US2684230A

US2684230A - End plate support in housing of regenerative heat exchange apparatus

Info

Publication number: US2684230A
Application number: US241821A
Authority: US
Inventors: William E Hammond
Original assignee: Air Preheater Co Inc
Current assignee: Alstom Power Inc
Priority date: 1951-08-14
Filing date: 1951-08-14
Publication date: 1954-07-20
Anticipated expiration: 1971-07-20
Also published as: FR1054557A; DE909136C

Description

July 20, 1954 W. E. HAMMOND EIND PLATE SUPPORT IN HOUSING OF REGENERATIVE HEAT EXCHANGE APPARATUS Filed Aug. 14, 1951 4x144 S A INVEN TOR.

llli/liam E Hammond A TTORNE Y Patented July 20, 1954 UNITED STATE-Iii FATEN T OFFICE END PLATE SUPPORT IN .HOUSING OF REGENERATiVE HEAT EXCHANGE AP- PARATUS William E. Hammond, Welisville, N. Y., assignui to The Air Preheater Corporation, New York,

5 Claims. 1

The present invention relates to regenerative heat exchangers of the rotary type and particularly to improvements in the construction and support of the housing that encloses the rotor so as to reduce or eliminate the efiects of mechanical .or thermal distortion.

In such heaters a cylindrical rotor carries heat transfer plates, usually metallic, which when positioned as in a gas passage absorb heat that is imparted as to air when the rotor is turned to dispose the plates in the air passage. The rotor is enclosed in a housing, to which the gas andair ducts are connected and this housing is provided with end plates that have spaced apertures alined with the gas and air passages through the rotor. Circumferential seals are provided to preclude bypassing of gas and air through the annular space between the rotor and the housing. Radial seals acting to prevent mingling of the gas and air streams across the ends of the rotor are provided on the partitions that divide the rotor into compartments that contain heat transfer material. All of these seals on the rotor engage the end plates or adjacent parts of the housing. To permit turning of the rotor certain clearances are required and heretofore 1 these clearances have been based upon calculations of deflections imposed solely on the rotor due to its being subjected to fluids at different temperatures as it rotates. Consequently, deflections of the housing due to mechanical loads, the method of rotor and housing mounting, and thermal expansion all serve to modify the presumed clearances.

In the so-called inverted type of heater in which the gas flows downwardly and the air upwardly so that the top is hottest, the thermal forces act to raise the duct side of the housing and are assisted by the reactions at the support feet adjacent the ducts, which forces are in the same direction and so further the distortion. The result of deflections of this nature in an inverted heater is to decrease the clearances between the seals at the cold end of the heater in the regions where the ducts are connected and to increase the seal clearance at the hot end of the heater.

In the case of the so-called vertical heaters where the gases flow upwardly and the air flow is downwardly so that the top end is colder, the thermal force couple acts to lower the duct side of the housing which is now resisted by the reaction at the duct feet. Thus, the reaction forces tend to restrain the distortion and maintain it at a low magnitude.

The present invention contemplates a housing structure for an air 'preheater in which the end plates of the housing are connected by columnar supports within the wrapper sheet of the housing that extends around the rotor and are exposed to the temperature of the heating gases and heated air so as to be maintained at a more uniform temperature by exposure to the heating gases and heated air so that the wrapper sheet may be of minimum thickness because it serves now as a part of the ducts, being only a fluid retainer or guide. This reduces the Weight of the housing. A further feature of the invention is that one set of the usual circumferential seals between the housing and the perimeter of the rotor at its ends .are eliminated preferably at the hot end so that sealing difficulties in this location are eliminated entirely. A corollary feature is the provision of axial seals in the annular space between the rotor and housing so that gas and air may not flow around the rotor in this space and become mingled which would defeat the purpose of conventional radial seals.

The invention will be best understood upon consideration of the following. detailed descrip tion of an illustrative embodiment thereof when read in conjunction with the accompanying drawmg in which:

Figure 1 is a sectional-elevational view on the line li of Figure 2 of a rotary air preheater constructed in accordance with the present invention and Figure 2 is a sectional plan View on the line 22 in Figure 1.

In Figure l of the drawings the numeral Hi designates a rotor having a cylindrical shell divided into sector shaped compartments by radial partitions i i (Fig. 2) connecting it with the rotor post I? which is driven by a motor and reduction gearing M to turn the rotor slowly about its axis. The rotor compartments contain regenerative heat transfer material in the form of closely spaced metallic plates it which first absorb heat from hot gases entering the preheater through a duct [6 from a boiler or other source to be discharged after passing over the heat transfer plates i5 through an outlet duct ll to which an induced draft fan is connected. As the rotor turns slowly about its axis, the heated plates l5 are moved into the stream of air admitted through the duct iii to which a forced draft fan isconnected and after passing over the plates l5 and absorbing heat therefrom the stream of air is conveyed to the boiler furnace or other place of use through duct l9.

