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Could Convection Current power a stirring device in a saucepan

  1. Sep 17, 2014 #1
    Hi my names Oliver and I'm new to this but I am currently studying engineering, maths and physics A levels and as part of my engineering I have to create an innovative product. My idea is a saucepan with a built in device to stir the contents without the need for human interaction. So far I've thought of a rotating form of blade on a pivot in the centre, however I've been thinking how to power it. I don't want to use electronics because it would get awkward with the heat so I've been thinking along the lines of convection currents, however I've never really studied them into great depths through my AS years so I don't know a great deal about them. So my question is could convection currents generate enough power to rotate a metal blade around a pivot? I've included a picture for anyone that doesn't understand my idea (I know I might not be that clear). And I understand about viscosity so to make It easy at the moment just say the saucepan is full of water.
    thanks for your time and replies if there's any more information needed just ask and I'll reply when I can.

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  3. Sep 17, 2014 #2


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    Convection currents stir the contents to some extent anyway. The problem is likely to be that convection is too slow to prevent burning especially in high viscosity liquids like soup.
  4. Sep 17, 2014 #3
    If you put a blade in there, the blade will probably _slow down_ the convection currents, rather than increase them, unless you put some external power into the blades. Think about it: if it takes power to turn the blades, then where is the power coming from?
  5. Sep 18, 2014 #4
    Thanks guys think I'm gonna go back to the drawing board to think of other power sources. Thanks for the quick replies.
  6. Sep 18, 2014 #5


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    Oh well, I can imagine you can power such a thing in water - with an additional blade somewhere to catch a convective flow and some means of directing this (sounds like a cleaning nightmare on its own). For other liquids (in particular, everything where such a thing could help) I doubt that you get enough convection.

    There are electronic components that can survive 100°C or even higher temperatures. I don't know about motors.
    In general, magnets could be interesting to transmit some force without a direct contact.
  7. Sep 18, 2014 #6
    To be honest I have been thinking along the lines of motors because I've seen a few videos on the Internet of "magnetic motors" however I didn't know if to trust them as quite a few videos show them as fake and not working. But I still think I could find a way to make it work... And if you guys think it's a good idea then that may be the way forward .
  8. Sep 18, 2014 #7


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  9. Sep 19, 2014 #8
    Thanks for that I'll look into and see if I could use that mechanism in a saucepan.
  10. Sep 20, 2014 #9


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    Slightly off-topic but still relevant: I have always wondered why "they" don't provide a suspended paddle system in turntable-type microwave ovens, to stir sauces etc. by the action of the turntable. It is a nuisance that you keep needing to stop the oven and stir sauces - despite the fact that you don't get the burning on the bottom effect that you get with a conventional saucepans on a gas ring. It annoys me so much that I do sauces on the hob. If you stir enough, you don't get burning.
    A device already exists to do what the OP wants. A bread maker will heat and stir - although the programming would need to change for it to do both at the same time. Kenwood make a food mixer that will make bread all in one go (ingredients in/ bread out). This would be better because the stirring is done from the top and you don't have the problem of possible leaking through the bottom of the pan.
  11. Sep 21, 2014 #10
    Could you make the pan bi-metallic in such a way as to generate thermo-electric power using the temperature difference between the sides and bottom, and then use that power to turn your blade? Making this thermo-electric power source and motor an add-on to the pan would be awkward, but casting the pan with the different metals in different places to produce the desired currents, magnetic fields, and ultimately, movement of the rotor, could be pretty elegant.
  12. Sep 21, 2014 #11


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    Except the efficiency of thermocouples depends upon temperature difference and you wouldn't be considering more than 10 C. There could be many more 'cordless' ways of getting power to a stirrer than a thermocouple. The old magnetic stirrer is a good system but that is limited to low viscosity liquids. Perhaps an acoustic agitator would work.
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