US3327771A

US3327771A - Regenerative heat exchangers

Info

Publication number: US3327771A
Application number: US483419A
Authority: US
Inventors: Andrew P Lecon
Original assignee: Babcock and Wilcox Co
Current assignee: Babcock and Wilcox Co
Priority date: 1965-08-30
Filing date: 1965-08-30
Publication date: 1967-06-27
Anticipated expiration: 1984-06-27
Also published as: FR1503608A

Description

June 27, 1967 P LECON REGENERATIVE HEAT EXCHANGERS 3 Sheets-Sheet 1 Filed Aug. 30, 1965 INVENTOR Andrew P. Lecon ATZTORNEY June 27, 1967 A. P. LECON REGENERATIVE HEAT EXCHANGERS 3 Sheets-Sheet 2 Filed Aug. 30, 1965 J1me 1967 A. P. LECON 7 3,327,771

REGENERATI VE HEAT EXCHANGER S Filed Aug. 30, 1965 5 Sheets-Sheet 3 United States Patent O Filed Aug. 30, 1965, Ser. No. 483,419 2 Claims. (Cl. 16510) The present invention relates to regenerative heat eX- changers, and more particularly to an improved construction of closely spaced heat exchange elements for rotary regenerative heat exchangers.

Rotary regenerative air heaters are well known wherein heat exchange elements are arranged in sector shaped compartments within a cylindrical drum where a heating fiuid and a fluid to be heated are passed in countercurrent relationship through separate compartments containing the heat exchange elements. Ordinarily the heat exchange elements are formed of parallel plates spaced for turbulent flow therethrough of the heating fluid and the fluid to be heated. It is also known to utilize various forms of spacers to establish the desired spacing between the parallel plates of the heat exchange elements. When using turbulent flow conditions for the fluid passing through the heat exchanger it is frequently desirable to arrange the heat exchange elements so as to permit limited vibration of plates during cleaning or soot blowing periods to aid in cleaning the heat exchange surfaces of the elements.

It has been found that heat exchange element-s formed of closely spaced parallel plates are highly eifective for heat exchange purposes Where the fluid flow velocity through the heat exchange elements is of a non-turbulent or laminar flow characteristic. In such heat exchangers the depth of the heating surfaces can be substantially less than the depth of surface in turbulent flow heaters with equal heat exchange efficiency.

It has been found that it is essential to assemble the heat exchange surfaces of a non-turbulent or laminar flow heater so as to maintain the desired plate spacing under all operating conditions. This has been accomplished in accordance with the present invention by use of a rigid structure which reinforces the assembly of heat exchange elements to maintain the desired spacing and the desired fluid flow characteristics through the heat exchange elements during operation. More specifically the invention involves, in its preferred form, the construction of heat exchanger elements where alternate plates in the assembly are flat while the remaining plates in the assembly are corrugated. The corrugated plates are formed with the corrugations extending on opposite sides of the plate with the displacement of the metal out of the plane of the plate being equal to the desired thickness of the flow space between a corrugated plate and the adjoining flat plate. When assembled the corrugated plates are reversed on opposite sides of the flat plate so that the corrugations contacting the opposite surfaces, of the intervening flat plate are in lateral abutting alignment. In the assembly of the elements, the corrugations are an ranged so as to be aligned parallel to the direction of fluid flow thereover. The assembled flat and corrugated plates are rigidly connected by wires or rods joined, as by welding, to the edge of the abutting corrugations on both faces of and throughout the extent of the heat exchange elements.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operation advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descrip- 3,327,??1 Patented June 27, 1967 tive manner in which I have illustrated and described a preferred embodiment of the invention.

Of the drawings:

FIG. 1 is an isometric view, partly in section, of a regenerative heat exchanger containing heat exchange elements constructed and arranged according to the present invention;

FIG. 2 is an enlarged View of an assembly of the regenerative heat exchange elements arranged for installation in a sector of the heat exchanger shown in FIG. 1 and showing the arrangement of the heat exchange elements;

FIG. 3 is an enlarged isometric view of a group or package of heat exchange plates constructed and arranged according to the invention; and

FIG. 4 is an enlarged isometric view of a modified assembly of heat exchange plates.

The rotary regenerative heater illustrated in FIG. 1 includes a stationary housing 10 arranged for the separate introduction and discharge of a heating fluid and a fluid to be heated. A cylindrical rotor 11 is mounted for rotation about a horizontal axis within the housing 10 and is constructed with radial partitions 12 extending substantially the full axial or longitudinal length of the rotor 11. The partitions 12 separate the cylindrical rotor into a plurality of sectons which are provided with heat transfer elements constructed in accordance with the present invention and arranged in axially space-d disk-like masses 13 adjacent the opposite ends of the rotor. Suitable seals, such as disclosed in copending application S.N. 249,736, now Patent No. 3,229,753, are mounted on the housing to cooperate with the rotor in directing separate counterourrent fluid flows through the housing and the sectors of the cylindrical rotor. As the rotor is rotated about a shaft 14, the sectors of heat transfer material are alternately heated by contact with the heating fluid and then cooled by contact with the fluid to be heated.

