US 3734176 A
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United States Patent [191 Hagnauer May 22, 1973 HEAT EXCHANGER ASSEMBLY HAVTNG A COMMON FLUID BOX  Inventor: Waldo W. Hagnauer, 910 Keith Avenue, Waukegan, 111. 60085  Filed: Apr. 16, 1970  Appl. No.: 29,065
 int. C1. ..F28f 9/02  Field of Search ..165/140, 143, 144, 165/145,158,176
 References Cited UNITED STATES PATENTS 3,393,731 7/1968 Friedman et al ..165/176 X 2,196,683 4/1940 Pickstone ..165/82 1,813,234 7/1931 Dodd ..165/176 X 2,956,787 10/1960 Raub ..165/82 2,995,343 8/1961 Gardner et a1 ..165/143 X FOREIGN PATENTS OR APPLICATIONS 640,680 7/1950 Great Britain ..165/143 952,965 3/1964 Great Britain...... ....l65/158 67,190 1/1951 Netherlands ..165/158 Primary Examiner-William F. ODea Assistant Examiner-William C. Anderson Attorney-Petherbridge, ONeill and Lindgren  ABSTRACT A plurality of heat exchanger units are joined together by a connecting member in an end to end relation. A fluid box is formed between the units by the walls of the connectingmember and the tube sheets of the joined units. The fluid box serves as a passageway to conduct the heat exchange fluid between heat exchanger units. A tie-bar connected to the tube sheets of the individual heat exchanger units assists in containing the bending stresses exerted on the tube sheets by the pressure of the exchange fluid.
10 Claims, 8 Drawing Figures PATENTEU HAY 22 5 SHEET 1 OF 4 RUE INVENTOR.
PATENTEU M122 I975 FIG?) SHEET 3 BF 4 INVENTOR. WALDO HAGNAUR PATENTEUHAYZZIQYS 3,734,176
SHEET U U? 4 FIG.5-
HEAT EXCHANGER ASSEMELY HAVING A COMMON FLUID BOX BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to heat exchangers and more particularly to means for coupling a pair of heat exchangers through a fluid chamber which is common to both the heat exchangers.
Although heat exchanger assemblies may be used for various purposes including those for cooling, for convenience, the present invention will be discussed in con nection with heat exchanger assemblies used for heating that provide a high heat exchange capacity with high fluid pressure.
2. The Prior Art In heat exchangers of the type to which this invention relates, there is usually provided a shell or housing within which is disposed a bundle of elongated tubular members over which a fluid heating medium is passed. The tube bundle is supported or connected at at least one end by a flat plate partition structure or tube sheet, which divides the exchanger into two compartments. One of the compartments is employed to direct a fluid through the tubes, while the other compartment is employed to permit a flow of warmer medium in good heat exchange relation with the outer surfaces of the tubes with attendant heating of the fluid within the tubes. Heat exchangers of this type are usually supplied with such fluids and operate at substantially high temperatures and pressures. In most installations such as a steam plant, a plurality of heat exchanger units is required for feed water heating purposes. In high pressure boiler feedwater heaters for a steam turbine plant, for example, it is common practice to circulate the feed water through the tubes and to extract steam from a turbine stage over the tubes of a plurality of heat exchanger units, generally two or more exchangers connected externally and arranged in series. In one form of such heat exchangers, the feedwater enters and leaves the tubes via fluid boxes or headers located at each end of the tubes. In another form of heat exchanger unit, the tubes are arranged in U-shaped banks and the inlet and outlet ends of the tubes are joined to a common tube sheet. The fluid boxes for the inlet or outlet of the feedwater are arranged side by side on the end face of the tube sheet remote from the tubes and are joined to the tube sheet. The fluid boxes may be formed by welding a housing in the form of a solid forging to the tube sheet and dividing the space within the housing into two separate fluid boxes by means of a dividing wall.
The pressures at which the feedwater and steam are circulated, through the heat exchanger require that the tube sheet be able to withstand very high pressures. In a modern steam plant, the highly stressed tube sheet may require a thickness of 12 to 18 inches in order to withstand pressures as high as several thousand pounds per square inch between opposite sides of the tube sheets because of the high pressure fluid within the box. The fluid boxes, to withstand such pressures, must be of a special strong design such as a spherical or hemispherical configuration. Because of the thickness of the tube sheet and the special designs required for the fluid boxes, these heat exchanger components are costly to fabricate and the art is continually seeking ways to simplify the design of the fluid boxes and reduce the thickness of the tube sheets.
