[Stoves] radiant heat capture, total heat measurement

[ajheggie at gmail.com]

On Sat, 10 Mar 2012 18:58:43 +0000 (UTC), rongretlarson at comcast.net
wrote:

>1. The last several paragraphs below are coming out more negatively on radiant heat capture than I think are appropriate. Remember, the initial information provided by Paul Olivier on March 2, when he said: 
>
>"When a wire mesh dome is placed on top of the burner and burner housing, 
>this roughly doubles the amount of heat being transferred to a pot: " 

Please see my other post today. I cannot judge the power emitted by
the radiant dome without an idea of its temperature  and cross section
subtended by the pot, even then my maths is rusty. Then we would also
need the massflow and temperature after the dome and temperature above
the pot.
>
>2. I think this doubling has little to do with the exchange below (and a few earlier that are similar). Radiant heaters are widely sold because of their efficiency in heat transfer - in many cases involving zero convection. 

Zero convection because there is zero mass flow? Electric radiant
heaters being the prime example. Of course we can consider the
possibilities of a gas fired radiant heater that uses staggered
radiating elements, from cherry red down to black heat and discards
the flue gas at a lowish (250c??) temperature that is comparable with
a conventional convective heater with similar exhaust temperature but
here we have one radiating element, the strainer/dome, at,guessing,
~1000C.



>Given we have only one (above) piece of data for one stove, the chances are that a doubling is not the maximum we can achieve. 
>
>3. I would look at this as a conservation of energy problem. We know that we can transfer more energy to the pot if the radiator is hotter. There may be catalysts that we can employ. We know how to use reflectors and obtain high absorption (and sometimes simultaneously low emissivity ) 
>In my reading on ceramic foam, I found that some foam is being employed so as to have gas combustion take place inside the foam!. 

We used a catalytic ("flameless") burner on the little recirculating
wood dryer I demonstrated to you many years ago. Yes I do like the
idea of the combustion taking place within the ceramic foam, it allows
micro mixing (Turbulence), high Temperature as there are few heat
losses in the tiny spaces and long dwell Time as the gases find their
way out.

AJH