463
29Instructables1,891,925Views283CommentsRedwood City, CAJoined December 16th, 2007
A Bay Area native interested in electronics, mechanics, and robotics, and automobiles. Formerly the electronics captain of Team 100 in the FIRST Robotics Competition, I now study Mechanical Engineering at UC Berkeley and participate as suspension assistant on Team Cal Simraceway, the school's FSAE team. Last summer I interned at Autodesk & Instructables' Pier 9 workshop, helping to develop Autodesk's CAM software. This summer I'll be interning at Alloy Product Development in San Francisco!

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• Awesome idea! You've got about a quarter of the story as to why this works. The first bit, like you said, is that rotating the can continually exposes "new" fluid to the inside surface of the can, making heat transfer into the ice water more efficiently. In addition to this, the same is happening with the ice water on the outside of the can, exposing "new" cold water to the outside surface. Convective heat flux is described as h*(T_s - T_infinity), so the greater the difference in temperatures around the area of interaction, the higher the heat flux. But see that h in the equation? That's the convective coefficient, and that also increases when you spin the can. h is proportional (though not linearly) to the relative velocity of the two mediums, so spinning the can t...

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Awesome idea! You've got about a quarter of the story as to why this works. The first bit, like you said, is that rotating the can continually exposes "new" fluid to the inside surface of the can, making heat transfer into the ice water more efficiently. In addition to this, the same is happening with the ice water on the outside of the can, exposing "new" cold water to the outside surface. Convective heat flux is described as h*(T_s - T_infinity), so the greater the difference in temperatures around the area of interaction, the higher the heat flux. But see that h in the equation? That's the convective coefficient, and that also increases when you spin the can. h is proportional (though not linearly) to the relative velocity of the two mediums, so spinning the can thereby increases h as well! If you're interested in the specifics of this, look up Nusselt Number correlations.

• 1 year ago

You can draw current at whatever rate you'd like, up to the burst rate.

• 2 years ago

Great, so it sounds like we're in agreement that KofiA5 should stick with OEM batteries :)

• 2 years ago

Ehhh, I wouldn't recommend it. It's probably a 1S2P pack, so there are two cells in there. The tablet could be reading voltages from both cells while in use, so dropping in a single cell LiPo could confuse and/or damage it. Unless it's an OEM part or you've read of other people doing this for your particular device, I wouldn't risk it.