Re: Suspension losses

On 1/16/2025 12:38 PM, Radey Shouman wrote:

Frank Krygowski <frkrygow@gXXmail.com> writes:
 

On 1/15/2025 1:28 PM, Zen Cycle wrote:

On 1/15/2025 1:16 PM, Frank Krygowski wrote:

On 1/15/2025 1:05 PM, Zen Cycle wrote:

On 1/13/2025 11:03 AM, Frank Krygowski wrote:

>
It's certainly true that 100% of the electricity consumed by an
electric blanket becomes heat.

>
No, that isn't true either.

>
Please explain. What electrical energy goes elsewhere?

A very small amount of power is used for the indicator lighting and
electronic controls.
>

>

I write "either" because even _if_ it were true that electric
heaters are 100% efficient (which isn't true), saying 100% of the
electricity consumed by the device become heat is very different
than saying it's 100% efficient.

>
What's your definition of "efficiency?" As I said earlier, I think
a common one used for engineering matters is Desired Output divided
by Required Input, or something similar.
>
Do you have a different one?

Nope, it's the notion that every watt of power directly goes into
heating the targeted space that I'm stuck on.

>
You're moving goalposts. You objected to my statement "It's certainly
true that 100% of the electricity consumed by an electric blanket
becomes heat."
>

There are other losses in the cabling and plug interface which -
while realized as heat - do not contribute the heating of the
targeted space. The heat generated by the plug and cord are rather
well insulated.

>
But it's still heat, delivered into the room. It's not lost elsewhere.

 Not necessarily true.  Heat is conducted thermally into the electrical
wires, which often run inside exterior walls, and can thus be conducted
to the outdoors without heating a room.
 But these are quibbles.  The definition of efficiency depends on the
purpose of the device, and the theoretical model used to compute the
minimum energy (or whatever) required to achieve that purpose.
 The purpose of an electric blanket is *not* to heat a room, it is to
make an individual human being more comfortable *without* heating the
room.  Grandpa can feel warm without requiring the thermostat at 90F.
 Note that the "blanket" part of an electric blanket is important.
Without insulation most of the heat produced electrically will be wasted
by heating the cold room, since the room is cooler than the person
warmed.  Most people that actually use electric blankets put more
blankets over them for this reason.
 What is the theoretical minimum heat required to make an individual feel
warm?  Every living human being produces metabolic heat constantly,
which must be lost to the environment to prevent overheating.  A 2000
Kcal/day diet implies an average power output of 97W, almost all of
which is heat for a typical sedentary person.
 The minimum heat required is the heat inevitably lost to the environment
less metabolic heat.  For a typical electric blanket application I'm
guessing the heat lost is mostly due to respiration (sensible heat and
latent heat of the moisture added to exhaled air).
 You're welcome to compute that; it should be easy once you estimate the
volumetric rate of respiration and assume a room temperature and
humidity.  I'm pretty sure the resulting efficiency of an electric
blanket is way below 100%.

Datuayins are on different channels.
Mr Krygowski is right regarding physics and the laws which yet obtain.
If you want to discuss efficiency in terms of product marketing (New! Heats gramps, not the room!) that's a different area.
--
Andrew Muzi
am@yellowjersey.org
Open every day since 1 April, 1971