THERMAL WHEEL

TECHNICAL FIELD

The present disclosure relates to heat transfer, mass transfer or a combination of heat and mass transfer, and more specifically to rotary thermal wheels of this kind provided with a support structure. The disclosure also concerns a method for assembling the thermal wheel.

BACKGROUND

Rotary wheels for heat and/or mass transfer are used for exchanging heat and/or mass between air flows, e.g. for regaining heat of outlet air and providing inlet air of domestic ventilation systems with such heat. A rotary wheel for heat and/or mass transfer is referred to as “thermal wheel” which is arranged such that one portion of the wheel is in contact with the outlet air and one with the inlet air. During use, the thermal wheel will rotate, such that a portion thereof having assumed the temperature of the outlet air at a subsequent stage will be in contact with the inlet air, such that the heat absorbed by the thermal wheel from the outlet air will heat the inlet air. By using a rotary wheel for heat and/or mass transfer, the thermal losses due to ventilation may be reduced significantly.

A “thermal wheel” usually comprises a hub assembly for fastening the thermal wheel to a rotary shaft.

WO2010/144032 discloses a rotor of a rotating heat exchanger having at least two sections and being provided with at least one peripheral element, at least one radial element and clamping means for fastening the at least two sections. Each clamping mean is connected to a radial element and to a peripheral element and it applies tension to the radial and peripheral elements when it is tightened.

A known technique used to fasten spokes to a hub is welding. This causes a poor working environment, due to produced welding gases. Welding of aluminum may result in crack formation, which may have negative impact on the shape of the wheel as a consequence; it will not be absolutely circular, which in turn affects the efficiency and the durability of the finished wheel. A more rational production may be accomplished without welding.

In U.S. Pat. No. 4,234,038A a rotating transfer wheel assembly is described which comprises a hub with a number of radial blades connected thereto. A condition transfer medium is arranged in the space between the blades. The blades extend between sections of the transfer medium and are secured to the hub by screws, which is both cumbersome and time consuming.

U.S. Pat. No. 4,924,934A describes a heat transfer wheel comprising a hub, a number of spokes extending between the hub and a peripheral band. Wedge shaped elements are provided between the spokes. The spokes are attached to the hub and the band by means of hooks which are connected to ridges of the hub. This fastening method requires that the spokes are flexible, which in turn requires certain means in order to provide the wheel with stability.

In U.S. Pat. No. 2,680,492A a heat transfer wheel is shown which comprises two hubs and a number of rods extending radially from the hub to an annular band is described. These rods are attached to the hub by means of threads.

A further heat transfer wheel is disclosed in U.S. Pat. No. 4,191,241A which comprises a hub, a heat transfer medium, a peripheral element extending around the wheel and arms extending radially between the hub and the peripheral element. These arms are welded to the structure. There are, as mentioned above, several disadvantages with a welded wheel.

Further background art is disclosed in EP2375211A2 and U.S. Pat. No. 6,422,299B1.

From the above it is understood that there is room for improvements.

SUMMARY

An object of the present disclosure is to provide a new type of thermal wheel which is improved over prior art and which eliminates or at least mitigates the drawbacks discussed above. This object is obtained by a thermal wheel having the features of appended claim 1 with preferred embodiments set forth in the dependent claims related thereto.

In a first aspect of the disclosure a rotary thermal wheel for heat and/or mass transfer is provided. The rotary thermal wheel comprises a hub, a number of radial spokes which are connected to the hub, and a heat and/or mass transferring media pack. The media pack is provided in a space defined by the hub and the spokes. Further, the hub comprises a tubular element provided with connection means. The spokes are connected to the hub by means of connection parts which match the correspondingly shaped connection means. The connection of the spokes is a complementary shaped connection. This thermal wheel is advantageous since the assembly is facilitated due to the complementary shaped connection between the hub and the spokes.

The connection means may comprise recesses formed on the inside of the hub. This is advantageous since the outer surface of the hub is kept even.

