Heat exchangers having brazed tube-to-fin joints and methods of producing the same

Abstract

Heat exchangers and methods of producing thereof having fins with slots formed therethrough, and a continuous tube having parallel tube runs connected by reverse bends to define a serpentine coil that traverses back and forth through the slots formed in the fins. Each fin has surface enhancements and is metallurgically joined to corresponding portions of the tube at the slots with brazed joints therebetween.

1 . A heat exchanger comprising:
 fins having dogbone-shaped slots formed therethrough, each of the slots defining one or more circular portions interconnected with and intersected by a rectilinear portion that has a width that is narrower than a diameter of the circular portions, each of the circular portions having an incomplete circular perimeter and a collar bordering the incomplete circular perimeter;   at least one tube having reverse bends forming at least two parallel tube runs to define a serpentine coil that traverses back and forth through the slots formed in the fins; and   surface enhancements located between the slots thereof and located along the rectilinear portions thereof;   wherein the collars of the slots are metallurgically joined to corresponding portions of the tube with brazed joints.   
     
     
         2 . The heat exchanger of  claim 1 , wherein each of the slots defines an entire dogbone shape comprising a pair of the circular portions interconnected with and intersected by the rectilinear portion therebetween. 
     
     
         3 . The heat exchanger of  claim 1 , wherein each of the collars has a reflare portion that defines a surface that bends away from a central axis of the collar and the circular portion bordered thereby. 
     
     
         4 . The heat exchanger of  claim 1 , wherein each of the collars defines a gap between the incomplete circular perimeter thereof and the corresponding portion of the tube and the gap is filled by one of the brazed joints. 
     
     
         5 . The heat exchanger of  claim 1 , wherein each of the slots has only one of the circular portions and the rectilinear portion defines an opening at an edge of the fin. 
     
     
         6 . The heat exchanger of  claim 5 , wherein each of the fins comprises a second slot having a single circular portion and a single rectilinear portion that defines an opening at the edge of the fin. 
     
     
         7 . The heat exchanger of  claim 5 , wherein each of the collars has a reflare portion that defines a surface that bends away from a central axis of the collar and the circular portion bordered thereby. 
     
     
         8 . The heat exchanger of  claim 5 , wherein each of the collars defines a gap between the incomplete circular perimeter thereof and the corresponding portion of the tube and the gap is filled by one of the brazed joints. 
     
     
         9 . The heat exchanger of  claim 1 , wherein the tube includes at least two adjacent circuits each having a first connection configured to feed a fluid into the circuit and a second connection configured to discharge the fluid from the circuit, wherein at least one of the first and second connections is shared by the at least two adjacent circuits to define a split connection. 
     
     
         10 . The heat exchanger of  claim 9 , wherein the tube is a continuous tube that defines the serpentine coil in its entirety, and the split connection is located at a corresponding one of the reverse bends in the tube. 
     
     
         11 . The heat exchanger of  claim 9 , wherein the tube comprises a plurality of continuous tubes that define the serpentine coil. 
     
     
         12 . A method of producing a heat exchanger, the method comprising:
 providing fins having dogbone-shaped slots formed therethrough, each of the slots defining one or more circular portions interconnected with and intersected by a rectilinear portion that has a width that is narrower than a diameter of the circular portions, each of the circular portions having an incomplete circular perimeter and a collar bordering the incomplete circular perimeter, the fins having surface enhancements located between the slots thereof and located along the rectilinear portions thereof;   forming at least one tube having reverse bends and at least two parallel tube runs to define a serpentine coil;   assembling the fins and the tube such that the tube traverses back and forth through the slots formed in the fins, the assembling of the fins and the tube including inserting each of the reverse bends through a corresponding one of the slots; and   performing a brazing operation on the fins and the tube such that a braze material clad on at least one of the tube and fins melts and the collars of the slots are metallurgically joined to corresponding portions of the tube with brazed joints formed by the braze material.   
     
     
         13 . The method of  claim 12 , wherein each of the slots defines an entire dogbone shape comprising a pair of the circular portions interconnected with and intersected by the rectilinear portion therebetween. 
     
     
         14 . The method of  claim 12 , wherein each of the collars defines a gap between the incomplete circular perimeter thereof and the corresponding portion of the tube, and the brazing operation causes the brazed material to fill the gap. 
     
     
         15 . The method of  claim 12 , wherein each of the collars has a reflare portion that defines a surface that bends away from a central axis of the collar and the circular portion bordered thereby. 
     
     
         16 . The method of  claim 12 , the method further comprising stacking the fins prior to the assembling of the fins and the tube such that at least some of the fins contact corresponding collars of the fins adjacent thereto. 
     
     
         17 . The method of  claim 12 , further comprising providing a hole in at least a first of the reverse bends and providing a connection fluidically coupled to the hole configured to either feed a fluid into or discharge the fluid from a pair of circuits of the tube coupled to opposite ends of the first reverse bend. 
     
     
         18 . The method of  claim 17 , wherein the hole is formed in the first reverse bend after the first reverse bend is formed. 
     
     
         19 . The method of  claim 17 , wherein the hole is formed in the first reverse bend before the first reverse bend is formed. 
     
     
         20 . The method of  claim 17 , wherein the hole has an elliptical shape before the first reverse bend is formed and a circular shape after the first reverse bend is formed.