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I’m trying to wrap my head around this. While shielding the focus from receiving any thermal radiation via surrounding objects ( ground, etc) you also provide a

I’m trying to wrap my head around this. While shielding the focus from receiving any thermal radiation via surrounding objects ( ground, etc) you also provide a 360 degree thermal radiation heat sink, making it as easy as possible for whatever is at the focus to shed heat?

ColinWright 7y ago
Yup. http://solarcooking.org/radiant-fridge.htm http://solarcooking.org/radiant-fridge.htm
- SamBam 7y ago
  Your description does not appear to be correct. Ice is not being formed at the "focal point," ice is being formed under the reflector. You can't focus coldness. "Cold" radiation is simply less radiation. When you focus it, you get more radiation, not less of it. More radiation means more energy. Instead you're simply seeing the effect of radiative cooling. See "Nocturnal ice making in Early India and Iran" [1]. By insulating the sides of a pan of water, and leaving the only window for radiation pointed to the night sky, you're ensuring that more radiation is leaving the water than entering it. Thus the water cools down. So it would work equally with an insulated box with high walls. It's not about focusing the coldness. [1] https://en.wikipedia.org/wiki/Radiative_cooling#Nocturnal_ice_making_in_Early_India_and_Iran https://en.wikipedia.org/wiki/Radiative_cooling#Nocturnal_ic...
  - ColinWright 7y ago
    I have a feeling we're talking past each other, and I'm not going to bother addressing everything you've said point-by-point. Experiments show that have a parabolic reflector configured correctly results in a stronger effect. You're not focusing coldness, but the radiation from the body being cooled emerges in every direction, so putting it at a parabolic focus ensures that all the radiated heat gets directed outwards to the night sky. Yes, simply having an insulated container and having an opening pointing at the sky does work, but it's not the best you can do.
  - likpok 7y ago
    The focusing effect will help, because you're focusing the infrared radiation from the object away. If you have an insulated box with tall sides, radiation from the object will reflect from the sides of the box back to it, keeping it warm (or less cold).
- drdrey 7y ago
  Off topic, but what's with the spammy links at the bottom of this page? Did the site get hacked? Screenshot: https://imgur.com/a/Oz4XEhy https://imgur.com/a/Oz4XEhy
  - delinka 7y ago
    Not seeing it. You got hacked? Plugins maybe?
    - ColinWright 7y ago
      They are there, and deliberately coded to render as invisible. This is the URL: http://solarcooking.org/radiant-fridge.htm http://solarcooking.org/radiant-fridge.htm Pull the source and look at the last few lines. Alternately, hover your mouse over the area at the bottom of the page and look at the URLs it would go to if you click. I've tried contacting the author but the email no longer works. I've not yet contacted the site owner.
      - delinka 7y ago
        I did view the source, but I was expecting exactly what GP screencapped rather than a single line. So, yep, it's there.

ColinWright 7y ago

Yup. http://solarcooking.org/radiant-fridge.htm http://solarcooking.org/radiant-fridge.htm

SamBam 7y ago
Your description does not appear to be correct. Ice is not being formed at the "focal point," ice is being formed under the reflector. You can't focus coldness. "Cold" radiation is simply less radiation. When you focus it, you get more radiation, not less of it. More radiation means more energy. Instead you're simply seeing the effect of radiative cooling. See "Nocturnal ice making in Early India and Iran" [1]. By insulating the sides of a pan of water, and leaving the only window for radiation pointed to the night sky, you're ensuring that more radiation is leaving the water than entering it. Thus the water cools down. So it would work equally with an insulated box with high walls. It's not about focusing the coldness. [1] https://en.wikipedia.org/wiki/Radiative_cooling#Nocturnal_ice_making_in_Early_India_and_Iran https://en.wikipedia.org/wiki/Radiative_cooling#Nocturnal_ic...
- ColinWright 7y ago
  I have a feeling we're talking past each other, and I'm not going to bother addressing everything you've said point-by-point. Experiments show that have a parabolic reflector configured correctly results in a stronger effect. You're not focusing coldness, but the radiation from the body being cooled emerges in every direction, so putting it at a parabolic focus ensures that all the radiated heat gets directed outwards to the night sky. Yes, simply having an insulated container and having an opening pointing at the sky does work, but it's not the best you can do.
- likpok 7y ago
  The focusing effect will help, because you're focusing the infrared radiation from the object away. If you have an insulated box with tall sides, radiation from the object will reflect from the sides of the box back to it, keeping it warm (or less cold).
drdrey 7y ago
Off topic, but what's with the spammy links at the bottom of this page? Did the site get hacked? Screenshot: https://imgur.com/a/Oz4XEhy https://imgur.com/a/Oz4XEhy
- delinka 7y ago
  Not seeing it. You got hacked? Plugins maybe?
  - ColinWright 7y ago
    They are there, and deliberately coded to render as invisible. This is the URL: http://solarcooking.org/radiant-fridge.htm http://solarcooking.org/radiant-fridge.htm Pull the source and look at the last few lines. Alternately, hover your mouse over the area at the bottom of the page and look at the URLs it would go to if you click. I've tried contacting the author but the email no longer works. I've not yet contacted the site owner.
    - delinka 7y ago
      I did view the source, but I was expecting exactly what GP screencapped rather than a single line. So, yep, it's there.