The return of incandescent bulbs?

[izentrop]

when you put a light source in a closed opaque box the light energy will end up in heat: at each reflection a part is reflected and another part not reflected is transformed into heat ... and after the number of reflection it everything must be in heat

Like an ultra-thin insulation? We have seen that thin insulators do not work

[Gaston]

Like an ultra-thin insulation? We have seen that thin insulators do not work

It is obvious that energy ends up leaving the box: since it is heated, its temperature increases and it therefore re-emits energy in the form of radiation (and convection if it is not in a vacuum) .
Nevertheless it has absorbed all of the energy supplied (including the visible part, UV, ...)

[Christophe]

Ok thank you Gaston, Mea Culpa, well I have to do a remedial session in wave physics ...

[izentrop]

It is obvious that energy ends up leaving the box: since it is heated, its temperature increases and it therefore re-emits energy in the form of radiation (and convection if it is not in a vacuum) .
Nevertheless it has absorbed all of the energy supplied (including the visible part, UV, ...)

Another detail which I had not thought of.
Indeed there is an almost perfect vacuum in the bulb, so no convection.
For the moment they are announcing a yield of 6.6%, there is still a long way to go.
I understand it like this: The thermal energy escaping with more difficulty, it is that less to provide to the filament to maintain its color temperature at 2700 k

[Gaston]

I understand it like this: The thermal energy escaping with more difficulty, it is that less to provide to the filament to maintain its color temperature at 2700 k

Absolutely.

[chatelot16]

useless to calculate in detail what will be transformed into heat with each reflection, only one thing is on, if the box is opaque, the number of reflection will be sufficient to transform everything into heat ... but what equation to give?

a filament lamp heats little by convection but a lot by infrared radiation: it works without problem in poorly cooled luminaires

LEDs are the opposite: they do not radiate infrared at all, they need to be cooled by convection, and in addition they require to be kept very cold to have a good lifespan ... this is a puzzle in the lighting provided for old lamp

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