A heat exchanger (10, 110) comprising: a first header including an inlet of the heat exchanger (10, 110); a second header downstream from the first header; a first tube (14a, 114a) defining a first flow pass, the first tube (14a, 114a) in fluid communication with the first header to receive a fluid from the first header, the first tube (14a, 114a) including first and second opposing flat broad sides joined by first and second opposing narrow sides; a second tube (14b, 114b) defining a second flow pass in series with the first flow pass, the second tube (14b, 114b) in fluid communication with the second header to supply the fluid to the second header from the first tube (14a, 114a); a third header coupled to the first tube (14a, 114a) and the second tube (14b, 114b) to direct the fluid from the first tube (14a, 114a) to the second tube, the third header including, a first plate (60, 60', 60", 160) including a first generally planar face approximately perpendicular to the first and the second opposing flat broad sides of the first and the second tubes (14a, 114a, 14b, 114b) and a first arcuate recess (74, 74") that extends from the first planar face (64, 164) to at least partially define a flow conduit between the first tube (14a, 114a) and the second tube (14b, 114b), a second plate (62, 62', 62", 162) including a second generally planar face (66, 166) parallel to the first planar face (64, 164) and coupled to the first planar face (64, 164), the second plate (62, 62', 62", 162) including a second arcuate recess (72, 72', 72") that extends from the second planar face (66, 166) to at least partially define the flow conduit between the first tube (14a, 114a) and the second tube (14b, 114b), characterized in that the first arcuate recess (74, 74") includes a first radius (80, 80") of curvature measured from a first axis generally parallel to the first planar face, wherein the second arcuate recess (72, 72', 72") includes a second radius (76, 76') of curvature measured from a second axis (78, 78') generally parallel to the second planar face, wherein the first axis and the second axis (78, 78') are located within a first plane generally parallel to and midway between the first and the second opposing flat broad sides of the first tube (14a, 114a) and the second tube (14b, 114b), wherein the first axis is located within a second plane defined by the first planar face (64, 164), and wherein the second axis (78, 78') is located within a third plane defined by the second planar face (66, 166). a first header including an inlet of the heat exchanger (10, 110); a second header downstream from the first header; a first tube (14a, 114a) defining a first flow pass, the first tube (14a, 114a) in fluid communication with the first header to receive a fluid from the first header, the first tube (14a, 114a) including first and second opposing flat broad sides joined by first and second opposing narrow sides; a second tube (14b, 114b) defining a second flow pass in series with the first flow pass, the second tube (14b, 114b) in fluid communication with the second header to supply the fluid to the second header from the first tube (14a, 114a); a third header coupled to the first tube (14a, 114a) and the second tube (14b, 114b) to direct the fluid from the first tube (14a, 114a) to the second tube, the third header including, a first plate (60, 60', 60", 160) including a first generally planar face approximately perpendicular to the first and the second opposing flat broad sides of the first and the second tubes (14a, 114a, 14b, 114b) and a first arcuate recess (74, 74") that extends from the first planar face (64, 164) to at least partially define a flow conduit between the first tube (14a, 114a) and the second tube (14b, 114b), a second plate (62, 62', 62", 162) including a second generally planar face (66, 166) parallel to the first planar face (64, 164) and coupled to the first planar face (64, 164), the second plate (62, 62', 62", 162) including a second arcuate recess (72, 72', 72") that extends from the second planar face (66, 166) to at least partially define the flow conduit between the first tube (14a, 114a) and the second tube (14b, 114b), a first plate (60, 60', 60", 160) including a first generally planar face approximately perpendicular to the first and the second opposing flat broad sides of the first and the second tubes (14a, 114a, 14b, 114b) and a first arcuate recess (74, 74") that extends from the first planar face (64, 164) to at least partially define a flow conduit between the first tube (14a, 114a) and the second tube (14b, 114b), a second plate (62, 62', 62", 162) including a second generally planar face (66, 166) parallel to the first planar face (64, 164) and coupled to the first planar face (64, 164), the second plate (62, 62', 62", 162) including a second arcuate recess (72, 72', 72") that extends from the second planar face (66, 166) to at least partially define the flow conduit between the first tube (14a, 114a) and the second tube (14b, 114b), characterized in that the first arcuate recess (74, 74") includes a first radius (80, 80") of curvature measured from a first axis generally parallel to the first planar face, wherein the second arcuate recess (72, 72', 72") includes a second radius (76, 76') of curvature measured from a second axis (78, 78') generally parallel to the second planar face, wherein the first axis and the second axis (78, 78') are located within a first plane generally parallel to and midway between the first and the second opposing flat broad sides of the first tube (14a, 114a) and the second tube (14b, 114b),