Dear All,
In my material, the curve between Change in entropy (ΔSm) v/s temperature (T) is very broad so that material exhibits very high relative cooling power (RCP= 700 J/kg) but the maximum value of ΔSm is only around 2.2 J/kg-K. Is this material good for cooling applications, how cooling power depends on ΔSm and RCP?
In other words, if we have two material: one has very high and narrow ΔSm, and other has low and very broad ΔSm. Out of both, which can give us better cooling power in real cooling applications?
Thank you very much,
Regards.
Hi Varun,
I agree with Sami Mahmood in that the width of your dS curve can be indicative of inhomogeneities in your samples. My colleague has developed a program using Matlab which uses the analysis of variance (a statistical method) to analyze the universal curves (V Franco et al 2008 J. Phys.: Condens. Matter 20 285207) of your samples. This could help uncover whether or not your large RCP is due to your unique material or due to inhomogeneities in your sample.
The link to the Matlab program is provided below, please let me know if you have any questions about it.
Best,
Tatiana
http://labs.cas.usf.edu/miller/software.html
Hi Sachin,
Thanks, yes exactly this material is having very high FWHM and so high RCP.
ΔTad is very important, I'll try it, but generally peoples are used to make comparison in two materials by RCP.
I am sure that very high and very narrow ΔSm is not useful for any of the application unless we use many materials (which have different Tc) inside the same cooling device.
Results are still unpublished but you can find this kind of behavior in nanostructured/superparamagnetic /2nd order phase transition materials.
In fact most of comparisons established by "specialists" like consider refrigeration at room temperature and efficiency is not only a question of materials but also of the working systems (magnetisation process, frequency of cycle, heat transfer...). For this doing, people like dispose of rather high ΔSm max, and not so broad (as your) thermal extension, application made with ~ Hz frequency systems working in regeneration mode.
Obviously your material corresponds to nanostructured (similarly amorphous) superparamagnetic (similarly short range correlated magnetism). Application (e.g. for liquefaction) depends also on the effective and mass production costs of your material, since a maximum value of ΔSm around 2.2 J/kg-K is not so ridiculous!
But what is the strength of the magnetic field you have applied to get such a value?
Dear Sir,
Thank you very much!
Yeah, agreed that the efficiency of these cooling devices depend on system but if we put all parameters of the system same than i think high RCP material should behave better. Am i right?
The field strength of magnetic field was 5T, and for cost point of view this is rare earth free material so that very cost effective.
Is there any article in your knowledge where I can get some comparison between these kind of systems. I would like to get a proper explanation.
Thanks and Regards
Dear Varun,
Yes 5 T is too high field for application. You must consider the practical limit of ~1 T !!!
Try to get informed of the previous THERMAG conferences (devoted to magnetocaloric materials and systems). The next ones is scheduled close: Sept. 7 to 11th. If there is something as you want, I will inform you back.
However, you can consult the Tishin's book (Wiley).
Daniel
Dear Sir,
Thank you, I will go through suggested references.
I am going to attend this THERMAG VI 2014 in Victoria BC. Will you also be there?
Best regards
Varun
The breadth of the magnetic entropy change curve is probably associated with structural and microstructural inhomogeneities. The value of the magnetic entropy change you obtained is not bad at all. For what field change was this value obtained?
In my opinion, a broad entropy curve indicates that the material is efficient as magnetic coolant in a broad temperature regime. This is an advantage. A narrow curve indicated that the material is efficient at a temperature around the peak position. Thus the suitability of the material for magnetic cooling is dependent on the working temperature as well as the magnitude of the magnetic entropy change.
Dear Sami Sir
The field strength of magnetic field was 5T, and for cost point of view this is rare earth free material so that very cost effective.
Varun, could this technology be miniaturized to cool electronic devices like a network router, say, like a module to be added over the circuit board?
Hi Varun,
I agree with Sami Mahmood in that the width of your dS curve can be indicative of inhomogeneities in your samples. My colleague has developed a program using Matlab which uses the analysis of variance (a statistical method) to analyze the universal curves (V Franco et al 2008 J. Phys.: Condens. Matter 20 285207) of your samples. This could help uncover whether or not your large RCP is due to your unique material or due to inhomogeneities in your sample.
The link to the Matlab program is provided below, please let me know if you have any questions about it.
Best,
Tatiana
http://labs.cas.usf.edu/miller/software.html
Dear Tatiana
Thank you for your comment and Matlab code, I'll go through with it and let you know if got any doubt.
So you mean if sample have inhomogeneities then dSm measured with different field should not collapse into a single universal curve?
Best regards
Varun
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