Abstract: A heat transfer assembly for a rotary regenerative air preheater has heat transfer plates which include means for spacing the plates apart to form flow passages and a plurality of rows of V-shaped ribs extending across the flow passages. Alternate rows of V-shaped ribs on each plate protrude outwardly from opposite surfaces of the plate. Several arrangements for aligning the ribs on one plate with the ribs on the adjacent plate are described as are alternate orientations of the adjacent rows of ribs on each plate. The relationship of the height of the ribs to the plate spacing is defined as is the relationship of the rib spacing to the rib height and the plate spacing to the length of the V-shaped rib sections.