A housing 20 enclosing the rotor I0 is provided ateither end opposite the latter with upper and lower end or sector plates El, 22 which are apertured at 23 and 25 (Fig. 2) in circumferentially spaced locations to admit and discharge streams of gas and air flowing through the rotor. In order that the streams of gas and air may not commingle, the end plates 2!, 22 have imperforate portions 25 located between the gas and air openings that are at least equal to but usually somewhat greater in circumferential extent than one rotor compartment for engagement by radial seals on partitions l i to isolate or block oil at least one compartment when it is in a position between the gas and air passages. In order that the streams of gas and air may not by-pass the heat transfer surface it by fiowing axially in the annular clearance space 2i between the rotor shell it and the housing Eli it is customary to provide circumferential seals, indicated diagrammatically at on the shell id which wipe against confronting parts of the end plates 2i, 22 or allied parts so as to seal on the space 2?.

Conventionally the air preheater is supported as illustrated in Figure l on the structural steel scaffolding E0 of a boiler. Support or duct feet 32 attached to the connecting pieces r inember between the ducts and the end plate of housing rest on the beams carried by the scaffolding diametrically located beam feet are also provided at 35 on the housing.

In an inverted vertical heater having downward gas flow as indicated in Fig. l, the rotor it when heated becomes dished in convex fashion because of the temperature differentials between its upper (hot) and lower (cold) ends. housing scalso distorts since the uppe d plate 2i is hotter than the lower end plate so that in erlect the housing diameter top of the housing and the duct f The duct foot reactions being in the same rection as the thermal deflection increase the deflection of the housing and the interference between housing and rotor as well as open up clearances between the seals and the end plates.

In accordance with the present invention circumferential seals are provided only at the cold end of the preheater, these being designated 23 in Figure 1. Consequently hot gas admitted through the preheater to the duct i6 and connecting plate 38 and flowing to the rotor it? through the aperture 23 in the upper end plate 2! may flOW through the gap 38 between the end plate and the perimeter of the rotor into the annular space 2? surrounding the rotor and located between the side of the latter and the wrapper sheet 26 of the housing. At the opposite side of the rotor i9 heated air enters space ZlA. Columnar supports ll connected at their ends at the upper and lower end plates El, 22 are located in the annular space 22? within the wrapper shell and hence assume the fluid temperatures as nearly as possible. These columns becone the main supporting members of the preheater unit and therefore the wrapper sheet 2E9 acts only a fluid retainer with the result that its thickness may be reduced to a minimum, thereby reducing the weight of the preheater. l'he weight of the preheater is sustained by the beams 33 on which rests the support feet 32, 35 attached to the lower so called connecting plate-s 3d. The lower end plate 22 is attached to the flange 22 of the lower connecting plate and the upper end plate ill is supported through the columns ail. The usual beam from which the rotor it is suspended together with the driv- 4 ing means id for the rotor are mounted on the upper connecting plates 36 which rest on the flanges it of the upper end plate 2! and are fastened thereto.

Inasmuch as the admission of the usual combination circumferential seals at the upper end of the rotor permits gas and air to enter the annular space 2'1, 21A between the housing 28 and rotor H) a mixture of these two fluids could occur and thus defeat the purpose of the radial seals which normally function to prevent cross flow and mixture of the two fiuids across the ends of the rotor. To preclude such mixture of the streams of gas and air in this annular space between the rotor and housing axial sealing members 56 are provided between these two parts at circumferentially spaced positions in the annular space at locations adjacent the imperforate portions 25 and the end pla es that intervene between the gas and air flow apertures it. i

The basic concept is to increase the temperature of the housing and connecting plate flanges to reduce distortion. In order to accomplish this the usual hot end circumferential seals are omitted and an axial seal substituted to control leakage. Through this means the temperature of the annulus space surrounding the rotor is raised and thus the differential between th sector plate and the connecting plate flange at the hot end of the heater reduced.

What I claim is:

1. In an air preheater having a cylindrical rotor turning on a vertical axis and carrying material for the transfer of heat between hot gases and relatively cool air, and end plates confronting the upper and lower ends of the rotor and formed with aligned apertures at opposite sides of the rotor axis for the flow of gas and air to and through the rotor; columnar support members spaced circumferentially around and radially outward of the rotor and connected at their ends to said end plates; a relatively thin light weight wrapper sheet extending around the rotor exteriorally of said columnar supports and together with said end plates forming a housing enclosing the rotor, the portion of the end plate at the upper end of the rotor adjacent the rotor perimeter being spaced from the rotor to admit gas and air to the annular space between the side of the rotor and said wrapper sheet; ducts connected with the end plate at the upper end of the rotor for admitting hot gas to and withdrawing heated air from the rotor ducts connected to the end plate at the lower end of the rotor for admitting cool air to and withdrawing cooled gas from the rotor; circumferential sealing means between the rotor and the lower end plate for excluding cold air and cooled gases from the annular space between the rotor and housing.

