve before the venturis on the intakes to adjust, and the venturis themselves are removable inserts that vary the restriction of the venturi. I found that rather than a cone, a large shim/slice works very well and is easy to modify. I can pretty much reatrict the water to a bare minimum if I want.

 

[rishma]

ChemE - as I was reading the thread I came up with this great idea to use air stones!!!....which I found out you had also thought of....and was probably the obvious evolution of this conversation.

I tried to decide why this would work better than just straight 3/16" air line injecting big bubbles. It not entirely clear to me why this would allow more air, but I visualize it per the following. This is really just an exercise in visualization and probably full of technical errors, so take it with a grain of salt.

I think the relatively large air bubbles from an air line entering the pump intake create a liquid/gas flow regime analogous to plug flow. The impeller intermittently chops the plugs of air and water and the very fine chopping/mixing only occurs at the interface of the air/water plugs. The intermittent plugs of air and water are of drastically different density and probably not good for impeller stability. Following this analogy further, if the air plugs become too large, the pump chokes.

Now, if we inject air in as tiny bubbles from an air stone, I imagine the flow behaves more like a single phase, lower density fluid. If you imagine the bubbles are infinitely small, the pump would not choke until we reached the lower limit on density which these pumps can handle. This is very different than the choking normally experienced when too much air is present around the pump impeller.

In reality, the actual flow regime is dictated by the realative amounts of gas and liquid and does not really change depending on the size of bubble injected; however, I do think the pump will behave differently and possibly allow higher vol% of air if the intake bubbles are smaller.

 

[hahnmeister]

From the test I did, and from what I could observe inside the clear acrylic venturi, the problem with the two concepts, or at least how we compare them, is that we assume that just because the air intake is larger or water intake is more restricted, etc... we assume that the air from the single large intake is going to travel in big gulps... but it doesnt really. It gets sheared into a very narrow stream that the pump doesnt notice. The water just flows too fast for a 'big gulp' of air to form. The threshold where the pump simply chokes from too much air happens before the amount of air is so great that there are any 'big gulps'. I was thinking that this might still be a valid way to do a forced air setup, but now that I think about it... the pump would choke out first.

The idea that an air line or suppy could be so large that it results in large bubbles that disrupt the impeller isnt really the case... the air gets sucked in in such a tiny stream anyways.

 

[BeanAnimal]

And I was going to suggest feeding with an airstone in my initial post but decided against it... (still like the idea but was then and now not convinced it is worth the trouble).

You did bring up a point or two that have not been mentioned in this thread (but I do believe I mentioned in a long ago pump thread).

The turbulant flow into the pump (some of it the "plug flow" you refer to) is very hard on the impeller.

As I mentioned the pump is a simple bernoulli device and when it runs correctly, the load on the impeller is very even and distributed. As the flow in the volute becomes rough (usually due to cavitation) the impeller is subjected to tremendous lateral torque. This is hard on the bearings but also causes an overal reduction in impeller (and hence output) efficiency. That is why cavitation is so hard on pumps.

Using the same logic (basically what you have stated above), the turbulance of the air water mixture on the intake of the pump can cuase many of the same problems.

Like I said before, if we can smooth out the inflow of the pump we should see performance gains and the ability to increase the air/water ratio (you would think).

Have a nice evening... it's getting late.

 

[smjtkj]

Well I think I have concluded tonight that the airstones in the pump loop idea is a whole lot moe trouble than it is worth.

 

[ChemE]

Ok, I've been kicking this around for a while now and since most of the sharp people here on RC are subscribed to this thread...

What would happen if we set things up so that the skimmer is air tight and the venturi drew air from the collection cup? It seems to me that this would increase the air through the venturi since there would be a slight positive pressure in the sealed collection cup. Your thoughts (or better yet your findings)?

 

[rishma]

I think there is an easy way to impliment an air stone injection. Put a Tee on the pump suction with a union. Glue a cap on the union with tapped hole or fitting to allow the airline to enter. Attach the air stone on the inside. The union will allow easy changing of the air airstone.

 

[hahnmeister]

ChemE, its an idea, but you would be taking a step backwards as far as fresh air is concerned... the fresher the air, the better the skimmer performs... some people even go so far as to draw their air from outside. Recycled air isnt going to work as well.

Besides... whats wrong with forced air anyways?

 

[ChemE]

Wait, what? You're saying that the higher the oxygen content in the air the better it removes proteins? Or are you speaking from an aeration point of view? The aeration I could buy for sure, the protein removal I'm less sure about. I too have to draw air from outside to help curb low pH (damn you Tyvek!).

Nothing wrong with forced air, but I've been wondering about this for a while now.

 

[hahnmeister]

Its a little bit of everything, since its all related anyways. ORP, oxygen, pH, protein removal...some have suggested that simply having air with a lower humidity content is the reason...

