A heat exchanger includes one or more hot medium flow regions and one or more cooling medium flow regions. Hot medium bars border the one or more hot medium flow regions and cooling medium bars border the one or more cooling medium flow regions. At least one cooling medium bar of the cooling medium bars is joined to a pair of partition sheets. The at least one cooling medium bar includes a base, a first leg, and a second leg. The first leg and the second leg each extend from the base. A cavity is provided between the first leg and the second leg. The cavity is in fluid communication with a first cooling medium flow region of the one or more cooling medium flow regions via an opening provided between the first leg and the second leg.