In one embodiment, the connection means are substantially rectangular shaped connection recesses. The advantage of the rectangular connection means are that they match correspondingly shaped connection parts.

Preferably, the rectangular connection means comprise wall elements which provide grooves. The spokes are attachable to the hub by means of connection parts fastened to one end of the spoke and inserted into the rectangular connection means of the hub. The advantage of the groove is that a matching part, e.g. a connection part fastened to a spoke, can be inserted into it. This is an efficient assembly method which does not include any harmful gases, like for instance welding does. Another disadvantage regarding welding is that it causes adverse effects on the wheel such as shape changes or cracks.

The connection means may be equidistantly arranged around the inside of the hub. It provides better stability to the wheel if the spokes are equidistantly arranged around the wheel.

In one embodiment, the thermal wheel comprises a peripheral member which extends around the outer periphery of the thermal wheel. The peripheral member is connected to the spokes by fastening means. The peripheral member encloses the media pack. An advantage with a thermal wheel equipped with a peripheral member is that a winded media pack is held in place and cannot unwind so easily.

Preferably, the spokes extends radially from the hub to the peripheral member. This is an efficient way to fasten the spoke, but it would also be possible to have a shorter spoke and transversal struts extending straight through the media pack at some distance between the hub and the last winding of the media pack. The transverse strut would be connected to the spokes at either side of the media pack.

In one embodiment, the peripheral member extends along the entire rim of the wheel. To hold the media pack in place it is advantageous to let the peripheral element extend along the entire rim. However, it could also be built up by segments, for easier handling, and in that case there may be small gaps between the different sections when mounting the wheel. That would not affect the ability to keep the media pack secured.

In one embodiment, the tubular hub comprises either an integral cylinder or two or more cylinder segments, which together form a cylinder. For smaller sizes of wheels it is advantageous to manufacture the hub as an integral cylinder and in that way be spared from an extra assembly step. For larger sizes of wheels it may be difficult to manufacture the hub in one piece, at least at reasonable costs. In that case a cylinder put together by cylinder parts is most advantageous.

Preferably, the cylinder or the cylinder segments comprises/comprise extruded profiles. Some advantages with an extruded profile are the surface finish, and the possibility to produce complex cross-sections, like the cylinder or cylinder sections of this thermal wheel hub.

In one embodiment, the cylinder segments are attached to each other by means of connection parts inserted into holding means of the hub. This is an efficient way of assembling the cylinder parts to a finished cylinder. It is also effective to use the same connection parts both for the cylinder assembling and for the connection of the spokes to the hub, but it is of course possible to use a connection part with one shape for the assembling, and a connection part with another shape for the spokes. One example would be to use a rectangular connection part for the assembly of the hub, and a circular connection part for the fastening of the spokes.

In another embodiment, the connection parts are substantially rectangular in cross section. If the connection means is rectangular it is advantageous to use a rectangular connection part. If the connection means has another shape, the connection part should be correspondingly shaped. It would also be possible to use two differently shaped connection parts, if the connection means and the holding means are of different shapes.

In one embodiment, the connection part comprises a recess in which an elongate elevation comprised by the holding means of two adjacent cylinder segments is fittable. The recess together with the elevation is what holds two cylinder segments together allowing for efficient assembly of the hub.

Preferably, the spokes are connectable to the connection parts by fastening means. Instead of making the spoke and the connection part as one integral piece it is advantageous to produce them as two separate pieces. The spoke may be an extruded profile and the connection part a piece that may be used both with the spoke and when assembling the cylinder parts.

In another embodiment, a cover plate is connectable to the hub by fastening means which are engageable with circular connection means on the inside of the hub. A cover plate is advantageous to mount on the wheel, forcing all air to pass through the heat and/or mass transferring media pack instead of going through the hub. The fastening is done with self-tapping screws, and the circular connection means are provided in the extruded hub profile. The cover plate also works as bearing seat for a shaft.