As shown specifically in FIG. 1, the housing 10 is provided with an upper heating fluid inlet 15 radially arranged relative to the rotor so that the incoming fluid enters the axial mid-portion of the flow compartments formed between adjacent partitions 12 of the rotor, divides as it turns to flow through the disk-like masses 13 of heat transfer material positioned adjacent the opposite ends of the rotor 11, and discharges upwardly through radial outlet ducts 16 positioned in the housing 10 out wardly adjacent the opposite ends of the rotor 11. The direction of flow of heating fluid is illustrated by the arrows 17.

A pair of radial inlets 20 are provided in the opposite ends of the lower portion of the housing 10, for the admission of the fluid to be heated. The incoming fluid flows axially of the rotor through the disk-like masses 13 to combine in the mid-portion of the rotor and to discharge radially through an outlet 21 formed in the lower portion of the housing 10. The direction of flow of the fluid to be heated is illustrated by the arrows 22.

In a regenerative heater of the type disclosed, the depth of the disk-like mass of heat transfer material positioned in the sectors is advantageously minimal in the direction of gas flow, i.e. longitudinally or axially of the shaft 14, and may be of the order of six to sixteen inches, for example, to meet heat exchange requirements in the usual installation. Advantageously, the thickness may be divided into two or more layers of elements for ease of installation and removal. For example, the cold end of the heat exchange mass, i.e. the outermost layer, may be only two or three inches in depth and may be constructed of low alloy metal to resist corrosion. The remaining layer or layers of heat exchange elements may be constructed of carbon steel, for example, two to six inches in thickness. Each layer may be assembled of a plurality of packaged elements positioned in side by side and end to end relationship and assembled as a pie shaped mass to fit as a single piece in the sector formed between adjacent partitions 12.

When installed in the rotor 11 the sector shaped layers will be spaced in the direction of gas flow to provide a clearance for separate insertion or removal of each layer and to provide a mixing and distribution eflect for the fluids passing through one layer into another layer. The space between layers may be of the order of A1. inch.

An assembly of heat exchange elements is shown in FIG. 2, where a plurality of packages of heat exchange plates are assembled in the necessary sector shaped configuration and mounted as a unit for insertion between partitions 12 in the rotor 11. Each of the packages of heat exchange elements in each layer are of the same depth 26 (see FIG. 4) in the direction of fluid flow and are of the same face height 27. However, the length 28 of some of the packages will differ to compensate for the width of the portion of the segment into which the packages are mounted.

As shown particularly in FIG. 2, a plurality of packages 25 are mounted in a frame or basket 31) which is formed by a pair of downwardly converging plates 31 which are spaced and dimensioned to snugly fit into the sector-like space 13 between adjacent partitions 12. A series of plates 32 are welded at their lower ends 33 on the inner surfaces of the plates 31, extend upwardly in a plane parallel to a plane bisecting the included angle between the plates 31 a distance substantially equal to the dimension 27 of each heat exchange package 25 and thereafter having a portion 34 extending outwardly in a plane normal to the plate 32. With this construction a series of step-like sections are formed into which packages 25 are installed. Where necessary reinforcing plates, such as 35 and 36, are inserted between packages. The number of such reinforcing plates is dependent upon the size of the sector into which the basket or layer of heat exchange elements is installed. Since the flow of fluids through the heat exchange surfaces is in a direction normal to the plane of the drawing, the triangular spaces 37 bounded by the

plates

32, 34 and 31 are closed by suitable plates to avoid fluid flow therethrough. Advantageously, the plates 31 are extended at their upper end portions 38 in a plane parallel to the plane bisecting the included angle between the downwardly converging plates 31. This construction is used to clear the circumferential seal plates (not shown) positioned on the ends of the partitions 12, so that the baskets 30 may be inserted and removed radially of the rotor 11. The triangular space 37 between the plate portions 38 and the corresponding portion of the partitions 12 may be closed by closure plates attached to the partitions 12.

As shown in FIG. 3 each package 25 of heat exchange elements is formed of a plurality of light gage metal plates where alternate plates 40 are flat and the remaining plates 41 are corrugated on opposite sides equal amounts at uniformly spaced locations. As shown, plate 41 is provided with a plurality of equally spaced corrugations 42 while immediately adjacent thereto corrugations 43 extend an equal amount on the opposite side of plate 41. The depth of

corrugations

42 and 43 are equal and correspond with the desired spacing between plates 40 and 41. The finished

dimensions

26 and 27 of plates 40 and 41 are equal and the plates are assembled so that alternate plates 41 are arranged in opposite hand so that the corrugations 43 of plates 41 on opposite sides of a flat plate 40 are in lateral alignment. This is shown in FIG. 3 where

plate

41A and 41B are assembled with corrugations 43 hearing on opposite sides of plate 40A. With this arrangement the corrugation 42 of plate 41B bears on 70 plate 408 at a location directly opposite corrugation 42 of plate 41C.

