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A heavy stainless teapot with a pressure
valve on top and a small hand pump
attached. The pour spout is a ball toggle
valve with a handle. This handle cannot
be turned unless the pressure has been
vented.
Prior to heating, the kettle is filled with
water and pumped up to about 10 psi.
Then the heat is applied.
Once the temperature rises enough for
the water to boil at atmospheric pressure,
the pressure in the kettle is released, the
ball valve is opened, and the water is
poured.
[link]
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What a stupid idea. This thing would
probably explode. Steam burns, anyone? |
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I forgot to mention that it would have
about three pressure release valves and
that it should not be used in households
with anyone. |
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I'm trying to figure out why a tea kettle needs to be pressurised by air pump....is it a safety device? I really don't like encolsing boiler vessels in the home. I'm even nervous about pressure cookers, although I know they are perfectly safe. My mother accidentally opened a PC before the steam had completely released...she was burned pretty badly. |
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There's a direct relationship between pressure and temperature. I'm assuming that pre-pressurizing the vessel would make it heat up a lot faster. I may be wrong. |
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//I'm assuming that pre-pressurizing the vessel would make it heat up a lot faster. I may be wrong.//
Well I guess technically you are right, because the pressurized air is slightly hotter than unpressurized, but in reality 10psi isn't going to make measurable difference. |
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Leave it 3/4 empty and pressurize it up to 300psi and you probably would see some change, but remember there is no free lunch. The energy you are adding comes from you pumping the pressure up. |
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Check your bike tires after they are brought from flat to 80psi (if they will take it), they are a little warm. |
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the relationship between presure and temperature is a direct one. If you take a fixed volume of gas and then increase its volume while maintaining the same mass of material, the temperature will decrease, likewise if you compress that material to a smaller volume the pressure will increase. In both circumstances you are doing work to bring about the change in temperature. If the mass of water in the kettle is the same it will still require the exact same amount of heat input to rise the temperature from room temp to 100 degrees C. If the kettle is at ambient presure it will begin to boil, if however it is at an elevated pressure it will have to reach a higher temperature to boil. It is this same relationship that explains those high altitude cooking directions you see on macaroni boxes, the lower presure means the water boils at a lower temperature(and thus cooking takes longer). |
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When a fluid reaches it boiling point the temperature of the fluid and the resulting gas remain at a constant temperature until ALL the fluid has turned into a gas. So with water no matter how high you set the burner the temperature in the kettle will not exceed 100 degrees C. If the kettle could be presurized then the temperature could be increased higher allowing for greater extraction of chemicals from the tea. |
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So to get back to the idea at hand, the kettle of this design will not in any way change the time it takes to boil the water and it could not produce water at any hotter temperature than a normal kettle(as once you release the pressure, the water will return to 100C and release a lot of steam.) |
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"Once the temperature rises enough for the water to boil at atmospheric pressure" - well, that's 100C any way you cut it. But releasing the pressure will lower the temperature, as the steam/water mix expands. So the resulting water will be cooler than 100C and you won't have gained anything from your contraption. |
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But, if you made that a pressure teapot, not kettle, you might well be able to get the tea to steep (brew) faster, by heating the water well above 100C. (Much the same way a superheated pressure cooker cooks food faster.) But tea brews pretty quickly anyway, compared to how long it takes to boil water, so you won't gain much. |
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This might, however, be useful at higher altitudes, where water boils at lower temperatures. Tea made at 15000 ft doesn't taste right, but use the same water and tea bags and electric boiler at sea level and it's fine. |
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Water under pressure, heats up to a higher temperature than at atmospheric pressure. When you finally release the pressure, the water will instantly vaporize and boil furiously until the temperature reduces to 100 C, when the remaining liquid, if any will boil at an ordinary rate. Some people call it exploding. Hence, I doubt you will be able to pour super-heated water into a cup for tea. |
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So, folks, watch-out unless you want to experience the pleasure of super-heated water vaporize. |
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Actually, good science for the wrong
reason. |
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It will boil faster, because you won't be
generating lots of steam as the water
approaches boiling point. In a
conventional kettle, quite a lot of energy
(or 'a large amount', if you prefer metric) is
wasted in producing steam while the water
is between 90 and 100 °C |
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Nope max still bad science, what you are describing comes from uneven heating of the water. no energy is being lost it is just not evenly distributed. |
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Nope, Jhomirigaus, good science. |
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Hold your hand over the spout of a kettle
