Block type heat exchanger for heat pipe reactor

Abstract

A block-type heat exchanger for a heat pipe reactor having multiple heat pipes extending from a reactor core, the heat exchanger including multiple primary channels, each for receiving heat transferred from the core via one of the heat pipes, the primary channels extending within one or more blocks of material, and the heat exchanger including multiple secondary channels defined within the blocks for directing a flow of a secondary heat transfer medium from an inlet to an outlet through the heat exchanger. The block is formed from one or both of a plurality of plates joined together, each plate defining at least a portion of one or more of the multiple primary channels and / or multiple secondary channels, and / or a single piece of material formed from an additive manufacturing process.

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims the benefit of U.S. Application No. 16 / 722,845, entitled "BLOCK STYLE HEAT EXCHANGER FOR HEAT PIPE REACTOR", filed on December 30, 2019, the content of which is incorporated herein by reference.

[0002] The present invention generally relates to heat exchangers, and more particularly to a block - type heat exchanger particularly suitable for transferring heat from a primary heat source to a secondary medium via a number of heat pipes.

Background Art

[0003] Supercritical carbon dioxide (sCO2) is a fluid carbon dioxide in which carbon dioxide is maintained above its critical temperature and critical pressure. Carbon dioxide typically behaves as a gas in air at standard temperature and pressure or as a solid called dry ice when frozen. When both the temperature and pressure are increased from standard temperature and pressure such that they are above the critical point of carbon dioxide, it can assume intermediate properties between a gas and a liquid. More specifically, carbon dioxide behaves as a supercritical fluid above its critical temperature (304.25 K, 31.10 °C, 87.98 °F) and critical pressure (72.9 atm, 7.39 MPa, 1,071 psi), expanding to fill its container with a density like that of a liquid but like a gas.

[0004] Supercritical carbon dioxide (sCO2) is chemically stable, reliable, low-cost, non-toxic, non-flammable, readily available, and a desirable candidate for a working fluid. Furthermore, due to its excellent thermal stability and non-flammability, it enables direct heat exchange from high-temperature sources, allowing for higher working fluid temperatures and thus higher cycle efficiencies. Unlike two-phase flows, the single-phase nature of sCO2 eliminates the need for heat input for the phase change required to convert water to steam, along with the associated thermal fatigue and corrosion. Despite the expectation of substantially higher efficiency and lower capital costs, the use of sCO2 presents material selection and design challenges. Materials for power generation components are required to have resistance to damage from high temperatures, oxidation, and creep. Candidate materials that meet these property and performance goals include alloys currently used in power generation, such as nickel-based superalloys for turbomachinery components and austenitic stainless steels for piping. Components within an sCO2 Brayton loop are plagued by corrosion and erosion, particularly erosion in turbomachinery and recuperator heat exchanger components, as well as intergranular corrosion and pitting in piping.

[0005] Prior to the present time, no feasible primary heat exchanger design and manufacturing route for integrating an sCO2 secondary cycle into a heat pipe reactor had been considered. Most designs envision a block-type heat exchanger with multi-tube (shell-and-tube type) headers at both ends of the heat exchanger along the path of the heat pipes. In this type of design, the space between the heat pipes is limited, but it is necessary to protect the heat pipes from the high-pressure sCO2 in the open headers. Integrating a protective heat pipe sleeve into the header chamber and the heat exchanger block section is difficult, if not impossible, due to the limited space available for connecting or welding the chamber and the sleeve to the heat exchanger section, and the remaining area for the sCO2 channels entering the heat exchanger block. A thicker protective material around the heat pipes also substantially reduces the heat transfer capacity of the heat exchanger. Accordingly, it is an object of the present invention to provide an integrated block-type heat exchanger design that can efficiently transfer the heat output of the heat pipe reactor to the secondary side of the sCO2 and operate with minimal maintenance. Summary of the Invention

