eli5: Why can hydro flasks (and all other thermoses) keep liquids cold for longer than they can keep them hot?
In: Other
Smaller temperature differential.
Cold drinks are, at lowest, 0C compared to a room temperature of ~20C.
The equivalent differential on the other side would be a 40C “hot” drink, which is just luke warm. A good hot drink is more like 80-90C, a ~60C+ differential.
The amount of heat that moves through a thermos basically scales directly with the temperature difference, so it’s losing heat from the hot drink a lot faster than it’s letting heat into the cold drink.
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