Preferably, radial grooves are comprised in the media pack from the hub to the periphery of the wheel, into which the spokes are placed. By placing the spokes into the grooves the surface of the wheel gets even, with no protruding parts.

In one embodiment, before arranging the spokes in the grooves, they are filled with glue to fix the spoke. Further, the glue holds together the cut up layers of the media pack and contributes to hold the wheel together.

In a second aspect of the disclosure, a kit for forming a thermal wheel is provided. The kit comprises a hub and spokes which are connectable to the hub. The hub and the spokes form together a structure for supporting a media pack, which is preferably enclosed by a peripheral member.

In a third aspect of the disclosure, there is provided an apparatus adapted for heat and/or mass transfer and comprising at least one rotary thermal wheel.

In a fourth aspect of the disclosure, a method of producing a rotary thermal wheel is provided. The method comprises the step of connecting the spokes to the hub by means of connection parts inserted into connection means. An advantage of this method for assembling the wheel is that no welding is necessary, which may cause crack formations, shape changes and which produce harmful gases.

In a fifth aspect of the disclosure a use of a hub and radial spokes is provided. The use comprises the hub with radial spokes connected thereto for supporting a media pack which is preferably enclosed by a peripheral member.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the disclosure will be described in the following; references being made to the appended diagrammatical drawings which illustrate non-limiting examples of how the inventive concept can be reduced into practice.

FIG. 1 is an end view of an assembled thermal wheel.

FIG. 2 is a cross section of a hub of the thermal wheel.

FIG. 3 corresponds to FIG. 2 and shows the hub with a spoke attached thereto.

FIG. 4 shows on a larger scale a portion of a segment-built hub with a connection part inserted into a holding means of the hub.

FIG. 5 shows the hub of FIG. 4 held together by connection parts.

FIG. 6 is a perspective view of a hub of a thermal wheel held together by connection parts and with an illustrative spoke mounted.

FIG. 7 shows on a larger scale the spoke of FIG. 6 connected to the hub.

FIG. 8 shows the connected spoke of FIG. 7 from a different angle.

FIG. 9 is an end view of another assembled thermal wheel.

FIG. 10 is a cross section of a spoke.

FIG. 11 is a cross section of a connection part.

FIG. 12 is a cross section of an integral hub of a thermal wheel.

FIG. 13 is a cross section of the hub of FIG. 12 with spokes attached.

FIG. 14 is a perspective view of a hub of two segments of a thermal wheel with a cover plate and a spoke.

FIG. 15 shows a schematic cross section of the cover plate in FIG. 14 on a larger scale, taken along section line XV-XV.

FIG. 16 is an end view of an assembled thermal wheel.

FIG. 17 is an end view of a segment-built hub of a thermal wheel.

FIG. 18 is an end view of another segment-built hub of a thermal wheel with spokes attached thereto.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, certain embodiments will be described more fully with reference to the accompanying drawings. The disclosure may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

In FIG. 1 a rotary thermal wheel 500 according to one embodiment of the present disclosure is shown. The thermal wheel 500 has an inner cylindrical hub 100, a media pack 300 wound onto the hub 100, a peripheral member 400, and four rigid spokes 200 attached to the hub 100 by connection parts 210 and to the peripheral member 400 by a screw 260. The rigid spokes 200 provide the wheel with stability. The media pack 300 is built up by alternately flat and corrugated metal sheets, and forms the heat and/or mass transferring part of the thermal wheel 500. The metal sheets may be coated with e.g. an epoxy lacquer, or other coatings. The peripheral member 400 encloses the outer periphery of the thermal wheel 500 and supports the media pack 300. Preferably, the peripheral member 400 consists of a one piece metal strip, but it may also be divided into several strips, dependent of the diameter of the thermal wheel 500. Easier handling is accomplished with several peripheral member 400 parts when it comes to a larger wheel diameter.

