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Heat Recycling Coffee Mug

It cools, then it heats!
  (+13, -1)(+13, -1)
(+13, -1)
  [vote for,
against]

A well insulated coffee mug similar to those which already exist. There is one major exception. The bottom of this mug has a heat sink in it. The heat sink is attached to a peltier junction and a thermostat. You set the thermostat to a desired drinking temperature and the peltier junction converts the excess heat present upon pouring fresh coffee into the mug to electricity to be stored in a capacitor or battery. As the coffee cools, the energy stored from the earlier cooling is released slowly to maintain temperature. It solves two problems at once, no more scalding your mouth minutes after pouring coffee, and no more nasty cold coffee later.

i.e. 200degF coffee poured in. Peltier junction uses excess heat to generate electricity until coffee reaches 100degF. when coffee goes below 95degF, capacitor switches on passing current through a heating coil warming the coffee.

I don't know how efficient peltier junctions are or if the heat sink is necessary, and I'm not really sure how feasible this is, so this is pretty half baked. I appreciate all comments!

_____________________________

[marked-for-engineering] -- are peltier junctions the most efficient small scale mechanism for converting heat to electricity?

bleh, Jun 22 2007

peltier junction http://en.wikipedia...tion#Peltier_effect
it uses one of these [bleh, Jun 22 2007]

Musical mug Musical_20self-stirring_20thermo-mug
Artistic, with hydrodynamics, but - unfortunately - thermally passive. [lurch, Jun 24 2007]

Tea-Cooling Dart Tea-Cooling_20Dart
Conducts heat away, then shuts off. [baconbrain, Jun 25 2007]

Zincup Zincup
See 8th of 7's first anno [bleh, Jun 26 2007]

Hot cubes Hot_20cubes
for TIB [xaviergisz, Jun 26 2007]

Grind Beans... http://www.halfbake...0Container%3a%20Cup
reference to the HB's guide to making coffee [csea, Jun 27 2007]

Two Cups of Coffee Two_20Cups_20Of_20Coffee
[Ian Tindale's] classic zen koan [csea, Jun 27 2007]

refrig-i-bottle refrig-i-bottle
[bleh, Jun 28 2007]

Scientists Make Temperature-Regulating Coffee Mug http://www.physorg....print170425949.html
This looks very clever [hippo, Nov 16 2009]

[link]






       nothing, The heat sink is inside the mug in the coffee, the heat that escapes through it is what the peltier junction converts into electricity to be later rereleased as heat.
bleh, Jun 22 2007
  

       Apparently, from wiki, this takes advantage of the Seebeck effect and the peltier effect. the Seebeck effect converts the temperature differential into electricity, the peltier effect converts ot back to heat.
bleh, Jun 22 2007
  

       //I have a coffee flask with a steel chamber inside a vacuum. That would act as a heatsink and keep the coffee warm after reaching temperature equilibrium (100F). I'm not sure the electronics adds anything.//   

       Shirley it doesn't keep it at 100 deg forever. The vacuum (were it a perfect vacuum) would not act as a heat sink, it would just not let any of the heat escape via convection through the air. Since it is not a perfect vacuum, the little air that is in there does act as a small heat sink, but not enough to effectively heat the coffee. I have a mug like that too, and it'll keep warm for a good hour or so. A stanley thermos can keep coffee HOT for about 12 hours if you don't open it.   

       Here's the catch. The insulating cups keep your beverage hot (too hot to drink) until they reach a drinkable temperature. Then they slow the cooling by insulating. This idea takes the initial excess of energy (too hot to drink) and stores it as electricity. the insulating cup still maintains the drink at temperature for a while, slowly loosing heat to the environment. When the coffee reaches a heat set by the user on the thermostat, the electricity stored earlier is then converted back to heat to help your coffee stay around just a little longer.   

       how much a little longer would be is beyond me.
bleh, Jun 22 2007
  

       //Contrast that with a chunk of steel to reduce the coffee temperature initially and some good insulation.//   

       The problem is the chunk of steel you allude to does not know when to stop sinking heat. The described mechanism will stop sucking heat out when it reaches a certain point, then starts trickling the heat back in. were talking about at best a 25% efficiency here, so in my previous example, 200deg is poured in and cooled by the peltier junction to about 100 deg, we could feasibly convert that energy back into 25deg of heat. Thats not too shabby, depending on how its trickled back in.   

