Magnetocaloric refrigerator

Abstract

The invention is for an apparatus and method for a refrigerator and a heat pump based on the magnetocaloric effect (MCE) offering a simpler, lighter, robust, more compact, environmentally compatible, and energy efficient alternative to traditional vapor-compression devices. The subject magnetocaloric apparatus alternately exposes a suitable magnetocaloric material to strong and weak magnetic field while switching heat to and from the material by a mechanical commutator using a thin layer of suitable thermal interface fluid to enhance heat transfer. The invention may be practiced with multiple magnetocaloric stages to attain large differences in temperature. Key applications include thermal management of electronics, as well as industrial and home refrigeration, heating, and air conditioning. The invention offers a simpler, lighter, compact, and robust apparatus compared to magnetocaloric devices of prior art.

1 . An apparatus for transferring heat from a cooler reservoir to a warmer reservoir while expending mechanical energy in the process; said apparatus comprising a member made of magnetocaloric effect (MCE) material, a first thermal conductor, a second thermal conductor, a means for producing a region of strong magnetic field and a region of weak magnetic field, and a thermal interface fluid (TIF); said first thermal conductor being arranged to be in a good thermal communication by means of said TIF with a portion of said MCE material when said portion of said MCE material is immersed in said weak magnetic field; and said second thermal conductor being arranged to be in a good thermal communication by means of said TIF with a portion of said MCE material when said portion of said MCE material is immersed in said strong magnetic field. 
     
     
         2 . The apparatus of  claim 1 , wherein said first thermal conductor and said member are arranged to form a first gap therebetween and said first gap is substantially filled with said TIF; and said second thermal conductor and said member are arranged to form a second gap therebetween and said second gap is substantially filled with said TIF. 
     
     
         3 . The apparatus of  claim 2 , wherein the width of said first gap and said second gap are each chosen to be between about 50 micrometers and 500 micrometers. 
     
     
         4 . The apparatus of  claim 2 , wherein said TIF is selected from the family consisting of liquid metal, gallium-based liquid metal alloy, gallium-indium-tin liquid metal alloy, gallium-indium-tin-zinc liquid metal alloy, nanofluid, and nanofluid substantially comprising carbon nanotubes. 
     
     
         5 . The apparatus of  claim 1 , wherein said member is arranged to be in motion relative to each said first thermal conductor and said second thermal conductor. 
     
     
         6 . The apparatus of  claim 5 , wherein said motion is causing said TIF to flow in a shear flow regime. 
     
     
         7 . The apparatus of  claim 5 , wherein said motion is causing a portion of said member to be cyclically exposed to said weak magnetic field and said strong magnetic field. 
     
     
         8 . The apparatus of  claim 1 , wherein said means for producing said region of strong magnetic field is selected from the family consisting of a permanent magnet, electromagnet, and superconducting coil. 
     
     
         9 . A staged magnetocaloric refrigerator (MCR) comprising a plurality of MCR stages;
 a) each said MCR stage comprising a member made of magnetocaloric effect (MCE) material, a first thermal conductor, a second thermal conductor, a means for producing a region of strong magnetic field and a region of weak magnetic field, and a thermal interface fluid (TIF);   b) within each said MCR stage, said first thermal conductor of that MCR stage being arranged to be in a good thermal communication by means of said TIF with a portion of said MCE material of that stage when said portion of said MCE material of that stage is immersed in a weak magnetic field;   c) within each said MCR stage, said second thermal conductor of that MCR stage being arranged to be in a good thermal communication by means of said TIF with a portion of said MCE material of that MCR stage when said portion of said MCE material of that MCR stage is immersed in a strong magnetic field;   d) the thermal conductor of the first MCR stage being thermally coupled to a lower heat reservoir;   e) for each subsequent said MCR stage, the first thermal conductor of that MCR stage being coupled to the second thermal conductor of the preceding MCR stage; and   f) said second thermal conductor of the last MCR stage being thermally coupled to an upper heat reservoir.   
     
     
         10 . The staged MCR of  claim 9 , wherein the temperature of said lower heat reservoir is substantially lower than the temperature of said upper heat reservoir. 
     
     
         11 . The staged MCR of  claim 9 , wherein within each said MCR stage said member of that MCR stage is arranged to be in motion relative to each said first thermal conductor of that MCR stage; and within each said MCR stage said member of that MCR stage is arranged to be in motion relative to each said second thermal conductor of that MCR stage. 
     
     
         12 . The staged MCR of  claim 11 , wherein said motion is causing said TIF to flow in a shear flow regime. 
     
     
         13 . The staged MCR of  claim 9 , wherein within each said MCR stage, said first thermal conductor of that MCR stage and said member of that MCR stage are arranged to form a first gap therebetween and said first gap is substantially filled with said TIF; and said second thermal conductor of that MCR stage and said member of that MCR stage are arranged to form a second gap therebetween and said second gap is substantially filled with said TIF. 
     
     
         14 . The staged MCR of  claim 13 , wherein the width of said first gap and said second gap are each chosen to be between about 50 micrometers and 500 micrometers. 
     
     
         15 . The staged MCR of  claim 9 , wherein said TIF is selected from the family consisting of liquid metal, gallium-based liquid metal alloy, gallium-indium-tin liquid metal alloy, gallium-indium-tin-zinc liquid metal alloy, nanofluid, and nanofluid substantially comprising carbon nanotubes. 
     
     
         16 . A method for pumping heat comprising the steps of:
 a) providing a magnetocaloric effect (MCE) material;   b) providing a first thermal conductor at a first temperature;   c) providing a second thermal conductor at a second temperature;   d) arranging said MCE material to be in close proximity of said first conductor with a first gap therebetween;   e) arranging said MCE material to be in close proximity of said second conductor with a second gap therebetween;   f) substantially filling said first gap and said second gap with a thermal interface fluid (TIF);   g) moving said MCE material with respect to said first thermal conductor;   h) moving said MCE material with respect to said second thermal conductor;   i) flowing said TIF in said first and said second gap in a shear flow regime;   j) exposing said MCE material to a weak magnetic field;   k) forming a good thermal communication between said MCE material and said first thermal conductor through said TIF;   l) exposing said MCE material to a strong magnetic field;   m) forming a good thermal communication between said MCE material and said second thermal conductor through said TIF.   
     
     
         17 . The method of  claim 16 , wherein said second temperature is higher than said first temperature. 
     
     
         18 . The method of  claim 16 , wherein said steps of (j) exposing said MCE material to a weak magnetic field and (k) forming a good thermal communication between said MCE material and said first thermal conductor through said TIF, are performed concurrently. 
     
     
         19 . The method of  claim 16 , wherein said steps of (l) exposing said MCE material to a strong magnetic field and (m) forming a good thermal communication between said MCE material and said second thermal conductor through said TIF, are performed concurrently. 
     
     
         20 . The method of  claim 16 , wherein said step of forming a good thermal communication between said MCE material and said first thermal conductor through said TIF further comprises flowing of heat from said first thermal conductor through said TIF to said MCE material.