JPH0660796B2 - Heat transfer element basket assembly for a heat exchanger - Google Patents

Description

BACKGROUND OF THE INVENTION The present invention relates to a heat transfer element basket, and more particularly to an assembly having a plurality of heat absorbing plates disposed within the basket for use in a heat exchanger, wherein heat is transferred from a hot heat exchange fluid to a cold heat exchange fluid by the heat absorbing plates.

More particularly, the present invention is particularly applicable to heat transfer devices in rotary regenerative heat exchangers in which heat transfer elements are heated by contact with a hot gaseous heat exchange fluid and then transferred to a cooler gaseous heat exchange fluid.

One type of heat exchanger commonly used for gas-to-gas heat exchangers in process industries and gas-to-air heat exchangers in utility steam generators is the very well-known rotary regenerative heat exchanger.

Typically, the rotary regenerative heat exchanger has a cylindrical rotor divided into multiple chambers, with multiple heat exchange elements disposed within the chambers. As the rotor rotates, the heat exchange elements are alternately exposed to a flow of heated gas and a flow of cool air or other gaseous fluid to be heated. The assembly of heat exchange elements typically includes multiple heat transfer element basket assemblies mounted within sector-shaped chambers. Each heat transfer element basket assembly contains multiple heat transfer plates that, when exposed to a heated gas, absorb heat from the heated gas and then, when exposed to cool air or other gaseous fluid to be heated, transfer the absorbed heat from the heated gas to the cool air or other gaseous fluid by the heat transfer plates.

Very generally, such heat transfer element baskets include a housing, such as a frame, having a plurality of heat transfer plates, such as sheets, disposed therein. Typically, the heat transfer element basket housing is as described, for example, in U.S. Pat. Nos. 3,314,472, 4,561,492, and 4,600,000.
As shown in the '6,400 patent, the heat transfer element includes a frame formed by a pair of spaced-apart, plate-like end members held together by paired side straps, which interconnect the end members along their sides. The heat transfer plates are stacked in closely spaced relation within the basket housing, forming passages for the passage of heat exchange fluid between each adjacent heat transfer plate. The side straps interconnecting the pair of spaced-apart end members typically extend in pairs along opposite sides of the stack of heat transfer elements.

On each side of the stack of heat transfer elements, a first side strap extends between the upper sections of a pair of spaced-apart end members, and a second side strap extends between the lower sections of the end members in spaced-apart, parallel relationship to the first side strap. The side straps are folded inwardly and flanged along their longitudinal edges that overlie the edges of the heat transfer element basket assembly, as shown in the aforementioned U.S. Pat. No. 3,314,472, to form retention surfaces that prevent the heat transfer plates from falling out the open ends of the heat transfer element baskets.

Typically, a plurality of retaining bars are welded across and between the top and bottom ends of a pair of spaced apart end members to further prevent the heat transfer element plates from falling out the open end of the heat transfer element basket.
The retaining rods may simply lie across the top and bottom edges of the heat transfer element plate, as shown in U.S. Patent No. 2. Alternatively, the retaining rods may be placed in recesses cut into the top and bottom edges of the heat transfer element plate to provide a shorter basket for a given plate height, as shown in the aforementioned U.S. Patent No. 4,606,400.

The retaining rods also serve as structural members for supporting lifting devices to facilitate handling of the assembled heat transfer element baskets, particularly for facilitating installation and removal of the heat transfer element baskets from the heat exchanger. Typically, the lifting devices include a pair of spaced apart holes formed in a centrally located retaining rod, as shown in U.S. Pat. No. 4,552,204, or a pair of spaced apart pins integral with and extending through a centrally located retaining rod, as shown in U.S. Pat. No. 4,557,318.

Thus, the lifting device is the same as that of the aforementioned U.S. Pat.
When the heat transfer element basket includes a pair of holes as shown in the '2204 patent, the heat transfer element basket is lifted by means of a pair of clevises surrounding each lifting hole and straddling the central retaining rod, each clevis being secured by a pin passing through each side of the lifting hole and the straddling clevis of the retaining rod.
It is engaged with the retaining rod.

On the other hand, the lifting device is disclosed in the aforementioned U.S. Pat.
In the case of incorporating a pair of lifting pins as shown in the '8 patent, the heat transfer element basket is lifted by means of a pair of lifting lugs which simply grip the pins extending through the central retaining rod.

