Printed circuit heat exchanger and method for manufacturing the same

Abstract

This invention provides a printed circuit heat exchanger and a method for manufacturing the same. [Solution] A printed circuit heat exchanger (PCHE) for use in facilitating heat transfer and a method for fabricating a PCHE include providing a plurality of plates, each containing a plurality of closely spaced channels configured to guide fluid through the PCHE. The method also includes applying a protective coating to a predetermined area identified on at least one of the plurality of plates, the protective coating facilitating the extension of the PCHE's service life, and joining at least two of the plurality of plates together to create the PCHE.

Description

Technical Field

[0001] The present disclosure generally relates to heat exchangers, and more particularly to coatings used to facilitate extending the service life of printed circuit heat exchangers.

Background Art

[0002] Heat exchangers have long been used to transfer heat from one medium to another, such as a liquid, gas, or air, to facilitate creating the lowest possible pressure drop within the heat exchanger. At least some known heat exchangers transfer heat between two fluids separated by a wall. Although the heating and cooling processes are continuous, over time, depending on the medium circulating through the heat exchanger, entrained materials can cause fouling, corrosion, and / or deposition along at least a plurality of portions of at least one of the heat transfer surfaces. Such fouling, corrosion, and / or deposition can reduce the heat transfer rate, increase the pressure loss, and / or generally reduce the effectiveness of the heat exchanger and / or ultimately lead to failure of the heat exchanger.

[0003] The effectiveness of known heat exchangers depends at least in part on the type of fluid circulating and / or the design of the heat exchanger. A printed circuit heat exchanger (PCHE) is designed to efficiently transfer thermal energy between two media while using a complex network of small fluid paths defined by microchannel surface plates. Moreover, compared to conventional heat exchangers, PCHE enables a high heat transfer rate while using a small physical footprint. Thus, PCHE is ideal for applications that require high efficiency in space-constrained applications.

[0004] At least some known printed circuit heat exchangers are fabricated using diffusion-bonded plates. More specifically, at least some known PCHEs are fabricated by etching fluid channels into plates and then diffusion-bonding those plates to each other to form a stack. Diffusion bonding typically uses high temperatures in a vacuum or non-oxygen environment. While the robust construction of some heat exchangers allows such heat exchangers to operate at higher pressures than conventional heat exchangers, this fabrication process can also create sensitized regions within multiple portions of the plates that can lead to corrosion and associated stress corrosion cracking over time. Over time, continuous operation with thermal transients can lead to increased crack propagation and / or eventual failure of the heat exchanger.

[0005] Therefore, there is a need for a method of fabricating printed circuit heat exchangers that facilitates the reduction of the likelihood of PCHE failure in a cost-effective and reliable manner. [Overview of the project]

[0006] In one embodiment, a method is provided for fabricating a printed circuit heat exchanger (PCHE) for use in facilitating heat transfer. The method includes providing a plurality of plates, each containing a plurality of closely spaced channels configured to guide fluid through the PCHE. The method also includes applying a protective coating to a predetermined area identified on at least one of the plurality of plates, wherein the protective coating facilitates extending the service life of the PCHE, and joining at least two of the plurality of plates to each other to create the PCHE.

[0007] In another embodiment, a method is provided for fabricating a printed circuit heat exchanger (PCHE) for use in facilitating heat transfer. The method includes applying a protective coating to a predetermined area on each of a plurality of plates, each containing channels defined thereon, via a chemical etching process, and bonding at least two of the plurality of plates to each other via a diffusion bonding process to create a PCHE.

[0008] In yet another embodiment, a printed circuit heat exchanger (PCHE) is provided. The PCHE comprises a plurality of plates bonded to one another via a diffusion bonding process, each plate comprising a plurality of channels defined thereon via a chemical etching process, and each plate also comprising a protective coating applied only to a predetermined area of ​​each plate, and the plates are bonded to one another such that a fluid flowing through the channels during use of the PCHE results in heat transfer within the PCHE. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram of an exemplary printed circuit heat exchanger (PCHE). [Figure 2] Figure 1 is an enlarged cross-sectional view of a portion of a heat exchange surface that may be used in a PCHE (Powered Chemistry and Energy Exchange) system. [Figure 3] Figure 2 is an enlarged cross-sectional view of a portion of the surface of a heat exchanger coated according to the invention described herein. [Figure 4] This flowchart shows an exemplary method for fabricating a PCHE heat exchanger surface. [Modes for carrying out the invention]

[0010] Embodiments described herein relate to systems and methods for facilitating the extension of the service life of printed circuit heat exchangers. At least some of the advantages of the systems described herein over the prior art include, at a minimum, (i) providing a substantially uniform and dense conformal protective coating extending across fluid channels on the heat exchanger plate; (ii) providing improved corrosion resistance under a variety of operating environments; (iii) reducing stress concentration and cracking in a given area extending across a defined potential sensitization area on the heat exchanger plate; and (iv) reducing the formation of localized hot spots that may occur across the heat exchanger plate during operation.

