Black layer coated heat exchanger

Abstract

A primary heat exchanger of a condensing furnace or a single heat exchanger of a mid-efficiency furnace is electrochemically coated with a coating of copper metal. The copper coating is oxidized with an aqueous oxidizing alkaline solution to form a matte black layer of cupric oxide. As the layer of cupric oxide is black, the layer has a high emissivity and emits more heat, increasing the efficiency of the primary heat exchanger. Alternatively, iron can be electrochemically coated on the primary heat exchanger and oxidized to black magnetite to increase emissivity.

What is claimed is:  
     
         1 . A method for making a heat exchanger of a furnace system comprising the steps of: 
 applying a layer of an oxidizable material on a first surface of said heat exchanger; and    oxidizing said layer of oxidizable material to form a layer of dark material having a high emissivity.    
     
     
         2 . The method as recited in  claim 1  wherein the step of applying said layer of said oxidizable material includes applying said layer of oxidizable material electrochemically.  
     
     
         3 . The method as recited in  claim 1  wherein step of oxidizing said layer of oxidizable material includes utilizing an oxidizing alkaline solution to oxidize said layer of oxidizable material.  
     
     
         4 . The method as recited in  claim 1  wherein said layer of oxidizable material is copper.  
     
     
         5 . The method as recited in  claim 4  wherein said layer of oxidizable material is oxidized to cupric oxide.  
     
     
         6 . The method as recited in  claim 1  wherein said layer of oxidizable material is iron.  
     
     
         7 . The method as recited in  claim 6  wherein said layer of oxidizable material is oxidized to magnetite.  
     
     
         8 . The method as recited in  claim 1  further including the step of applying said layer of oxidizable material to a second surface of said heat exchanger component.  
     
     
         9 . The method as recited in  claim 1  wherein said first surface is an inner surface and said layer of oxidizable material applied on said first surface is copper which is oxidized to cupric oxide and said second surface is an outer surface and said layer of oxidizable material applied on said second surface is iron which is oxidized to magnetite.  
     
     
         10 . A heat exchanger of a furnace system comprising: 
 a first surface; and    a layer of dark material having a high emissivity applied on said first surface.    
     
     
         11 . The heat exchanger as recited in  claim 10  wherein said layer of dark material is cupric oxide.  
     
     
         12 . The heat exchanger as recited in  claim 10  wherein said layer of dark material is magnetite.  
     
     
         13 . The heat exchanger as recited in  claim 10  wherein said heat exchanger is made of a steel alloy.  
     
     
         14 . The heat exchanger as recited in  claim 10  wherein said heat exchanger is made of a metal coated steel.  
     
     
         15 . The heat exchanger as recited in  claim 10  wherein said heat exchanger is a primary heat exchanger.  
     
     
         16 . The heat exchanger as recited in  claim 10  wherein heat exchanger further includes an opposing second surface and said layer of dark material is also applied on said opposing second surface.  
     
     
         17 . The heat exchanger as recited in  claim 10  wherein said first surface of said heat exchanger is an inner surface and said layer of material applied on said first surface is cupric oxide and said second surface of said heat exchanger is an outer surface and said layer of dark material applied on said second surface is magnetite.  
     
     
         18 . A primary heat exchanger of a condensing furnace system comprising: 
 an inner surface and an outer surface; and    a layer of cupric oxide having a high emissivity applied on said inner surface and said outer surface.    
     
     
         19 . The heat exchanger as recited in  claim 18  wherein said heat exchanger is made of a steel alloy.  
     
     
         20 . The heat exchanger as recited in  claim 18  wherein said heat exchanger is made of a metal coated steel.