A tube for use in a heat exchanger comprises a base portion, an upper portion spaced from and opposing the base portion, and a partitioning wall extending between the base portion and the upper portion to divide a hollow interior of the tube into a first flow channel and a second flow channel. The partitioning wall includes a plurality of windows spaced from each other in a longitudinal direction of the tube to provide fluid communication between the first flow channel and the second flow channel. At least one of the windows includes a tabbed portion of the partitioning wall bent to extend into one of the first flow channel or the second flow channel.