[0011] When introducing elements of the various embodiments disclosed herein, the articles “a,” “an,” “the,” and “said” mean that there is one or more of those elements. The terms “comprising,” “including,” and “having” are intended to be comprehensive and mean that there may be additional elements other than those listed.

[0012] Unless otherwise specified, the approximation terms used herein, such as “generally,” “substantially,” and “about,” indicate that the terms thus modified may only apply to an approximate degree as recognized by those skilled in the art, and not to an absolute or complete degree. Therefore, values ​​modified by one or more terms such as “about,” “approximately,” and “substantially” should not be limited to the exact values ​​specified. In at least some examples, the approximation terms may correspond to the precision of the instruments used to measure the values. Furthermore, unless otherwise specified, terms such as “first,” “second,” etc., are used herein merely as labels and do not impose any order, position, or hierarchical requirements on the items they refer to. Moreover, for example, a reference to a “second” item does not require or exclude the existence of a “first” or lesser numbered item, or a “third” or more numbered item.

[0013] All methods described herein may be performed in any suitable order, unless otherwise specified herein and in accordance with the context. The use of any examples or illustrative language (e.g., "such as") is merely to better illustrate the invention and does not limit the scope of the invention or any embodiment unless otherwise claimed.

[0014] Figure 1 is a schematic diagram of an exemplary printed circuit heat exchanger (PCHE) 100. Figure 2 is an enlarged cross-sectional view of a portion of an exemplary heat exchange surface 110 that may be used in the PCHE 100. Figure 3 is an enlarged cross-sectional view of a portion of the heat exchanger surface 110 shown in Figure 2 and coated according to the invention described herein. The heat exchanger 100 described herein utilizes a structure comprising at least two plates 112 stacked on top of each other in a close arrangement. In one embodiment, the plates 112 are bonded to each other using diffusion bonding after the plates 112 are chemically etched. The term “heat exchanger” can include any component configured to transfer as much heat as possible from one fluid to a second fluid circulating through the heat exchanger, in order to facilitate a reduction in pressure drop within the heat exchanger. The term “fluid” as used herein refers to, but is not limited to, gases, liquids, and / or two-phase mixtures of gas and liquid. Therefore, although the present invention is described herein in relation to printed circuit heat exchangers (PCHEs), it should be understood that the present invention is applicable to other configurations and designs of heat exchangers.

[0015] At least some known printed circuit heat exchangers 100 are fabricated using substantially flat metal plates 112 formed on a surface 110 containing internally defined channels 120. The plates 112 are stacked and joined together to form the internal core structure of the heat exchanger 100. For example, fluid flow channels 120 for water and / or gas are defined or printed across the plates using chemical cutting or etching. More specifically, in exemplary embodiments, the etching process produces fluid flow channels 120 typically defined in semicircular cross-sectional profiles. Furthermore, the plates 112 are masked to control where chemical etching occurs. Thus, etching allows the fluid flow channels 120 to be oriented in complex patterns that facilitate improved heat transfer across the plates. For example, the fluid flow channels 120 may be of different sizes, have different lengths, or be formed in different orientations within the same plate 112. Furthermore, etching allows for a relatively small overall size of the fluid flow channels 120, resulting in an improved amount of heat transfer surface area per unit volume within the PCHE100 compared to conventional shell-and-tube heat exchangers. For example, in one embodiment, these fluid flow channels are defined to a depth of approximately 1 mm to 3 mm. As a result, the PCHE100 described herein can be fabricated with a smaller physical footprint than is possible with at least some known heat exchangers operating at substantially the same heat transfer capacity.

[0016] Next, the etched plates 112 are coupled to each other in a dense stack such that the alternating spacing between adjacent plates 112 forms the respective high-temperature and low-temperature channels within the heat exchanger 100. Thus, heat transfer is facilitated as the lower-temperature fluid flows through some defined spacings and the higher-temperature fluid flows through other defined spacings. The etched circuitry allows the PCHE 100 to operate at higher temperatures and pressures compared to at least some known heat exchangers. Moreover, the high density of fluid flow channels makes it easier to increase the overall efficiency of the heat exchanger 100.