Typically, such heat transfer element baskets have a trapezoidal frustum profile. However, the outer heat transfer element baskets located in the radially outer regions of the sectorial chambers of a cylindrical rotor cannot necessarily have a trapezoidal cross section due to the curvature of the rotor surrounding them. If these outer baskets truly had a trapezoidal cross section, gaps would exist between the radially outer ends of the baskets and the cylindrical wall of the rotor surrounding them. Such gaps are undesirable because they allow gas and air flowing through the rotor to bypass the surfaces of the heat transfer plates contained within the baskets, thereby reducing the heat exchange rate. Furthermore, such gaps prevent the rotor from being completely filled with heat transfer plates.

Therefore, conventionally, the outer basket is
Rather than having parallel trapezoidal end members at both ends, the baskets are frustum-shaped, with non-parallel sides, and the radially outer ends of the outer baskets are conventionally provided with arcuate end members that have the same curvature as the rotor surrounding the basket.

In such an outer basket, the length of the heat transfer element plates located within the basket at its radially outer end must be shortened due to the curvature of the outer end members. Therefore, these shorter heat transfer element plates cannot extend across the entire width of the basket. Conventionally, these shorter heat transfer element plates are held in place by a tight fit between the side straps, just as are the remaining heat transfer element plates extending across the entire width of the basket.

Therefore, the force of the high velocity jets of cleaning media during soot blowing or water washing can loosen the hold of these short and long heat transfer element plates, causing them to move or
To prevent bending, it has been conventional practice to attach a respective retaining clip to each of these short heat transfer element plates within the outer basket assembly.

However, each of these clips must be manually welded to the arched end member in a position that will engage one of the short heat transfer element plates, and because two clips must be installed for each short heat transfer element plate, i.e., one at the top and one at the bottom of the basket, the assembly of such an outer basket assembly is very tedious, laborious, and time-consuming.

SUMMARY OF THE INVENTION In an outer heat transfer element basket assembly according to the present invention, a plurality of heat transfer element plates are arranged in a stack between first and second end members, the first and second end members being disposed at opposite ends of the stack of heat transfer element plates in abutting relationship therewith and interconnected by one or more side straps welded to and extending between the end members. The radially outer end member is preferably arcuate in shape having a curvature substantially the same as the curvature of the cylindrical wall of the rotor to which the outer basket is attached.

Also in accordance with the present invention, a pair of blanking plates are mounted within the outer heat transfer element basket assembly adjacent its outer end to abut against the short heat transfer element plates as a means for retaining the short heat transfer element plates within the basket assembly. One blanking plate is welded to the upper edge of the outer end member so as to extend across the upper edges of the short heat transfer element plates, and the other blanking plate is welded to the lower edge of the outer end member so as to extend across the lower edges of the short heat transfer element plates.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view of a rotary regenerative heat exchanger.

2 is a plan view of the rotary regenerative heat exchanger of FIG. 1 taken along line 2--2 of FIG. 1; FIG.

FIG. 3 is a perspective view of a heat transfer element basket assembly constructed in accordance with the present invention.

FIG. 4 is an enlarged plan view looking down on the heat transfer element basket assembly of FIG. 3 with a blanking plate therein.

FIG. 5 is a cross-sectional end view taken along line 5--5 of FIG.

FIG. 6 is a cross-sectional side view taken along line 6--6 of FIG.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 illustrates a rotary regenerative heat exchanger 2 employing a heat transfer element basket assembly in accordance with the present invention.

The rotary regenerative heat exchanger 2 includes a housing 10 surrounding a rotor 12 within which is carried a heat transfer element basket assembly in accordance with the present invention.
The rotor includes a cylindrical shell 14 connected to a rotor post 16 by a plurality of radially extending partitions 15. The heated fluid is ducted
18, while the fluid to be heated enters the housing 10 through duct 22 at the end opposite the heated fluid.

The rotor 12 is rotated about its axis through suitable reduction gears by a motor connected to the rotor post 16. The motor and reduction gears are not shown in FIG.
As the rotor 12 rotates, a plurality of radially extending partitions
Heat transfer element plates carried in heat transfer element basket assemblies disposed within sectorially defined chambers in the rotor by 15 are first moved into contact with a heating fluid entering housing 10 through duct 18 to absorb heat from the heating fluid, and then into contact with a fluid to be heated entering housing 10 through duct 22. As the heating fluid passes through the heat transfer element plates, the heat transfer element plates absorb heat from the heating fluid. As the fluid to be heated subsequently passes through the heat transfer element plates, the fluid to be heated absorbs from the heat transfer element plates the heat that the heat transfer element plates absorbed when they contacted the heating fluid.