In FIG. 2, the hub 100 of the thermal wheel 500 is shown separately. The tubular hub 100 is substantially circular with a substantially even outer surface 110, and its inside 120 is provided with substantially rectangular connection means 130 and substantially circular connection means 140. As is shown, the hub 100 has four substantially rectangular connection means 130, and four substantially round connection means 140. The rectangular 130 and the round 140 connection means are equidistantly and alternately arranged over the inner surface 120 of the hub 100.

Each rectangular connection means 130 is built up by two wall elements 135, 136, 135′, 136′. The wall element 135′, 136′ of each connection means 130 has one straight portion 135′ closest to the inner surface 120 of the hub 100, the straight portion 135′ extending generally perpendicularly thereto, and one holding portion 136′, closer to the center of the hub 100, wherein the holding portion 136′ extends perpendicularly to the straight portion 135′, i.e. generally parallel with the inner surface 120. Together, the straight portion 135′ and the holding portion 136′ provide a hook shaped part.

More specifically, an inner surface 137′ of the right wall element 135′, 136′, i.e. the surface on the inside of the connection means 130, extends into the inner of the hub 100 with a certain angle and it extends for a certain length, providing an inner side of the straight portion 135′. The inner surface 137′ of the wall element 135′, 136′ connects to a surface 131′ which extends transversally against the inner surface 137′ and has a certain length. Together, the two surfaces 137′, 131′ form the holding portion 136′ of the wall element 135′, 136′ making up a detaining part of the connection mean 130.

The surface 131′ connects to another surface 132′, which extends transversely with respect to the surface 131′. A surface 138′ connects to this surface 132′ and extends in a circumferential direction with respect to the center of the hub 100. Moreover, the surface 138′ is slightly curved so as to receive a flange provided on the inside of a cover plate 600, which will be further described in the following. The surface 138′ is connected to a surface 133′, and the angle between these two surfaces 138′, 133′ is slightly larger than 90 degrees. The surface 133′ forms an outer surface of the holding portion 136′ and it extends to the level of a corner formed by the connection between the surfaces 137′, 131′. Finally, a surface 134′ is parallel with the surface 137′ of the straight portion 135′, and continues to the inner surface 120 of the hub 100. The left wall element 135, 136 of the rectangular connection mean 130 is mirrored compared to the right one 135′, 136′ and are marked with the numerals 131-138.

A shallow groove 139 is provided in the inner surface 120 of the hub 100, centrally between the right wall elements 135′, 136′ and the left wall elements 135, 136. The shallow groove 139 extends approximately a third of the distance between the wall elements 135′, 136′ and the wall elements 135, 136. The dotted part of the rectangular connection means 130 to the left in the figure is where the connection part 210, mentioned in conjunction with FIG. 1 and to be explained later, is to be inserted.

The circular connection means 140 each has a bridge portion 141 and a circular portion 142. The bridge portion 141 connects the circular portion 142 to the inner surface 120 of the hub 100. The circular portion 142 comprises about three quarters of a circle, which is open in a direction towards the center of the hub 100. The circular connection means 140 are arranged to function as screw pockets for attaching a cover plate 600 (to be explained in conjunction with FIG. 14-16) to the hub 100 by the fastening means 260. The dotted part of the connection means 140 in the left of the figure is where the fastening means 260 is to be inserted.

The wall elements providing the rectangular connection means 130 and circular connection means 140 extend along the entire length of the hub cylinder 100.

FIG. 3 shows a connection part 210, connecting a spoke 200 and the hub 100. The connection part 210 has a shape of a rectangular cuboid which is limited by six surfaces, wherein one large surface 240 faces an internal of the hub 100. An opposite surface 220 thereof faces the inner surface 120 of the hub 100 and is provided with an elongate recess 280, the function of which will be explained later. The large surfaces 240 and 220 are joined by side surfaces 230, 230′, which side surfaces run parallel to a rotational axis of the hub 100. Finally, the rectangular cuboid is provided with two end surfaces, wherein only one end surface, facing upwards in FIG. 3, is shown. Moreover, the rectangular cuboid comprised in the connection part 210 is provided with a through opening (not shown) extending between the large surface 220 and the large surface 240.

