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Physics/Magnetocaloric effect with


QUESTION: This idea shows how to use "drinking bird" toy with magnetocaloric effect.

The main thing is the toy needs just temperature difference in a few Kelvin. I understand what system is not closed. The magnetocaloric effect will heat and cool the paramagnetic element based on fluctuation redistribution process. The outside temperature will work in both ways of this process and will try to minimize temperature difference of this effect. However, the paramagnetic element changes liquid temperature in certain amount of time and it will increase position instability of "drinking bird". Also the air has less thermal conductivity than paramagnetic element with liquid and effect with temperature difference will be enough to keep "drinking bird" in motion.
Will this idea work?

Thank you.

ANSWER: I don't see a problem with any particular step of the process you have, aside from efficiency.  The only way to know if it will work would be to build it and tweak it to see.  Unless you have a technical diagram with numbers and specifications, I can't tell you where you might be going wrong.

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Entropy Engine
Entropy Engine  
QUESTION: Thank you for answer. The idea was use low boiling liquid to increase magnetocaloric effect efficiency.
However, I added new model in my blog which will work using Curie point phase transition. Now, depend on temperature active elements they will have ferromagnetic and paramagnetic properties.
The question is: Will changes of heat capacity in magnetocaloric effect will be enough to overcome Curie point temperature and change its own ferromagnetic property?
Thank you

ANSWER: That's the problem.  I don't know your alloy, and I'm not an alloy expert.  It'll have to operate under 173K (that's very cold), because the phase transition you're relying on doesn't work for any such alloy at room temperature yet.  You really will have to build it and see if such a complicated system will actually work, there's no simple answer to that, especially without detailed knowledge of things like your alloy or the dimensions of your design.  The ferromagnetic property of a material is generally a second-order phase change that involves no latent heat, so I don't see a problem.

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QUESTION: Thank you for your answers. It was very useful. Sounds good. The Gadolinium alloy Gd5Si2Ge2 has temperature Curie 293 K and temperature difference for magnetocaloric effect is a few K. This alloy is not very expensive for an experiment. However, it has a toxic hazard and I think, companies have some distribution restrictions for it. I hope make this experiment which can prove or disprove the idea of using magnetic intensity difference as another version of heat engine. I hope science labs can help me with that.
I have one more question. The substance changes its own heat capacity in open thermodynamic system and it has a heat convection to outside this system. After long time of heat capacity changes process. Will middle of range between low and high temperature of heat capacity process is equal to middle temperature of the system?
Thank you.

The Curie temperature of this allow is actually dependent on both applied pressure and the external magnetic field, so you might want to consider that carefully.

Anyhow, the grammar of your actual query makes it difficult to understand what you're asking.  The sentences don't quite make sense.  Perhaps you can re-state them.


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Dr. Stephen O. Nelson


I can answer most basic physics questions, physics questions about science fiction and everyday observations of physics, etc. I'm also usually good for science fair advice (I'm the regional science fair director). I do not answer homework problems. I will occasionally point out where a homework solution went wrong, though. I'm usually good at explaining odd observations that seem counterintuitive, energy science, nuclear physics, nuclear astrophysics, and alternative theories of physics are my specialties.


I was a physics professor at the University of Texas of the Permian Basin, research in nuclear technology and nuclear astrophysics. My travelling science show saw over 20,000 students of all ages. I taught physics, nuclear chemistry, radiation safety, vacuum technology, and answer tons of questions as I tour schools encouraging students to consider careers in science. I moved on to a non-academic job with more research just recently.

Ph. D. from Duke University in physics, research in nuclear astrophysics reactions, gamma-ray astronomy technology, and advanced nuclear reactors.

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