Increasing boiling heat transfer using low thermal conductivity materials

Abstract

An apparatus having a heat transfer surface for transfer of heat from the apparatus to a liquid. The heat transfer surface includes at least two different materials and at least two of said materials have different thermal conductivities. A method of boiling at least one liquid which provides increased heat transfer from a heat transfer surface of an apparatus to a liquid comprising a step of boiling said liquid in contact with the apparatus, is also disclosed. Also described is a method of tuning a heat transfer surface by forming the heat transfer surface using at least two different materials having different thermal conductivities arranged in a predetermined spatial relationship including a spacing between the portions of one said material that is from about 0.1λ C to about 5λ C , wherein λ C is a capillary length of a bubble of a predetermined liquid to be boiled using said heat transfer surface.

What is claimed is: 
     
         1 . An apparatus having a heat transfer surface for transfer of heat from the apparatus to a liquid, said heat transfer surface comprising at least two different materials and wherein at least two of said materials have a ratio of thermal conductivities of greater than about 10:1, and the material having the lowest of said thermal conductivities forms from about 1-60% of said heat transfer surface. 
     
     
         2 . The apparatus as claimed in  claim 1 , wherein at least two of said different materials have a ratio of thermal conductivities of greater than about 100:1. 
     
     
         3 . The apparatus as claimed in  claim 1 , wherein the material having the lowest of said thermal conductivities forms from about 8-25%, of said heat transfer surface. 
     
     
         4 . The apparatus as claimed in  claim 1 , wherein said heat transfer surface is formed by only two said materials. 
     
     
         5 . The apparatus as claimed in  claim 1  wherein the heat transfer surface is a flat or substantially flat surface that is configured to generate a spatial variation in a temperature of the heat transfer surface at least when heat is provided to the heat transfer surface. 
     
     
         6 . The apparatus of  claim 1 , wherein a critical heat flux from the heat transfer surface to a liquid is greater than a critical heat flux of a heat transfer surface made from only one of said at least two materials. 
     
     
         7 . The apparatus of  claim 1 , wherein a heat transfer coefficient of the heat transfer surface is greater than a heat transfer coefficient of a heat transfer surface made from only one of said at least two materials. 
     
     
         8 . The apparatus of  claim 1 , wherein a spacing between surface portions of one of said at least two materials is from about 0.1λ C  to about 10λ C , wherein λ C  is a capillary length for a bubble of a predetermined liquid represented by: 
       
         
           
             
               
                 λ 
                 C 
               
               = 
               
                 
                   σ 
                   
                     g 
                      
                     
                       ( 
                       
                         
                           ρ 
                           i 
                         
                         - 
                         
                           ρ 
                           v 
                         
                       
                       ) 
                     
                   
                 
               
             
           
         
         σ is a surface tension at the interface, g is the acceleration of gravity and ρ i  and ρ v  are the densities of the liquid and vapor phases of said liquid, respectively. 
       
     
     
         9 . The apparatus of  claim 8 , wherein a spacing between surface portions of one of said at least two materials is from about 0.5λ C  to about 2λ C . 
     
     
         10 . The apparatus of  claim 1 , wherein surface portions of each said material are rectangular or substantially rectangular in shape. 
     
     
         11 . The apparatus of  claim 1 , wherein surface portions of one said material are in the form of dots having a length of from 0.01-50 mm in a longest dimension. 
     
     
         12 . The apparatus of  claim 11  wherein said dots have a shape selected from circular, elliptical, square, substantially circular, substantially elliptical, substantially square, rectangular, substantially rectangular or any combination of one or more of said shapes. 
     
     
         13 . The apparatus of  claim 1 , wherein the apparatus is selected from a vessel and an immersion heater. 
     
     
         14 . A method of boiling at least one liquid which provides increased heat transfer from a heat transfer surface of an apparatus to a liquid comprising a step of boiling said liquid in contact with an apparatus as claimed in  claim 1 . 
     
     
         15 . A method for increasing one or both of a critical heat flux from a heat transfer surface of an apparatus to a liquid and/or a heat transfer coefficient of the heat transfer surface comprising a step of providing an apparatus with the heat transfer surface as claimed in  claim 1 . 
     
     
         16 . A method of tuning a heat transfer surface of an apparatus comprising a step of forming the heat transfer surface using at least two different materials having different thermal conductivities arranged in a predetermined spatial relationship configured to further increase the critical heat flux from the heat transfer surface to a liquid and/or the heat transfer coefficient of the heat transfer surface by providing a spacing between surface portions one said material that is from about 0.1λ C  to about 5λ C , wherein λ C  is a capillary length of a bubble of a predetermined liquid to be boiled using said heat transfer surface. 
     
     
         17 . The method as claimed in  claim 16 , wherein the spacing between surface portions of is from 0.5λ C  to about 2λ C , wherein λ C  is a capillary length for a bubble of a predetermined liquid represented by: 
       
         
           
             
               
                 λ 
                 C 
               
               = 
               
                 
                   σ 
                   
                     g 
                      
                     
                       ( 
                       
                         
                           ρ 
                           i 
                         
                         - 
                         
                           ρ 
                           v 
                         
                       
                       ) 
                     
                   
                 
               
             
           
         
         σ is a surface tension at the interface, g is the acceleration of gravity and ρ i  and ρ v  are the densities of the liquid and vapor phases of said liquid, respectively.