Flattened tube finned heat exchanger and fabrication method

Abstract

A multiple tube bank heat exchanger includes a first tube bank including at least a first and a second flattened tube segments extending longitudinally in spaced parallel relationship and a second tube bank including at least a first and a second flattened tube segments extending longitudinally in spaced parallel relationship. The second tube bank is disposed behind the first tube bank with a leading edge of the second tube bank spaced from a trailing edge of the first tube bank. A continuous folded fin extends between the first and second flattened tube segments of both of said first tube bank and said second tube bank.

What is claimed is: 
     
         1 . A heat exchanger for transferring heat between a fluid to be cooled and a cooling fluid comprising:
 a first heat exchanger slab including a first manifold, a second manifold spaced from the first manifold, and a first tube bank extending between the first manifold and the second manifold and including a plurality of flattened tube segments extending longitudinally in spaced parallel relationship and defining a flow passage for the fluid to be cooled; and   a second heat exchanger slab including a first manifold, a second manifold spaced from the first manifold, and a second tube bank extending between the first manifold and the second manifold and including a plurality of flattened tube segments extending longitudinally in spaced parallel relationship and defining a flow passage for the fluid to be cooled, said second heat exchanger slab disposed downstream of said first heat exchanger slab, the second manifold of said second heat exchanger slab being connected in fluid flow communication with the second manifold of said first heat exchanger slab;   wherein:
 the first manifold of said second heat exchanger slab defines an inlet header for receiving the fluid to be cooled and distributing the fluid to be cooled amongst the flattened tube segments of the second tube bank; 
 the second manifold of said second heat exchanger slab defines an intermediate header for receiving the fluid to be cooled from the flattened tube segments of the second tube bank; 
 the second manifold of said first heat exchanger slab defines an intermediate header and a separate outlet header, the intermediate header for receiving the fluid to be cooled from the second manifold of the second heat exchanger slab and distributing the fluid to be cooled to a first number of the flattened tube segments of the first tube bank, the outlet header for receiving the fluid to be cooled from a second number of the flattened tube segments of the first tube bank; and 
 the first manifold of said first heat exchanger slab defines an intermediate header for receiving the fluid to be cooled from the first number of the flattened tube segments of the first tube bank and for distributing the fluid to be cooled amongst the second number of the flattened tube segments of the first tube bank. 
   
     
     
         2 . The heat exchanger as recited in  claim 1  wherein the plurality of flattened tube segments of the second tube bank collectively define a first flow pass for the fluid to be cooled, the first number of the plurality of flattened tube segments of the first tube bank collectively define a second flow pass for the fluid to be cooled, and the second number of the plurality of flattened tube segments of the first tube bank collectively define a third flow pass for the fluid to be cooled. 
     
     
         3 . The heat exchanger as recited in  claim 2  wherein:
 the third flow pass is disposed above the second flow pass within the first tube bank; and 
 the second manifold of said first heat exchanger slab defines a lower intermediate header and an upper outlet header, the lower intermediate header in flow communication with the second flow pass and the upper outlet header in flow communication with the third flow pass. 
 
     
     
         4 . The heat exchanger as recited in  claim 3  wherein the first fluid flow pass comprises at least a refrigerant desuperheating pass, the second fluid flow pass comprises a refrigerant condensing pass, and the third fluid flow pass comprises at least a refrigerant subcooling pass. 
     
     
         5 . The heat exchanger as recited in  claim 3  wherein the first fluid flow pass comprises a refrigerant desuperheating and condensing pass; the second fluid flow pass comprises a refrigerant condensing pass, and the third fluid flow pass comprises a refrigerant condensing and subcooling pass. 
     
     
         6 . The heat exchanger as recited in  claim 4  wherein a ratio of the first number of flattened tube segments defining the second refrigerant flow pass to the second number of flattened tube segments defining the third refrigerant flow pass ranges from a 70%/30% split to a 80%/20% split. 
     
     
         7 . The heat exchanger as recited in  claim 3  wherein the second manifold of the second heat exchanger slab is connected internally directly in fluid flow communication with the lower intermediate header only of the second manifold of the first heat exchanger slab. 
     
     
         8 . The heat exchanger as recited in  claim 3  wherein the second manifold of the second heat exchanger slab is connected by at least one return bend tube in fluid flow communication with the lower intermediate header only of the second manifold of the first heat exchanger slab. 
     
     
         9 . The heat exchanger as recited in  claim 1  wherein the first manifold of said second heat exchanger slab defines an interior volume having a first cross-sectional area, the second manifold of said second heat exchanger slab defines an interior volume having a second cross-sectional area, the second manifold of said first heat exchanger slab defines an interior volume having a third cross-sectional area, and the first manifold of said first heat exchanger slab defines an interior volume having a fourth cross-sectional area, the first cross-sectional area being greater than fourth the cross-sectional area. 
     
     
         10 . The heat exchanger as recited in  claim 9  wherein the first cross-sectional area has the largest magnitude and the magnitude of the cross-sectional areas decreases successively from the first cross-sectional area to the fourth cross-sectional area. 
     
     
         11 . In a multiple slab heat exchanger having:
 a first heat exchanger slab having a first plurality of flattened tube segments extending longitudinally in spaced parallel relationship to form a first tube bank;   a second heat exchanger slab having a second plurality of flattened tube segments extending longitudinally in spaced parallel relationship to form a second tube bank, said second tube bank disposed in generally parallel alignment with said first tube bank with a longitudinal edge of the plurality of flattened tube segments of said second tube bank disposed at a spacing gap from a longitudinal edge of the plurality of flattened tube segments of said first tube bank; and   a plurality of continuous folded fins extending between the first plurality of flattened tube segments of said first tube bank and the second plurality of flattened tube segments of said second tube bank from at least a leading face of said first tube bank to a trailing face of said second tube bank and spanning said gap;   a method for adjusting a ratio of the primary heat transfer surface area collectively defined by the first and second plurality of flattened tube segments to the secondary heat transfer surface area collectively defined by the plurality of folded fin strips, the method comprising increasing or decreasing a depth of said gap.