During use, the connection part 210 is inserted into the space limited by the inner surface 120 of the hub 100, the surface 137, 137′ and the surfaces 131, 131′. In other words, the connection part 210 will be held in place due to engagement between the inner surface 120 of the hub 100 and the large surface 220 of the connection part, the side surfaces 230, 230′ of the connection part 210 and the surfaces 137, 137′ of the rectangular connection means 130 and the surfaces 131, 131′ of the rectangular connection means 130 and the large surface 240 of the connection part 210, respectively. This results in a complementary shaped connection. In other words, the other shape of the connection part 210 matches the recess defined by the surfaces 120, 131, 131′, 137 and 137′ as illustrated in FIG. 2.

The rigid spoke 200 is connected to the connection part 210 by a self-tapping screw 260, extending through the opening and engaging a part of the large surface 240 and a recess 270 running in an axial direction of the spoke 200. An end of the spoke 200 may be fitted into the elongate recess 280, which fit will give a more reliable connection between the connection part 210 and the spoke 200. In other embodiments of the disclosure, the spoke 200 may be fastened to the connection part 210 by a screw 260 extending into a threaded opening of the connection part 210 through an opening provided in the spoke 200, i.e. such that one side of the spoke 200 will engage the end surface of the connection part 210.

The spoke 200 comprises a long and narrow rectangular cuboid, having almost the same length as the radius of the thermal wheel 500 (to be more specific, the length of the spoke 200 is the radius of the thermal wheel minus the radius of the hub 100).

In FIG. 4, the connection between two cylinder segments 150c, 150d of another embodiment is shown. In this embodiment, the hub 170 is built up by four cylinder segments 150c, 150d, 150e, 150f (to be further explained in conjunction with FIG. 5), which are joined to one another by holding means 290 resembling the design of the rectangular connection means 130 and the connection part 210. The few differences will be elaborated on below:

As mentioned, the holding means 290 resembles the rectangular connection means 130—in fact, all components are similar, except for the provision of an elongate elevation 293, 293′, which runs parallel to a longitudinal axis of the hub 170 instead of the elongate recess 280 of the connection means 130. Between the elongate elevations 293, 293′ is the splice between the cylinder segments 150c-150d.

In use, two cylinder segments 150c, 150d are placed in the desired position with regard to one another, and a connection part 210 is inserted in the space limited by the inner surface 120 of the hub 170, the surface 137, 137′ and the surfaces 131, 131′. In other words, the connection part 210 will be held in place due to engagement between the inner surface 120 of the hub 170 and the large surface 220 of the connection part 210, the side surfaces 230, 230′ of the connection part 210 and the surfaces 137, 137′ of the rectangular connection means 130 and the surfaces 131, 131′ of the rectangular connection means 130 and the large surface 240 of the connection part 210, respectively. Furthermore, due to cooperation between the elongate elevations 293, 293′ and the elongate recess 280 of the connection part 210, the cylinder segments 150c, 150d will be locked to one another.

In FIG. 5, a complete hub 170 is shown. The hub 170 is built up by four cylinder segments 150c, 150d, 150e, 150f joined by eight connection parts 210 as described in connection with FIG. 4, four from one end of the hub 170 and four from the other. It is, of course, also possible to join the cylinder segments by only four connection parts 210; if only four connection parts are used, they should preferably have a length corresponding to the length of the hub 170.

A hub 170 with one rigid spoke 200 attached is shown in FIG. 6. The spoke 200 is attached by a connection part 210, as described in connection with FIG. 3. A groove is cut out in the hub 170 with the same dimensions as the spoke 200, so as the connection part 210 can be completely inserted into the connection means 130 such that the surface 294 of the spoke 200 is at the same level as the surface 295 of the hub 170 (This is also shown in FIG. 14).

