CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application Serial No. 63/316,103, filed March 3, 2022, titled MULTI- ANNULAR HEAT EXCHANGER, which is incorporated by reference herein in its entirety.

FIELD

[0002] The present disclosure relates to the field of heat exchangers and catalytic reactors.

BACKGROUND

[0003] In a variety of conventional heat exchanger configurations, a wall or heat transfer surface separates two fluids, through which wall heat flows from one fluid to the other. The shell and tube configuration is advantageous in containing fluids at elevated pressures compared to heat exchangers with flat heat transfer surfaces, whether smooth or textured.

[0004] Disadvantages of the shell and tube configuration are in the poor heat transfer coefficient between the tube side fluid and the tubes, the inconsistent heat transfer coefficient between the shell side fluid and the tubes, and stress on the tube sheets induced by different thermal expansion of the tubes and shell.

[0005] The tube side fluid flows parallel to the tube walls, requiring high velocity in conventional heat exchangers to bolster the tube side heat transfer coefficient. The need for high velocity in turn requires a high aspect ratio of tube length to cumulative tube cross section. The need to arrange the heat transfer surface area in a high aspect ratio results in long tubes, which induce high inlet to outlet pressure drop. The temperature difference between the shell and tubes exacerbated by tubes of greater length notoriously induces high stress on the welds of the tube sheets that join the shell and tubes.

[0006] The heat transfer coefficient of the shell side fluid can be enhanced by sets of baffles, which direct the shell side fluid to flow in a serpentine pattern between the tubes to advantageously impinge tube heat transfer surfaces. The shell side impingement of the tubes is inconsistent, however, in that the fluid channels itself through fractions of the flow path available to it.

SUMMARY

[0007] In a first aspect, a heat exchanger includes a plurality of concentric tubes defining a first set of multiple annuli therebetween and a second set of multiple annuli therebetween, the annuli of the first and second sets being radially interspersed, wherein at least one annulus of the first set or the second set of multiple annuli contains a structured packing.

[0008] In some embodiments, the annuli of the first set of multiple annuli contain a structured packing.

[0009] In some embodiments, the annuli of the first set of multiple annuli and second set of multiple annuli contain a structured packing.

[0010] In some embodiments, the structured packing comprises a catalyst.

[0011] In some embodiments, the heat exchanger further includes a first manifold in fluid communication with the first set of multiple annuli; and a second manifold in fluid communication with the second set of multiple annuli. In some embodiments, a portion of each annulus of the first set of multiple annuli adjacent to the first inlet manifold does not include the structured packing, and wherein a portion of each annulus of the second set of multiple annuli adjacent to the second inlet manifold does not include the structure packing.

[0012] In some embodiments, the plurality of concentric tubes further define a third set of multiple annuli radially interspersed with the first and second sets of multiple annuli.

[0013] In a second aspect, a heat exchanger includes a plurality of concentric tubes; and at least one tube sheet joined to first ends of individual tubes of the plurality of concentric tubes, wherein the plurality of concentric tubes define a first set of multiple annuli between consecutive tubes and a second set of multiple annuli between consecutive tubes, and wherein the first set of multiple annuli communicate with a first manifold through a first set of apertures in the at least one tube sheet and the second set of multiple annuli communicate with a second manifold through a second set of apertures in the at least one tube sheet. [0014] Tn some embodiments, the at least one tube sheet comprises a single tube sheet having the first set of apertures and the second set of apertures extending therethrough.

[0015] In some embodiments, the first set of apertures are in fluid communication with a first manifold and wherein the second set of apertures are in fluid communication with a second manifold.

[0016] In some embodiments, at least one annulus of the first set of multiple annuli or the second set of multiple annuli includes a structured packing therein.

[0017] In some embodiments, the plurality of concentric tubes further define a third set of one or more annuli.

[0018] In some embodiments, the third set of one or more annuli communicate with a third manifold through a third set of one or more apertures in the at least one tube sheet.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG. 1A is a longitudinal cross section of an example heat exchanger in accordance with the present disclosure.

[0020] FIG. IB shows a transverse cross sections taken along the lines B-B.

[0021] FIG. 1C shows a transverse cross section taken along the lines C-C in FIG.

1A.

[0022] FIG. ID shows a transverse cross section taken along the lines D-D in FIG. 1A.

[0023] FIG. IE shows a transverse cross section taken along the lines E-E in FIG. 1A.

