[Gasification] [Stoves] Radiant heat and heat transfer

[Thomas Reed]

Dear Andrew and All:

Heat is transferred by radiation, convection and conduction.  But 
radiation increases as T^4, while the other two only increase as T, so 
at higher temperatures (over for instance 500C) you can forget convection. 

Even at room temperature we are sensitive to the radiation from our 
bodies and can feel warm at 30F in the sunlight and cold at 60 F under a 
starry sky.

TOM REED       BEF

andrew wrote:
> On Monday 26 November 2007 19:15, frank wrote:
>   
>> Stovers,
>>
>> Trying to understand radiant heat in our biomass stoves. Is this
>> the heat produced within the 'line of sight'
>>     
>
> Yes radiant heat energy is the same as light energy but in the infra 
> red  wavelengths, so we cannot see it only feel it. Any body emits 
> radiation if it is above absolute zero, given similar bodies the 
> hotter one emits more energy that it absorbs from the other and the 
> cooler one emits less than it receives.
>
>
>   
>> of the combustion: 
>> and also heat transfered by metal to water?
>>     
>
> No, this is conduction, where neighbouring molecules jostle with each 
> other the hotter one loses some of its excitement to the cooler 
> neighbouring one.
>
> The third means of transfer is convection where a fluid carries heat 
> from a hot area to a cooler one.
>
> What you later describe is like a heat pipe (look at the single pipe 
> steam systems used to heat high rise buildings before electric pumps 
> became cheaply available) but you haven't allowed for the mixing 
> with the flue gases which effectively mean you cannot condense all 
> the water.
>
> AJH
>
>
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