In FIGS. 7 and 8, two details of FIG. 6 are shown on a larger scale. Two cylinder segments 150c, 150d are attached to one another by means of a connection part 210 inserted into the holding mean 290. The rigid spoke 200 is attached to the connection part 210 by means of a screw 260, and the connection part 210 is inserted into a rectangular connection means 130.

With reference to FIG. 9 a complete thermal wheel 500 is shown. The wheel 500 has an inner cylindrical hub 150, a media pack 300 winded onto the hub 150, a peripheral member 400 and six rigid spokes 200 attached to the hub 150 by connection parts 210, and to the peripheral member e.g. by screws 260. The hub 150 has two cylinder parts 150a, 150b attached to one another by connection parts 210. The media pack 300 comprises alternately flat and folded metal sheets, winded onto the cylindrical hub 150. The media pack 300 forms the heat and/or mass transferring part of the thermal wheel 500. The peripheral member 400 limits an outer periphery of the thermal wheel and encloses the media pack 300.

Grooves 900 are cut in the media pack 300 along a line extending from the hub 150 to the peripheral element 400 in which the spokes 200 are placed. Glue is, as an option, provided in the grooves 900 in the media pack 300 to fix the spokes 200. The thermal wheel 500 structure is symmetrical and even though it is shown from one side in the figure, the other side looks just alike.

With reference to FIG. 10, a cross section of a spoke 200 is shown. This cross section is mainly rectangular with two parallel long sides 201 and two parallel short sides 202. The spoke 200 is mirror symmetrical with reference to a central axis parallel with the long sides 201. In one of the short sides 202, the one which faces the media pack 300 when mounted on the thermal wheel 500, a groove 270 is provided. The groove 270 has a surface 203 which begins close to a corner where the long surface 201 meets the short surface 202, and it stretches towards the central axis of the spoke 200 with a slope of approximately 45 degrees in relation to the short side 202. A surface 203′ is mirror-symmetrical to the surface 203 with respect to the central axis parallel with the long sides 201. A second surface 204 of the groove 270 is circularly shaped, approximately three quarters of a circle and connects the two surfaces 203 and 203′. The spoke 200 may have this cross section appearance along its whole length, or it may have this appearance in the end portions and e.g. be solid in a middle portion.

The space enclosed by the surface 204 is configured to receive a fastening means 260 which attaches a connection part 210 to one end of the spoke 200 and a fastening means 260 which connects the spoke 200 to the peripheral member 400 in an opposite end of the spoke 200. The space enclosed by the surface 204 is prepared for a self-tapping screw. The sloped opening provided by the surfaces 203, 203′ is optionally filled with glue which fixes the spoke 200 to the media pack 300 when the thermal wheel 500 is mounted.

With reference to FIG. 11, a cross section of a connection part 210 is shown. The connection part 210 is mainly rectangular, with one even long side 701 and two short sides 702. Parallel with the even long side 701 is a long side comprising a recess 710. The recess 710 has a surface 703 which is parallel with the long surface 701 and which has the same width as the surface 202 of the spoke 200. The surface 703 is provided centrally on the long side 701. The recess 710 further comprises two short sides 704 parallel with the short sides 702 of the connection part 210. At each side of the recess 710 is a surface 705, 705′. The surfaces 705, 705′ are each provided with two small protrusions 706. The recess 710 has two purposes. The first is to engage with the spoke 200 when the two are mounted to each other. The second purpose is to engage with the elongate elevations 293, 293′ of the holding means 290, 290′ to ensure that two adjacent cylinder segments are kept together.

FIG. 12 shows a cross section of a hub 100 of a thermal wheel 500. The view is similar to the one of FIG. 2, but in FIG. 12 a dashed line showing the purpose of the surface 138, 138′ is plotted, i.e. a flange of a cover plate 600 are to be arranged along the dashed line to keep the cover plate 600 in place.

