Heat transfer elements for a closed channel rotary regenerative air preheater

1. A closed channel rotary regenerative air preheater comprising:

element supporting baskets configured to rotate about a vertical axis, each element supporting basket supporting a discrete stack of a plurality of heat transfer elements resting in a parallel planar relationship along an entire length of each heat transfer element, said discrete stack of heat transfer elements comprising a plurality of first heat transfer elements and a plurality of second heat transfer elements, wherein the discrete stack of the plurality of heat transfer elements comprises an alternating order of one of the first heat transfer elements with one of the second heat transfer elements;

each of the plurality of first heat transfer elements having a straight central first plane and being fabricated to comprise uniform alternating longitudinal first arches, the first arches being parallel to one another;

each of the plurality of second heat transfer elements having a straight central second plane that is parallel to the straight central first plane, and each of the plurality of second heat transfer elements being fabricated to comprise a plurality of pairs of uniform alternating longitudinally adjacent opposing second arches relative to opposing sides of the second plane, the adjacent opposing second arches being parallel to one another, and an interval of longitudinally uniform undulations parallel to one another and angled at a non-zero angle with respect to the adjacent opposing second arches, the interval of longitudinally uniform undulations extending between each pair of adjacent opposing second arches, the interval of longitudinally uniform undulations being rigidity promoting features;

the adjacent opposing second arches of the second heat transfer elements defining a spacing between the first heat transfer elements and the second heat transfer elements;

each of the first arches of the first heat transfer element has an arcuate first apex and a concave segment on a first side of the first apex;

each of the adjacent opposing second arches of the second heat transfer element has an arcuate second apex and a convex segment on a second side of the second apex, the convex segment transitioning into a flat section configured at a non-zero angle relative to a line perpendicular to the straight central second plane, the flat section transitioning into the interval of longitudinally parallel uniform undulations; and

each of the convex segments is nested in a respective one of the concave segments thereby defining a contact line therebetween, the contact line extending an entire length of the first heat transfer element and the second heat transfer element, adjacent pairs of the contact lines being spaced apart from one another by a linear distance along a common plane parallel to the straight central second plane thereby defining a closed passageway therebetween and between the first heat transfer element and the second heat transfer element for heat transfer fluid flow therethrough, and the contact lines for successive first and second heat transfer elements being aligned perpendicular to the first and second straight central planes.

2. The air preheater of claim 1 , wherein a peak-to-peak height of the first arches of the first heat transfer elements is depicted as Hu and a peak-to-peak height of the adjacent opposing second arches of the second heat transfer elements is depicted as Hs, with the ratio of Hu:Hs approximately 1:2.5 to approximately 1:4.0.

3. The air preheater of claim 1 , wherein the first arches of the first heat transfer elements are parallel to one another and to a main direction of flow of fluid, the adjacent opposing second arches of the second heat transfer elements are parallel to one another and to a main direction of flow of fluid, and the uniform undulations of the second heat transfer elements are parallel to one another and are angled with respect to the main direction of flow of fluid.

4. The air preheater of claim 1 , wherein the first arches of the first heat transfer elements are parallel to one another and to a main direction of flow of fluid, the adjacent opposing second arches of the second heat transfer elements are parallel to one another and to a main direction of flow of fluid, and the uniform undulations of the second heat transfer elements are parallel to one another and are angled at approximately 20 degrees to approximately 50 degrees with respect to the main direction of flow of fluid.

5. The air preheater of claim 1 , wherein one or more of the adjacent opposing second arches of the second heat transfer elements include one or more hips or ridges for added strength.