A heat exchanger, such as a water cooled charge air cooler, is disclosed for cooling of charge air with the aid of coolant. In at least one embodiment, the heat exchanger includes charge air tubes and coolant turbulators made of corrugated sheet metal interposed between the air tubes. The turbulators define coolant channels and including at least one turbulating device provided therein. According to at least one embodiment of the invention, at least one channel includes at least one continuously shaped side wall which is non-apertured along its entire length and thus promotes coolant flow along the channel by inhibiting cross flow of coolant to a neighbouring channel.