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JMac
JMac
13:37
@RichardTingle Do you have any source for that? As far as I know most of the energy from a lightbulb should be radiation, which will heat up any surfaces that the radiation can reach. Generally lights dont just light up the ceiling (and even that would cause the people in the room to heat up from the radiation of the heated ceiling)
 
1 hour later…
Richard Tingle
Richard Tingle
14:48
@JMac See mrsec.psu.edu/content/light-bulb-efficiency for a reference. Incandescent blubs only emit 10% of their energy as light (they are physically very hot to touch). The rest as heat. That's why everyone hates them (LED bulbs are much much better). [But we're getting off topic; the point I'm making is that it's plausible for different formats of heaters to be better/worse in practice despite both theoretically being 100% efficient]
 
1 hour later…
JMac
JMac
16:13
@RichardTingle That doesnt suggest that most of the heat goes near the ceiling, which is why I wanted a source. I would think most of the heat released is still through radiation, and so it wouldnt just spread based on closeness, or worry much about heat rising. It would produce what is generally the most "comfortable" type of heat.
 
1 hour later…
Richard Tingle
Richard Tingle
17:18
@JMac I don't really know how much of a light bulbs wasted power goes into infrared (that escapes the bulb) vs how much remains as thermal heat in the bulb. But it doesn't really matter (it was just an example of an electric heater), it clearly is red hot to touch (even after being turned off) so clearly plenty goes into heat directly at the bulb
 
2 hours later…
JMac
JMac
19:01
@RichardTingle None of that means that a light is mostly heating the ceiling. Like I understand what you are trying to get at, but a lightbulb might be a really bad example. Radiant ceiling tiles actually work quite well for human comfort heat, for example. I'd say if anything a light is closer to a low power radiant panel than something that warms the air in the top of the room

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