this post was submitted on 29 Nov 2023
106 points (97.3% liked)
Technology
59292 readers
4136 users here now
This is a most excellent place for technology news and articles.
Our Rules
- Follow the lemmy.world rules.
- Only tech related content.
- Be excellent to each another!
- Mod approved content bots can post up to 10 articles per day.
- Threads asking for personal tech support may be deleted.
- Politics threads may be removed.
- No memes allowed as posts, OK to post as comments.
- Only approved bots from the list below, to ask if your bot can be added please contact us.
- Check for duplicates before posting, duplicates may be removed
Approved Bots
founded 1 year ago
MODERATORS
you are viewing a single comment's thread
view the rest of the comments
view the rest of the comments
Radiant heat transfer in the real world often appears quite odd in its behaviour despite being seemingly simple. I learned quite a bit about it when I decided to implement radiant ceilings in my home.
Yes, the panel radiates the same amount regardless of where it's pointing. However, other rays are incident on it from other surfaces that deliver heat back to the surface. Thus the point of a selective emitter that emits more than it absorbs. Likewise solar thermal panels are optimally made from selective absorbers, but IRL flat black paints are so much cheaper that it's not worth it.
So thermal comfort often is a result of radiant balance. Your 20° clothing radiates to the walls - the 20° walls radiate to you - there is no net loss of heat, and you are warm.
Step out under the dry, cloudless prairie sky at night, you radiate into the infinite blackness of space. Nothing radiates back. You cool off rapidly. It's not so much that the heat needs to be dumped into space, but that space offers no heat in return.
Seriously it's pretty neat to point my thermal scanner at the night sky and see it read -INF. The night sky is an effectively unlimited radiant sink.