In FIG. 1, the heating fluid is hot gas and the fluid to be heated is cold air. Such a rotary regenerative heat exchanger 2 is often used as an air preheater. In such air preheaters, the heat transfer elements serve to transfer heat from hot gases generated in a fossil fuel-fired furnace to the ambient air supplied to the furnace as combustion air. This is done to preheat the combustion air and improve overall combustion efficiency. Very often, the flue gas (hot gas) leaving the furnace carries with it particulates generated during combustion. These particulates tend to accumulate on the heat transfer elements, particularly on the cold end of the heat exchanger, resulting in problems with moisture condensing in the flue gas at these locations.

To enable periodic cleaning of the heat transfer element plates disposed within the heat transfer element basket assembly, the heat exchanger includes cleaning nozzles disposed in the passageway for the fluid to be heated adjacent the cold end of the rotor 12 and the open end of the heat transfer element basket assembly opposite the cold end.
The rotor includes a cleaning nozzle 20, which directs a high-pressure cleaning fluid, typically steam, water, or air, toward the slowly rotating heat transfer element plate. The cleaning nozzle itself sweeps across the end face of the rotor, as indicated by the dashed arrow in FIG. 1. As the high-pressure cleaning fluid passes over the heat transfer element plate, the turbulence of the fluid flow causes the heat transfer element plate to vibrate, thereby vibrating and loosening any loose fly ash and other particulate deposits adhering to the heat transfer element plate. These loose particulates are then entrained in the high-pressure cleaning fluid flow and carried away from the rotor.

The heat exchange material carried within the rotor 12 consists of a number of metallic heat transfer element plates (or sheets) which are generally formed in a corrugated or wave-like configuration so that when stacked in abutting relation to one another in a stack, they form a series of internal passages therebetween;
Through these passages flow the heating fluid and the fluid to be heated. Typically, the heat transfer element plates are assembled into a quadrilateral frame, called an element basket, which houses the stack of heat transfer element plates such that each heat transfer element plate maintains its stacked arrangement so that the heat transfer element plates can be handled as a unitary assembly 30 (see FIG. 2) and placed in a sectorial chamber in the rotor of the heat exchanger.

As illustrated in Figure 3, the heat transfer element basket assembly 30 includes a plurality of heat transfer element plates 32. These heat transfer element plates 32 are juxtaposed in a spaced apart relationship such that
A stack of heat transfer element plates is configured having a plurality of flow passages therebetween, which flow passages form flow paths for a heat exchange fluid to flow in heat exchange relationship with the heat transfer element plates 32 .

The heat transfer element plate 32 is typically a thin metal sheet that can be rolled or forged into the desired shape, although the invention is not necessarily limited to the use of such metal sheets.
Various surface configurations may be used, such as, but not limited to, flat or corrugated or wave-shaped surfaces, or a combination thereof, i.e., alternating flat and corrugated or wave-shaped plates, and in either case, the stack of heat transfer element plates 32 may be formed by a first end member 34 at one end and a second end member 35 at the other end.
It is placed between 36.

These end members 34 and 36 abut opposite ends of the stack of heat transfer element plates 32 and are held in place by means of side straps 40, 42 and 50, 52, as shown in Figures 3-6.
and 50, 52 are spaced apart first end members disposed at the upper and lower edges of the heat transfer element plates 32 and along opposite sides of the stack of heat transfer element plates 32, respectively.
34 and a second end member 36.

It should be understood that the end members 34 and 36 may each be formed from a single large plate, but are not necessarily limited to this.
One or both of the slats 36 may be formed by two spaced apart vertical side members 82 and 84, as best shown in Figure 5. These side members 82 and 84 are joined by a horizontally disposed, laterally extending upper member 86 and a horizontally disposed, laterally extending lower member 88.
These four members 82, 84, 86 and
88 are welded together at their respective intersections to form substantially rectangular end plates, as best seen in FIG.

The side straps 40 and 42 are welded at one end to the upper right and upper left corners, respectively, of the end member 34, and at the other end to the upper right and upper left corners, respectively, of the opposite end member 36. Similarly, the side straps 50 and 52 are welded at one end to the upper right and upper left corners, respectively, of the end member 34.
The ends of the end members 34 are welded to the lower right and left corners of the end member 34, respectively, and are welded at their other ends to the lower right and left corners of the opposite end member 36, respectively.

