Why can’t thermos cups or vacuumfoodcontainerbe used for direct external heating?

It's a short holiday again, and everyone's enthusiasm for traveling is high, especially those friends who like outdoor adventures and outdoor camping. For seasoned veterans, the tools to use outdoors, what to carry, and if it's safe to work outside are familiar. But for some newcomers and friends, in addition to the lack of tools and items, the most important thing is that there are many irregularities in outdoor work and even a certain degree of danger.

Regarding the fact that the thermos cup and the vacuum food container cannot be directly heated and used externally, the editor has a special explanation in the previous article. But the editor recently found out when I was watching a short video that someone was using a vacuum food container for direct external heating when they were camping outdoors. In the video, the other party is still wondering why the outside has been heated for 5 minutes, but the inside is still not heated. Fortunately, the other party finally gave up using the vacuum food container to heat and caused no danger.

Today, the editor will explain in detail again why the thermos cup and the vacuum food container cannot be directly heated externally.

Both the thermos cup and the vacuum food container are made of double-layer stainless steel, and both adopt the vacuuming process.

Both the thermos cup and the vacuum food container are made of double-layer stainless steel, and both adopt the vacuuming process. After vacuuming, the vacuum state between the double-layer stainless steel plays the role of heat preservation and rejection of temperature conduction.

Why does the editor say that it may be dangerous? If you continue to heat at a high temperature outside the thermos cup or vacuum food container, there is a professional term in the industry called dry burning. However, if the external temperature is too high or the high temperature heating time is too long, the outer wall of the thermos cup or the vacuum food container will expand and deform at high temperature.

Since the interlayer is in a vacuum state, once the outer wall is deformed or continuously heated due to high temperature, the tensile force of the material is reduced. Then the internal pressure will be released, the pressure released is huge, and the destructive force generated at the moment of release is also huge, so the thermos cup and the vacuum food container can be heated directly from the outside.

Then a fan friend asked, if there is no vacuumed stainless steel water cup or utensil between the double layers, can it be heated externally?The answer is also no. First of all, even if there is no air between the double layers, heating from the outside will greatly reduce the temperature conduction, increasing carbon emissions and a waste of heat energy.

Second, there is air between the double layers. The externally heated interlayer air will continue to expand as the temperature of the outer wall increases, allowing the expansion to a certain extent. When the pressure generated by the expansion is greater than the pressure that the outer wall can bear, it will explode, and the harm caused is also not small.

Finally, the editor recommends that friends who exercise outdoors, in addition to the thermos cup, if you want to use one thing with multiple functions, you can carry a single-layer stainless steel lunch box or a single-layer stainless steel water cup, which can meet the needs of external heating.