A primary object of the present invention is to provide a heat exchanger assembly wherein the means for providing heat exchange of fluids is simplified.
Another object of this invention is to provide a heat exchange apparatus for heating fluids in applications requiring two or more separate heat exchangers wherein the number of fluid boxes and attendant equipment, such as external interconnecting piping, is reduced.
A further object of the invention is to provide a heat exchanger in which the thickness of the tube sheet is reduced and which may be manufactured at much less cost.
The various novel details of construction and the advantages inherent in the heat exchanger assembly of the present invention are pointed out in detail in conjunction with the following descriptions of typical embodiments of the invention,
SUMMARY OF THE INVENTION In view of the foregoing it is contemplated by the present invention to provide a heat exchanger assembly including a plurality of heat exchange units of which each unit has a housing closed by a formed end and an open end closed by a tube sheet. A tube bundle comprised of a plurality of tubes is disposed in each of the housings with the ends of the tubes being secured to the tube sheet. The heat exchanger units are joined together in an end-to-end relation with a connecting member of which the walls and the spaced-apart tube sheets of the heat exchange units form a fluid box which serves as a passageway to conduct heat exchange fluid between the heat exchanger units.
The common fluid box interposed between the units of the heat exchanger assembly of the present invention eliminates the need for the plurality of specially designed costly fluid boxes or closures, ordinarily employed in the art in the fabrication of such heat exchanger assemblies. This reduces the initial construction cost and the subsequent interconnecting external piping between single exchangers.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal cross-sectional view through one embodiment of a heat exchanger assembly having a common fluid box interposed between the heat exchange units in accordance with the present invention.
FIG. 2 is a cross-sectional view taken generally along the line 2-2'of FIG. I.
FIG. 2A is a cross-sectional view similar to FIG. 2,
showing a modified embodiment of the tie bar within the heat exchanger.
FIG. 3 is a longitudinal cross-sectional view through a second embodiment of a heat exchanger assembly constructed in accordance with the present invention.
FIG. 4 is a cross-sectional view taken generally along the line 4-4 of FIG. 3.
FIG. 5 is a partial cross-sectional view of a tube sheet and a portion of the tie-bar illustrating the tie-bar encased within a covering to act as a heat transfer retardant. I
FIG. 6 is a partial cross-sectional view of a tube sheet and a portion of the tie-bar illustrating a tubular tie-bar functioning as a cascade vent between opposite heat exchanger units as well as a force-containment device.
FIG. 7 is a partial cross-sectional view of a tube sheet and a portion of the tie-bar illustrating a tie-bar wherein the thickness thereof is varied according to the structure of the connecting member.
' Referring to FIGS. 1 and 2 of the drawing the reference numeral generally designates an embodiment of a heat exchanger assembly according to this invention. The heat exchanger assembly 10 consists of two heat exchanger units 11 and 12 which are joined together in a tandem or end-to-end relationship by a lowcost, high strength in tension cylindrical coupling or connecting member 13, which is joined to the outer faces 15 and 16 of the tube sheets 17 and 18 of the individual heat exchanger units 11 and 12 by welding or other suitable attachment means.
Each of the heat exchange units 11 and 12 includes an elongated, cylindrical housing or shell 20 and 21 respectively, the open ends of which are closed with the plate-like tube sheets 17 and 18, which are sealingly fixed to the ends of walls 23, 24 of the housings as by welding. The shells 20 and 21 and the inner walls 25, 26 of the tube sheets 17 and 18 form individual spaces 28, 29. Inlet openings 30, 31 in the upper walls of respective shells 20 and 21 communicate the spaces 28, 29 with a source of heat exchange medium.
Outlet openings 33 and 34 are provided in the lower walls of shells 20 and 21 to permit the exhaust of the heat exchange fluid from spaces 28, 29 afterthe heat exchange fluid has undergone heat exchange.