2. In an inverted air preheater having a cylindrical rotor turning on a vertical axis and carrying material for the transfer of heat between hot gases and relatively cool air, and end plates confronting the upper and lower ends of the rotor and formed with aligned apertures at opposite sides of the rotor axis for the flow or" gas and air to and through the rotor; columnar support members spaced oircumferentially around and radially outward of the rotor and connected their ends to end plates; a relatively thin, light weight wrapper sheet extending around the rotor exteriorally or said columnar supports and together with said end plates forming a housing enclosing the rotor, the portion of the end plate at the upper end of the rotor adjacent the rotor perimeter being spaced from the rotor to admit gas and air to the annular space between the side of the rotor and said wrapper sheet; ducts connected with the end plate at the upper end of the rotor for admitting hot gas to and withdrawing heated air from the rotor; ducts connected to the end plate at the lower end oi the rotor for admitting cool air to and withdrawing cooled gas from the rotor; circumferential sealing means between the rotor and the lower end plate for excluding cold air and cooled gases from the annular space between the rotor housing; and structural supports upon which the preheater rests associated with said lower end plate.

3. In apparatus having a cylindrical rotor carrying material for contact by relatively hot and cold gaseous fluids, a housing including a wrapper sheet surrounding the rotor in radially spaced relation thereto, end plates for the housing confronting the rotor and formed with alined apertures separated by imperiorate portions or said plates and located at opposite sides of the rotor axis for the flow of said fluids, and inlet and outlet ducts for said fluids connected to said end plates in communication with said apertures; circumferential sealing means disposed between the rotor and housing only at that end of the housing to which the outlet duct for the heating fluid is connected outwardly of the apertures in said end plates for closing the annular space oetween the rotor and housing at the cold end of the heater and leaving open the end of the annular space between the rotor and housing at the end thereof to which the inlet duct for the heating fluid is connected so that heating fluid may enter said space.

4. In an air preheater having a cylindrical rotor turning on a vertical axis and carrying material for the transfer of heat between hot gases and relatively cool air, and end plates confronting the upper and lower ends of the rotor and formed with aligned apertures at opposite sides of the rotor axis for the flow of gas and air to and through the rotor; columnar support members spaced circumferentially around and radially outward of the rotor and connected at their ends to said end plates; a relatively thin light weight wrapper sheet extending around the rotor exteriorally of said columnar supports and together with said end plates forming a housing enclosing the rotor, the portion of the end plate at the upper end of the rotor adjacent the rotor perimeter being spaced from the rotor to admit gas and air to the annular space between the side of the rotor and said wrapper sheet; ducts connected with the end plate at the upper end of the rotor for admitting hot gas to and withdrawing heated air from the rotor ducts connected to the end plate at the lower end of the rotor for admitting cool air to and withdrawing cooled gas from the rotor; circumferential sealing means between the rotor and the lower end plate for excluding cold air and cooled gases from the annular space between the rotor and housing; and sealing means between housing and rotor extending axially of the preheater in the space between the rotor and housing at circumferential positions adjacent the locations or" said imperforate portions of the end plates that intervene between the gas and air openings therein.

5. In an air preheater having a cylindrical rotor carrying material for heat exchange between relatively hot gases and cold air, a housing including a wrapper sheet surrounding the rotor in radially spaced relation thereto, housing end plates confronting the rotor and formed with aligned apertures separated by imperforate portions of said plates located at opposite sides of the rotor axis for the flow of said fluids, and inlet and outlet ducts for said fluids connected to said end plates in communication with said apertures; supporting means attached to the lower end plate for sustaining the weight of the preheater; support columns extending axially of the preheater at points spaced circumierentially of the rotor in positions between the rotor and said housing and interconnecting said end plates; circumferential sealing means disposed between the rotor and housing only at that end of the housing to which the outlet duct for the heating fluid is connected outwardly of the apertures in said end plates for closing the annular space between the rotor and housing at the cold end of the heater and leaving open the end of the annular space between the rotor and housing at the end thereof to which the inlet duct for the heating fluid is connected so that said space may fill with the heating fluid, and sealing means between the r0- tor and housing extending axially of the preheater in the space between the rotor and housing at circumferential positions adjacent the 10- cations of said imperforate portions of the end plates.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,660,788 Foresman Feb. 28, 1928 2,224,787 Horney Dec. 10, 1940 2,480,277 Yerrick Aug. 30, 1949 2,516,992 I-Iochmuth Aug. 1, 1950 2,549,656 Yerrick et al. Apr. 1'7, 1951 FOREIGN PATENTS Number Country Date 700,760 Germany Dec. 30, 1940