[0017] Unlike at least some known heat exchangers that use welding during the fabrication process, the PCHE100 is diffusion-bonded. More specifically, during the fabrication of the PCHE100, in exemplary embodiments, water and gas channels are etched into the plates 112 before the plates 112 are joined to each other via diffusion bonding. During diffusion bonding, high temperature and high pressure are used to bond the materials, i.e., the plates 112, to each other. For example, if plates 112 made from stainless steel are used in the PCHE100, the temperature used to bond the plates 112 may be about 2000°F. While diffusion bonding creates a strong bond between the plates 112, the combination of higher temperature and higher pressure may also create sensitized areas 130 within the plates 112, more specifically, within portions 130 of the etched channels 120. More specifically, the fabrication process, i.e., the diffusion bonding process, may create areas 130 of cracking or pitting corrosion, which may contribute to a reduction in the overall service life of the PCHE100.

[0018] During operation, continuous exposure to higher temperatures and pressures within the PCHE100 over time can lead to stress cracking and / or thermal excursion or "hot spots" occurring within the sensitized channel region 130. For example, localized areas of the etched channel 120 can generate thermal transients, thermal excursion, and / or unstable boiling conditions, which over time can exacerbate stress corrosion cracking and / or flow instability in the sensitized region 130.

[0019] To facilitate the reduction of the possibility of thermal excursion, stress cracking, and / or hot spots occurring and / or limiting the service life of PCHE100, in exemplary embodiments, a protective coating 150 is applied to predetermined and / or identified sensitized regions 130 after the chemical etching process. More specifically, in exemplary embodiments, after each plate 112 has completed the chemical etching process, the protective corrosion-resistant coating 150 is applied to the unmasked areas, i.e., sensitized regions, of each plate 112. In one embodiment, the unmasked areas may include both sensitized and non-sensitized regions. The coating 150 may be applied to the plate 112 using any known coating method, including, but not limited to, physical vapor deposition (PVD) and / or cathode arc evaporation processes, liquid metal coating processes, chemical vapor deposition (CVD) processes, electroplating processes, and / or via electrolytic deposition processes. More generally, any coating process may be used that allows for substantially uniform application of the coating 150 across the plate 112 within the sensitized regions 130. In one embodiment, the coating is applied in a fairly thin layer, such as a layer with a thickness of about 0.1 to less than 50 micrometers. In one embodiment, all of the plates 112 joined together include at least some coating 150. In another embodiment, the coating 150 extends substantially over all of the plates 112.

[0020] The coating is made from any material that facilitates the suppression of corrosion of existing cracks in plate 112 that may have formed during the manufacturing process. In fact, in some embodiments, the coating substantially prevents additional damage, including stress corrosion cracking, from occurring in the sensitized area during use of the PCHE. In some embodiments, once cured, the coating material substantially conforms to and adheres to plate 112, forming a thin film of the material that extends through and over the unmasked areas of plate 112. For example, in one embodiment, the coating may be, but is not limited to, at least one of titanium (Ti) coatings, nickel (Ni) coatings, chromium coatings, and / or any combination thereof. In another embodiment, the coating may comprise iron and at least one additional element, but is not limited to, carbon (C), silicon (Si), manganese (Mn), nitrogen (N), phosphorus (P), sulfur (S), and / or combinations thereof.

[0021] Figure 4 is a flowchart illustrating an exemplary method 400 for fabricating a PCHE heat exchanger surface. To facilitate the reduction of possible effects of sensitized areas that may occur during the manufacturing process, a substantially uniform coating is applied over defined or identified sensitized areas of the etched plate 402. In exemplary embodiments, the coating 402 is applied to all chemically etched surfaces on each plate. More specifically, in some embodiments, each PCHE plate is inspected 404 to determine whether the masking applied during the etching process is intact after each plate has been chemically etched to form channels that extend at least partially across the plate. If the masking appears intact after the etching process, the plate is ready to be coated 402 when dried. However, if the masking is inadvertently damaged or removed after the etching process, which may occur, for example, during handling of the plate, those PCHE plates require masking 406 before the protective coating is applied 402 to ensure that only the sensitized areas of the plate remain unmasked.

[0022] In exemplary embodiments, a protective corrosion-resistant coating is applied to the unmasked areas, i.e., sensitized areas, of each plate 402. The coating may be applied using any known coating method, including, but not limited to, using a physical vapor deposition (PVD) process, a liquid metal coating process, a chemical vapor deposition (CVD) process, an electroplating process, and / or via an electrolytic deposition process 402. Any coating application process may be used that allows the coating to be applied to the sensitized areas with a substantially uniform thickness 402. Furthermore, any coating material may be used that creates a thin film of the coating in a manner that facilitates high adhesion and extends the service life of the PCHE plates, as described herein. For example, in exemplary embodiments, the coating may be, but is not limited to, at least one of a titanium (Ti) coating, a nickel (Ni) coating, a chromium coating, and / or any combination thereof. After the coating is applied, the masking is removed 408, and the plates are bonded to each other via a diffusion bonding process 410.