       It was an idea, I never said it was a good one. thanks for the bun. anyone else want to weigh in?
bleh, Jun 23 2007
  

       I think this is an excellent half baked idea. I think it would sell. Especially if you added other sources of energy to keep the coffee warm after it reaches drinking temp. Oh, and the temp needs to be dialed in. Some people like their coffee a lot hotter than others.(+)
Galbinus_Caeli, Jun 23 2007
  

       //Oh, and the temp needs to be dialed in. Some people like their coffee a lot hotter than others//   

       it is... //You set the thermostat to a desired drinking temperature and the peltier junction converts the excess heat //
bleh, Jun 23 2007
  

       Definitely an excellent idea - I'm fed up with coffee that burns, then goes cold. Doubt very much that this is feasible, but when did we ever need that around here?
wagster, Jun 23 2007
  

       The effectiveness could be readily improved by the simple expedient of washing the cup with very hot water before use. (I understand that some coffee-drinkers live in some kind of symbiosis with the grunge living in the depths of the mug, and would refuse to do any more severe cleaning than a quick leveling of the playing field with a napkin, but, whatever)   

       Make a separable junction in the space under the cup liner. When the coffee reaches the desired temperature, the lower half of the heat sink releases and drops to the bottom shell of the cup. This greatly reduces heat loss, plus creating a nice "thunk" alerting you that the kaffe-caustic is now safe to drink. The co-worker startlement at the noise is a nice benefit, too.
lurch, Jun 24 2007
  

       Forget the electronic version of this. We keep hearing about various little companies claiming to get 50% of Carnot efficiency, but have yet to see anything that can, in all practicality, do anything better than single-digits.   

       I propose my own, and admittedly made up on the spot without any research whatsoever, version of this idea:   

       Design a cup that has a hollow section within the walls that contains a phase-changing material, and an insulator. The insulator stops heat from transferring to the outside wall of the cup, while the interior wall is not insulated, and is exposed to the hot beverage (the inside wall being a good heat exchanger).   

       The phase change material is designed to go from a liquid to a gas at the temperature deemed to be optimal for, let’s say, coffee.   

       This is how it works:   

       Said cup is filled with steaming hot liquid beverage. The phase-change material rapidly begins to boil away into a gas, absorbing a great amount of energy from the beverage. It continues to boil until it has completely evaporated, at which point the gas continues to absorb energy until it equals the temperature of the beverage. At this stage, the temperature of the beverage should be just above optimal, and the gas somewhat pressurized.   

       As the beverage cools, the gas starts to condense at the predetermined temperature, giving up its energy to the drink thus tending to maintain the temperature around set point. Once all the gas has changed back to a liquid, normal cooling will ensue, but hopefully the beverage will have been consumed by that time.   

       Maybe there’s a real invention in this??   

       Edit:   

       Heater cubes (thermostasis cubes??), instead of ice cubes. Same idea as I just described, but all ya do is throw a few into your hot coffee and they do their magic. Just wash them when done and use again forever. Various cubes could have different set points for tea, coffee, sake, whatever. Sinker types may be a little more efficient, but not as cool as having, what looks like, ice in your coffee.
TIB, Jun 24 2007
  

       I think you could get most of what is discussed here by carrying a packet of clean stainless steel pellets. Drop in a few pellets at a time until the drink is at desired temperature. The now-hot pellets will keep the drink warm after that.   

