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We all know that small amounts of water will reach boiling point more quickly than one large amount. Then why do kettles only have one boiling chamber?
I propose a kettle which has six or more separate chambers. Each could have its own low-powered concealed element and when the kettle is filled,
these chambers would fill sequentially. The weight of the water could be used to determine how many of the chambers contain water. When the kettle is turned on, only the chambers that contain water are activated.
I don't know about the figures as yet, but I'm sure that boiling 6 x 200ml of water would be much quicker than boiling 1,200ml at once.
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As far as I can tell, this wouldn't be too different from having the same number of heating elements in various locations in a single chamber. |
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You might be right. In that case, it would use less energy for a smaller load, as for example only two of the low-output elements would be powered for a 400ml load. Wouldn't this be more efficient? |
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No, because by turning some of the elements off with less water you will increase the boiling time. A near empty kettle boils far quicker than a near full one. All this idea will do is to make the boiling time constant for a variable amount of water! |
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Ignoring heat loss, a given amount of water takes the same amount of energy to heat regardless of what size element you use. |
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//small amounts of water will reach boiling point more quickly than one large amount// |
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//boiling 6 x 200ml of water would be much quicker than boiling 1,200ml at once// ... Wrong. |
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Welcome to the halfbakery. |
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Puzzle: Which is quicker? Add the milk straight away to a cup of hot coffee, then wait for it to cool down the rest of the way; |
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Let the hot coffee cool down first, then add the milk?
(Or does it make no difference either way?) |
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Answer: The hotter coffee loses heat faster than the not-so-hot coffee, because of Stefan-Boltzmann's law (radiation is proportional to the fourth power of the temperature), and (probably more significantly) heat loss carried away by steam. |
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Therefore the second method is (slightly) faster. |
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By this reasoning, for the same amount of power heating small batches of water would actually take longer than heating water in bulk, because of the insulating effect of the cooler water. |
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Must think these things through!
Thanks for the feedback, anyway. |
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You may be on to something anyway though... One of the biggest energy wastes (=money waste =CO2 production) in our world is people (like my partner!) boiling a full kettle for one mug of tea. If you designed a kettle that had a chamber at the bottom from which the kettle poured (with a pipe from the chamber going up to the spout), you could boil the water using a 'one mug' switch for that chamber only, pour the water into the mug and the chamber would then refill with cold from the full kettle above. If you needed more, you would use the 'full kettle' switch which would boil both chambers at once. I must say this site regularly tests my ability to describe visual concepts in words - hope this all makes sense. |
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[wagster] Sounds a bit like [million]'s intelligent kettle (see above). |
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For one cup, why not use the microwave? |
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Yeah, croissant for [million]. He doesn't seem to have thought about how to do it, but I do the the 'press once for one mug / press twice for two' bit. |
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Henceforth you shall be known as 'Lateral Ling'... |
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As Boy Scouts, we boiled water in paper kettles. |
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Is Lateral Ling flattering or am I getting a battering? |
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Lateral's generally a good thing round here! |
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//The hotter coffee loses heat faster than the not-so-hot coffee, because of Stefan-Boltzmann's law (radiation is proportional to the fourth power of the temperature)// |
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radiation is the least contributor to the heat trasfer discussed herein. Mostly convection, some conduction. Of course, mccracken, your still right, as all heat transfer methods are proportional to temperature difference. |
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If heating elements could be added to the metal walls inside the kettle, then the water would surely heat faster. This is because heat transfer is porportional to surface area as well, which wil be significantly increased if heating elements are added to the walls. |
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of course, even solid body walls will tranfer heat to the surrounding water faster than the single mass of water will. heat will flow faster, though not much. However, the change could be noticed statistically, probably 20 seconds or so... I'd put money on it... |
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and the integrity of all the thermodynamics classes I ever took in college... |
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Add heating elements inside the inner walls of the kettle, get a bun. |
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