Backyard Aquaponics
A place to discuss aquaponics

So if I understand the above Frank.... and referring to your drawing...and comments ...

You intend to pump water from the sump to virtually no head... then gain aeration through the venturi affect of passively drawing air through a series of corrugated plates that will be mounted at virtually the same (no) head... stacked closely together so as they have both minimal surface area and minimal fall between them....

By flowing water delivered from a sump supplied by an intermittent device... (bell siphon) through a 100*100mm open gutter to a tank that will intermittently supply a low volume of water via chift pist to a growbed that intermittently drains via a bell siphon..... etc etc...

And you feel that you will gain more aeration... at greater efficiency.... than just inserting a venturi into the return line....

Good luck...

Still think we should rename this thread. Because in a few hrs or days this subject it going to come up in another thread. At least we can redirect it back here and not clutter up a dozen threads. Over and over again.

So Frank what is the turn over of your system? Ie in that 10minutes of pumping how many litres are you moving?

Naaahhh...........not purple frogs - - - CANE TOADS!

Because the pump, pumps to the top gutter Stuart... which is 100mm*100mm*2.7m...

Even if it was to be filled to overflowing.... this will limit the volume that can be pumped in any period of time... unless it were to be pumped very slowly....

But could you drive this system by timer.... i.e the sump is filled by growbed drain via bell siphon... surely you'd need to activate the pump in the sump by float/level switch....

can you guys please drop the anger?

this is supposed to be an exchange of ideas to advance together in trying to understand the physics of hydraulics and optimize aeration at the least possible cost,

hopefully not a battle over hills where each time a victory flag is hoisted

I have drawn your attention to the inefficiency of pumps used in AP
not only airlift pumps, but pumps in general

shouldn't we better join forces in trying to coax the industry in constructing better pumps?
and if the industry doesn't react, shouldn't we exchange ideas on how we ourselves can improve this efficiency?

that is what I'm trying to do

now I'm spending hours and hours in trying to convince you of my positive attitude
which should be obvious
as spending this much time in patiently trying to explain my reasonings is proof of my respect for all of you

I am on this thread drawing your attention to the fact which all of you accept that pressurized Venturi's diminish the already inefficient volume output of our pumps
it is my impression that the gain of aeration by Venturi's does not compensate the lost volume which can be put to good use for passive aeration
and I have painstakingly tried to explain why I am convinced of this

and I have pointed out that the extra volume serves at least one other purpose too: faster removal of solids out of the fish tank
which diminishes DO consumption in same tank to a great extent and by that fact DO needs.

my design of a passive oxygenator is in the first place oriented to exposing more water to air surface by exposing both sides of the water to air
I would not call it a passive Venturi oxygenator and I would not like it to be called that
not before the efficiency of the Venturi effect that I am convinced is present is confirmed to be more important than all the other effects I am seeking which are increased exposure, cascading, turbulence. I expect these to be more important than the Venturi effect which is a welcome by effect.

I don't own a DO meter and have no budget for it as they are horribly expensive
so I cannot prove my reasoning
but I am convinced it is sound
if I had one I would do the experiments and publish the results in all honesty even if I am proven wrong

peace, please, and cooperation

frank

I don't know if we could put much stock in anything you published. Sorry you have to stay on the fence when doing any real research and not let preconceived notions cloud the results.

But will you actually acheive that "extra" volume Frank... by pumping through an open gutter... which surely (even if unfilled with media or plants) can only deliver xxx volume of water to your tank....

And looking at the scale/size of the growbed.... how many times will you be pumping from the sump???

The growbed would appear to have about the same volume as the fish tank.... and wont empty into the sump until filled and the siphon activated....

Surely you agree, that the sump pump can't pump continuously....

To me the growbed limits your sump volume.... and length/volume of your pump cycle.... and the top gutter limits your flow/volume capacity... which limits the return to the tank... which limits the flow/fill to the growbed....

How often do you think you will turnover the volume of the tank each hr/day???

I think Duff is right Frank, you might read your own signature, or at least have something other than a hunch to back up the theories

There are plenty of other people on this forum that want general information adaptable to their own systems. And, like it or not, sometimes efficiency is not going to be a major contributing factor to design decisions... Not that venturis are necessarily inefficient.

Therefore, venturis can be quite useful in many applications of an aquaponics system, it depends on your priorities in system design.

