Algae Scrubber Basics
- Thread starter srusso
- Start date
degibson84
New member
the picture makes it look much worse than it really is. I ran some water down the drain lines and it was dispersed fairly evenly across the screen
Floyd R Turbo
Either busy or sleeping
That will work, but a little blue has been shown to boost growth.
Most of the information I have based my recommendations off of are from what I learned from many discussions with someone who had decades of experience with plant growth and IIRC he also had a degree of some kind that was related to it.
Basically there was one large university study (Cornell IIRC) and a NASA study that said the optimal ratio was on the order of 6 to 8 parts red to one part blue. However, it was unclear to me what the ratio represented exactly.
If we take into consideration that true deep red LEDs cannot be measure by lumens, but instead by radiant flux, then this throws the whole ratio discussion in a different direction.
My personal experiences were with about 30 scrubbers that had a single full power blue in the middle of an array of 6 reds. Every one of them had a bare spot in front of the blue.
When I switched to dual 50% current blues, this issue disappeared. So my recommendation is based on what seemed to work very well. If you go by strict number of LEDs, the ratio is 6:1 red:blue.
If you figure in the intensity of blue LEDs being "perceived" as brighter, then one could argue that my recommendation results in more of a 4:1 ratio. So IMO you would be fine doing 1 50% blue for every 10 or 12 reds, since the blue is only supplementing the reds.
The reason I say that is because there were several people who were running red-only arrays, and when they added blues to the mix, they noticed that the growth did not so much change in volume/mass and it changed in structure.
FYI the 440-450nm Royal Blues that Steve's carries seem to hit all across the A & B spectrum. You don't need much supplemental blue is the point, and you don't need more than one bin of LED for it, at least not from what I have seen.
Will this angle be an issue?
Yes, for many reasons. One being that due to gravity your screen will not get completely covered, and the second being that once you get growth at the slot pipe / screen junction, the water is going to follow the endcap of the pipe and end up on your floor.
silverwolf72
New member
Has anyone tried just blue?
Floyd R Turbo
Either busy or sleeping
I would say that yes, blue-only has been tried, but not many reported results.
SantaMonica
Well-known member
It the Black Body Radiator effect.
Floyd R Turbo
Either busy or sleeping
Are you serious?
Trolling?
BeanAnimal
Premium Member
Is you floating heat sink hot enough to glow?
Most of the thermal transfer at our delta t is conduction to the air. The thermal conductivity of the paint is lower than that of the heat sink. You likely to lose more in conductivity than you are to gain in emissivity. Also, the flat black is happy to gain via radiation from other objects, further negating any theoretical benefit in our application.
Crazy_Beaver
New member
Well said!:thumbsup:
Floyd R Turbo
Either busy or sleeping
Ok, thanks for the confirmation that I am not an idiot for missing some major component behind the Black Body Radiator concept. Because the latter part you mention (the black paint coat being an insulator) was exactly what I thought - painting something black does not make it a 'black body radiator'
Other than that, I had to do quite a bit of re-reading on Black body radiators. Until now, I had only really considered a Black body radiator to be essentially a theoretical object of sorts, defined as such:
This is the type of language I had always read on "black body radiators" - "Ideal body" "infinitely small thickness", etc. All terms that are referencing something not real, except in the case of the Sun or any star for instance, which I recalled (correctly) were considered to be close to perfect black body radiators.
The most discussion I had read on BBRs was related to the Kelvin rating of light sources, by which their output is compared to the perceived output when compared to the radiation put out by a theoretical BBR at a given kelvin. I.E. the BBR was heated until it glowed and gave off certain colors at a certain Kelvins and thus, the color temperature of the light source in question is given a Kelvin rating.
It had never occurred to me to paint something black and then call it a "black body radiator".
Some extremely deep googling revealed a few rather out-of-context statements about something that was painted black was better at transmitting heat, but they seemed to be very obscure discussions and not scientific at all, except for some discussions that had some thermal coefficients thrown in to show that any color paint had the same thermal coefficients.
Plus I was thinking that if this indeed is true, then why isn't everyone painting their heat sinks black?
Now thanks to Bean I can stop :headwalls: because I am not an idiot after all. I can stop questioning myself. Thanks!
herring_fish
Crazy Designer
Bless his little hart.
BeanAnimal
Premium Member
Simply a case of somewhat misapplied terminology and science used to...
Yes, surface emissivity has a lot to do with roughness and/or conmposition. There are "idea" colors that in theory (and practice) could/would radiate more at given temperatures than other colors at given temperatures.
The problem (as mentioned above) is that the emissivity of this type of heatsink is not really that relevant, as most of the cooling is done by conduction to air. We have a (in context) almost non-existant delta T and contextually low temeratures overall.
Raw polished (or even dull smooth) aluminum has both a poor emissivity and a poor conductivity to air. Anodizing the aluminum and/or roughing the surface (prior to anodizing) can greatly increase conductivity to air. The color is really not relevant, but black could be used to some theoretical tiny benefit that could not likely be measured.
The plans SM posted also indicate a "waterproof" coating. This will greatly (maybe cut in half or worse) the conductivity of the heatsink as well... so anodizing is again the better option.
Many transistor heatsinks are painted or anodized black. Not so much for the theoretical benefit of higher emissivity, but instead to create an electrical insulator.
This very question comes up rather often in the DIY electronics (especially high power DIY audio) circles. If you DO paint, it needs to be extremely thin and sprayed, not dipped or brushed and to that end there is likely no real world bennefit from a thermal standpoint.
Floyd R Turbo
Either busy or sleeping
I think he was referring to LEDseal being sprayed on the front side of the array, after the LEDs were attached and wired. I think the concept is that all of the heat would be dissipated off the back side of the heat sink anyways.
In follow up to this, I noticed that when I ran my blues at full power (did not yet have dimming hooked for my ATS http://www.reefcentral.com/forums/showthread.php?t=2295749), it took longer for the center stripe of the screen to fill in (more blues there). I have since hooked up the dimming and dialled the blues back to 40% for a 5:1 ratio of red/blue. I will see over the next week (cleaning today) if it makes a difference.
Hmm come to think of it, I could do an all blue test for a week by leaving the reds off ... :hmm5:
Dennis
herring_fish
Crazy Designer
Floyd R Turbo
Either busy or sleeping
I know it's not the easiest to lay out, but I do not recommend striping the blues in a line. They need to be intermixed with the reds, otherwise you get the growth inhibition you are describing (not really inhibition, as it is saturation)
SantaMonica
Well-known member
Yes it does
Makes a big difference spraying a thin coat of satin black on it; cuts the temp in half as felt by hand. And this is before being in contact with water.Delta T does not play a part; it's radiation, not conduction. And it's not insulated on the top; just the sides and bottom.
Plus, it's working on multiple units