[0024] FIG. IF shows a transverse cross section taken along the lines F-F in FIG. 1A.

[0025] FIG. 2A is a longitudinal cross section of the heat exchanger of FIG. 2A, additionally showing packings.

[0026] FIG. 2B is a transverse cross section taken along the line D-D of FIG. 2A.

[0027] FIG. 3A depicts a transverse cross section of an example inlet-outlet portion of an example heat exchanger, at a location similar to line B-B or F-F of FIG. 2A. [0028] FIG 3B is a transverse cross section of an example annulus portion of an example heat exchanger, at a location similar to line C-C or E-E of FIG. 2A.

[0029] FIG. 4 is a longitudinal cross section of a further example heat exchanger in accordance with the present disclosure.

DETAILED DESCRIPTION

[0030] Various embodiments of the present technology may provide a number of advantages relative to conventional heat exchangers. Some embodiments of the present disclosure can cause each of two fluids exchanging heat to impinge heat transfer surfaces between them consistently over those entire surfaces. Some embodiments of the present disclosure can reduce the length and pressure drop of the flow paths. Some embodiments of the present disclosure can reduce thermal stress between the shell and the tubes of shell and tube heat exchangers. Some embodiments of the present disclosure can provide a high density of heat transfer surfaces. Some embodiments of the present disclosure can reduce or minimize the cost of manifolding the flow of two fluids into and out of an improved heat exchanger. Moreover, some embodiments of the present disclosure can accomplish any or all of the above advantages within curved containments suitable for high pressure service and pressure differentials. Some embodiments of the present disclosure can replace multiple-pass shell and tube heat exchangers with single-pass heat exchangers for improved heat recovery or transfer and can avoid the need for baffles, which can increase pressure drop across a heat exchnager. Embodiments of the present disclosure can also reduce the heat transfer surface area required from that for in shell and tube heat exchangers, and may reduce heat exchanger costs of construction. These and other objectives will be observed by those reasonably skilled in the art.

[0031] The current development has found that structured packings can be designed to cause fluid both to flow along a length of a heat transfer surface and to impinge on the heat transfer surface at lower velocity in the direction of flow along the heat transfer surface than a fluid flowing parallel to the heat transfer surface without structured packing, while providing similar and pressure drops per unit of travel along the heat transfer surface lengths and at similar heat transfer coefficients between the fluids and the heat transfer surfaces. This discovery permits the design of heat exchangers with lower aspect ratios and distances between their inlets and outlets and accordingly lower pressure drops from inlet to outlet. Conversely, heat exchangers with the said designs of structured packings can be designed to provide higher heat transfer coefficients at similar pressure drops to heat exchangers with fluid flow parallel to heat exchange surfaces. Combinations of higher heat transfer coefficients and lower inlet to outlet pressure drops are also possible with the said structured packings.

[0032] In some aspects, the heat exchangers described herein include a series of concentric tubes forming a series of annuli therebetween. A first fluid flows through a first annulus or set of multiple annuli, and a second fluid flows through a second annulus or set of multiple annuli, the annuli of the first and second annuli or sets of annuli being radially interspersed. In some embodiments, the first and second sets of annuli can be interspersed in an alternating sequence of annuli of the first and second sets.

[0033] One or more of the first and second annuli may advantageously contain a packing, such as a structured packing, to enhance heat transfer between the fluid flowing through the annulus and the walls or tubes enclosing or defining the annulus. The packing may be a structured packing. The packing may contain a catalyst suitable for promoting a reaction of at least one of the fluids flowing through the heat exchanger.

[0034] In some embodiments, a structured packing can be a monolithic form having a repeating pattern as opposed to a packing consisting of a foam or of a bed consisting of individual particles or pores randomly oriented or disposed within a containment. The structured packings disclosed in U.S. Patent No. 8,235,361 are examples of a suitable structured packing. U.S. Patent No. 8,235,361 is incorporated by reference herein in its entirety.

[0035] Each tube of the heat exchanger has two ends. In some embodiments, each annulus of the first set of annuli is connected to a common first inlet manifold at one end and a common first outlet manifold at a second end opposite the first end. In some embodiments, each annulus of the second set is connected to a common second inlet manifold at one end and a common second outlet manifold at a second end opposite the first end. The first and second inlet manifolds may be at the same end for concurrent flow or at opposite ends for counter-current flow. [0036] Tn some embodiments, each of the manifolds includes a housing, an inlet or outlet tube, a mask or tube sheet, and apertures in the mask. The openings in the mask may cause each of the annuli of a set of annuli to communicate with an inlet or outlet tube via the housing, and the mask may isolate the housing from the annuli of the other set of annuli.

