Abstract: A heat exchanger that includes a heat exchange tube for flow of a liquid therethrough and including a turbulator on the interior of the tube at the inner wall surface thereof with the turbulator comprising a strip of expanded metal arranged in a helix and having spacing projections at the opposite side edges of the strip with the spacing projections being integral with the expanded metal and in contact with the inner surface of the tube for spacing the turbulator from the wall surface. The strands and bridges of the expanded metal which define the openings through the metal are arranged with relation to the tube axis and the wall surface to direct a portion of the liquid toward the inner wall surface for controlled heat transfer and to direct the remainder of the liquid flow adjacent to the wall surface toward the main liquid stream on the interior of the tube, thereby achieving improved and preselected heat transfer through the tube wall with minor pressure drop of the liquid flowing through the tube.