With reference to FIG. 13, a cross section of a hub 100 of a thermal wheel 500 is shown. The view is similar to the one of FIG. 3, but in FIG. 13 rigid spokes 200 connected to connection parts 210 are attached to all four rectangular connection means 130.

FIGS. 14-16 illustrate a hub 150 having two cylinder segments 150a, 150b with a cover plate 600, a cover plate 600 in cross section and a cover plate 600 mounted on a thermal wheel 500, respectively. The cover plate 600 is circularly shaped with an even top surface 601, which has a diameter slightly larger than the diameter of the hub 150 which it will fit on. Perpendicular to the surface 601 is a peripheral surface 602 of the cover plate 600 and perpendicular to the surface 602 and parallel with the surface 601 is a surface 603. The width of the surface 603 corresponds to the height of the rectangular connection mean 130. Perpendicular to the surface 603 and parallel with the surface 602 is a surface 604, perpendicular to the surface 604 and parallel with the surfaces 601, 603 is a surface 605. In the center of the cover plate 600 there is provided a circular through hole or opening with the same diameter as a driving shaft 910 of the thermal wheel 500. A bearing is also arranged in the center of the cover plate 600.

The surfaces 604 and 605 shown in FIG. 15 provide a flange to the cover plate 600 which is fitted into the hub 150. The cover plate 600 is held in place by the close fit to the rectangular connection means 130 and by fastening means 260 fitted into the circular connection means 140. The dashed line in FIG. 12 shows where the surface 604 lays against surface 138, 138′ of the rectangular connection means 130. The cover plate 600 provides a lid to the thermal wheel hub which can be either of the hubs 100, 150, 170, 800 in order that the air cannot go through the hub 100, 150, 170, 800 but instead is forced through the media pack 300. The slightly larger diameter of the cover plate 600 surface 601 compared to the hub 150 diameter provides an edge which keeps the first round of the media pack 300 still when winded onto the hub 150.

Remaining hubs 100, 170, 800 are provided with corresponding cover plates 600 as well, in order not to let air pass through the hubs 100, 170, 800. The cover plate 600 has in each case a diameter slightly larger than the diameter of the current hub 100, 170, 800. Further, applicable to larger hubs 150, 170, 800 comprising several cylinder parts 150a-b, 150c-f, 150g-i, the cover plate 600 keeps the cylinder segments 150a-b, 150c-f, 150g-i together, along with the holding means 290.

In FIG. 14 the spoke 200 is connected to the hub 150 by a connection part 210 and fully inserted into the connection recess 130, thereby ready to receive the cover plate 600. The hub 150 is provided with cut outs 610 in the outer surface 110 of the hub 150 at the same level as every rectangular connection means 130. The spoke 200 is fitted into the recess 610 when the thermal wheel 500 is put together. The top surface of the connection part 210 is thus on the same level as the end surface of the hub 150.

With reference to FIG. 17 a larger segment-built hub 170 of a thermal wheel 500 is shown. The hub 170 is built up by four cylinder segments 150c, 150d, 150e, 150f, connected to each other by means of connection parts 210 inserted into the holding means 290. Eight rigid spokes 200 are connected to the hub 170 by means of connection parts 210 inserted into the rectangular connection means 130.

In FIG. 18 a hub 800 comprising three segments 150g, 150h, 150i is shown. As in the previously described embodiments, the joints (152a, 152b, 152c) of these segments 150g, 150h, 150i are connected by means of rectangular connection parts 210. Like the previously described hubs, this hub 800 comprises circular connection means 140 and rectangular connection means 130. Rigid spokes 200 are attached by means of rectangular connection parts 210 inserted into the rectangular connection means 130.

In one embodiment the complementary shaped connection of the spokes may be a wedged shaped connection or a wedge connection. In this embodiment the connection part fastened to one end of the spoke is wedged into the rectangular connection means of the hub.

