Path: news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail
From: Radey Shouman <shouman@comcast.net>
Newsgroups: rec.bicycles.tech
Subject: Re: Suspension losses
Date: Thu, 16 Jan 2025 17:47:23 -0500
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Frank Krygowski <frkrygow@sbcglobal.net> writes:

> On 1/16/2025 1:38 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.  
>
> I guess it's possible to define the Desired Output more and more
> narrowly, down to "The heat delivered to the parts of the body that
> have nerve endings that detect temperature." IOW, if Grandpa's hair
> and toenails get warmer, that's wasted heat. But I think few people
> want to go to that extreme.
>
> Slightly more reasonable would be to demand wrapping the electric
> blanket around Grandpa, like a sleeping bag, then wrapping that with a
> perfectly adiabatic blanket. All the heat would eventually go into
> Grandpa.

The only thing I demand is a meaningful definition of efficiency for an
electric blanket.  I proposed one, and I haven't seen any others.

Your "perfectly adiabatic blanket" does not address respiration, unless
it has a perfect heat exchanger between air in and air out, which is
water saturated.  If it worked, then Grandpa would die of overheating in
short order, without an electric blanket, cold blooded though he might
be.

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