       Gratuitous link to my Tea-Cooling Dart, which is similar to one of the annos.   

       I don't know enough about the topic to say if it would work or not, but I assume it works on difference in potential, so I think it's going to have a lot of losses.
baconbrain, Jun 25 2007
  

       //Make a separable junction in the space under the cup liner//   

       I had intended it to be, Just forgot to mention it in the body. Thanks.   

       on to another issue   

       The problem with the real heat sink ideas is that they would only work for a pre-calibrated amount of coffee at a particular initial temp. (I think, please correct me if I'm wrong) otherwise it would either cool the coffee too much, or not cool it enough.   

       This one stops sinking heat when it reaches a certain temp. Then it slowly releases the energy back into the coffee as heat. I'm thinking the peltier junction may not be the best to convert the electricity back to heat, an incandescent light bulb can get as much as 40% efficiency in converting electricity to heat. Maybe just a heating coil to rerelease the heat.   

       //The effectiveness could be readily improved by the simple expedient of washing the cup with very hot water before use.//   

       Genius! I hadn't thought of this.
bleh, Jun 25 2007
  

       //If you used a Seebeck array (thermocouples) around the mug to extract power when the mug was hot, which you then stored in a rechargeable battery or SuperCap, this could then power a CMOS thermometer which monitors the temeprature and beeps when the setpoint is reached. The setpoint is stored in Flash so it's retained between powerdowns. The whole system is heat powered by the beverage itself.//   

       Thats from an anno on Zincup. I found it through Lurch's idea. Strange how these things keep coming back up with a twist. [8th of 7] wanted a cup cooling indicator powered by the heat of the beverage, I want a cup thermo-stasis mechanism powered by the heat of the beverage. cool.
bleh, Jun 26 2007
  

       Weird but halfbaked feasible. Peltiers are notoriously inefficient as coolers, and yet that's the most common use for them. They generate quite a bit of waste heat of their own as they're working.   

       On the upside, Peltiers are considerably more effective as heaters, since now that waste heat can be channeled to the hot side and used.   

       Big downside: a coffee cup with a volume of ~32oz, weighing a solid pound and a half, that holds only 12oz. I like nerdy bragging rights as much as the next guy, but there are limits. I also like my coffee, and lots of it.
elhigh, Jun 26 2007
  

       // On the upside, Peltiers are considerably more effective as heaters, since now that waste heat can be channeled to the hot side and used.   

       That's right. The peltier is the best heater option as it works as a heat pump with more than 100% "efficiency". The inefficiency is in using it as a generator, still it's probably the best option for that too as it's solid state.   

       bun for this, but I really LOVE [TIB]'s idea.
TheLightsAreOnBut, Jun 27 2007
  

       I didn't know peltiers were so efficient as heaters. Is there some more efficient way to draw power from the excess heat?   

       thanks for the votes and all the annos!
bleh, Jun 27 2007
  

       >The problem is the chunk of steel you elude to
<pedant> to which you allude </pedant>
  

       Interesting discussion. + But I prefer to grind beans and pour hot water on them. Sometimes I'll have 2 cups of coffee. [links]
csea, Jun 27 2007
  

       //<pedant> to which you allude </pedant>//   

       No, I thought [bigsleep] was trying to escape from the chunk of steel by putting it in their coffee.   

       Only kidding, I fixed the error. Thanks.
bleh, Jun 27 2007
  

       Just want to point out that 100F is really too cold for coffee. That is just barely lukewarm, the temperature of a baby's bottle. I am not sure what the ideal temperature for a cup of coffee is, but I suspect it is more in the 140 to 160 range.   

       In the interests of science I am going to keep track of my coffee temperature today (or until I lose interest).   

       I know that my results are going to be personal, but I think 100 is going to be too cool for pretty much everyone.   