[0037] In some embodiments, first and second manifolds at each end of the heat exchanger are separated by a wall between their respective housings.

[0038] In some embodiments, each of the first and second inlet and outlet manifolds of the heat exchanger are as described above. The heat exchanger may be enveloped in an insulator, insulating material, or vacuum. The heat exchanger may be constructed of any suitable material, such as a metal.

[0039] Referring now to FIGS. 1A-1F, a heat exchanger 100 includes a first set of annuli 1 and a second set of annuli 2 arranged in alternating radial sequence between concentric tubes or tube walls 3. The first annuli 1 are in fluid communication with inlet manifold 4 and outlet manifold 5. Inlet manifold 4 joins first annuli 1 to inlet tube 6. Outlet manifold 5 joins first annuli 1 to outlet tube 7. Second annuli 2 communicate with inlet manifold 8 and outlet manifold 9. Inlet manifold 8 joins second annuli 2 to inlet tube 10. Outlet manifold 9 joins second annuli 2 to outlet tube 11. Inlet manifold 4 and outlet manifold 9 are bounded by housing 12, which may be dome-shaped in some embodiments, and by upper mask 13. Inlet manifold 4 and outlet manifold 9 are separated from each other by a dividing wall 14. Inlet manifold 8 and outlet manifold 5 are bounded by housing 15, which may be dome-shaped in some embodiments, and by lower mask 16. Inlet manifold 8 and outlet manifold 5 are separated from each other by a dividing wall 17. A central cylindrical volume 18 at the axis of the concentric tubes, indicated by crosshatching, can block fluid flow.

[0040] In some embodiments, the tubes and manifolds of the heat exchanger are enclosed in insulation 19. The insulation 19 may be flexible or lose-fitting such that differences in thermal expansion between the tubes and the insulation 19 or any containment of the insulation 19 does not cause stress between those respective components. The thickness of any combination of the outermost tube 3 and housings 12 and 15 may be greater than that of other tubes 3 to act as a pressure containment vessel, as desired in accordance with the pressure and local temperature to be employed. For example, the hot end of a cocurrent heat exchanger may have a thicker housing than the housing at the cold end.

[00411 I ⁿ operation, a first fluid enters the heat exchanger 100 through inlet tube 6 and into inlet manifold 4 flows through first annuli 1, flows through outlet manifold 5, and exits the heat exchanger 100 via outlet tube 7. A second fluid can enter the heat exchanger 100 through inlet tube 10 to inlet manifold 8, flows through second annuli 2, flows through outlet manifold 9, and exits the heat exchanger via outlet tube 11. The first fluid is in contact with an inner surface of the first annuli 1, and the second fluid is in contact with the inner surface of the second annuli 2. The inner surfaces of the first and second annuli 1, 2 can be the same structure, or tube walls 3. That is, the first fluid contacts a first surface of the tube walls 3, and the second fluid contacts a second surface of the tubes 3. Heat is transferred between the first and second fluids through the tube walls 3. Transverse cross section B-B of FIG. 1A, shown in FIG. IB, also shows the cross section of manifolds 4 and 9 bounded by housing 12 and separated by dividing wall 14. Transverse cross section F-F of FIG. 1A, as shown in FIG. IF, shows manifolds 5 and 8 bounded by housing 15 and separated by dividing wall 17.

[0042] FIG. 1C is the transverse cross section C-C, which section passes through upper mask 13 of the heat exchanger of FIG. 1A. Upper mask 13 includes a wall, shown as a dotted area, that causes first annuli 1 to communicate through arc shaped slots 21 with inlet manifold 4, and that causes second annuli 2 to be isolated from inlet manifold 4. The wall also causes second annuli 2 to communicate through arc shaped slots 22 with outlet manifold 9 and causes first annuli 1 to be isolated from outlet manifold 9. Dividing wall 14 is joined to a central portion 23 of upper mask 13.