As shown in Figure 5, side straps 4
Side straps 40, 42, 50, and 52 preferably have flanges 41, 43, 51, and 53 attached along their longitudinal edges that overlie the upper and lower edges of the heat transfer element basket assembly. Flanges 41 and 43 extend inwardly from the inner longitudinal edges of side straps 40 and 42, respectively, closely adjacent the upper edge of heat transfer element plate 32. Flanges 51 and 53 extend inwardly from the inner longitudinal edges of side straps 50 and 52, respectively, slightly adjacent the lower edge of heat transfer element plate 32.

The upper flanges 41, 43 and the lower flanges 51, 53 are
Support surfaces are formed along the upper and lower edges of the heat transfer element basket assembly 30 to allow the stack of heat transfer element plates 32 within the basket assembly 30 to be held together.
This prevents the basket assembly 30 from falling out of the open end during transportation or installation of the basket assembly 30.

Additionally, a plurality of low-height element retaining rods 38 are tack-welded between the end members 34 and 36 at the open top and bottom of the heat transfer element basket assembly 30, between the side straps 40 and 42 and between the side straps 50 and 52, respectively, to further prevent the stacked heat transfer element plates 32 from falling out of the open ends of the basket assembly 30. Such retaining rods 38
Suitable examples include those described in U.S. Pat. Nos. 4,552,204 and 4,557,333.
As disclosed in the '18 patent, a lifting device is provided to facilitate the attachment and detachment of the basket assembly to and from the rotor.

Thus, for the outer heat transfer element basket assembly, the second end member, i.e., the radially outer end member of the heat transfer element basket assembly 30 lying on the rotor 12,
36 is arched in shape, as best seen in FIG. 4. More effectively, this arched end member
The curvature of 36 is the same as the curvature of the cylindrical wall of shell 14.
The curvature of the arched end members 36 allows several heat transfer element plates to be positioned in a sectorial area defined within the basket adjacent the arched end members 36 at the outer region of the outer heat transfer element basket assembly 30 by the curvature of the end members 36.
The length of the heat transfer element plates 32' must be short. These heat transfer element plates 32' are therefore
2, 52 are shorter in length than the remaining heat transfer element plates 32 across the entire width of the heat transfer element basket assembly 30.

As best shown in Figures 4, 5, and 6, in the heat transfer element basket assembly of the present invention, sector-shaped blanking plates 60 and 62 are provided across the upper and lower edges, respectively, of the short heat transfer element plate 32' adjacent to the arched end member 36. The short heat transfer element plate 32' is thus sandwiched between the blanking plates 60 and 62, thereby loosely but not tightly holding the short heat transfer element plate 32' in place within the outer region of the outer heat transfer element basket assembly without the use of retaining clips typically required in the previously described conventional outer heat transfer element basket assemblies. The simplified installation of the outer heat transfer element basket assembly of the present invention is shown in Figures 4, 5, and 6 with the heat transfer element plates 32 and 32' removed, except that a portion of the heat transfer element plate 32 and the short heat transfer element plate 32' are shown in Figure 4 to more clearly illustrate the structure of the heat transfer element basket frame of the outer heat transfer element basket assembly.

The procedure for fabricating the outer heat transfer element basket assembly 30 of the present invention shown in FIGS. 4, 5 and 6 will now be described.

The first and second end members 34 and 36 are assembled by first welding their respective flanged side members 82 and 84 and upper and lower cross members 86 and 88 together, thereby forming substantially rectangular flanged end members, with the smaller inner end member 34 being substantially flat and having a side flange 35 extending outwardly from the flat portion, and the larger outer end member 36 being arched and having a side flange 37 extending outwardly from the arched portion.

Side straps 40 and 42 are then welded to the outer side of one flange 35 of the smaller inner end member 34, with these side straps 40 and 42 extending outwardly from the end member 34 at the upper and lower regions thereof, respectively. Similarly, side straps 50 and 52 are welded to the outer side of the other flange 35 of the smaller inner end member 34, with these side straps 50 and 52 extending outwardly from the end member 34 at the upper and lower regions thereof, respectively.

At this point, the partially assembled heat transfer element basket frame is inverted with the end member 34 as its base.
32 are stacked side by side in a basket frame,
This means that the basket frame will accommodate the desired number of heat transfer element plates.
32. Then, the required number of short and long heat transfer element plates 32' are stacked on top of the heat transfer element plate 32.
The lengths of these short heat transfer element plates 32' are gradually reduced toward the end member 36, as best seen in Figure 4. This allows the short heat transfer element plates to lie on the stack in decreasing order of length, and therefore lie adjacent the outer end member 36 when the basket assembly is complete.