The alined, spaced outer walls 15, 16 of the tube sheets 17 and 18 and the walls of the connecting member 13 form a common fluid distribution box 35 between the heat exchangers 11 and 12. The fluid box 35 provides a passageway for conducting heat exchange fluid from the tubes of one heat exchange unit to the tubes of the other heat exchange unit. A partition structure 36 is provided and disposed within the fluid box 35 in abutting relation withv a partition plate 37 attached to the upper portion of the outer wall 15 of the tube sheet, and partition 38 attached to the upper wall of the connecting member 13 to jointly form therewith a box or chamber 40 so that chamber 40 is in communication with the upper portion of tube sheet 17. Similarly, a
partition structure 43 is provided and disposed within the fluid box 35 in abutting relation with partition 45 attached to the lower portion of the outer wall 16 of the tube sheet 18 and partition plate 46 attached to the lower wall of the cylindrical connecting member 13 to jointly form therewith a chamber 48 so that chamber 48 is in communication with the lower portion of the tube sheet 18. Inlet conduit 51 attached to the lower wall of the coupling member 13 connects chamber 48 to a suitable source of heat exchange fluid through fluid inlet port 52 in the lower wall of coupling member 13.
Outlet conduit 54 in the upper wall of coupling member 13 permits exhaust of the heat exchange fluid that collects in chamber 40 through fluid outlet port 55 in the upper wall of coupling member 13 as will hereinafter be described.
Within the spaces 28 and 29 of shells 20 and 21, respectively, are disposed tube bundles 57 and 58 comprising a plurality of tubes 59 and 60. Each of the tube bundles consists of a plurality of various radius U section tubes 61 and 62 with continuing straight portions extending substantially parallel to each other and the longitudinal axis of the shells 20 and 21. The opposite ends 63, 64 of the tubes 59 and the opposite ends 65, 66 of the tubes are secured in their respective tube sheets 17 and 18 in any suitable manner as by swaging, welding or the like. The opposite ends 63, 64 of the tubes 59 are secured to the tube sheet 17 so that tube end 63 communicates with fluid outlet chamber 40 and tube end 64 communicates with fluid distribution box 35. The opposite ends 65, 66 of the tubes 60 are secured in tube sheet 18 so that the tube ends 65 communicates with common fluid box 35 and tube ends 66 communicates with fluid inlet chamber 48.
Accordingly, as thus far described, a first heat exchange fluid is admitted to the heat exchange assembly 10 through inlet 51 where it passes to chamber 48 and then through the tube ends 66 of tubes 60 secured to the lower portion of tube sheet 18 disposed in heat exchange unit 12 of heat exchanger assembly 10.
The fluid traverses heat exchange tubes 60 and is then directed into the common fluid box 35. From the fluid box 35 the first heat exchange fluid is passed to the tubes 59 disposed in heat exchanger unit 11 of the heat exchanger assembly 10, which communicate with fluid box 35 through the tube ends 64 secured to the lower portion of the tube sheet 17. The first heat exchange fluid is exhausted from tubes 59 into the chamber 40 through the tube ends 63 secured in the upper portion of the tube sheet 17. The exhausted fluid then leaves the chamber 40 and the heat assembly 10 through outlet conduit 54. Concomitantly therewith, as a second fluid is admitted into the chambers 28 and 29 of the individual heat exchanger units of the heat exchanger assembly 10 through the inlet conduits 30 and 31 and flows around the outer surfaces of tubes 59 and 60, heat exchange between the fluid flowing in the tubes and the fluid flowing through the spaces 28 and 29 is obtained.
Preferably as shown in FIG. 1, there is provided in the fluid box 35 at least one longitudinally extending tie-bar 70 which is secured, as by welding at its opposite ends to the outer walls 15, 16 of the tube sheets 17 and 18. The tie-bar 70 extends perpendicular to the tube sheets 17 and 18 and forms therewith an H-shaped assembly when viewed in cross-section. The H-frame assembly formed by the tube sheets 17 and 18 and the tie-bar 70 produces an extremely rigid structure which by containment of forces minimizes the diaphragmatic bending effect acting on the tube sheets by the high pressure exchange fluid within the fluid box 35. The minimization of the stress forces acting on the tube sheets reduces the strength requirements for the tube sheets and permits the thickness of the tube sheets to be substantially reduced. The reduction of the thickness of the tube sheets accounts for a substantial savings in the fabrication costs of the heat exchanger assembly. Because of a thinner tube sheet, the heat exchanger can accept more rapid changes in operating conditions with less harmful affect on the device as a whole, particularly with reference to temperature changes between the thin-walled tubes and the heavy tube sheets.
