Abstract: An air-cooled condenser has a first stage comprising both a K and a D section with fin tubes fed with steam at both ends, and a second stage comprising a D section. Each core tube in the first stage has at least one extraction channel at the trailing edge of the core tube located in an unfinned section of the core tube and separated from the main section of the core tube by a rib or baffle. Extraction channels may be provided at both the leading and trailing edges or rounded ends of the core tube, or at the trailing edge only. Openings in the rib connect at least a central portion of the main section to the extraction channel. The upper end of each extraction channel of each core tube is connected via an extraction passageway and transfer duct to the lower ends of the D-section fin tubes. The D-section creates a strong suction action to draw steam and non-condensibles out of the first stage.