An advantage of the hub 100, 150, 170, 800 of the embodiments described herein is the standardized production. The connection part 210 is used both when assembling the cylinder segments 150a-b, 150c-f, 150g-i to form a hub 150, 170, 800 with a larger diameter, and when attaching the spokes 200 to the hub 100, 150, 170, 800. Furthermore, the connection part 210 has the same size irrespective of the diameter of the hub 100, 150, 170, 800 to be mounted. It is of course possible to have differently shaped connection parts 210 to connect the hub segments 150a-b, 150c-f, 150g-i with one another and to connect the spokes 200 to the hub 100, 150, 170, 800, but it is not necessary.

The wheels 500 described in the embodiments above preferably include a peripheral member 400, but it would be possible to manufacture a wheel 500 without this member 400, e.g. by struts connecting the spokes 200 straight through the media pack 300. The thermal wheels 500 described in the embodiments have media packs 300 winded onto the hub 100, 150, 170, 800, but this is not necessary. The media pack 300 may be attached to the hub 100, 150, 170, 800 in sections, and in that case it is not necessary for the connection means 130, 140 to be placed on the inside of the hub 100, 150, 170, 800 since this design does not demand an even outer surface of the hub 100, 150, 170, 800.

The thermal wheels 500 described herein are all provided with an efficient supporting structure for keeping together the media pack 300. This supporting structure is formed by the hub 100, 150, 170, 800, the spokes 200 and the related connection means 130, and preferably the peripheral member 400.

The shape and number of the rectangular connection means 130, circular connection means 140, or the holding means 290 may vary depending on the size of the thermal wheel 500 or by other factors.

Advantages of some embodiments described herein are that the media pack is not affected during the assembly of the heat transfer wheel. There is no weld seam which prohibits airflow. Also, if a media pack comprising alternating flat and corrugated layers is exposed to welding the corrugated layers are affected and may collapse, leading to a chain reaction of collapsed layers, which ultimately leads to a collapsed media pack, i.e. a collapsed heat transfer wheel. This scenario is effectively eliminated by the structure described herein.

A further advantage of some embodiments is that a complementary shaped connection is more stable than e.g. a weld seam when the heat transfer wheel is in operation. The wheel in operation is constantly affected by an alternating air pressure: an upper section is affected by an air pressure in one direction and a lower section by an air pressure in an opposite direction. Since the wheel rotates every specific area of the wheel will be affected by two different air pressure, with opposite directions, during each revolution of the wheel. A welded wheel is more prone to break during operation than a wheel comprising complementary shaped connections.

In an additional aspect, a hub for a thermal wheel is provided. The hub comprises two or more cylinder segments having holding means. Adjacent segments are connected to each another by means of matching, correspondingly shaped connection parts inserted into the holding means. These connections are complementary shaped connections. The cylinder segments preferably comprise extruded profiles. The holding means comprise recesses formed on an inside of the hub. Preferably, the holding means are of substantially rectangular shape and equidistantly arranged around the inside of the hub.

It is appreciated that the inventive concept is not limited to the embodiments described above, and many modifications are feasible within the scope of the disclosure set forth in the appended claims. For instance the number of spokes, the number of cylinder segments and the number of sections of a finished wheel may vary. Also the number of circular connection means may vary, in particular with the diameter of the wheel. The shapes of the connection parts and corresponding connection means may also vary. Some examples of shapes are for instance square, round, oval or rectangular.

The connection means and holding means may have the same shape, but may also be of different shapes. For example it is possible to use rectangular connection means and circularly shaped holding means. The complementary shaped connection could comprise small connection parts, one part inserted into the hub from each side, or it could comprise one long connection part. The peripheral member may be formed as one long strip, or several shorter strips. The spokes as well as the connection parts may have the described cross sections, but they could also have other cross sections.

THERMAL WHEEL

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