The entire fluid box design, the tie bar, tube sheet diameter and thickness, number of tubes, ligament spac ing resulting from tube spacing, and other such parameters are computer calculated to arrive at an optimum design for the condition imposed.
Since the tie-bar 70 is exposed to fluid flow conditions on all sides, whereas the connecting member 13 is only exposed to fluid contact on the internal wall surfaces thereof, the temperature response of the tie-bar 70 to the fluid in the fluid box 35 may not always be coequal to that of the connecting member 13. The temperature sensitivity of the tie-bar 70 may be adjusted by any suitable means. For example, to equalize the expansion and contraction response of the tie-bar 70 and the walls of the connecting member 13 to the fluid in the fluid box 35, the thickness of the tie-bar 70 may be increased to compensate for the difference in area exposed to the fluid. To further compensate for the difference in exposure area or as an alternative to the use of a tie-bar of varying thicknesses (70"), the tie-bar 70 may be encased in a sheath or sleeve (70A), or a suitable heat insulating material to permit equalized expansion and contraction with fluid temperature change.
Although the tie-bar 70 as shown in FIG. ll is of uniform cross-section, in the event that tube sheets of unlike size or cross-section are employed in a heat exchanger assembly, it is understood to be within the purview and scope of the present invention that tie-bars of various cross-section, as for example tie-bars having a conical, oval, tubular, or other cross-section may be employed when required. FIG. 2A illustrates one such embodiment wherein the tie bar 70a is shown to be in form of a tubular member, which may thereby serve the additional function of a cascade vent (7013) between the opposed heat exchangers.
To permit access to the tubes 59, 60 for inspection, repair and cleaning of the tubes, the fluid box 35 is provided with a conventional manway or manhole door 71. Partitions 36 and 43 may be in the form of removable plates to permit access for cleaning and repair of the tube ends in communication with the chambers 40 and 48. For example, partition plate covers 36 and 43 may be fastened to partition plates 37, 38 and 45, 46 respectively, by suitable bolts, welding or other means for removal not shown.
In FIGS. 3 and 4 there is shown a modified fluid box of the present invention. Since the only difference between this embodiment and the embodiment shown in FIGS. 1 and 2 lies in the fluid box, the heat exchanger units being identical, parts of the embodiment shown in FIGS. 3 and 4 corresponding to like components of the heat exchanger shown in FIGS. 1 and 2 shall be designated by the same reference numbers.
In FIGS. 3 and 4, the fluid box 35 interposed between the heat exchanger units 11 and 12 is divided into chamber 75, by centrally disposed force-containing horizontal partition plate 76 which is welded'or otherwise secured to the outer walls 15, 16 of tube sheets 17, 18 and the walls of the coupling member 13 and into chambers 78 and 79 by vertically extending partition plate 80, which is centrally disposed in fluid box 35 and is welded or otherwise secured to the bottom wall of partition plate 76 and the bottom wall of the coupling member 13.
The partition plates 76 and 80 serve the multiple purpose of dividing the fluid box 33 into chambers 75, 78, 79 as well as reinforcing the tube sheets 17 and 18 so that the tube sheets are sufficiently able to withstand the bending forces imposed thereon by the pressure of fluids flowing into the fluid box 35 in much the same manner as the tie-bar 70 shown in the embodiment of the present invention illustrated in FIGS. 1 and 2.
Inlet conduit 81 attached to the lower wall of coupling member 13 communicates chamber 79 with a suitable source of a first heat exchange fluid through inlet port 82. Outlet conduit 83 permits exhaust of the heat exchange fluid that collects in chamber 78 through fluid outlet port 84. Chamber provides a passageway for conducting a heat exchange fluid between the tubes of the individual heat exchange units.
In operation, a first exchange fluid is admitted to the heat exchanger assembly 10 through inlet conduit 81 where it passes into chamber 79 and then through tube ends 66 of tubes 60. The fluid traverses tubes 60 and is then directed into chamber 75 and then into the tube ends 63 of tubes 59. The fluid is passed from tubes 59 through the tube ends 64 into chamber 78 from which the fluid is exhausted from the heat exchanger assembly through outlet conduit 83. A second fluid is passed through the units 11 and 12 in the same manner as described for the heat exchanger assembly illustrated in FIGS. 1 and 2, so that heat exchange between the first and second fluids is caused to occur.