until a few moments before it comes to
the boil. |
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The pain you will feel is caused by what,
exactly, if not very hot water vapour? And
the energy for that comes from where,
exactly, if not the kettle? |
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The hand pump is pointless--leave it off. The heating from the fire would add that much energy and pressure in just a few seconds, but there is NO need for excess pressure in the kettle at 100C, the normal boiling point for standard pressure. |
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The pressure lid (which isn't actually mentioned in the idea, just assumed) will function even better than a standard lid at holding heat in the pot as passive insulation. Up near 100C, it WILL do as [MaxwellBuchanan] says, and keep vapor from escaping, evaporating and cooling the pot. So that's all good. |
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However, at exactly 100C, the pressure in the pot will still be at standard atmospheric pressure. (Right, [MaxBa]?) That's the laws of physics, innit? Well, if sealed up or
pumped up it'll be higher, but releasing pressure will drop everything back to 100C, and even lower through expansive cooling, as was said above. If sealed up, the pressure will start to climb, as will the temperature above 100C. If left long enough, either the valve will pop or the kettle will blow up. But if pulled off the fire at 100C, it's just a teakettle with an irritating lid. |
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The pressure kettle is faster than a lidless kettle, and perhaps somewhat faster than a comparable non-pressure lidded kettle. (Variables include the insulation of the kettle, the surface area and the heat of the fire.) Practically, the thing reduces down to a whistling teakettle. |
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//at exactly 100C, the pressure in the
pot will still be at standard atmospheric
pressure. (Right, [MaxBa]?)// |
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Errr, well, Kandinsky's law applies, but
when you get close to the boiling point
it breaks down and you're more into a
Pinot/Grigio equilibrium across the
phase boundary. Of course, nucleation
caused by limescale particles will pull it
more towards a Bose and Orfer
condensate, and you know what
THEY're like! |
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//Bose and Orfer condensate// - never actually seen one, but I'm guessing it'd be "grand" for tasseography, what with the photonic time-distortion & all... |
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Yes max at some minutely inconsequential level some miscule quantity of heat is released that would be retained by the OPs fancy lid, however this is not what the OP intended or believed with the idea, if it where than the idea would be no different than me posting about an extra insulated Tea Kettle. |
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Lets not split hairs here. the OPs idea is flawed by bad science and that is the bottom line. |
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I'll accept "bad science", 'though I'd call it "a bad understanding of science", instead. I mean, compared to some of the whackoddity we get here, this is a tempest in a teakettle. The design might not do any better than a normal kettle, but at least it would allow the water to get hot. |
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And have a chance of geysering the skin off your face, too. |
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I don't see what the pump is for, but an electric teakettle with an enclosed boiler that shuts down when it hits a certain internal atmospheric pressure sounds doable. |
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[marked-for-tagline] //sounds doable// |
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I am boning this idea to prove that this world is a cruel and arbitrary place. |
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//I don't see what the pump is for// |
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I don't either. It may have been meant to save heating time, on the assumption that this thing needed pressure, which it doesn't. |
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But the energy available from a hand pump is a minuscule fraction of the energy coming from the fire. So it's pointless to use a hand pump, even if pressure was wanted. Just give it a half-second on the stove, and more energy is gained than muscles could put in in half an hour. |
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Here's a handy comparison of human-power and stove-power: Get out your tea kettle and a polishing cloth. Polish up the bottom of the teakettle, really putting your elbows into it, for one minute. Then press the bottom of the kettle against your cheek, and see if you can feel the heat that your work put into the kettle. Next, pop the empty kettle onto the fire for one minute. Then press the bottom of the kettle against your cheek, and see if you can feel the heat that your stove put into the kettle. Compare and contrast. |
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To heat 1 liter of water from 30C to 100C requires the input of 70,000 calories of energy. The typical person burns about 3000 calories on an average day. You can do the math from there. |
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I told you it was a stupid idea. |
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// You can do the math from there.// |
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Sometimes, it's as well to use common
sense as a backup to doing the maths |
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A person burns about 3000 KILOcalories
per day. The problem is that dieters
typically say "calorie" when they mean
kilocalorie. Did you seriously imagine
that a person's total energy
consumption over 20 days would be
insufficient to heat a litre of water? |
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// person's total energy consumption over 20 days would be insufficient to heat a litre of water // |
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Well, if you take the brainpower of some of the contributors here as your metric .... |
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