[0043] FIG. IE is the transverse cross section E-E, which section passes through lower mask 16 of the heat exchanger of FIG. 1A. Lower mask 16 includes a wall, shown as a dotted area, that causes first annuli 1 to communicate through arc shaped slots 31 with outlet manifold 5, and that causes second annuli 2 to be isolated from outlet manifold 5. The wall also causes second annuli 2 to communicate through arc shaped slots 32 with inlet manifold 8 and causes first annuli 1 to be isolated from inlet manifold 8. Dividing wall 17 is joined to a central portion 33 of lower mask 16. [0044] Dividing walls 14 and 17 and masks 13 and 15 may be of any rotational orientation about the axis of the concentric tubes. Fluids may flow in either direction through first annuli 1 and second annuli 2, causing manifolds to have the resultant inlet and outlet functions. Hence, either co-current or counter current heat transfer may be practiced with the heat exchanger.

[0045] FIG. 2A illustrates the heat exchanger 200, which can be similar to that described with regard to FIG. 1A. The heat exchanger 200 includes packings 40 in the heat exchanger in areas of first and second annuli depicted in the cross hatched area. In some embodiments, the packing 40 fills first annuli 1 and second annuli 2. In some embodiments, the packing 40 fills only a portion of first and second annuli, or extends along only a part of the length of the first and second annuli. The packing 40 may enhance the heat transfer coefficient between a fluid flowing through an annulus and the walls of the annulus. The packings may be, for example, a monolithic structure, a fixed structure, a monolithic fixed structure, packed beds, or the like. The packings may cause fluid flowing through the packings to impinge the walls of the annuli containing the packing and can substantially reduce the fluid velocity required to generate a given heat transfer coefficient, permitting the surface area of the heat exchangers to be arranged with greater cross section for fluid flow and shorter inlet to outlet distance for lower inlet to outlet pressure drop and lower longitudinal thermal expansion than if the annulus contained no packing and provided the same heat transfer coefficient. In some embodiments including packings, portions of first annuli 1 and second annuli 2 may contain no packing or may be substantially free of packing. For example, as shown in FIG. 2A, terminal portions of the lengths of first annuli 1 and second annuli 2 near masks 13 and 16 do not contain packing, so as to permit good circumferential distribution of fluids through the annuli near their ends.

[0046] Fig. 2B shows a transverse cross section taken about the line D-D of the heat exchanger of FIG. 2 A. As shown in FIG. 2B, each annulus contains the packings 40, with the central cylindrical volume 18 being free of packings as fluid does not flow through the central cylindrical volume 18. It will be understood that the cross-sections about lines B- B, C-C, E-E, and F-F of FIG. 2A will appear substantially the same as those illustrated in FIGS. IB, 1C, IE, and IF, respectively, as those portions of the heat exchanger 100 of FIG. 2 A do not include packings 40. [0047] FIGS. 3A and 3B illustrate an exemplary configuration of a heat exchanger 300 similar in construction to heat exchangers 100 and 200. FIG. 3A illustrates a cross-sectional view of an inlet-outlet portion of the exemplary heat exchanger taken at a location similar to the lines B-B and F-F of FIG. 1A or 2A. The inlet-outlet portion of the heat exchanger 300 comprises three manifolds. Housing 44 encloses manifolds 41, 42, and 43, which manifolds are separated from each other by separating walls 45. Each end of the heat exchanger has similar, complementary inlet-outlet portions having 3 manifolds. Having 3 manifolds allows for heat exchange between 3 fluids in a single heat exchanger 300.

[0048] FIG. 3B illustrates a cross-sectional view of a heat exchanger 300 taken at lines in locations similar to C-C and E-E of FIG. 1A or 2A. Heat exchanger 300 has first and second annuli, as described elsewhere herein, and also has third annuli separated from the first and second annuli by tube walls and mask 46. Mask 46, shown as a dotted area, causes, in the illustrated embodiment, only a first set of one annulus to communicate through arcshaped slot 47 with upper and lower manifolds 41 (as depicted in FIG. 3 A), only a second set of 3 annuli to communicate through arc-shaped slots 49 with upper and lower manifolds 42, and only a third set of three annuli to communicate through arc-shaped apertures 48 with upper and lower manifolds 43. The quantity of annuli depicted in the heat exchanger 300 is exemplary only. A person of skill in the art, guided by the current disclosure, would understand that each set of annuli could include various quantities of annuli, without departing from the scope of this disclosure. In heat exchanger 300, heat may be exchanged between three fluids. Greater numbers of fluids can exchange heat in a common heat exchanger, whether in co-current or counter current heat exchange by appropriate subdivisions of end housings and placement of arc-shaped slots.

