Jeez, some of you are strong believers
I have a little story to tell about this:
In Western culture "historically" based adventure movies about the "Holy Land" invariably show the crusaders clad in white, shiny armor, and the heretic opponents are in dark clothes.
I like a bit of experiment, so one day I went to have a haircut with an (immigrant) Turkish barber in Ghent, where I live.
All through my "treatment", the overhead television set was on.
Thanks to satellite television, it was a Turkish channel.
I didn't understand a word of it, but it obviously was an old black and white adventure movie and for most of these movies action prevails on dialog.
I saw knights clad in white shiny armor and dark clothed culprits doing sword fights and horse chases.
So I naturally assumed these were knights coming to free the "holy land", voices dubbed in Turkish.
It was quite fun even though I couldn't exactly follow the plot.
I almost fell off the barber stool laughing (luckily the barber wasn't holding a razor to my throat) when suddenly I realized that what we westerners consider as the knights were the dark clothed subjects and all the shiny armor was reserved to the locals.
We were the invaders, they were the heroes.
So much for perception and how easy it is to manipulate it.
back to subject:
again I read expressions like "... I reckon..." followed by "...would...", this time related to another issue.
apparently there is another rumor accepted as a fact that airlift pumps supposedly are limiting or even avoiding biofilm buildup.
again that is perception:
Not facts are expressed, but fears and assumptions. Like in:
Quote:
would get blocked extremely quickly
the biofilm is not intelligent enough to discern what type of pump is moving the water. It is not following our discussion. And it doesn't care.
here is an interesting read on biofilm buildup and how to reduce or limit it (it cannot be avoided, no matter what type of pump): flow is the key.
http://www.edstrom.com/doclib/biofilm.pdfI quote from it:
Quote:
High flow will not prevent bacteria attachment nor completely remove existing biofilm, but it will limit biofilm thickness. Regardless of the
water velocity, it flows slowest in the zone adjacent to pipe surfaces. Even when water flow in the center of the pipe is turbulent, the flow velocity
falls to zero at the pipe wall.
a boat propeller (quasi immediately) and even a boat hull (which moves at incredibly lower speed than the propeller) will eventually shed even the biofilm built up after several days of rest (and we are not talking about rest in AP).
In relation to the speed of the water passing by, most of the biofilm will be washed away (besides, we looove
a thin layer of biofilm).
A more efficient pump in the same tube will create more flow for the same energy input, thus reduce biofilm thickness more efficiently. Thus reduce friction, thus even more increase pump energy efficiency.
Thanks to the speed of the propeller, the biofilm on it's surface will be negligible.
So blades and vanes will NOT collect crap. That is fear expressed, not reality.
It has nothing to do with "regular maintenance", or better, the speed guarantees self cleaning even after a rest, which cannot be said -or will be much slower- with an airlift pump.
Myles,
Quote:
I am constantly looking for more efficient methods
In your challenge you leave the search AND the proving to me (but thanks for the useful links).
Quote:
I have experimental evidence that they (airlift pumps) outperform a typical centrifugal pump
No, you haven't, as I already pointed out: you have compared an airlift pump to a centrifugal pump that wasn't designed for this low head.
So all the following reasoning
Quote:
I would be significantly better off to using my centrifugal pump with a 1 meter head pipe
is irrelevant: You missed the main point I put forward: this pump is NOT designed for low heads.
So it cannot be used in any comparison whatsoever.
Quote:
Simply saying that a pump has poor efficiency based on power in to power out ratios is of little value
No it is not, quite the contrary (especially with efficiencies of less than 5%), it is of very high value (as shown in the return on investment calculation): this conclusion will hopefully entice US ALL (and not only me, for the sole purpose of acknowledgment) to look for better solutions.
Even if I would have no ready-cut solution at this time.
But I have suggested one:
While it is true that for small propeller pumps (as they are just about nonexistent) I can hardly backup my conclusions with hard figures, in industrial applications propeller pumps are considered as (one - I am careful) the way to go for small heads.
AND, I have provided you with one example:
http://www.advancedaquarist.com/issues/ ... review.htm
from which I quote (again):
Quote:
A pump rated at less than 20% the flow of the Gemini appears to be generating as much turbulent flow as the Gemini.
That is not less than a
fivefold improvement. Which reduces the return on investment to two months.
AND the Gemini is NOT a 12V bilge pump, Rupert !!!
Maybe someone should make a proper, comprehensive list of all supposed arguments in favor of airlifts in an excel sheet.
I am ready and eager to counterargument each and every one of them with facts and figures, even the one on possible alternatives as you have just read.
Frank
Backyard Aquaponics
