Abstract: A corner frame construction for a heat exchanger includes an elongated L-shaped member disposed between the top and bottom plates of the heat exchanger. The L-shaped member has a first leg extending parallel to a first edge of the media layers and a second leg extending perpendicular to the first leg and parallel to a second edge of the media layers. A first flange is connected to the first leg and extends inwardly toward the edge of the media layer and a second flange is connected to the second leg and extends inwardly toward a second edge of the media layer. A layer of flowable sealant is disposed along the length of the L-shaped member and is contact with both the first and second legs, the first and second media edges and the first and second flange members.