Heat pipe

Abstract

A heat pipe includes a casing and a plurality of wick layers. The casing has an inner wall. The wick layers stack at an inner surface of the casing in turn. The wick layers respectively define a plurality of pores therein. Diameters of the pores of each of the wick layers gradually decrease from the inner wall to center of the casing.

1 . A heat pipe comprising:
 a casing, the casing having an inner wall; and   a plurality of wick layers stacked at an inner surface of the casing in turn, the wick layers respectively defining a plurality of pores therein, diameters of the pores of the wick layers gradually decreasing from the inner wall to a center of the casing.   
     
     
         2 . The heat pipe of  claim 1 , wherein the wick layers are more than three and less than eight. 
     
     
         3 . The heat pipe of  claim 1 , wherein the wick layers comprises a first wick layer adjacent to and connect to the inner wall of the casing, the first wick can be selected from groove-type wick layer, fine-mesh wick layer or sintered powder wick layer. 
     
     
         4 . The heat pipe of  claim 1 , wherein the wick layers comprises a second wick layer near a center of the casing and away from the inner wall of the casing, the inner wick being a sintered powder wick layer, and the others being a fine-mesh wick layer. 
     
     
         5 . The heat pipe of  claim 1 , wherein the wick layers are groove-type wick layers and fine-mesh wick layers alternating stacked together each other. 
     
     
         6 . The heat pipe of  claim 5 , wherein the wick layers comprise a first wick layer adjacent to and connect to the inner wall of the casing, the first wick layer being a fine-mesh wick layer. 
     
     
         7 . The heat pipe of  claim 1 , wherein the wick layers are fine-mesh wick layers and sintered powder wick layers alternating stacked together. 
     
     
         8 . The heat pipe of  claim 7 , wherein the wick layers comprise a first wick layer adjacent to and connect to the inner wall of the casing, the first wick layer being a fine-mesh wick layer. 
     
     
         9 . The heat pipe of  claim 1 , wherein a porosity of all the wick layers ranges from 40 to 65 percents. 
     
     
         10 . The heat pipe of  claim 1 , wherein wick layers are communicated with each other. 
     
     
         11 . A heat pipe comprising:
 a sealed cylindrical casing, the casing having an inner wall; and   more than three wick layers stacked at an inner surface of the casing in turn, the wick layers respectively defining a plurality of pores therein, diameters of the pores of the wick layers gradually decreasing from the inner wall to center of the casing, and a porosity of all the wick layers ranging from 40 to 65 percents.   
     
     
         12 . The heat pipe of  claim 11 , wherein the wick layers comprises a second wick layer near a center of the casing and away from the inner wall of the casing, the inner wick being a sintered powder wick layer, and the others being a fine-mesh wick layer. 
     
     
         13 . The heat pipe of  claim 11 , wherein the wick layers are groove-type wick layers and fine-mesh wick layers alternating stacked together. 
     
     
         14 . The heat pipe of  claim 11 , wherein the wick layers are fine-mesh wick layers and sintered powder wick layers alternating stacked together.