To permit access to the fluid box for repair and maintenance of the box and the heat exchanger tubes, manway 86 is provided which is sealed by removable manway cover 87 and provides access to chamber 75. From chamber 75 access to chambers 78 and 79 is provided through manways 88 and 89 which are sealed by removable partition plate covers 91 and 92.
The manway cover 87 and the partition plate covers 88 and 89 are held in place by clamps 93, 94 and 95 respectively. By means of nuts 96, 97 and 98 threaded on bolts connected to the covers and bearing against the clamps 93, 94 and 95, the manway cover 87 and partition plate covers 91 and 92 are seated in fluid-tight engagement with the manways 86, 88 and 89. To insure a fluid-tight seal the covers 87, 91 and 92 may be provided with gaskets designated by the numeral 100.
From the foregoing it should be readily apparent that the present invention provides a heat exchanger assembly which is relatively simple and less costly to fabricate and which is capable of easy access for inspection and repair.
Although two embodiments of the invention have been illustrated and described in detail, it is to be ex pressly understood that the invention is not limited thereto. Various changes can be made in the arrangement of parts without departing from the spirit and scope of the invention as the same will now be understood by those skilled in the art.
What is claimed is:
l. A heat exchanger assembly comprising in combination,
at least a first and a second heat exchanger unit in series flow,
each of the heat exchanger units being comprised of a housing closed at both ends,
at least one of the housing ends of each exchanger being closed by a tube sheet,
a cavity defined by each tube sheet and the walls of each housing,
a plurality of tubes disposed in each cavity,
the opposite ends of said tubes being secured to said tube sheets,
first inlet and outlet means in communication with said plurality of tubes disposed in each cavity for the delivery and exhaust of a first heat exchange fluid flowing in series,
a connecting member joining the heat exchanger tube sheets serially in an end to end relation for series flow of said first heat exchange fluid,
a fluid chamber formed between said heat exchanger units by the walls of the connecting member and the opposed tube sheets of the first and second heat exchanger units, the fluid chamber serving as a conduit for the passage of said first heat exchange fluid between said units,
second inlet means in communication with said cavities of said first and second heat exchanger units for delivery of a second heat exchange fluid to the heat exchanger assembly and a second outlet means in communication with said cavities of said first and second heat exchanger units to provide an exhaust for the second heat exchange fluid from the heat exchanger assembly, and
means positioned within said fluid chamber and secured to each of said tube sheets to form a rigid structural member minimizing bending of said tube sheets resulting from pressure differentials acting across the respective tube sheets.
2. The assembly of claim 1, wherein the tubes secured to the tube sheet are U-shaped.
3. The assembly of claim 1 wherein a single fluidtight scalable manway is provided in the fluid box for access to the tubes of opposed heat exchanger units.
4. The assembly of claim 1 wherein the common connecting fluid chamber of said first and second exchangers in series flow is partitioned into chambers for the inlet and exhaust of said first heat exchange fluid to pass said first heat exchange fluid sequentially between said first and second heat exchanger units.
5. The apparatus of claim 1 wherein said means positioned within said fluid chamber and secured to each of said tube sheets to form a rigid structural member minimizing bending of said tube sheets resulting from pressure differential forms a partition within said fluid chamber to pass a second heat exchange fluid from said first heat exchanger unit to said second heat exchanger unit.
6. The apparatus of claim 1 wherein said means positioned within said fluid chamber and secured to each of said tube sheets to form a rigid structural member minimizing bending of said tube sheets resulting from pressure differential comprises a tie-bar secured at its opposite ends to the opposed tube sheets of said first and second heat exchanger unit to minimize the diaphragmatic bending effect acting thereon due to the high pressure heat exchange fluid.
7. The assembly of claim 6 wherein one tie-bar is secured perpendicular to the tube sheets to form an H- frame assembly with said opposed tube sheets.
8. The assembly of claim 6 wherein said tie-bar is encased within a covering to act as a heat transfer retardant.
9. The assembly of claim 6 wherein said tie bar is tubular thereby to function as a cascade vent between opposite heat exchanger units as well as functioning as a force-containment device.
10. The assembly of claim 6 wherein the thickness of said tie-bar is varied according to the construction of the connecting member.