Rotor for rotary heat exchangers

A rotor for a rotary heat exchanger comprising a plurality of successive circumferential layers of corrugated foil. The corrugated foil in the adjacent layers may be joined by plane foil layers interposed between adjacent layers of corrugated foil, or may be joined directly to each other. The foil adjacent the hub of the rotor is of greater strength than the foil adjacent the periphery, preferably by providing a greater thickness in the foil in the inner layers as compared to the foil in the outer layers.

This invention relates to a rotor for rotary heat exchangers for heat 
exchange between two airstreams. 
Regenerative heat exchangers are highly suitable for use in the recovery of 
heat from ventilation air or from air or gases from industrial processes, 
because such heat exchangers have a relatively high efficiency degree and, 
besides, can transfer moisture. Regenerative heat exchangers usually 
comprise a rotary disc-shaped heat exchanger body, which is assembled of 
alternatingly plane and corrugated foils of paper, asbestos or metal. The 
plane and corrugated foils usually are joined by gluing. 
In the case of heat exchanger rotors of paper, asbestos or similar 
material, the rotor most often must be assembled about bearing structural 
members of metal in order to provide the rotor with the necessary 
mechanical strength. This applies particularly to large rotors having a 
diameter of several meters. The bearing structural members may consist of 
radial spokes and annular elements, which are concentric with the rotor 
hub. Rotors of this design are described in the Swedish patent 
specification No. 348,826. 
Heat exchanger rotors assembled of metal foils, for example aluminium, have 
the advantage of rendering it possible to manufacture relatively large 
rotors without having to provide them with extra bearing structural 
members. This, of course, reduces the manufacturing costs. However, also 
in the case of rotors assembled of metal foils, problems arise with 
respect to achieving a mechanical strength, which is sufficient also for 
really large rotors. The strength of the rotor, certainly, can be 
increased by increasing the thickness of the metal foils, but this results 
in a higher rotor weight, which in its turn implies higher stresses on the 
rotor portions or zones closest to the hub. An increase of the thickness 
of the foil material, moreover, renders the rotor substantially more 
expensive. 
The object of the present invention is to produce a heat exchanger rotor 
without the aforesaid disadvantages. 
This object is achieved by a rotor assembled of alternatingly plane and 
corrugated foils of aluminium, and the design advantageous from the aspect 
of strength is obtained by the thickness of these foils decreasing with 
the distance from the hub, preferably in two, three or more steps. The 
principle, of course, is also applicable to other materials and to 
different designs of the corrugated web. 
The rotor, for example, can also be assembled of a single corrugated web of 
suitable design.

The heat exchanger rotor 1 shown in FIG. 1 is assembled about a cylindric 
hub 2 with an axle 3. The rotor is manufactured by winding alternating 
circumferential layers of a plane foil 7 and a corrugated foil 8 about the 
hub 2. The rotor portion or zone 4 closest to the hub 2 is built up of 
thicker foils 7a and 8a than corresponding foils in the rotor portions or 
zones 5 and 6. In like manner, the foils 7b and 8b have a greater 
thickness in the layers of rotor zone 5 than in the layers of rotor zone 
6. The foils 7 and 8 must not necessarily have equal relative thickness in 
the layers of different rotor zones 4, 5 and 6, nor is it necessary to 
simultaneously increase the thickness of the plane foil 7 and corrugated 
foil 8 in the layers of inner rotor zones 4 and 5. It also is possible to 
choose a material of greater strength in the layers of rotor zone 4 than 
in the layers of the remaining zones of the rotor, and different materials 
may also be chosen in the layers of rotor zones 5 and 6. 
As appears from FIG. 2, the plane foil 7 can be joined with the corrugated 
foil 8, for example by a glue line 9. In the rotor zone 4, the joining of 
the foils 7a and 8a is required to be more efficient than in the remaining 
zones of the rotor. This can be achieved, provided the joining is carried 
out by gluing, by laying a relatively substantial glue line in the rotor 
zone 4. 
At a rotor assembled of aluminium foils of the kind shown in FIGS. 1 and 2, 
the foil thickness in the layers of rotor zone 4 may be in the range 
between 0.12 and 0.20 mm, for example 0.15 mm, in the layers of rotor zone 
5 may be in the range between 0.07 and 0.12 mm, for example 0.10 mm, and 
in the layers of rotor zone 6 may be in the range between 0.03 and 0.07 
mm, for example 0.05 mm. As an example may also be mentioned that at an 
outer diameter of the rotor of 3.5 m, the diameter of the rotor zones 4 
and 5 preferably can be chosen to be about 0.8 m and about 1.7 m, 
respectively. 
In FIG. 3, another mode of assembly of the rotor 1 is shown where only a 
corrugated foil 10 is utilized in each layer. In this figure, the 
corrugated foil 10 is wrapped around a hub 12 in layers and consists of 
V-shaped corrugations 14 which are spaced apart circumferentially by 
spacer segments 17. The corrugations 14 of one layer are joined to the 
segments 17 of the adjacent layer, for example by glue lines 19. The 
aforedescribed principle of using in the inner rotor zones 4 and 5 thicker 
foils or foils of materials having a higher strength can be applied also 
in this case. 
The corrugation embodiments of the foils shown in FIGS. 2 and 3, of course, 
can be varied in several ways. As one example, the thickness or strength 
of the foil may be decreased gradually and continuously from the hub 
outwardly to the outer periphery.