Re: Suspension losses

On Fri, 17 Jan 2025 12:06:29 -0500, Frank Krygowski
<frkrygow@sbcglobal.net> wrote:

On 1/17/2025 12:33 AM, Jeff Liebermann wrote:

On Mon, 13 Jan 2025 14:33:13 -0500, Catrike Ryder
<Soloman@old.bikers.org> wrote:
 

On Mon, 13 Jan 2025 11:28:12 -0800, Jeff Liebermann <jeffl@cruzio.com>
wrote:
>

On Mon, 13 Jan 2025 08:57:18 -0500, zen cycle
<funkmasterxx@hotmail.com> wrote:
>

On 1/13/2025 2:01 AM, Jeff Liebermann wrote:

On Mon, 13 Jan 2025 13:20:04 +0700, John B. <slocombjb@gmail.com>
wrote:
>

But long before the days of transistors and "circuit boards" my folks
had an electric blanket... used it all the rest of their lives. Is the
modern one better?

>
Not really better, but certainly safer.  Electric heaters are all 100%
efficient.  Every watt you shove into the heating wires is turned into
heat.  There's no way to improve on 100% efficiency.

>
Nothing is 100% efficient

>
Well, the heater wires might radiate some EM radiation, which then is
absorbed by nearby objects and is converted to IR which adds to the
heat produced by the heater wires.  There might be some radiation at
other frequencies (RFI, EMI, microwaves, visible light, UV, etc) but
most of the radiation is ends up somewhere in the IR bands.
>
Incidentally, I'm usually amused at the advertising for electric
heaters all claiming that their more "efficient" than the competition.
Of course, no numbers and certainly no calculations are ever provided.

 

They could always do a study where they ask people which heater made
them feel warmer.

 
I've seen that in advertisements and ad agency generated "scientific"
studies.  Usually, the winner is the electric heater with a parabolic
reflector to concentrate the heat in a small area.  The dish is not a
true parabola.  If it were, such a heater could probably burn a hole
in whatever it's pointed at.

>
A mathematical quibble: You may be thinking of an ellipsoidal reflector.
An ellipsoid would take the radiation emanating from its focal point and
concentrate it at its other focal point. And at other locations, there
wouldn't be much concentration anyway.
>
A parabolic (or parabaloid) reflector would take the radiation emanating
from its focal point and send it out in parallel lines. Again, no great
concentration.
>
See
https://sciencetech-inc.com/web/content/?model=product.template.website_pdf&id=1297&filename_field=name&field=doc&filename=doc.pdf

Nope.  I used the term "parabolic dish" to describe a directional
reflector which recognizes.  I don't know exactly the shape of the
reflector in the heater, but I do know that with such small f/D (focal
length to diameter ratio) and very wide heating element, the reflector
could be almost any shape and work much in the same way.

The design of such a directional bathroom heater has some goals:
1.  Spreading the IR radiation over an area that approximates the
width of a human.
2.  NOT concentrating the IR radiation to produce hot spots that might
injure the user or start a fire.
3.  Convince UL that it's safe and won't turn into a death ray.

Argh... I need to go somewhere.  I'll fill in the tech stuff when I
return.


--
Jeff Liebermann                 jeffl@cruzio.com
PO Box 272      http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann      AE6KS    831-336-2558