Thermal interface device

Abstract

The invention is for an apparatus and method for removal of waste heat from heat-generating components including high-power solid-state analog electronics such as being developed for hybrid-electric vehicles, solid-state digital electronics, light-emitting diodes for solid-state lighting, semiconductor laser diodes, photo-voltaic cells, anodes for x-ray tubes, and solids-state laser crystals. Liquid coolant is flowed in one or more closed channels having a substantially constant radius of curvature. Suitable coolants include electrically conductive liquids (including liquid metals) and ferrofluids. The former may be flowed by magneto-hydrodynamic effect or by electromagnetic induction. The latter may be flowed by magnetic forces. Alternatively, an arbitrary liquid coolant may be used and flowed by an impeller operated by electromagnetic induction or by magnetic forces. The coolant may be flowed at very high velocity to produce very high heat transfer rates and allow for heat removal at very high flux.

1 . A heat transfer device comprising:
 a) a body having a first surface, a second surface, and a flow channel;
 said flow channel formed as a hollow cylinder inside said body; 
 said hollow cylinder comprising an inner cylindrical surface and an outer cylindrical surface; 
 said outer cylindrical surface having a central axis of symmetry, a first radius of curvature, and azimuthal direction; 
 said inner cylindrical surface having a second radius of curvature and being substantially concentric with said outer cylindrical surface; 
 said radii of curvature being substantially constant; 
 said first surface of said body being in a good thermal communication with a heat generating component; 
 said first surface of said body being generally tangential to said outer cylindrical surface with only a small separation between the two; 
 said second surface of said body arranged to be in a good thermal communication with a heat sink; 
   b) a liquid coolant substantially filling said flow channel; and   c) a means for flowing said liquid coolant in said azimuthal direction.   
     
     
         2 . The heat transfer device of  claim 1 , wherein said liquid coolant is electrically conductive and wherein said means for flowing said liquid coolant are selected from the group consisting of an MHD drive and an inductive drive. 
     
     
         3 . The heat transfer device of  claim 1 , wherein said liquid coolant comprises a ferrofluid and wherein said means for flowing said liquid coolant comprise a magnetic drive. 
     
     
         4 . The heat transfer device of  claim 1 , wherein said liquid coolant comprises substantially of liquid selected from the group consisting of water, alcohol, Freon and nanofluid, wherein said means for flowing said liquid coolant comprise an impeller drive. 
     
     
         5 . The heat transfer device of  claim 1 , wherein said liquid coolant substantially filling said flow channel does not entirely fill said channel and leaves a void space; said void space being filled by at least one of elastic material, crushable material, air, gas, and vapor. 
     
     
         6 . The heat transfer device of  claim 1 , wherein said small separation between said first surface of said body and said outer cylindrical surface is less than 1 millimeter. 
     
     
         7 . The heat transfer device of  claim 1 , wherein the difference between said first radius of curvature said second radius of curvature is less than 2 millimeters. 
     
     
         8 . The heat transfer device of  claim 1 , further comprising a passage for a secondary coolant; said secondary coolant being in a good thermal contact with said second surface of said body. 
     
     
         9 . The heat transfer device of  claim 8 , wherein said secondary coolant is arranged to flow in the direction generally transverse to the direction of flow of said liquid coolant. 
     
     
         10 . The heat transfer device of  claim 8 , wherein said secondary coolant is arranged to flow in the direction generally opposite to the direction of flow of said liquid coolant. 
     
     
         11 . A heat transfer device comprising:
 a) a body having a first surface, a second surface, and a flow channel;   b) a liquid metal coolant substantially filling said flow channel; and   c) a means for flowing said liquid metal coolant in said azimuthal direction;
 said flow channel formed as a cylindrical chamber inside said body; 
 said cylindrical chamber comprising an inner cylindrical surface and an outer cylindrical surface; 
 said outer cylindrical surface having a central axis of symmetry, a first radius of curvature, and azimuthal direction; 
 said inner cylindrical surface having a second radius of curvature and being substantially concentric with said outer cylindrical surface; 
 said radii of curvature being substantially constant; 
 said first surface of said body being in a good thermal communication with a heat generating component; 
 said first surface of said body being generally tangential to said outer cylindrical surface with only a small separation between the two; and 
 said second surface of said body arranged to be in a good thermal communication with a heat sink. 
   
     
     
         12 . The heat transfer device of  claim 11 , further comprising
 a) a permanent magnet generating a magnetic field within at least a portion of said liquid metal coolant;   b) a ferromagnetic yoke; and   c) a pair of electrodes for drawing electric current through said portion of said liquid metal coolant in a direction substantially perpendicular to the direction of said magnetic field.   
     
     
         13 . The heat transfer device of  claim 11 , wherein said liquid metal coolant is substantially immersed in a magnetic field having a component that rotates substantially in said azimuthal direction. 
     
     
         14 . The heat transfer device of  claim 13 , wherein the speed of rotation of said magnetic field component is in the range of 10 to 1,000 hertz. 
     
     
         15 . The heat transfer device of  claim 13 , wherein said rotating magnetic field component is generated by an electromagnet coils fed by polyphase alternating current. 
     
     
         16 . The heat transfer device of  claim 13 , wherein said rotating magnetic field component is generated by a rotating permanent magnet. 
     
     
         17 . A heat transfer device comprising:
 a) a body having a first surface, a second surface, and a flow channel;   b) a liquid coolant substantially filling said flow channel; and   c) an impeller drive for flowing said liquid metal coolant in said azimuthal direction;
 said flow channel formed as a cylindrical chamber inside said body; 
 said cylindrical chamber comprising an inner cylindrical surface and an outer cylindrical surface; 
 said outer cylindrical surface having a central axis of symmetry, a first radius of curvature, and azimuthal direction; 
 said inner cylindrical surface having a second radius of curvature and being substantially concentric with said outer cylindrical surface; 
 said radii of curvature being substantially constant; 
 said first surface of said body being in a good thermal communication with a heat generating component; 
 said first surface of said body being generally tangential to said outer cylindrical surface with only a small separation between the two; and 
 said second surface of said body arranged to be in a good thermal communication with a heat sink. 
   
     
     
         18 . The heat transfer device of  claim 17 , wherein said liquid coolant comprises substantially of liquid selected from the group consisting of water, alcohol, Freon and nanofluid. 
     
     
         19 . The heat transfer device of  claim 17 , further comprising an impeller having a cylindrical surface substantially inside said flow channel and concentric with said outer cylindrical surface; said impeller arranged to rotate about said central axis of symmetry. 
     
     
         20 . A method for transferring heat from a heat generating component to a heat sink comprising the steps of:
 a) providing a body having a first surface, a second surface, and a cylindrical chamber;
 said cylindrical chamber formed within said body; 
 said cylindrical chamber comprising a cylindrical surface having a central axis of symmetry, a constant radius of curvature, and an azimuthal direction; 
 said first surface being in a good thermal communication with a heat generating component;
 said second surface being in a good thermal communication with a heat sink; 
 
   d) providing a liquid coolant substantially filling said cylindrical chamber; said liquid coolant being selected from the group consisting of ferrofluid and electrically conductive liquid;   e) providing a drive means for flowing said liquid coolant in said cylindrical chamber in the azimuthal direction of said cylindrical surface; said drive means selected from the group consisting of an MHD drive, inductive drive, magnetic drive, and impeller drive.   f) receiving heat from said heat generating component;   g) transferring heat to said coolant;   h) flowing said liquid coolant in said azimuthal direction; and   i) transferring heat from said liquid coolant to a heat sink.