Heat exchanger and process for fabricating same

Abstract

A heat exchanger ( 1 ) which comprises a plurality of flat hollow bodies ( 2 ) arranged in parallel, and an aluminum fin ( 3 ) disposed between each pair of adjacent flat hollow bodies ( 2 ) and brazed thereto. The flat hollow body ( 2 ) is made from two plates ( 6 ) of an aluminum clad material comprising an aluminum core and a cladding of Al—Si brazing material covering at least one outer surface of the core, by brazing peripheral edges of the two plates to each other. The core of the clad material is made of an alloy containing 0.4 to 1.5 mass % of Cu and the balance Al and inevitable impurities. A line graph representing variations in potential relative to the depth of a surface layer portion of an outer surface of the flat hollow body ( 2 ) from the outermost surface thereof to a depth of 100 μm has a potential gradient of at least 0.25 mV at points on the line of the graph. The heat exchanger can be fabricated easily at a low cost and has satisfactory resistance to pitting corrosion.

1 . A heat exchanger which comprises a plurality of flat hollow bodies arranged in parallel and each having a fluid passage portion, and an aluminum fin disposed between each pair of adjacent flat hollow bodies and brazed thereto and wherein a refrigerant flowing thereinto through a fluid inlet flows through the fluid passage portions of all the flat hollow bodies and is run off through a fluid outlet, 
 each of the flat hollow bodies being made from an aluminum clad material having an aluminum core and a cladding of Al—Si alloy brazing material covering at least an outer surface of the core, the core of the clad material being made of an alloy containing 0.4 to 1.5 mass % of Cu and the balance Al and inevitable impurities, a line graph representing variations in potential relative to the depth of a surface layer portion of an outer surface of the flat hollow body from the outermost surface thereof to a depth of 100 μm having a potential gradient of at least 0.25 mV at points on the line of the graph.    
   
   
       2 . A heat exchanger according to  claim 1  wherein the flat hollow body is made from two plates of an aluminum clad material having an aluminum core and a cladding of Al—Si brazing material covering opposite surfaces of the core, by brazing peripheral edges of the two plates to each other, the flat hollow body having between the two plates a bulging fluid passage portion and a tank portion communicating with the fluid passage portion.  
   
   
       3 . A heat exchanger according to  claim 1  wherein the core of the aluminum clad material forming the flat hollow body further contains 0.4 to 1.5 mass % of Mn.  
   
   
       4 . A heat exchanger according to  claim 1  wherein the core of the aluminum clad material forming the flat hollow body further contains 0.06 to 0.35 mass % of Ti.  
   
   
       5 . A heat exchanger according to  claim 1  wherein the core of the aluminum clad material forming the flat hollow body contains up to 0.4 mass % of Si as an inevitable impurities.  
   
   
       6 . A heat exchanger according to  claim 1  wherein the core of the aluminum clad material forming the flat hollow body contains up to 0.3 mass % of Fe as an inevitable impurities.  
   
   
       7 . A heat exchanger according to  claim 1  wherein the core of the aluminum clad material forming the flat hollow body contains up to 0.4 mass % of Mg as an inevitable impurities.  
   
   
       8 . A vehicle having an air conditioner comprising a compressor, a condenser and an evaporator and adapted for use with a chlorofluorocarbon refrigerant, the evaporator comprising a heat exchanger according to any one of  claims 1  to  7 .  
   
   
       9 . A process for fabricating a heat exchanger which comprises a plurality of flat hollow bodies arranged in parallel and each having a fluid passage portion, and an aluminum fin disposed between each pair of adjacent flat hollow bodies and brazed thereto and wherein a refrigerant flowing thereinto through a fluid inlet flows through the fluid passage portions of all the flat hollow bodies and is run off through a fluid outlet, 
 the process being characterized in that the process includes making each of the flat hollow bodies from an aluminum clad material having an aluminum core and a cladding of Al—Si brazing material covering at least an outer surface of the core, the core being made of an alloy containing 0.4 to 1.5 mass % of Cu and the balance Al and inevitable impurities, and brazing the fin to the pair of flat hollow bodies by maintaining a temperature of at least 550° C. for 5 to 45 minutes.    
   
   
       10 . A process for fabricating a heat exchanger according to  claim 9  wherein the fin and the pair of flat hollow bodies are quenched to 400° C. at a cooling rate of at least 50° C./min after heating for the brazing.  
   
   
       11 . A process for fabricating a heat exchanger according to  claim 9  which includes making the flat hollow body from two plates of an aluminum clad material having an aluminum core and a cladding of Al—Si brazing material covering opposite surfaces of the core, by brazing peripheral edges of the two plates to each other, and the plates are brazed for making the flat hollow body simultaneously with the brazing of the fin.  
   
   
       12 . A process for fabricating a heat exchanger according to  claim 9  wherein the brazing is effected by vacuum brazing.  
   
   
       13 . A process for fabricating a heat exchanger according to  claim 9  wherein the core of the aluminum clad material forming the flat hollow body further contains 0.4 to 1.5 mass % of Mn.  
   
   
       14 . A process for fabricating a heat exchanger according to  claim 9  wherein the core of the aluminum clad material forming the flat hollow body further contains 0.06 to 0.35 mass % of Ti.  
   
   
       15 . A process for fabricating a heat exchanger according to  claim 9  wherein the core of the aluminum clad material forming the flat hollow body contains up to 0.4 mass % of Si as an inevitable impurities.  
   
   
       16 . A process for fabricating a heat exchanger according to  claim 9  wherein the core of the aluminum clad material forming the flat hollow body contains up to 0.3 mass % of Fe as an inevitable impurities.  
   
   
       17 . A process for fabricating a heat exchanger according to  claim 9  wherein the core of the aluminum clad material forming the flat hollow body contains up to 0.4 mass % of Mg as an inevitable impurities.