Re: mercury vs amalgam in CFLs

On Mon, 19 Mar 2007 05:24:20 +0000 (UTC), don@xxxxxxxxxxxxxx
(Don Klipstein) wrote:

In <j3vrv2518m8omghvrmomfvtdc9bbse6imb@xxxxxxx>, Victor Roberts wrote:
On Mon, 19 Mar 2007 03:01:42 +0200, "Ioannis"
<morpheus@xxxxxxxxxxxx> wrote:

"Victor Roberts" <xxx@xxxxxxxxxxxxxxxxxxxxx> wrote in message
news:lmkrv25skg00ate9o7etsorvoqlsjna67c@xxxxxxxxxx
[snip]

Some amalgam lamps use a dual amalgam system with one
amalgam that is heated by the electrodes or some other means
to dump mercury into the discharge as soon as power is
applied. I even have a patent on a version of this idea :-)

Amalgam Heating System For Solenoidal Electric Field Lamps
U.S. Patent #4,437,041, March 13, 1984.
http://www.robertsresearchinc.com/Patents/US4437041.pdf

Fascinating. I guess it is too much speculation to infer how the SL-18W [*]
releases mercury or what kind of mercury release mechanisms it uses, but
obviously mercury must be released very slowly because of the very low initial
lumen output and the fact that the lamp takes as long as 3 minutes to reach
optimum output.

That sounds like a normal single amalgam system. The 3
minutes is the time it takes for the amalgam to come up to
operating temperature.

Maybe in newer systems (such as in the DULUX 21W) more modern
methods such as yours are employed and mercury is released faster in the arc
stream?

They may use a dual amalgam system.

Are these lamps (or some variation thereof) you describe in the .pdf manual
used today?

No. These were a precursor to the GE Genura, but as you can
see, these use a closed ferrite core while the Genura uses
an open core - actually a rod.

If not the lamps what about the proposed mercury release mechanism?

I don't know of any inductively heated amalgams, or any with
separate heating systems either. Most dual amalgam systems
place the "fast" amalgam on or near the electrodes, and use
the electrode heat to heat the amalgam.

How old is this mercury amalgam technology anyway? I see from your patent that
it goes at least back to 1981.

I'm not sure. I think Philips was using amalgams in some
fluorescent lamps well before 1970.

Do the classic linear fluorescents use
amalgams?

Some do - only the higher power lamps in which the
temperature of the bulb is too high to produce the optimum
mercury pressure.

Did they always?

Always is a long time :-)

At least to my eyes, back in 1978-80, when I was
firing regular 40W old-style daylight halophosphates, the maximum output was
reached almost instantly. How come?

Your eyes are probably fooling you. Peak output occurs when
liquid mercury is at 40C. The output at 25C should be about
50% to 70% of peak, but I'll have to check that.

It appears to me that in T12 lamps with liquid mercury peak output is
with cold spot in the upper 30's, and T8 may optimize at a full 40.

Somehow I suspect that at 25 C output is a goodly 75% maybe 80% of
"full". At 20 C in T8 and T12 lamps it may be around 70% IIRC.

Based on my memories of reading things in a university library authored
by Waymouth and Elenbaas and the like, maybe some edition of the IES
Handbook.

- Don Klipstein (don@xxxxxxxxx)

Figure 2.6 in Electric Discharge Lamps by Waymouth shows a
curve of efficacy vs wall temperature. for a T12 lamp (For
lamps with liquid mercury, of course.) Waymouth states that
his data was taken from CW Jerome, Illuminating Engineering,
Vol. 51, p 205, 1965.

Note that his data, like much of the best data and all of
the calculations I have seen, presents EFFICACY as a
function of temperature.

The light output data is complicated by the fact that lamp
voltage also changes with mercury pressure so even if the
current is held constant, the light output vs. temperature
curve would not the same as the efficacy vs. temperature
curve. Then we have the added complication that as the
lamp voltage changes, the current may or may not also
change, depending upon the design of the ballast. Therefore,
there is no universal answer to light output vs.
temperature.

However, the IESNA Handbook has a set of curves showing
efficacy, power and light output as a function of
temperature, again for a T12 lamp. The Handbook does not
state the type of ballast used, but based on the age of this
graph (I have seen the same one in much older versions of
the Handbook) it must have been taken with a two-lamp
US-style rapid start ballast, such as the old 8G1022 that
was "standard" for so many years.

Data in the IESNA Handbook shows that the efficacy does peak
at 40C, but the light output peak occurs at lower wall
temperature, perhaps as low as 35 to 36C, though it's hard
to read the graph accurately. Based on the same graph,
both the efficacy and light output are 80% of their peak
values at 25C. (The two curves happen to cross at this
temperature.) So, my earlier estimate of 50% to 70% was
too low.

Using the data in Waymouth I would get a slight bit lower
than 80% efficacy at 25C.

There's a great paper on the performance of T12 fluorescent
lamps as a function of temperature that was done as a PhD
thesis by someone at Philips way back in the 1970's or
earlier. If my memory is correct, they immersed a T12
quartz tube filled with argon and mercury in an oil bath and
measured all the key parameters as a function of temperature
and at a fixed current. I'll have to try to find my copy.

--
Vic Roberts
http://www.RobertsResearchInc.com
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