Magnetocaloric Effect / Discussion

This is the discussion related to the wiki page Magnetocaloric Effect.

Actual working

satyesh 30 Apr 2009 18:26

Good job.

Can you elaborate on how is it possible to transport solid materials from heat to sink as required in cooling cycle of any cooling mechanism.

Re: Actual working

rueckert 05 May 2009 10:08

I asked the same question myself. In short, the MCE material interacts with a heat transfer fluid which can be more easily transported to different sections of the device. I hope I've addressed your question in the refrigeration section.

mariael84 30 Apr 2009 19:38

Very interesting work. Just curious to know what kind of MCE materials have been used up to know and how strong magnetic fields need to be applied to obtain the effect.

Re:

rueckert 05 May 2009 10:10

A wide range of materials exhibit MCE. The field necessary varies widely depending on the selection of materials. Typical numbers are from 7 to 50 kOe. I have tried to include information on these facts in the materials and refrigeration sections above.

Jialan Zhang 01 May 2009 17:45

Hi, rueckert:

Your page is well organized. Actually I did some research on electrocaloric effect, and I learned more from your page. I find the cycle used in electrocaloric effect seems to be different with the MCE you showed from the second step. Instead of transfering heat by lowing the temperature in your second step, it keeps the temperature constant. So I wonder if you know something about this isothermal condition, and do you know the difference of it with the steps you showed in details?

Thanks.

Re:

rueckert 05 May 2009 10:14

I'm unfamiliar with the electrocaloric effent in detail, but I imagine the processes involved would be similar. I should point out that the heat transfer stages in a working device are significantly more complicated the idealized system I mention at the beginning of the article. I've tried to address that in more detail in the refrigeration section

coupled effects

Dharma Maddala 01 May 2009 22:00

Good job rueckert,
Magnetocaloric Effect is a coupled and here are some interesting diagrams in understanding coupled effects

left one is the Heckmann's triangle (describes the coupled effects among
electric field, stress field and temperature field) and the right one is Thurston’s model(changed Heckmann’s model by replacing the thermal items with light items to form another model)
in the same way different energies can be combined to see the coupled effects

Schematic diagram of effects between four kinds of energies.

Model of physical effects about six kinds of energies.

source for these images: S. Baoyuan et al. / Journal of Materials Processing Technology 139 (2003) 444–447

Last edited on 01 May 2009 22:02 by Dharma Maddala Show more

Re: coupled effects

rueckert 05 May 2009 10:16

Very interesting. Perhaps you could comment a bit on the best way to read the energy transfer process from the diagrams, with regard to the Magnetocaloric effect.

Fangxiao 02 May 2009 18:08

Great job!

While I am just curious, does magnetocaloric effect have some relation with pyroelectric properties? Do they have similar mechanism from the view of molecular motion?

Re:

rueckert 05 May 2009 10:21

In my understanding, they are related in that both effects depend heavily on the coupling of structural and electronic/magnetic properties. In pyroelectricity, changes in temperature shift the position of atoms and in turn affect the polarization. In many giant MCE materials, the change in temperature occurs due to a large change in entropy as the material undergoes both a structural and magnetic phase change.