'Where is my damn coffee?'
So if you were like me you boiled some water this morning for fix of caffeine found in a cup of coffee. When man first boiled water for soups, pasta and later damn coffee he likely did not take care to really understand boiling. Man just wanted some coffee but did not take the time to look into the pot. Now that we have a little more time on our hands we can really take the time to look into the pot and see the boiling in action.
Boiling can be divided into two regimes: 1) Buoyancy dominated boiling 2) Surface tension dominated boiling. The buoyancy dominated boiling is the one found common on Earth. This is the one you see when boiling the water for your damn coffee. As the water is heated and vaporizes into a bubble the bubble grows and is held on the surface by surface tension forces. These push the bubble off the bottom of the pos so it rises out of the water. Liquid rushes behind the bubble works its way (through convective forces) and the boiling repeats until you get water for some damn coffee.
What happens in space? At lower gravity levels like in space the boiling behaviour is controlled more by surface tension dominated boiling. One single bubble covers a large portion of the heater surface. This could be a large bubble and its size is determined by the vaporization of the liquid, the smaller bubbles that feed it, condensation of vapor at the top of the bubble and lastly the surface tension of the liquid.
So the astronauts determined after several experiments that boiling water to make damn good coffee is different in space than it is on Earth. I wonder if the coffee tastes better?
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