[0006] These and other objects are achieved, in one aspect of the invention, by an integrated modular heat exchanger for use with a heat pipe reactor having a plurality of heat pipes extending from a core. The heat exchanger comprises a plurality of primary channels configured such that each primary channel receives heat transferred from the core via a corresponding one of the plurality of heat pipes, the plurality of primary channels being defined within a block of one or more materials, each primary channel extending in a first direction along the longitudinal axis of the heat exchanger from a first end of the heat exchanger to a second end of the heat exchanger, a plurality of primary channels, and a plurality of secondary channels defined within the block, each secondary channel being configured to convey a flow of a secondary heat transfer medium through the heat exchanger from an inlet of the heat exchanger to an outlet of the heat exchanger, each secondary channel comprising a first portion extending adjacent to at least one of the primary channels from the inlet, a second portion proximate to and spaced apart from at least one of the primary channels and extending along a heat transfer path, and a third portion extending from the second portion to the outlet, wherein each of the first portion and the second portion is disposed at an angle other than 0 degrees with respect to the second portion, a plurality of secondary channels, and the block comprises one or both of a plurality of plates joined together, each plate defining at least a portion of one or more of the plurality of primary channels and / or the plurality of secondary channels, and / or a single piece of material formed from an additive manufacturing process.

[0007] Each second portion of each secondary channel may comprise a plurality of discrete sub-channels, each sub-channel being spaced around at least one of the primary channels and extending between the first portion and the third portion of the secondary channel.

[0008] The block may comprise a plurality of plates joined together.

[0009] The plurality of plates may be stacked before or when they are joined together.

[0010] The plurality of plates may be joined to each other via one or more of diffusion bonding, brazing, or hot isostatic pressing.

[0011] One or more portions of the plurality of primary channels and / or one or more of the plurality of secondary channels may be formed via one or more of machining, laser cutting, chemical etching, electrical discharge machining, electrochemical machining, and / or stamping.

[0012] The block may include a single-piece mass formed from an additive manufacturing process.

[0013] At least one of the inlet and / or outlet may include a peripheral header cavity configured to direct a flow of a secondary heat transfer medium to or from each of the plurality of secondary channels.

[0014] The peripheral header cavity may extend only along a portion of the periphery of the heat exchanger.

[0015] The peripheral header cavity may extend along the entire periphery of the heat exchanger.

[0016] At least one of the inlet and outlet may include an integral header.

[0017] The integral header may be a flanged header.

[0018] The plurality of secondary channels may exit the block through the plurality of plates.

[0019] The plurality of secondary channels may exit the block through a single plate.

[0020] As another aspect of the present invention, a nuclear reactor includes a core, a modular heat exchanger as described herein, and a plurality of heat pipes, each heat pipe extending from the core to a corresponding primary channel of the heat exchanger and each heat pipe being configured to transfer heat from the core to the corresponding primary channel of the heat exchanger.

[0021] These and other objects, features, and characteristics of the present invention, as well as the methods of operation and functions of the related elements of the structure, and the combinations of parts and economies of manufacture, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification, and wherein like reference numerals designate corresponding parts in the various figures. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the present invention.

Brief Description of the Drawings

[0022] A further understanding of the present invention can be obtained from the following description of the preferred embodiments when read in conjunction with the accompanying drawings.

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DETAILED DESCRIPTION OF THE INVENTION

[0029] Embodiments of the present invention provide an arrangement of modular heat exchangers that enables the incorporation of an sCO2 secondary cycle into a heat pipe reactor. Modular heat exchangers are generally formed from blocks of material (generally referred to herein as "blocks" in any suitable form) and include channels for heat pipes coming from the reactor, along with smaller channels for sCO2 defined / formed therein. The smaller channels extend between an inlet and an outlet, are disposed around the heat pipes, and extend along the heat pipes. The central heat exchange portion of the block is composed of thin sheet metal shims or plates, which include through-holes for both the heat pipe channels and the sCO2 channels. The shims or plates may be manufactured, for example, by machining, laser cutting, chemical etching, EDM (electrical discharge machining), ECM (electrochemical machining), stamping, or other metal manufacturing methods, but are not limited thereto. The ends of the block can also be made from similar shims to create sCO2 flow paths perpendicular to the heat pipes such that the sCO2 channels converge on headers on the periphery of the block. This shim includes holes and channels generated, for example, by laser cutting, machining, EDM, ECM, or chemical etching. The entire plate portion of the heat exchanger is joined into a single block using, for example, diffusion bonding, brazing, or hot isostatic pressing. The heat exchanger headers may be internal chambers, slots, or channels within the blocks cut / formed in individual shims, or chambers attached outside the main heat exchanger blocks.

