Abstract: A system for heat exchange processing of particulate solid material is disclosed. The particulate solids are flowed by gravity through a housing packed with flat, internally cooled (or heated) heat exchange panels spaced apart to define generally vertical channels for the passage of the solid particulate. The panels are formed of opposed metal sheets, sealed around their edges, spot welded together in limited areas of joinder, in a predetermined pattern over their surfaces, and hydrostatically expanded in the areas between to form surfaces that are quilt-like in appearance. The panels are configured in two alternate forms such that, when a plurality of panels are assembled in a stack, the hydrostatically expanded portions of one panel are disposed opposite the areas of joinder of an adjacent panel of alternate configuration, creating a sinuous, but relatively uniform flow path for the flow of particulate solids between panels.