They are all valid reasons.

Bottom Line: I would not recirculate air.

 

[ChemE]

ORP, oxygen, and pH are clearly interrelated but I'm still unconvinced about protein removal. Do you have anything I can take a look at to support this? I'm always willing to learn new things but this is the first I've heard of a relationship between O2 content and protein removal.

Thanks Hahn,
Chris

 

[hahnmeister]

I dont...no... I never did any research myself...lol. Im sure if you contact Holmes-Farley or Calfo (marine depot forums), they would tell you. Perhaps a good Google search.

 

[smjtkj]

Just a quick update; The silicone oring worked like a champ! I can now adjust the water level half way up the neck again. Also the Tiny might is running at 69-70 watts for a couple days now with no more fluctuation issues. ROCK Solid!!!

 

[spazz]

well i just got some acrylic tube so i can make a new input and output for my test skimmer. i plan to install the tubes on the intake and out put to see how the air water mix runs through the pump. im hoping to get the air water mix to run smoothly into the intake of the pump with out the up and down drawing of the air into the pump. i would like to figure out how to get the amximum 13% air to water ratio comming out of the pump with ut the spikes in there. it would increase the performance of the pump and make adjustments alot easer. i also want to experment with injection points along the intake pipe. i think the elbows in the plumbing might help to chop up the air a little more before it hits the pump. im counting on the turbulance to help do the chopping.
im hoping to have a new wheel for my skimmer cut and running by sunday. i will be working on the dradwings for it this weekend. then i will cut 2-3 different designs to see what works the best. im also planning on making a clear end cap for the pump so visual inspection of the bubble choping is easer. i dont know if i will get the end cap made this weekend or not. but its a future thing.

 

[spazz]

<a href=showthread.php?s=&postid=7917827#post7917827 target=_blank>Originally posted</a> by smjtkj
Just a quick update; The silicone oring worked like a champ! I can now adjust the water level half way up the neck again. Also the Tiny might is running at 69-70 watts for a couple days now with no more fluctuation issues. ROCK Solid!!!

ok now that everything is good to go you might want to try to inject more air and less water. or vice versa. also try to get new numbers for tinygiants to run. I feel that should be doing better than 9.6% air to water ratio. I would try doing it the way we had talked about on the phone. basically shut the system down and seal it so nothings going out and nothing is coming in. then run the numbers on it. I think it will be a lot better. also try one thing for me. when you go to time the bubbles rising up in the main chamber. first just shut off the air and time it. then shut both the tiny might and the air pump off at the same time. I think when you shut off the air the extra push from the water squirting out the diffuser holes is blowing the bubbles up faster in the skimmer body. there for showing a false number for dwell time. may be im wrong but in theory it sounds good. LoL also would you hook both the air pump and tiny might to the kill-a-watt meter and post a pic next time you post them. proof is in the pics. I had a guy ask what the total is with the air pump running and he didn't believe me. right now it seams to be running about 1.13 cubic feet of air per watt of power if my calculations are right. that is lower than bubble kings numbers. there about 1.4-1.5 watts per cubic foot of air. and the dart pump was about 1.23 watts per cubic foot. so the numbers are looking better all the time for the tiny might. im also going to run the temps on 3 different pumps. I have 2 iswakies running on my 120g tank. and then I will run them on the tiny might to see how they compare. I will be using an inferred temp gun and will hold the gun at 12" from each pump so the readings are accurate. this should give us a real good indicator as to the tiny might running temps and if there too excessive. I might be getting a little paranoid about the temps of the tiny might. I just about fried my hand putting it on an iswaki 30 tonight. super hot running pump. and the iswaki 40 I have is no better. these 2 pumps would be real good canidates for wrap around heat sinks. then re measure the temps of the pumps after a couple of days go by.

 

[smjtkj]

Here's the proof! The Tiny might runs fine at 68 watts, I was able to add a little more air to it with the pump restricted a little more.
I got it down to 66 watts without cavitating, but it cavitated when I cranked the air up more. So I settled out at 68 watts for the tiny might and 26 watts steady on the air pump and got the needle valve turned down for a little more air. There comes a point when the air starts to make larger bubbles pop at the surface of the foam. So I backed it off just enough to stop that. I am really impressed with this setup!

 

[spazz]

well with those numbers and the fact your under 100 watts and aprox 100 cfh those numbers are about the best we can expect to get. this dont mean i wont try the other wheels. it just means we cant evpect to get any better than this in the end. is the motor running any cooler now that its at 68 watts? we are so close to a perfect pump.

 

[smjtkj]

It doesn't burn me when I put my hand on it it is just uncomfortable. I don't think it is anything to worry too much about. But I would still like to see what heatsinks do for it.

 

[marcusbigdady]

meter

meter

where did you get the kill a watt meter ,by the way sweet skimmer.....