Abstract: A heat exchanger (10) in accordance with the invention includes first and second heat conductive, spaced apart plates (12 and 14) and a heat conductive sheet (16) disposed between the plates and having repeating ridges (18) in thermal contact with the plates with successive ridges facing a different one of the plates and sections (22) of the sheet between successive ridges being inclined with respect to the axis of fluid flow and containing at least one aperture (32, 34 and 38) extending between the opposed surfaces of the section for passing fluid flow through the at least one aperture when fluid flows along the axis of fluid flow with fluid flow through the at least one aperture of the plurality of sections producing jets of fluid contacting one of the plates.