Alternately, as shown in FIG. 4, with the arrangement of plates 40 and 41 as described in connection with FIG. 3, rods or wires 46 may be welded to the plates 40 and 41 along the top and bottom ends of the plates.

With the described assembly of heat exchange elements or plates, the package 25 forms a rigid unit for ease of individual package 25 handling, and when installed in and welded to the basket 30 the spacing between plates 40 and 41 will be maintained during use.

By way of example, the plates 40 and 41 may be formed from 26 gage steel strip four inches wide and cut for a finished length of three and one-half inches, either mild carbon steel or of low alloy corrosion resistant steel, and the spacing between the plates 40 and 41, as determined .by the depth of

corrugations

42 and 43, may be .045 inch for high efficiency heat transfer in a heater such as shown in FIG. 1.

While in accordance with the provisions of the statutes I have illustrated and described herein the best form and mode of operation of the invention now known to me, those skilled in the art will understand that changes may be made in the form of the apparatus disclosed without departing from the spirit of the invention covered by my claims, and that certain features of my invention may sometimes be used to advantage without a corresponding use of other features.

What is claimed is:

1. In a rotary regenerative fluid heater of the laminar flow type having a stationary housing, a cylindrical rotor having radial partitions forming a plurality of sector shaped compartments therein, regenerative heat exchange material positioned in said compartments, means for passing a heating fluid and a fluid to be heated in counterflow relationship separately through said compartments containing said regenerative heat exchange material, said regenerative heat exchange material comprising a plurality of superimposed thin layers of substantially flat closely spaced plates, alternate plates being corrugated to define peaks on opposite sides of each of said plates,

means for arranging a flat plate between adjacent corrugated plates with the peaks of the corrugations of said alternate plates abutting opposite sides of said flat plate, and continuous metallic means perpendicular to and rigidly attached to each of said plates at least half of the matching and adjacent peaks of said corrugated plates to maintain said closely spaced relation therebetween.

2. In a rotary regenerative fluid heater according to claim 1 wherein said continuous metallic means are attached to said plates on the gas entrance and gas exit ends of said he at exchange material.

References Cited UNITED STATES PATENTS 1,762,446 6/1930 Ljungstrom -7 X 2,432,198 12/1947 Karlsson et a1 16510 2,549,583 4/ 1951 Eckersley 1655 2,983,486 5/1951 Rosenberg 165-10 X 3,191,666 6/1965 Brandt 16510 X 3,164,891 1/1965 Gier 165--166 X ROBERT A. OLEARY, Primary Examiner.

T. W. STREULE, J R., Assistant Examiner.

plates along the abutting areas of the corrugations 42 or

Claims

1. IN A ROTARY REGENERATIVE FLUID HEATER OF THE LAMINAR FLOW TYPE HAVING A STATIONARY HOUSING, A CYLINDRICAL ROTOR HAVING RADIAL PARTITIONS FORMING A PLURALITY OF SECTOR SHAPED COMPARTMENTS THEREIN, REGENERATIVE HEAT EXCHANGE MATERIAL POSITIONED IN SAID COMPARTMENTS, MEANS FOR PASSING A HEATING FLUID AND A FLUID TO BE HEATED IN COUNTERFLOW RELATIONSHIP SEPARATELY THROUGH SAID COMPARTMENTS CONTAINING SAID REGENERATIVE HEAT EXCHANGE MATERIAL, SAID REGENERATIVE HEAT EXCHANGE MATERIAL COMPRISING A PLURALITY OF SUPERIMPOSED THIN LAYERS OF SUBSTANTIALLY FLAT CLOSELY SPACED PLATES, ALTERNATE PLATES BEING CORRUGATED TO DEFINE PEAKS ON OPPOSITE SIDES OF EACH OF SAID PLATES, MEANS FOR ARRANGING A FLAT PLATE BETWEEN ADJACENT CORRUGATED PLATES WITH THE PEAKS OF THE CORRUGATIONS OF SAID ALTERNATE PLATES ABUTTING OPPOSITE SIDES OF SAID FLAT PLATE, AND CONTINUOUS METALLIC MEANS PERPENDICULAR TO AND RIGIDLY ATTACHED TO EACH OF SAID PLATES AT LEAST HALF OF THE MATCHING AND ADJACENT PEAKS OF SAID CORRUGATED PLATES TO MAINTAIN SAID CLOSELY SPACED RELATION THEREBETWEEN.