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Re: [AGA Member] Fluorescent Reflectors efficiency
Thank you Scott!
Amit
----- Original Message -----
From: "S. Hieber" <shieber@yahoo.com>
To: <aga-member@thekrib.com>
Sent: Friday, April 09, 2004 11:33 PM
Subject: Re: [AGA Member] Fluorescent Reflectors efficiency
> What makes a good reflector are thre things:
>
> How little light it absorbs--how much light it reflects
> without further diffusing it;
>
> How durable it is--how fast it wil corrode and lose it's
> specular properties;
>
>
> How well it reflects light to where you want it.
>
>
> That third one varies on circumstances. If you want the
> light to spread as little as possible, then a parabolic
> shape is best. Consider a point source of light. If you
> properly place a point source in the center of a prabolic
> reflector, all the rays coming from the light source and
> going to the reflector will be reflected straight forward.
> Smooth curves would be ideal, other things being equal.
>
> With a line source, like fluorescent tube, then the choice
> would be a long straight relfector whose sides are
> parabolic curves. However, fluorescent light is so diffuse
> comeing from the bulb, you'll never get a straightforward
> (pardon the pun) reflection. Double tube bulbs (PCs) make
> things a tad worse since neither tube will be right on
> center. And making things a bit harder is the fact that
> fluorescents are really a line source either; the light is
> emitted from all over the tube. A fluorescent is a tube
> source and not really a line source of light; the light is
> spread out right at the bulb.
>
> If you want light to spread more than a parabolic provides,
> then something less than praboic is preferred and vice
> versa if you want it be narrower.
>
> The best material around for the first and second
> properties (reflectivity and durability), I believe, is
> Miro, a coated polished aluminum. The coating that makes
> the aluminum resist corrosion absorbs very little light and
> that's the key.
>
> For an example of very good reflector made of Miro,
> consider the AHS reflectors. They are angled because, I
> suspect, it's tons easier to get them into shape by bending
> them on a brake than to try to get smooth curves with a
> more complex machine that rolled or stamped the shape.
>
> The diff between the psuedo-parabolic shape of an AHS
> reflectors and one that was true parabolic is probably
> negligible -- bigger diffs exst between brands of bulbs,
> how well the bulb and ballast are matched, how long you use
> the bulb, and maybe even room temps.
>
> Also, being angled, they are easier to adjust to suit your
> particular purposes. You can relatively easily widen or
> narrow the angles, and thereby widen or narrow the spread
> of the refelcted light, without damaging the reflector. It
> would not be as easy, I think, with smooth curves -- some
> portion of the curve would always want to "give" first and
> you'd end up with a dent or a buckle instead of a smooth
> curve.
>
> The amount of UV coming from a good fluorescent bulb isn't
> much. Enough to darken your Photo-gray eyeglass lenses but
> not to darken them al the way. If you have a glass top on
> your tank between the bulbs and the water, then there isn't
> much UV getting through to the water. Water also abosrbs
> true UV pretty well. So there isn't much UV getting down
> into the water.
>
>
> Btw, the worst reflectors in terms of shape are ones that
> are flat or square in cross section. So individual
> refelctors for each bulb do a better job than refelctors
> that wrap several bubls. Theorhetically, straight tube T5
> bulbs can beat out bent tube/u-tube PCs with the right
> reflectors.
>
> So the short answer is, no angled isn't better, other
> things being equal. But given real workd conditions, you
> won't find better refelctors than AHS's, imo.
>
> Hope that's some help. It's a complicated subject and I
> only know this [ ] much. ;-)
> sh
>
> --- Amit Brucker <amitb@gtek.co.il> wrote:
> > Thank you all for your help on deep tanks.
> > I was reading that reflectors (depending on their
> > material, shape and quality) can increase the light
> > source in about 40-60%. I am aware of two kinds of
> > reflectors:
> > 1. The rounded ones
> > 2. Angled ones - which are better than the first kind
> > because of their shape which increases the light even
> > more.
> >
> > Questions:
> > 1. Can anyone approve this info ?
> > 2. Is it 'Fair' to include the reflectors when
> > calculating the W/G into account ?
> > 3. There are some special fluorescent that are covered
> > with a special coating which acts as a UV filter that is
> > helping to prevent algae - Is that so?
> >
> > Thanks
> >
> > Amit Brucker
> > www.plantica.com
> >
> >
> >
> > --- StripMime Report -- processed MIME parts ---
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> > text/plain (text body -- kept)
> > text/html
> > ---
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>
>
> =====
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