Heat pipe

Abstract

A heat pipe includes a hollow elongated casing, which defines therein an enclosed chamber, a working fluid filled in the enclosed chamber; and a wick, which is formed on the inside wall of the casing around the enclosed fluid chamber and has two parts that have different porosities.

1 . A heat pipe comprising: 
 a hollow elongated casing, said casing defining therein an enclosed chamber;    a working fluid disposed in said enclosed chamber; and    a wick formed on an inside wall of said casing;    wherein said wick has a first part and a second part, said first part and said second part have different porosities.    
   
   
       2 . The heat pipe as claimed in  claim 1 , wherein said first part of the wick has a porosity within 55%-60%; said second part of the wick has a porosity within 65%-80%.  
   
   
       3 . The heat pipe as claimed in  claim 2 , wherein said casing has a heating end and a cooling end opposite said heating end; said first part of the wick is located at said heating end, and said second part is located at said cooling end.  
   
   
       4 . The heat pipe as claimed in  claim 2 , wherein said casing has a heating end and a cooling end opposite to said heating end; said wick further has a third part, said third part having a porosity within about 55%-60%, said first part of the wick being disposed at said heating end, said third part of the wick being disposed at said cooling end, said second part of the wick being located between said first part and said third part of the wick.  
   
   
       5 . The heat pipe as claimed in  claim 1 , wherein said wick is sintered from copper powder or alloy powder of copper and silver.  
   
   
       6 . The heat pipe as claimed in  claim 1 , wherein said first part and said second part of the wick are axially arranged in a line.  
   
   
       7 . The heat pipe as claimed in  claim 1 , wherein said first part of the wick is bonded to the inside wall of said casing, and said second part of the wick is bonded to said first part of the wick.