Heat transfer device and method of making same

Abstract

A capillary structure for a heat transfer device, such as a heat pipe is provided having a plurality of particles joined together by a brazing compound such that fillets of the brazing compound are formed between adjacent ones of the plurality of particles and one or more vapor vents are defined in the capillary structer. In this way, a network of capillary passageways are formed between the particles and vapor-vents through the capillary structure so as to aid in the transfer of working fluid by capillary action, while the plurality of fillets provide enhanced thermal transfer properties between the plurality of particles so as to greatly improve over all heat transfer efficiency of the device. A method of making the capillary structure according to the invention is also presented.

1 . A capillary structure for a heat transfer device comprising:
 a plurality of particles joined together by a brazing compound such that fillets of said brazing compound are formed between adjacent ones of said plurality of particles so as to form a network of capillary passageways between said particles wherein at least one vapor vent is defined through said capillary structure.   
     
     
         2 . A capillary structure according to  claim 1  wherein said plurality of particles comprise a first melting temperature and said brazing compound comprises a second melting temperature that is lower than said first melting temperature. 
     
     
         3 . A capillary structure according to  claim 1  wherein said brazing compound comprises about sixty-five percent weight copper and thirty-five percent weight gold particles such that said fillets of said brazing compound are formed between adjacent ones of said plurality of particles so as to create a network of capillary passageways between said particles. 
     
     
         4 . A capillary structure according to  claim 1  wherein said fillets are formed by capillary action of said braze compound when in a molten state. 
     
     
         5 . A capillary structure according to  claim 1  wherein said metal particles are selected from the group consisting of carbon, tungsten, copper, aluminum, magnesium, nickel, gold, silver, aluminum oxide, and beryllium oxide. 
     
     
         6 . A capillary structure according to  claim 1  wherein said metal particles comprise a shape selected from the group consisting of spherical, oblate spheroid, prolate spheroid, ellipsoid, polygonal, and filament. 
     
     
         7 . A capillary structure according to  claim 1  wherein said metal particles comprise at least one of copper spheres and oblate copper spheroids having a melting point of about one thousand eighty-three ° C. 
     
     
         8 . A capillary structure according to  claim 3  wherein said brazing compound comprises six percent by weight of a finely divided copper/gold brazing compound. 
     
     
         9 . A capillary structure according to  claim 3  wherein said brazing compound is present in the range from about two percent to about ten percent. 
     
     
         10 . A capillary structure according to  claim 3  wherein said metal particles comprise copper powder comprising particles sized in a range from about twenty mesh to about two-hundred mesh. 
     
     
         11 . A capillary structure according to  claim 3  wherein said braze compound particles comprise about minus three hundred and twenty-five mesh. 
     
     
         12 . A capillary structure according to  claim 1  wherein said metal particles that are a constituent portion of said braze compound comprise a smaller size than said metal particles. 
     
     
         13 . A capillary structure according to  claim 1  wherein said braze compound is selected from the group consisting of nickel-based Nicrobrazes, silver/copper brazes, tin/silver, lead/tin, and polymers. 
     
     
         14 . A capillary structure according to  claim 1  wherein said plurality of metal particles comprise aluminum and magnesium and said brazing compound comprises an aluminum/magnesium intermetallic alloy. 
     
     
         15 . A capillary structure for a heat transfer device comprising:
 a plurality of particles joined together by a brazing compound such that fillets of said brazing compound are formed between adjacent ones of said plurality of particles so as to form a network of capillary passageways between said particles wherein a plurality of vapor vents are defined through said capillary structure.   
     
     
         16 . A capillary structure according to  claim 15  wherein said vapor vents comprise a cross-sectional profile selected from the group consisting of cylindrical, conical, frustoconical, triangular, pyramidal, rectangular, rhomboidal, pentagonal, hexagonal, octagonal, polygonal and curved. 
     
     
         17 . A heat pipe comprising:
 a hermetically sealed and partially evacuated enclosure, said enclosure comprising internal surfaces;   a wick disposed on at least one of said internal surfaces and comprising a plurality of particles joined together by a brazing compound such that fillets of said brazing compound are formed between adjacent ones of said plurality of particles so as to form a network of capillary passageways between said particles wherein at least one vapor vent is defined through said capillary structure; and   a two-phase fluid at least partially disposed within a portion of said wick.   
     
     
         18 . A heat pipe according to  claim 17  wherein said plurality of particles comprise a first melting temperature and said brazing compound comprises a second melting temperature that is lower than said first melting temperature. 
     
     
         19 . A heat pipe according to  claim 17  wherein said brazing compound comprises about sixty-five percent weight copper and thirty-five percent weight gold such that said fillets of said brazing compound are formed between adjacent ones of said plurality of particles so as to create a network of capillary passageways between said particles. 
     
     
         20 . A heat pipe according to  claim 17  wherein said fillets are formed by capillary action of said braze compound when in a molten state.