This is where your "hypothesis" is flawed like you MUNCHY...and I know you know more than these people. YOU FUCKING DON'T.
It was the reflective glass (mirror glass if you ever knew) that was the best insulator...not the vacuum.
A narcissist like you can't admit they don't know SHIT. You are one condescending egotistical know nothing.
Your quote:
Thermal radiation is not listed. Because much like your head, outer space consists mostly of vacuum. And "THERMAL RADIATION CAN'T TRAVEL IN A VACUUM " . Anybody who uses a thermos container should know there is usually a stainless steel vacuum bottle inside. They used to be made out of glass. And when you dropped it, and your thermos of coffee got hot on the outside, you knew you broke the glass
Down goes MUNCHY...down goes MUNCHY...down goes MUNCHY.
If heat can travel through a vacuum (radiation), then how is heat conserved in a thermal flask where the vacuum blocks the heat?
10 Answers
Robert Nolan
Answered Dec 28, 2017 · Author has 274 answers and 64k answer views
As others have touched on, a thermal flask with a vacuum layer mostly eliminates two forms of heat transfer - conduction (transfer via direct contact) and convection (transfer via a moving fluid such as a liquid or gas). It leaves radiation, sometimes mitigated to some degree by a reflective layer in the outer shell, but even without that reflective layer a key element of what makes this system effective is that radiation is itself much less effective in transferring heat than conduction and convection.
To highlight, consider three scenarios involving a hot stove (don't actually try the last one, please, and take care if you try the second) -
- Place your hand to the side of the burner. The burner is now radiating heat to your hand.
- Place your hand directly over the burner at the same distance. Since hot air rises, the air provides minor convection to transfer heat to your hand. For a more profound difference, throw a pot of water on the stove and put your hand over it in the steam once the water is boiling, or stir it with your hand as it heats up.
- Place your hand directly on the burner. Heat is now conducted directly into your hand.
I'm sure you can satisfactorily imagine which one transfers heat into your hand most effectively and which transfers least effectively.
265 views ·
Brian Turner
Answered Dec 28, 2017 · Author has 181 answers and 119.7k answer views
Because at the temperatures we use flasks, radiation is a really slow way for heat to move. Flasks also use another trick. They are made of shiny material. Shiny material has low
Emissivity - Wikipedia. That means it does not radiate heat well. It also tends to not absorb heat well. The small amount of heat that does radiate bounces around in that vacuum and has a 50/50 chance of absorbing back on the inside.
If you tried to use a flask at the temperature of a light bulb filament the heat would get out quickly.
Flasks are not perfect at keeping heat in or out, just really good at it.
291 views ·
View 3 Upvoters
Bill Otto, studied Physics & Chemistry at The University of Alabama in Huntsville (1976)
Answered Dec 28, 2017 · Author has 3.6k answers and 8.4m answer views
If you define thermal radiation as heat (I don’t) then it can travel through a vacuum. If you define heat this way then all electromagnetic radiation from VLF radio waves to gamma rays are heat. It just is not useful to call all EM radiation “heat.”
A thermal flask, known as a Dewar in the UK and a Thermos in the US, is coated with a polished low emissivity material like silver so that very little thermal radiation can be emitted. If it were black (high emissivity) then the amount of radiation would be much higher and the heat would escape (or get in as the case may be) in the form of radiation much faster.
Less expensive vacuum bottles are coated with aluminum instead of silver. They do not hold heat in as well as those coated with silver or gold.
609 views ·
View 5 Upvoters
James Cibulka, Physics Teacher
Answered Dec 28, 2017 · Author has 233 answers and 49.3k answer views
Thermal energy can travel through conduction (touching) convection (moving air or fluid) or radiation. Since the gap is vacuum sealed, the first two are greatly reduced (still touches at the top!) . . . . Leaving radiation. . . . Which is how it travels in space. . . . . They mirror the inside to reflect it back into the thermos, but nothing is perfect. . . . Some radiation still gets out.
Does this make sense to you?
Pradeep Saminathan, ASIC designer, INFP, Dreamer, Non-Theist, Creative, Destructive, Liar
Answered Dec 28, 2017
Even though radiation can travel through vacuum, the inner layer of a thermos flask is typically made reflective (Silver coated in case of traditional glass flask; Polished steel in case of a metal flask) . The reflective nature of the inner wall ensures that any radiation from the hot contents get bounced back in to the content.
Now there is a small amount of radiation that may escape through the top lid and tiny gaps between the neck and lid. But the non reflective surface area is typically much less than the total area the the hot content is in contact with. Narrower the neck , lesser the loss through radiation .
Conduction heat loss is minimized by using poor conductors in the lid and body.
Convection heat loss is minimized by the partial vacuum. Less air molecules, less convection.
229 views ·
View 1 Upvoter