[0030] Alternatively, the modular heat exchangers described herein may be manufactured in whole or in part using various additive manufacturing techniques including large-scale powder bed fusion, directed energy deposition, binder jetting, ultrasonic, friction stir, and / or hybrid additive manufacturing. As used herein, the phrase "and / or" is intended to mean one or both of the items so separated by such phrase (i.e., something that includes A and / or B may include A alone, B alone, or both A and B).

[0031] FIG. 1 shows a schematic perspective view of a part of a heat pipe nuclear reactor 2 having a core 4 and a plurality of heat pipes 6, with each heat pipe 6 extending from the core 4 to a block-type heat exchanger 10. The heat exchanger 10 is generally formed as a block of material (such as the cylindrical block in FIG. 1) and includes a plurality of primary channels 12 defined therein that extend generally in a first direction along the longitudinal axis A of the heat exchanger 10. Each of the primary channels 12 is generally formed as a tubular member configured to pass a flow of a primary heat transfer medium through the heat exchanger 10. In the embodiment shown in FIG. 1, each heat pipe 6 extends from the core 4 to a corresponding primary channel 12. Each heat pipe 6 is configured to transfer heat from the core 6 to the corresponding primary channel 12 of the heat exchanger 10. The heat exchanger 10 also includes a plurality of smaller secondary channels 14 defined within the block of material, with each secondary channel 14 configured to pass a secondary heat transfer medium (e.g., sCO2) between a peripheral inlet header 16 and a peripheral outlet header 18. In the example illustrated in FIG. 1, each secondary channel 14 extends from the inlet header 16 along a first portion 20 adjacent to the corresponding primary channel 12, where the secondary channel 14 then transitions from the first portion 20 to a second portion 22 disposed along the primary channel 12 across the heat exchange portion of the heat exchanger 10. The second portion 22 of each secondary channel 14 is adjacent to but isolated from the corresponding primary channel 12. As will be understood from the examples discussed herein, the second portion 22 of each secondary channel 14 may be formed as a single channel extending along the primary channel 12 or may be a plurality of (i.e., two or more) sub-channels disposed around the primary channel 12. At the lower end of the heat exchange portion of the heat exchanger 10, each secondary channel 14 transitions from the second portion 22 to a third portion 24 that extends from near the primary channel 12 to the outlet header 18. In the example shown in FIG. 1, the second portion 22 of the secondary channel 14 is disposed generally perpendicular to the longitudinal axis A, while the first portion 20 and the third portion 24 of the secondary channel 14 are disposed generally perpendicular to the axis A (i.e., at approximately 90°).However, it should be understood that the first portion 20 and the third portion 24 of the secondary channel 14 may be oriented at any non-zero angle with respect to the second portion 22 without departing from the scope of the present invention.

[0032] Continuing to refer to FIG. 1, the surrounding inlet header 16 and outlet header 18 may extend entirely around the heat exchanger 10 as illustrated by the outlet header 18 of FIG. 1, or may extend only partially around the heat exchanger 10 as illustrated by the inlet header 16 of FIG. 1. The surrounding headers 16 and 18 may be formed as separate components and attached to the heat exchanger 10 via any suitable means (e.g., but not limited to, mechanically or by welding), or may be integrally formed with the heat exchanger 10 via any suitable means.

[0033] FIG. 2 illustrates another heat exchanger 10 according to a second embodiment of the present invention that includes an integral inlet header 16 and outlet header 18 instead of the surrounding inlet header 16 and outlet header 18 shown in FIG. 1. In all other respects, the heat exchanger 10 illustrated in FIG. 2 is the same as the heat exchanger 10 illustrated in FIG. 1.

