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The Problem with Microwaving Tea:
Typically, when a liquid is being warmed, the heating source — a stove, for example — heats the container from below. By a process called convection, as the liquid toward the bottom of the container warms up, it becomes less dense and moves to the top, allowing a cooler section of the liquid to contact the source. This ultimately results in a uniform temperature throughout the glass.
Inside a microwave, however, the electric field acting as the heating source exists everywhere. Because the entire glass itself is also warming up, the convection process does not occur, and the liquid at the top of the container ends up being much hotter than the liquid at the bottom.
A team of researchers from the University of Electronic Science & Technology of China studied this nonuniform heating behavior and presents a solution to this common problem in the journal AIP Advances, from AIP Publishing.
By designing a silver plating to go along the rim of a glass, the group was able to shield the effects of the microwave at the surface of the liquid. The silver acts as a guide for the waves, reducing the electric field at the top and effectively blocking the heating. This creates a convection process similar to traditional approaches, resulting in a more uniform temperature.
Placing silver in the microwave may seem like a dangerous idea, but similar metal structures with finely tuned geometry to avoid ignition have already been safely used for microwave steam pots and rice cookers.
Journal Reference:
Peiyang Zhao, Weiwei Gan, Chuanqi Feng, et al. Multiphysics analysis for unusual heat convection in microwave heating liquid [open], AIP Advances (DOI: 10.1063/5.0013295)
(Score: 0) by Anonymous Coward on Wednesday August 05 2020, @04:28PM (2 children)
That story is funny, but also apocryphal... and also a good example of those "stupid government stories" which shows that narrow minded-ness of critics of the government.
Specifically, pencils are (1) flammable, and (2) leave dust and shards floating when being used. Both of those are very bad in a closed microgravity environment.
It's like the story of the $5000 wrench (which is guaranteed to not spark when struck against metal... would you want to use a regular $5 wrench when working next to large containers of jet fuel?).
(Score: 2) by tangomargarine on Wednesday August 05 2020, @05:53PM (1 child)
You say this, but you know that the Apollo 1 tragedy was partly due to the fact that they launched manned rockets with 100% oxygen atmosphere inside, right?
Just because people are critical of the government doesn't mean the government doesn't also do stupid things sometimes.
If the fuel is inside the containers, and properly insulated? Sure, why not?
"Is that really true?" "I just spent the last hour telling you to think for yourself! Didn't you hear anything I said?"
(Score: 2) by deimtee on Wednesday August 05 2020, @11:11PM
Not just pure O2, but it was over-pressure as well. 16psi at the time of the fire.
If you cough while drinking cheap red wine it really cleans out your sinuses.