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From: AMuzi <am@yellowjersey.org>
Newsgroups: rec.bicycles.tech
Subject: Re: Suspension losses
Date: Thu, 16 Jan 2025 13:13:15 -0600
Organization: Yellow Jersey, Ltd.
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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