Heat exchange element with hydrophilic evaporator surface

Abstract

The present invention provides a heat exchange element for particular use in a film heat exchanger, such as a distillation system. The heat exchange element includes a substrate having a first surface and an opposing second surface. The first surface acts as a condenser surface. The heat exchange element further includes a composition disposed on at least a portion of the second surface. The composition has an exposed hydrophilic surface so as to provide a hydrophilic evaporator surface due to the composition being hydrophilic in nature. In contrast, the condenser surface is typically hydrophobic in nature. The use of the hydrophilic composition eliminates the nucleation of vapor bubbles and prevents gas film (or gas blanket) formation on the evaporator surface. As a result, the thermal resistance through the heat exchange element is decreased and the efficiency of the heat exchange element is increased.

What is claimed is:  
     
         1 . A heat exchange element comprising: 
 a substrate having a first surface and an opposing second surface, the first surface acting as a condenser surface; and    a composition disposed on at least a portion of the second surface, the composition having an exposed hydrophilic surface so as to provide a hydrophilic evaporator surface,    wherein the substrate is formed of plastic.    
     
     
         2 . The heat exchange element of  claim 1 , wherein the composition substantially covers the second surface.  
     
     
         3 . The heat exchange element of  claim 1 , wherein the first surface comprises a hydrophobic surface.  
     
     
         4 . The heat exchange element of  claim 1 , wherein the substrate is formed of a water and vapor impermeable material.  
     
     
         5 . The heat exchange element of  claim 1 , wherein the substrate is formed of a plastic material selected from the group consisting of polypropylene and polyethylene.  
     
     
         6 . The heat exchange element of  claim 1 , wherein the composition comprises a metal oxide.  
     
     
         7 . The heat exchange element of  claim 1 , wherein the composition comprises at least one of titanium oxide and nickel oxide.  
     
     
         8 . The heat exchange element of  claim 1 , wherein the second surface has hydrophilic properties such that liquid flowing therealong during an evaporation process is maintained below the critical heat flux value for the liquid.  
     
     
         9 . A distillation apparatus comprising: 
 an evaporator having an evaporator chamber;    a condenser having a condenser chamber; and    a heat exchange element disposed between the evaporator and the condenser such that the heat exchange element is in fluid communication with the condenser and evaporator chambers, the heat exchange element comprising: 
 a substrate having a first surface and an opposing second surface, the first surface acting as a condenser surface; and  
 a composition disposed on at least a portion of the second surface, the composition having an exposed hydrophilic surface so as to provide a hydrophilic evaporator surface,  
 wherein the substrate is formed of plastic.  
   
     
     
         10 . The distillation apparatus of  claim 9 , wherein the composition substantially covers the second surface.  
     
     
         11 . The distillation apparatus of  claim 9 , wherein the first surface comprises a hydrophobic surface.  
     
     
         12 . The distillation apparatus of  claim 9 , wherein the substrate is formed of a water and vapor impermeable material.  
     
     
         13 . The distillation apparatus of  claim 9 , wherein the composition comprises a metal oxide.  
     
     
         14 . The distillation apparatus of  claim 9 , wherein the composition comprises at least one of titanium oxide and nickel oxide.  
     
     
         15 . The distillation apparatus of  claim 9 , wherein the apparatus is used to distill sea water into desalinated water.