A heat-exchanger assembly, which can be advantageously employed as an intercooler for an air-charging system for an internal combustion engines includes a plurality of generally wedge-shaped coolant tubes through which coolant is directed for effecting cooling of compressed air flowing about the tubes. In order to promote efficient operation, each of the wedge-shaped cooling tubes includes a plurality of coolant passages of substantially identical hydraulic diameter or cross-sectional area, thereby promoting uniform flow of coolant through each coolant tube. Each coolant tube includes outer walls which may be of a substantially uniform thickness, or which may increase in thickness across the width of the tube.