Amps Per Square Inch... (APSI)

this is a copy of a post from another thread that is important enough to re post here I think.
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OK I want to cure the questions I have about the APSI formulas....
I started them at first by using a Known good working cell.... that happened to be the "Randy cell Mk1"
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that cell's configuration is as follows
11- 2" S.S. Washers with 1/2" holes in the center
area of a circle is Pi X (RxR)
so 3.14159 X (1x1)
1 x1=1
so each side of the washer has 3.14159sqr inches (strangely enough)
however they do have a large hole in the center of 1/2" in diam
...so 3.14159 X(.25 X.25)
.25 x .25=.0625
3.14159 x.0625=.1963 (area of the hole in the center)
so 3.14159-.1963=2.9452 sqr inches per side on each washer
sense we only count one side for simplicity sake, that's 2.94 X 11 plates which is 32.3972
square inches in the cell
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the cell was ran at 20 amps so to get the Amps per square inch of the cell we devide the amps by the inches...
20/32.3972=0.617 APSI
(this is a great deal Higher than my previous calculations! by almost double!)
...never the less the cell worked fantastically at that configuration
and 2LPM at 20 amps was constant !
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I've been telling everyone that we need .3 to .5 APSI for ages... yet the cell I based the calculations on had 0.6 APSI.... OOOOOPS !
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Now with Randys new cell, the calcs come out a bit different...
cell configuration is as follows...
5-4"washers (with 1/4" holes in the center I think)
we already calculated the area of this washer so I'll use those figures of 12.568sqr in per side.
5plates so thats 5 X 12.568=62.84 square inches for the cell
21 amps used on it to achieve a tad more than 2LPM
so..
21/62.84=0.334 APSI
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that's Half the APSI of the original "Randy Cell" Yet the Output is the same if not a bit better....
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So that changes what I thought I knew.... so we need at least .3 to .6 APSI to achieve the 10:1 ratio of amps to liter output... a wider margin than I used to think
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I think Randy is correct in his theory that the APSI needs to be adjusted on a PER CELL Basis in other words, get the cell working at the wanted Amperage and add/remove plates until the output drops and back up one step.
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I don't think Many people will go for this remove plates and try it again idea as its a time consuming process and a royal pain in the Ars to put it mildly...but it does tune the cell to maximum output for the given amperage....
I Apologize if my previous figures caused anyone problems, but it is a learning process and I am still learning ! <grin>
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you'll notice that on the MK1 Cell I subtracted the hole in the center of the washers
and on the new cell I didn't... and on both cells I did not subtract the holes in each washer for the mounting of each plate..
I think its close enough for our uses, close enough to give us a ball-park figure on Amps needed per cell size.... and that's what its all about.
the MK1 cell had a tenancy to run warm and it may well be because of its High APSI and low plate area
the new cell works great without heating at all which is a good thing !.
the question is , is how low of amperage can you run a cell and still make it worth while to operate because of the decreased output?
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Its obvious to me that you will get Some production from the very start all the way up to say 10 amps per inch... but where is the threshold for best production ? and good operation too ?
could it be at 0.2APSI or is it better at 0.9 APSI...
Under 0.3 APSI and you start dropping in output fast
over 0.5 APSI and heat starts to be a problem in the running of the cell.
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so the ticket is to go with as Little APSI as you can get away with and still have good Output
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Bob...