After the heat transfer element plates 32' are thus arranged in a stacked arrangement within the partially assembled basket frame, the arcuate end members 36 are attached to complete the assembly of the outer heat transfer element basket assembly of the present invention. To attach the arcuate end members 36, side straps 40 and 42 are attached to the outer arcuate end members, respectively.
The upper and lower sections of the end member 36 are welded to the outer side of one flange 37 of the end member 36, and side straps 50 are also welded to the outer side of one flange 37 of the end member 36.
and 52 are welded to the outer side of the other flange 37 of the outer arched end member 36 at the upper and lower regions of the end member 36, respectively.

The blanking plates 60 and 62 are welded in place to the arched end member 36 prior to welding the arched end member 36 to the side straps 40, 42 and 50, 52. Then, by welding the arched end member 36 to the side straps 40, 42 and 50, 52, the fabrication of the outer heat transfer element basket assembly 30 is completed, and the basket assembly is fully filled with a plurality of heat transfer element plates and is ready for transportation by ship or the like and subsequent installation on site.

6, the upper blanking plate 60 is welded to the arched end member 36 at a location such that it extends very adjacent across the upper edge of the short length heat transfer element plate 32' when the arched end member 36 is subsequently welded to the side straps 40, 42 and 50, 52 to complete assembly of the outer heat transfer element basket assembly 30. Meanwhile, the lower blanking plate 62 is welded to the arched end member 36 at a location such that it extends somewhat adjacent across the lower edge of the short length heat transfer element plate 32' when the arched end member 36 is subsequently welded to the side straps 40, 42 and 50, 52 to complete assembly of the outer heat transfer element basket assembly 30.
Welded to 36.

Although the heat transfer element basket assembly is shown for use in a rotary regenerative heat exchanger of the type in which a number of heat absorbing materials are selectively rotated between a heating fluid and a fluid to be heated, those skilled in the art will understand that the heat transfer element basket assembly of the present invention can be used in many other known heat exchangers, not just regenerative but also heat transfer types.

Additionally, reinforcing members of various configurations, some of which are suggested in the preceding description, may be readily employed by those skilled in the art in heat transfer element basket assemblies according to the present invention.

Therefore, the following appended claims are intended to encompass the modifications shown in the foregoing description and all other modifications which fall within the spirit and scope of the invention.

Claims (4)

[Claims] [Claim 1] A heat transfer element basket assembly for use in a rotary regenerative heat exchanger, the heat transfer element basket assembly being of the type housed within a cylindrical rotor shell adjacent to the outer peripheral wall of the rotor shell, comprising: (a) a plurality of heat transfer element plates arranged side by side in a stack; (b) a basket frame surrounding and supporting the stack of heat transfer element plates, the basket frame including first and second end members disposed at opposite ends of the stack of heat transfer element plates in abutting relationship therewith, and at least a pair of side members disposed along sides of the stack of heat transfer element plates interconnecting the first and second end members, the second end member adjacent the second end member defining a sector area within the basket frame; and (c) a basket frame surrounding and supporting the stack of heat transfer element plates, the basket frame including first and second end members disposed at opposite ends of the stack of heat transfer element plates in abutting relationship therewith, and at least a pair of side members disposed along sides of the stack of heat transfer element plates interconnecting the first and second end members, the second end member adjacent the second end member defining a sector area within the basket frame. a pair of blanking plates attached to the second end member, one blanking plate positioned to extend across the sector along the top side of the basket frame and the other blanking plate positioned to extend across the sector along the bottom side of the basket frame, whereby a stack of heat transfer element plates positioned within the sector of the basket frame is held in place between the pair of blanking plates. 2. The heat transfer element basket assembly of claim 1, wherein the second end member defining the sectorial area comprises:
a heat transfer element basket assembly which is an arched plate having a curvature substantially the same as the curvature of the outer peripheral wall of said cylindrical rotor shell; [Claim 3] A heat transfer element basket assembly as described in claim 1, wherein the at least one pair of side members include a pair of spaced apart upper side straps arranged along opposite sides of the stack of heat transfer element plates and interconnecting the upper edge of the side of the first end member and the upper edge of the side of the second end member, and a pair of spaced apart lower side straps arranged along opposite sides of the stack of heat transfer element plates and interconnecting the lower edge of the side of the first end member and the lower edge of the side of the second end member. [Claim 4] A heat transfer element basket assembly as described in claim 3, wherein each of said pair of spaced apart upper side straps has a flange extending laterally inward from each upper side strap closely adjacent to said stack of heat transfer element plates, and each of said pair of spaced apart lower side straps has a flange extending laterally inward from each lower side strap slightly adjacent to said stack of heat transfer element plates.