Patent ID: 8622115

Claim:
A heat transfer element in a rotary regenerative heat exchanger comprising: notches extending parallel to each other on the heat transfer element and configured to form passageways between adjacent heat transfer elements upon stacking thereof such that the notches on the heat transfer element are located between notches on adjacent heat transfer elements, each of the notches including lobes projecting outwardly from opposite sides of the heat transfer element and having a peak-to-peak height; first undulations extending parallel to each other on the heat transfer element between the notches, each of the first undulations including lobes projecting outwardly from the opposite sides of the heat transfer element having a peak-to-peak height; and second undulations extending parallel to each other on the heat transfer element between the notches, each of the second undulations being immediately adjacent to and alternating with corresponding first undulations, each of the second undulations including lobes projecting outwardly from the opposite sides of the heat transfer element having a peak-to-peak height, wherein the peak-to-peak height of the second undulations each of is less than the peak-to-peak height of the first undulations each of.