[0034] FIG. 3 shows a partial exploded view of a portion of the outlet header 18 of the heat exchanger 10 of FIG. 2, showing a third portion 24 of the secondary channel 14 that extends from the adjacent primary channel 12 to the outlet header 18, and the second portion 22 of the secondary channel 14 crosses a plurality of layers of block segments 26, also referred to herein as shims or plates. The upper segment 28 and the lower segment 30 of FIG. 3 are shown as thick portions of the heat exchange portion, but each of the segments 28 and 30 may preferably be composed of a plurality of layers of plates 26 joined together. Each of the secondary channels 14 may be formed by any suitable machining process or by chemical etching or laser etching. From this perspective, in such an example, it should be understood that the second portion 22 of each secondary channel 14 is constituted by a plurality of small conduits or sub-channels circumferentially spaced around the respective primary channel 12.

[0035] FIG. 4 shows a configuration similar to that of FIG. 3, except that instead of the integral headers 16, 18 as shown in FIGS. 2 and 3, the configuration of FIG. 4 can be coupled to the peripheral headers 16, 18 as shown in FIG. 1.

[0036] FIGS. 5 and 6 show an arrangement similar to that shown in FIGS. 3 and 4, except for the third portion 24 of the secondary channel 14, and the third portion 24 of the secondary channel 14 is defined only within and extends within one layer of the plate 26, rather than through a plurality of layers as shown in the arrangement of FIG. 3. In such an example, it should be noted that the layer 26 that houses the third portion 24 of the secondary channel 14 is much thicker than the other layers of the plate 26 in order to accommodate a sufficient volume of the secondary heat transfer medium.

[0037] The heat exchanger configuration described herein is particularly suitable for coupling a heat pipe reactor to an sCO2 secondary cycle, but it should be understood that this configuration is also applicable to other applications where a primary fluid crosses a primary channel 12 and a secondary fluid crosses a secondary channel 14. The manufacturing and joining options for the various shims (i.e., plates or block segments) enable multiple design feature options, including heat exchanger size, length, primary channel size, secondary channel size, shape, and path, as well as header size, shape, and location. Alternatively, or in addition, the heat exchanger may be manufactured using various additive manufacturing techniques, including powder bed fusion, binder jetting, directed energy deposition, or hybrid additive manufacturing, in a similar layered approach. The layered approach enables automation during manufacturing, such as laser cutting, CNC (computer numerical control) machining, forming processes, and plate stacking and handling automation processes, and enables automated manufacturing of the reactor.

[0038] While specific embodiments of the invention have been described in detail herein, it will be understood by those of ordinary skill in the art that various modifications and alternative forms can be developed in light of the overall teachings of the disclosure. Accordingly, the specific embodiments disclosed are merely illustrative and are not intended to limit the scope of the invention, which is given by the appended claims and all equivalents thereof.

Claims

1. An integrated block type heat exchanger (10) for use with a heat pipe reactor (2) having a plurality of heat pipes (6) extending from a reactor core (4), the heat exchanger comprising: A plurality of primary channels (12) each configured to receive heat transferred from the reactor core (4) via a corresponding one of the plurality of heat pipes (6), the plurality of primary channels (12) being defined within a block of one or more materials, each primary channel extending in a first direction along the longitudinal axis (A) of the heat exchanger (10) from a first end of the heat exchanger to a second end of the heat exchanger, the plurality of primary channels (12); A plurality of secondary channels (14) defined within the block, each secondary channel (14) being configured to direct a flow of a secondary heat transfer medium through the heat exchanger from an inlet (16) of the heat exchanger to an outlet (18), each secondary channel (14) comprising: A first portion (20) extending adjacent to at least one of the plurality of primary channels (12) from the inlet (16); A second portion (22) proximate to and spaced apart from the at least one of the plurality of primary channels (12) and extending along the heat exchanger (10) and located within the heat exchanger (10); A third portion (24) extending from the second portion (22) to the outlet (18), and The plurality of secondary channels (14) wherein each of the first portion (20) and the third portion (24) is disposed at an angle other than 0 degrees with respect to the second portion (22); The block comprising: A plurality of plates (26) joined to each other, each plate defining at least a portion of one or more of the plurality of primary channels (12) and / or the plurality of secondary channels (14), and A single piece of material formed from an additive manufacturing process, The heat exchanger comprising one or both of the foregoing.

