[Stoves] radiant heat capture, total heat measurement

Kevin kchisholm at ca.inter.net
Wed Mar 7 15:54:27 CST 2012


Dear Frank
----- Original Message ----- 
From: "Frank Shields" <frank at compostlab.com>
To: "'Discussion of biomass cooking stoves'" 
<stoves at lists.bioenergylists.org>
Sent: Wednesday, March 07, 2012 5:30 PM
Subject: Re: [Stoves] radiant heat capture, total heat measurement


> Stovers,
>
> Quick question - does radiant heat require the subject be 'n sight' of the
> object being heated?

"Radiant Heat" is basically the same as "conventional light", in that it 
goes in straight lines, but can be reflected. A "low emissivity" surface, 
such as polished silver, will reflect "radiant heat" to areas that cannot 
"see teh source" directly. (Same as a mirror will reflect light "around 
corners.")

Best wishes,

Kevin
>
> Thanks
>
> Frank
>
>
>
>
> -----Original Message-----
> From: stoves-bounces at lists.bioenergylists.org
> [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of Richard
> Stanley
> Sent: Wednesday, March 07, 2012 12:27 PM
> To: Discussion of biomass cooking stoves
> Subject: Re: [Stoves] radient heat capture, total heat measurement
>
> Andrew,
> Its the old quandry of  Brownian movement then, eh ?
>
> Still that "sense we an animals all have of "heat' and "warmth "
> remains well beyond degrees of temperature oer se.
> Something missing between science and perception that unless clarified and
> quantified would seem to leaves stove performance assessment abit untidy.
>
> Richard Stanley
> www.legacyfound.org
> =======
>
> On Mar 7, 2012, at 11:44 AM, ajheggie at gmail.com wrote:
>
> On Tue, 6 Mar 2012 07:47:03 -0800, Richard Stanley wrote:
>
>> If radient energy is the mother and conductive convective "heats" are
> added expressions of it,  then why does one rely only upon measurement of
> thermal heat only in these more tangible but not necessarily more
> influential bands of the spectrum,  as the standard  measure of cooking
> efficiency ?
>
> I suppose it's to do with what means we have of producing the power to do
> the cooking, fire is the easiest way of liberating the energy and
> transferring it to the cooking pot. Plants have concentrated sunlight into
> wood.
>
> Light can plainly be used for heating, didn't one of the ancient greeks
> write of the concentrated beams reflected from polished bronze shield
> setting fire to ships rigging?
>
>> Micro waves in themselves are not "hot" but they do a wonderful job of
> heating by disturbing molecules, just as the visible band of radiation we
> call heat, does.
>
> Presumably there was no evolutionary advantage in having an organ that can
> sense infra red in the same way eyes interpret light but many animals do
> have increased sense of warmth, snakes can hunt by it.
>
> Microwaves for cooking have only become commonplace in the last 60 years
> but the principle is the same as other means of heating, they selectively
> excite water molecules. The microwave radiation is tuned to deliver in
> frequencies which water molecules will accept in discrete amounts, 
> otherwise
> they would just pass straight through.
>
>> My naked supposition is therefore, that beyond a normal thermometer or 
>> one
> measuring just IR, one needs a more comprehensive "molecule disturbing"
>> measurment device
>
> A thermometer is something that reacts to change in temperature, it 
> doesn't
> measure the activity of molecules but rather compares the effect the
> molecules have on a substance.
>
> I don't think it is possible to directly measure the state of a molecule
> without changing it.
>
> AJH
>
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