Re: Season misconceptions in newspaper

[Brian Whatcott <betwys1@SBCGLOBAL.NET>]

At 01:18 AM 6/22/2003 -0500, John Clements, you wrote:

> /snip/ they were implying that the 60W halogen bulb would save
> money because it was more efficient than a regular 60W light bulb.

 If a hot filament is surrounded by an inert atmosphere
it loses tungsten to its surroundings. In a local region of the filament,
the deltaR leads to a 2*(deltaV), providing increased
energy dissipation in that region; a recipe for local filament failure.
One limits the filament temperature to keep its life at acceptable
 levels in the  700-2000 hours range.

Some commercial examples of halogen lamps have provided
consumers with discouraging service.
In particular, there was a rash of free standing tall halogen lamps
("lumieres")which provided a source of bad smells if insects flew
 into their hot surface, which started house fires if curtain
drapes blew onto them,and which oxidized their bulb connectors
at the high temperature in effect at the small contact areas of
 base metal provided  (in contrast to the generous contact
surfaces provided in auto headlamp usage.)

/snip/ I have also seen efficiency claims being made for other halogen bulbs
> which have similar light output compared to standard bulbs of the same
> wattage.

/snip/

> John M. Clement
> Houston, TX
>
> Bernard Cleyet <anngeorg@PACBELL.NET> said earlier:
> /snip/
> >  From an old table (< '68 ca.) two comparable lamps:
> >
> > Both std. and Iodine cycle  (quartzline) 500 W operated at a color
> > Temp. of 3200.    /snip/
> > They both emit ~ 10K Lumens; the iodine has a life of  2,000
> > hr..,  the std (CZX projection) only 25 hr.

/snip/

I took a pack of GE soft white incandescents off the shelf:
the claim is
Light Output: 1690 lumen
"Energy Used:"   (Power)   = 100 watts
Life: 750 hours

A rational  lamp selection parameter would be
 lumen.hours per watt.cent (of first cost)

If the unit cost were $1.50, the parameter would give
 84.5  lumen.hours per watt.cent

Supposing that Bernard paid $4.20 for his Quartzline 500 W bulb,
that would represent 95.2 lumen.hours per watt.cent.

The projector bulb, on account of its reduced life and increased cost
is not a candidate for general purpose illumination on this account,
at < 1 lumen.hour per watt.cent  and would be replaced in a modern
 design by a halogen incandescent or xenon strobe  source.

Brian Whatcott    Altus