2. Each said second portion (22) of said secondary channels (14) comprises a plurality of separate sub-channels, each of said sub-channels being spaced around said at least one of said plurality of primary channels (12), extending between said first portion (20) and said third portion (24) of said secondary channels (14), the integrated block type heat exchanger (10) according to claim 1.

3. The block comprises said plurality of plates (26) joined to each other, the integrated block type heat exchanger (10) according to claim 1.

4. Said plurality of plates are arranged stacked before or when they are joined together, the integrated block type heat exchanger (10) according to claim 3.

5. Said plurality of plates (26) are joined to each other via one or more of diffusion bonding, brazing, or hot isostatic pressing, the integrated block type heat exchanger (10) according to claim 3.

6. One or more of said one or more of said plurality of primary channels (12) and / or said plurality of secondary channels (14) are formed via one or more of machining, laser cutting, chemical etching, electrical discharge machining, electrochemical machining, and / or stamping, the integrated block type heat exchanger (10) according to claim 3.

7. The block comprises said single piece of material formed from said additive manufacturing process, the integrated block type heat exchanger (10) according to claim 1.

8. At least one of said inlet (16) and / or said outlet (18) comprises a surrounding header configured to pass the flow of said secondary heat transfer medium to or from each secondary channel of said plurality of secondary channels (14), the integrated block type heat exchanger (10) according to claim 1.

9. The surrounding header extends only along a part of the periphery of the heat exchanger (10), the integrated block type heat exchanger (10) according to claim 8.

10. The surrounding header extends along the entire periphery of the heat exchanger (10), the integrated block type heat exchanger (10) according to claim 8.

11. At least one of said inlet (16) and said outlet (18) defines a header, The header is integrated with the block, The integrated block type heat exchanger (10) according to claim 1, wherein each of the plurality of secondary channels (14) extends through the header in an isolated manner.

12. The integrated block type heat exchanger (10) according to claim 11, wherein the header has a flange.

13. The block includes the plurality of plates (26), The integrated block type heat exchanger (10) according to claim 3, wherein the plurality of secondary channels (14) exit the block through two or more of the plurality of plates (26).

14. The block includes the plurality of plates (26), The integrated block type heat exchanger (10) according to claim 3, wherein the plurality of secondary channels (14) exit the block through only one of the plurality of plates (26).

15. A nuclear reactor (2), A core (4), A block type heat exchanger (10), A plurality of primary channels (12), each primary channel being configured to receive heat transferred from the core (4) through a corresponding one of the plurality of heat pipes (6), the plurality of primary channels (12) being defined within a block of one or more materials, each primary channel (12) extending in a first direction along the longitudinal axis (A) of the heat exchanger (10) from a first end of the heat exchanger to a second end of the heat exchanger (10), the plurality of primary channels (12); A plurality of secondary channels (14) defined within the block, each secondary channel (14) being configured to pass a flow of a secondary heat transfer medium through the heat exchanger (10) from an inlet (16) of the heat exchanger (10) to an outlet (18), each secondary channel (14) having A first portion (20) extending from the inlet (16) adjacent to at least one of the plurality of primary channels (12); A second portion (22) extending along the heat exchanger (10) adjacent to and isolated from the at least one of the plurality of primary channels (12) and located within the heat exchanger (10); A third portion (24) extending from the second portion (22) to the outlet (18), wherein each of the first portion (20) and the third portion (24) is disposed at an angle other than 0 degrees with respect to the second portion (22), the third portion (24). comprising the plurality of secondary channels (14); the block is a plurality of plates (26) joined to each other, each plate (26) defining at least a part of one or more of the plurality of primary channels (12) and / or the plurality of secondary channels (14), and a single piece of material formed from an additive manufacturing process, the block-type heat exchanger comprising one or both of the foregoing; a plurality of heat pipes (6), each heat pipe (6) extending from the core (4) to a corresponding primary channel (12) of the heat exchanger (10), and a nuclear reactor (2), wherein each heat pipe (6) is configured to transfer heat from the core (4) of the heat exchanger (10) to the corresponding primary channel (12).

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