thermodynamics of cores.2nd law breach?

[MileHigh]

Profits:

To me it looks like you are mixing up or mashing up the concepts of molecular phase change and the Curie point.  When you transition past the Curie point temperature, no phase change takes place.  There is no puff of energy released.

Also, heat is sucked from hot matter into another form for the magnetocaloric effect.  There is never a release of heat like you are suggesting for the Curie point as far as I am aware of.  And again, you have to supply power up front for the heat sucking to take place.  In a way it's similar to expanding gas having a heat sucking effect.

The Curie point is just a threshold temperature that gauges the activity level of the molecular mosh pit.  If the mosh pit is too active, then you can't get magnetic domains to line up.  Drop the temperature a bit and the mosh pit settles down enough for magnetic domains to line up if there is an external influence.  There is no thermal change per se that takes place at the Curie point.

So I disagree with your premise.

MileHigh

[picowatt]

Profits:

To me it looks like you are mixing up or mashing up the concepts of molecular phase change and the Curie point.  When you transition past the Curie point temperature, no phase change takes place.  There is no puff of energy released.

Also, heat is sucked from hot matter into another form for the magnetocaloric effect.  There is never a release of heat like you are suggesting for the Curie point as far as I am aware of.  And again, you have to supply power up front for the heat sucking to take place.  In a way it's similar to expanding gas having a heat sucking effect.

The Curie point is just a threshold temperature that gauges the activity level of the molecular mosh pit.  If the mosh pit is too active, then you can't get magnetic domains to line up.  Drop the temperature a bit and the mosh pit settles down enough for magnetic domains to line up if there is an external influence.  There is no thermal change per se that takes place at the Curie point.

So I disagree with your premise.

MileHigh

MH,

I believe the amount of heat released and absorbed by magnetocaloric materials is greater when those materials transition their Curie temps.  However, even if the process were 100% efficient, the heat released and absorbed during each mag/demag cycle would be identical.  Straddling the Curie temp is used in refrigeration cycles to increase pumping efficiency, but the process is still not 100%.

Some researchers have acheived COP=5 using magnetocaloric heat pumps to replace the mechanical heat pumps in consumer refrigerator prototypes.

However, just as with mechanical heat pumps, magnetocaloric heat pumps are not 100% efficient, regardless of the COP acheived.

PW

[MileHigh]

PW:

Thanks for the information.  Something is telling me that magnetocaloric heat pumps are used in recreational vehicles but not for home refrigerators.  Perhaps cost and energy efficiency are the determining factors?

MileHigh

[picowatt]

PW:

Thanks for the information.  Something is telling me that magnetocaloric heat pumps are used in recreational vehicles but not for home refrigerators.  Perhaps cost and energy efficiency are the determining factors?

MileHigh

MH,

I know of no currently available refrigeration systems for consumer use that rely on magnetocalorics (RV's or otherwise). 

There is much research in this field however, as it would eliminate the use of fluid refrigerants and the moving parts associated with the mechanical heat pump.  In theory, magnetocaloric heat pumps could be more efficient than their mechanical counterparts.  However, materials costs have been one of several issues preventing their implementation.

As I understand, a recent breakthrough in alloying methods allows the use of less pure Gd to make suitable Gd(SiGe) alloys, for example, that reduces material costs while maintaining adequate pumping efficiencies.  However, Gd remains a fairly expensive material.  A breakthrough that eliminates the need for very expensive alloys and salts would go a long way toward bringing the technology to the consumer market.

I think it will be a bit longer before we see magnetocaloric refrigerators at Lowe's.  However, a substantial amount of research and money is being applied toward that end.

PW

[profitis]

@milehigh,true.let me give another analogy.evrybody knows that if you take a permanent magnet and heat it,it loses magnetic strength.the opposite is also true thus if you cool a permanent magnet the domains fall into more orderly alignment and magnetic strength increases.thus in our inductor the aligned domains order suddenly increase at moment of cooling,thus magnetic field strength increases,thus back-inductance is stronger than forward-inductance.additional heat intake is now required to re-randomize those domains to original state due to this increased shifting alignment of domains.its a sinkhole for ambient heat.ambient heat ontop of heat exhausted by our battery.