Ceramic heat pipe with porous ceramic wick

Abstract

A heat pipe for transporting heat from light emitting elements includes a sealed body made of a non-porous ceramic, a vapor channel inside the body that extends between two heat transfer locations spaced apart on an exterior surface of the body, a ceramic wick inside the body that extends between the two heat transfer locations, and a working fluid that partially fills the vapor transport channel. In a method of making this heat pipe, the body and wick are desirably formed together as a seamless monolithic structure made of the same ceramic material. Using a ceramic makes the heat pipe corrosion resistant and allows electrical components like LEDs to be mounted directly on the body because the ceramic is a dielectric.

1 . A heat pipe comprising:
 a body made of a non-porous ceramic, said body being sealed and having a ceramic wick inside the body that extends between two heat transfer locations spaced apart on an exterior surface of said body;   a vapor transport channel inside the body that extends between said two heat transfer locations; and   a working fluid that partially fills said vapor transport channel.   
     
     
         2 . The heat pipe of  claim 1 , wherein said wick is made of a porous ceramic with plural interconnected pores that extend continuously between said two heat transfer locations. 
     
     
         3 . The heat pipe of  claim 2 , wherein said body and said wick together are a seamless monolithic structure made of a same ceramic material. 
     
     
         4 . The heat pipe of  claim 1 , wherein said wick is made of a porous ceramic that is directly on an interior wall of said body and surrounds said vapor transport channel, said porous ceramic having plural interconnected pores that extend continuously between said two heat transfer locations. 
     
     
         5 . The heat pipe of  claim 4 , wherein said body and said wick together are a seamless monolithic structure made of a same ceramic material. 
     
     
         6 . The heat pipe of  claim 1 , in combination with a light emitting diode that is mounted directly on said body at one of said two heat transfer locations. 
     
     
         7 . The heat pipe of  claim 1 , wherein the body contains multiple vapor transport channels that are spaced throughout the wick and extend between the two heat transfer locations. 
     
     
         8 . A heat pipe comprising:
 a body made of a non-porous alumina ceramic, said body being sealed and having a ceramic wick inside the body that extends between two heat transfer locations spaced apart on an exterior surface of said body, the ceramic wick being made of a porous alumina ceramic having interconnected pores that extend continuously between said two heat transfer locations;   a vapor transport channel inside the body that extends between said two heat transfer locations; and   a working fluid that partially fills said vapor transport channel.   
     
     
         9 . The heat pipe of  claim 8 , wherein the body and wick are integrally formed. 
     
     
         10 . The heat pipe of  claim 8 , wherein the body contains multiple vapor transport channels that are spaced throughout the wick and extend between the two heat transfer locations. 
     
     
         11 . The heat pipe of  claim 8  wherein the wick surrounds the vapor transport channel. 
     
     
         12 . A method of making a heat pipe comprising the steps of:
 providing a body of a non-porous ceramic;   providing a ceramic wick and a vapor transport channel inside said body, said wick and vapor transport channel extending between two heat transfer locations spaced apart on an exterior surface of said body;   evacuating said body;   providing a working fluid inside said body that partially fills the vapor transport channel; and   sealing said body closed.   
     
     
         13 . The method of  claim 12 , wherein said body and said wick are provided from a same ceramic material and are formed together as a seamless monolithic structure made of the same ceramic material. 
     
     
         14 . The method of  claim 12 , wherein said ceramic wick is provided by inserting plural ceramic spheres into said hollow interior and heating said spheres to induce viscous sintering that produces interconnected pores that extend through said wick between said two heat transfer locations. 
     
     
         15 . The method of  claim 12 , wherein said body and said wick are provided by extruding said body and said wick together from a same ceramic material, and further comprising the step of creating interconnected pores through said wick that extend between said two heat transfer locations. 
     
     
         16 . The method of  claim 12 , wherein said body and said wick are provided by forming said body and said wick together from a same green ceramic material, inserting fugitive material into said wick, causing said fugitive material to decompose to provide interconnected pores that extend through said wick between said two heat transfer locations, and sintering said green ceramic material. 
     
     
         17 . The method of  claim 12 , wherein said body is provided by preforming a green ceramic body, and said wick is provided by coating interior walls of said body with an organic gel precursor and pyrolyzing the precursor to form a porous structure, and further comprising the step of firing the green ceramic body and precursor to form a monolithic structure of said body and said wick, said wick having interconnected pores that extend between said two heat transfer locations. 
     
     
         18 . The method of  claim 12 , wherein said body is provided by providing a first green ceramic part having one of a first density and first particle size distribution, and wherein said wick is provided by inserting a second green ceramic part into said body, said second green ceramic part having one of a second density lower than the first density and second particle size distribution larger than said first particle size distribution, and further comprising the step of completely sintering the first green ceramic part and incompletely sintering the second green ceramic part so that said second green ceramic part has interconnected pores that extend through said wick between said two heat transfer locations.