       Off to make the coffee!
Galbinus_Caeli, Jun 28 2007
  

       I will much appreciate the results [G_C]!! I had a feeling 100 was a little too cool, but nothing to quantify my instincts.
bleh, Jun 28 2007
  

       // a liquid that boils at 100F would be ideal as the heat-sink   

       That was [TIB]'s idea, as I understood it. I think it's a great one, but I've just thought of a problem... Liquid boils at a constant temperature only at a constant pressure. As the vapour develops, the pressure will ramp and the boiling temperature will too. This wouldn't be desirable, so you would need to find a way of keeping constant pressure.
TheLightsAreOnBut, Jun 28 2007
  

       Results!   

       Fresh from the Pot: 160, too hot to do more than slurp.   

       150, on the hot side of drinkable.   

       140, very drinkable.   

       135. I would call this perfect.   

       130. Still perfect.   

       125. Cool side of good, gulpable.   

       120. Cool, drinkable, wish I had a warm up.   

       110. Very cool. If I had my druthers I would set it aside until I could add more.   

       100. Just barely drinkable. Finished, time for another cup.   

       So I think perfect (for me) is 130 to 145. I suspect most people are going to be within ten to fifteen degrees of this.   

       Apologies for the SAE units, my kitchen thermometer is in these units, and honestly is what I am more comfortable cooking with.
Galbinus_Caeli, Jun 28 2007
  

       //the pressure will ramp and the boiling temperature will too//   

       I had that same thought a little while back. I did some study into refrigerants for another idea of mine (refrig-i-bottle). most of the ones I looked into were very toxic. I was looking for ones on the other end of the spectrum though.   

       Beautiful [G_C], thanks! so there's only about 20 deg of excess heat. I like [lurch]'s idea of washing out with warm water before use. That greatly increases the potential. How far apart were your readings?
bleh, Jun 28 2007
  

       Timewise? About ten minutes at first, then faster and faster as the cup emptied. I tried to keep track at first, but was not consistent, so I did not include the time measurements.   

       Time is also going strongly depend on size and structure of container too. I am drinking out of an eight ounce fairly thin walled china mug. A twenty ounce thick walled mug would cool more slowly, and an insulated one even less so.
Galbinus_Caeli, Jun 28 2007
  

       what would you say the total time from pour to 100 was? about 45 min? just trying to figure our from apower standpoint.   

       thanks again
bleh, Jun 28 2007
  

       [TheLightsAreOnBut]: the same problem occurred to me as well, but i just thought of a way around it, that then led to another idea.   

       place the phase-change material within a bladder (which would also make the insulation of the 'exterior' surface more simple). the bladder would be inserted into a void surrounding the inner volume of the cup.   

       when cool, the bladder (if you could see it before insertion) would have a vacuum-packed look to it, filled with liquid phase-change material and no gas. when hot it would fill the void (as the liquid becomes a gas), displacing any air, but remain unpressurized. no matter its state, the gas is never under pressure and the technology remains user transparent - unless they purchase a transparent mug to show how this all works (which i'm sure we all would).   

       the other idea i mentioned was this: a sleeve that allows one to retrofit a conventional mug with this system (within reason).
TIB, Jun 28 2007
  

       A bit less than 45 minutes, I would say. An insulated mug would have lasted quite a bit longer though. I have one that I can let sit in the cup holder (full) for an hour and still be drinkable. And of course a thermos flask can last several hours.
Galbinus_Caeli, Jun 28 2007
  

       Link added to a temperature-regulating mug, which absorbs heat from hot liquids, and then puts it back into the liquid as it cools, keeping your coffee at a constant temperature.
hippo, Nov 16 2009
  

       With a liquid to gas phase change material, couldn't you have a screw adjusted plate that compressed the storage space? That would allow for changes in pressure, and thus some tweaking of the transition temperature.
MechE, Nov 16 2009
  

       This could be done with sodium acetate, couldn't it?
nineteenthly, Nov 16 2009
  
      
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