(not taking wall thickness into account) the section of a 50 mm tube is 1964 mm², that of a 100*100 mm gutter is 10000 mm², five times more
20 mm of water is enough to allow the capacity of a 50 mm tube to flow through the gutter
so there is absolutely no need for slow pumping
quite the contrary: I have put a partial obstruction at the end of the gutter (with a small gap at the bottom and a bigger gap at the top) to create an ebb and flow effect
when the pump kicks in, the level rises in the gutter to the point where the obstruction is overflowed (about 70 mm, which leaves 30 mm open)
when the pump stops, the gutter slowly drains completely through the bottom gap
for the moment I use a timer, but I realize that this is risky
I will add a float switch for pump protection

I am very impressed by Novaris's sequencer
http://backyardaquaponics.com/forum/vie ... 02#p157202
and will include his technology in my design, so I can have the pump recirculating water over only the upflow filter and straight to the sump for aeration purposes only, and independently from the flooding/draining of the growbeds

... I wish I had a DO meter...
anybody have connections with Santa?

frank

Thanks Frank, too busy with other things to have done the maths...

OK... perhaps you can clarify another point before any further comment is made....

Do you intend to fill (partially?) the top gutter... or in some way use net pots to contain any plants you grow there??

if the balance of the increased aeration by a pressurized Venturi is not compensating the loss of volume everybody agrees it causes, (volume that can be used for passive aeration and doubtlessly allows for faster removal of solids which efficiently diminishes DO demands),
then a pressurized Venturi is redundant and contra productive in AP, Joel

my reasoning is backed up by explanations of why I think that balance is not reached and TMHO cannot be reached as every conversion of energy has been proven to include energy losses
it is somewhat more than a hunch: it is motivated
so far nobody has tried to explain to me why a pressurized Venturi would swing that balance

so don't try to have my signature fire back to me please
it is what I stand for and defend:

we make it very hard for ourselves to learn new things when we start out with too many preconceived notions

please reread my previous post:
shouldn't we join forces to improve systems instead of engaging in fights over hills and raising flags on those hills?

I am very disappointed by the fact that so far you have not replied to my PM
I am also disappointed by you, as a system manufacturer, repeatedly expressing that energy consumption is not one of your priorities

unless everybody accepts my positive attitude for a fact or at least for an assumption
I will never start a thread on my own setup

I am sick and tired of having to defend my attitude
I refuse to have a repetition of this on what might possibly become my personal thread

please all forgive me for this
I hope you understand

frank

Thanks to you, Rupert (sincerely, no pun intended at all)
I am aware of the risks of drying out plants and how fast this can occur
so all plants in the gutters will be planted in pots that hold media that suck up water and hold it for as long as possible
I am told that coco fibres might perform best at this task
but expanded clay, vermiculite, ... etc... might be good enough
I would really appreciate your guidance on this subject.

frank

Frank, you have sent me no PM for me to respond to. And so far as you judging my system designs and priorities? Think what you will, I can't change that. But I am the one who who facilitates these very discussions?

Glad to hear you're not thinking of actually filling the gutter with media... to do so would have reduced your capacity by about 40-50%... and slowed your flow rate...

As to media in the pots.... given you're essentially "flooding and draining"... or ebb& flow...

And the height of the flood... 70mm.... then I think coco coir fibres are out... they just stay too wet IMO.... more suited to drip feed... although in very hot climates (ie Plachon in Thailand) they might work OK...

Choices then.... Vermiculite holds water really well... but the fine grade wouldn't allow enough air to the roots in that flood height... unless the drain period was fairly long...

Perlite (a pain to work with) on the other hand has much better air holding abilities... but not great water retention.... in your case with that height of flood, in may be suitable...

Again depending on just how long the "ebb/drain" period is... and air temp.... remembering that the channel will also impart a degree of ambient heat transfer...

Expanded clay has great aeration ability, but not great water retention... so again ... depends on the drain period....

You may need to actually determine the drain period to determine the best media....

Flooding that high for extended periods will compromise the ability of the plants to uptake oxygen IMO.... this can be compensated somewhat by flow... if the flow is highly oxygenated...

Question is... will this be the case....

Second possible problem I see is whether the sump receives a large amount of "unfiltered" solids, suspended matter... directly from the overflow, rather than passing through the growbed...

If this was the case, then the chances of solids adhering to the root balls... causing channeling of the water flow.... and/or dry spots or root rot... are increased markedly...

Much of the success or failure of the design... depends on flow rate... and frequency of the flow cycle...

Have you been able able to calculate just how long your timer cycle... sump fill cycle might be?