Re: Re: food for thought
Re: Re: food for thought
Ken Feldman has graciously given me permission to post his reply to the questions that were raised in this thread regarding the published article "The Development of a Method for the Quantitative Evaluation of Protein Skimmer Performance" found here:
http://www.advancedaquarist.com/2009/1/aafeature2
<a href=showthread.php?s=&postid=14165711#post14165711 target=_blank>Originally posted</a> by bosborn1
Funny how they didn't include one "modern" skimmer in the test. Most of those use designs that have been trumped by todays skimmers. Why only use mid-grade skimmers? Why not throw in a R.E. Bubbleking or an ATB? Even perhaps a high end Beckett?
Our skimmer choices were dictated by two concerns:
1) We only had a 30 gallon sample of reef tank water which came from a water change on my tank (total volume ~ 175 gallons). So, we felt constrained to use small skimmers rated for small water volumes. At the time that these skimmers were purchased (April 2006), we were unaware of any "high-end" skimmers that were appropriate for this small of a water volume.
2) Money. We operate on a very limited budget, and the cost of one "high-end" skimmer (large size) was more that all four of the small skimmers that we purchased.
<a href=showthread.php?s=&postid=14165711#post14165711 target=_blank>Originally posted</a> by bosborn1
Most of those use designs that have been trumped by todays skimmers.
What does "trumped" mean in this context? What criteria are you using to judge that one skimmer "trumps" another? Once you educate me on this point, perhaps I can comment further.
<a href=showthread.php?s=&postid=14165711#post14165711 target=_blank>Originally posted</a> by bosborn1
Why only use mid-grade skimmers? Why not throw in a R.E. Bubbleking or an ATB? Even perhaps a high end Beckett?
I'm not sure what "mid-grade" means. If mid-grade refers to price, see above. If by "mid-grade" your are referring to some aspect of skimmer performance, then you will have to explain to me what metric specifically you are using to measure "performance" before I can comment further. We plan to return to the question of skimmer performance with an RC80 from Euroreef. That skimmer uses an independent means to control air flow and water flow, so it will allow us to measure skimmer performance metrics at different flow rates. I note that the Bubble King mini is an appropriate size to test, but at almost $900, it may be a little too pricey for us.
<a href=showthread.php?s=&postid=14165711#post14165711 target=_blank>Originally posted</a> by bosborn1
Also I noticed that their was no citing of P.R. Escobal. I always refer to Escobal's work when evaluating skimmer design.
I am familiar with Escol's work. In fact, I have his book on my shelf. I did not reference it because Escobal's treatment of skimmers points to different aspects of skimmer operation that those that interested us. For example, our mathematical modeling was aimed at connecting a measureable figure-of-merit for skimmer performance (the rate constant k) to system parameters such as flow rate (Q), reservoir volume (Vr) and skimmer volume (Vs). As near as I can figure, Escobal actually ASSUMES a certain organic removal efficiency (the "9.2" in Eq. 9.1) that he calls a purity coefficient, and then proceeds to use that value to estimate other quantities that are of interest to him. These quantities primarily relate to the properties of bubbles in water ("bombardment rate", etc.). As an aside on this latter point, Escobal's treatment is hopelessly naïve. He does not take into account bubble coalescence, foam formation and drainage, etc., that all play a big role in determining overall skimmer performance. In addition, part of his physical model for how bubbles remove organic impurities from saltwater (see Fig. 9.2) â€"œ "like striking a dusty cushion with a stick" - is implausible, to say the least. If you are interested in mathematical modeling of the whole "bubbles-in-water" phenomenon, there are much more sophisticated and realistic approaches to be found in the references from the "History of Protein Skimming" section of the AA article.
<a href=showthread.php?s=&postid=14165711#post14165711 target=_blank>Originally posted</a> by bosborn1
His book on skimmers is considered the bible on skimmer physics by most industry professionals
?? I don't know how to respond to this claim. Perhaps I might just point out that Escobal proposes several models (= hypotheses) regarding skimmer performance (he calls them "laws", Chpt. 8), but he never performs any experiments or generates any data to test these hypotheses. In our AA article, we do generate data that tests our hypotheses (e.g., Figs. 9 and 12 = straight lines; Figs. 8 and 11; theoretical curve (green line) fits the actual data (purple squares)).
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