[0049] Fig. 4 shows a longitudinal cross section of another embodiment of heat exchanger 400. Dotted areas indicate the passages for a first fluid to flow into the heat exchanger from inlet tube 405 into and through manifold 404, through mask 413 to a first set of annuli 401 residing between tubes 403, through a second mask 413 to and through manifold 405. The first fluid then exits the heat exchanger through outlet tube 407. Housing 412 encloses manifold 404, and housing 416 encloses manifold 405. Crosshatched areas indicate the passages for a second fluid to flow into the heat exchanger from inlet tube 410, into manifold 408, over and around mask 416 to a second set of annuli 402 residing between concentric tubes 403. The second fluid then flows over and around second portions of the mask 416 into manifold 409. The second fluid exits the heat exchanger through outlet tube 411.

[0050] Along axis of the tubes resides a central volume 418, shown with horizontal lines, which is impervious to fluids and through which no fluid flows. In some embodiments, the flow of the second fluid may be co-current to the first fluid as the fluids pass along their respective annuli. In some embodiments, all annuli 411 and 412 may contain a packing to enhance heat transfer at low fluid velocity to permit the annuli to be of relatively large cross section and short length compared to annuli with no packing providing similar heat transfer coefficients. Although the inlet tube 410 and the outlet tube 411 are depicted as being on the same side of the heat exchanger 400, the inlet and outlet tubes 410 and 411 can be offset along a length of the heat exchanger. For example, the outlet tube 410 and manifold 409 may be offset from inlet tube 410 and manifold 408 by 90°, 180°, or some other amount. In some embodiments, the manifolds 408 and 409 may extend around a portion of the circumference of the heat exchanger 400. For example, the manifolds 408 and 409 may extend around half the circumference of the heat exchanger 400, or may extend around a larger or smaller portion than half the circumference. The manifold 408 may extend around a first half of the circumference of the heat exchanger, and the manifold 409 may extend around a second half or the other half of the heat exchanger.

[0051] Masks 413 and 416 can be similar to the masks described elsewhere herein. The masks 413 and 416 form a fluid flow boundary between the first and second annuli. Heat transfer can occur across the masks 413 and 416.

[0052] The width of the first set of annuli may be different from the width of the second set of annuli. Outer concentric tubes may be thicker walled than inner tubes, as described elsewhere herein.

[0053] The outermost tube may be insulated from the ambient temperature and is in thermal communication with the fluid in the outermost anulus. Each component of the heat exchanger may be metal and/or may be constructed of any other suitable material.

[0054] In some embodiments the heat exchanger comprises a multiplicity of concentric tubes defining a first set of multiple annuli therebetween through which a first fluid flows in a first direction and a second set of multiple annuli therebetween through which a second fluid flows in a second direction, the annuli of the first and second set being interspersed, wherein at least the annuli of one set contain a packing to cause fluid flowing through the first set of annuli to impinge the tubes defining the annuli of the one set. The packing can be one of a packed bed and a structured packing. The first direction is one of the same direction as and the opposite direction to the second direction. The packing contains a catalyst.

[0055] In other embodiments, the heat exchanger comprises a multiplicity of consecutive concentric tubes wherein the tubes define a first set of multiple annuli between consecutive tubes and a second set of multiple annuli between consecutive tubes and wherein first ends of the concentric tubes are joined to a tube sheet, wherein the first set of multiple annuli communicate with a first manifold through apertures in a first tube sheet and the second set of multiple annuli communicate with a second manifold through apertures in a second tube sheet, and the first and second tube sheets are first and second portions of a common sheet.

[0056] Other advantages and other embodiments of the current invention will be obvious to those skilled in the art. Their omission here is not intended to exclude them from the claims advanced herein.

[0057] Although the present technology has been described in terms of certain preferred embodiments, various features of separate embodiments can be combined to form additional embodiments not expressly described. Moreover, other embodiments apparent to those of ordinary skill in the art after reading this disclosure are also within the scope of this disclosure. Furthermore, not all the features, aspects and advantages are necessarily required to practice the present technology. Thus, while the above detailed description has shown, described, and pointed out novel features of the present technology as applied to various embodiments, it will be understood that various omissions, substitutions, and changes in the form and details of the apparatus or process illustrated may be made by those of ordinary skill in the technology without departing from the spirit or scope of the present disclosure. The present technology may be embodied in other specific forms not explicitly described herein. The embodiments described above are to be considered in all respects as illustrative only and not restrictive in any manner.