[0023] During use, the coating facilitates improved performance and extends the service life of the associated PCHE. Furthermore, the coating facilitates the reduction of otherwise occurring thermal transients and simultaneously prevents corrosion-related failures of the PCHE plate. Additionally, the coating facilitates the suppression of stress corrosion cracking of the PCHE plate. Moreover, experimental tests have demonstrated that the coating facilitates the improvement of the heat transfer coefficient of chemically etched PCHE plates. In addition, in some embodiments, controlled surface features can be formed via the coating to facilitate the induction of further turbulence at the wall boundaries of each channel. As a result, the PCHE failure rate is easily reduced, and therefore the service life of the PCHE is extended.

[0024] The methods described herein enable extending the service life of the associated PCHE, thereby reducing the likelihood of PCHE failure. In some examples, the method provides a coating that substantially reduces, if not eliminates, the likelihood that the sensitized area of the PCHE plate will fail during PCHE operation. When applied as described herein, the coating facilitates suppressing corrosion and stress corrosion cracking within the PCHE.

[0025] The above description is intended to be illustrative only, and those skilled in the art will recognize that modifications may be made to the described embodiments without departing from the scope of the disclosed invention. Modifications that fall within the scope of the present invention will be apparent to those skilled in the art in light of the present disclosure, and such modifications are intended to fall within the scope of the appended claims. The systems described herein are not limited to the specific embodiments described herein; rather, multiple portions of the various systems may be utilized separately and independently of other systems described herein.

[0026] Certain features of the various embodiments of the present invention may be shown in some drawings and not in others, but this is merely for convenience. Moreover, references to "one embodiment" in the above description are not to be construed as excluding the existence of additional embodiments that also incorporate the same described features. In accordance with the principles of the present invention, any feature of a drawing may be referenced and / or claimed in combination with any feature of any other drawing.

[0027] Exemplary embodiments for fabricating plates for use with printed circuit heat exchangers have been described in detail above. The systems and methods described herein are not limited to the specific embodiments described herein, and rather, several parts of the fabrication methods may be used separately and independently of other parts of the fabrication methods described herein. For example, the methods described herein are not limited to their implementation in printed circuit heat exchangers described herein. Rather, the exemplary embodiments may be implemented and used in connection with any heat exchanger using components that may include sensitized areas that occur during fabrication.

[0028] Further aspects of the present invention are provided by the subject matter of the following clauses.

[0029] 1. According to a first aspect, a method is provided for fabricating a printed circuit heat exchanger (PCHE) for use in facilitating heat transfer, the method comprising: providing a plurality of plates each having a plurality of closely spaced channels configured to guide fluid through the PCHE; applying a protective coating to a predetermined area identified on at least one of the plurality of plates, wherein the protective coating facilitates extending the service life of the PCHE; and joining at least two of the plurality of plates to each other to create the PCHE.

[0030] 2. The method according to Clause 1, further comprising inspecting each of several plates to determine whether the masking applied for use in creating channels remains intact after those channels have been defined.

[0031] 3. The method of any preceding clause, further comprising masking at least one of a plurality of plates that has been identified having one of the following after the channel has been defined: a missing mask and a damaged mask.

[0032] 4. The method of any preceding clause, further comprising applying a protective coating such that a thin film of the coating extends only over a predetermined area of ​​each of the multiple coated plates.

[0033] 5. The method of any preceding clause, further comprising applying a protective coating using at least one of the following processes: physical vapor deposition (PVD), liquid metal coating, chemical vapor deposition (CVD), electroplating, and electrolytic deposition.

[0034] 6. The method of any preceding clause, further comprising applying a protective coating, which is a coating comprising at least one of titanium, nickel, and chromium.

[0035] 7. The method of any preceding clause, further comprising applying a protective coating which is a coating comprising iron and at least one of carbon, silicon, manganese, nitrogen, phosphorus, and sulfur.

[0036] 8. The method of any preceding clause, further comprising applying a protective coating to a predetermined area to at least one of a plurality of plates after that plate has been chemically etched.

[0037] 9. The method of any preceding clause, further comprising applying a protective coating to a predetermined area identified on at least one of a plurality of plates, wherein the protective coating facilitates the extension of the service life of the PCHE.

[0038] 10. The method of any preceding clause, further comprising using diffusion bonding to bond at least two of a plurality of plates to each other.

[0039] 11. The method of any preceding clause, wherein joining at least two of a plurality of plates together further includes removing the masking from each of the plates before joining the plates together.

[0040] 12. In another embodiment, a method is provided for fabricating a printed circuit heat exchanger (PCHE) for use in facilitating heat transfer, the method comprising applying a protective coating to a predetermined area on each of a plurality of plates having channels defined thereon via a chemical etching process, and bonding at least two of the plurality of plates to each other via a diffusion bonding process to create a PCHE.

[0041] 13. The method according to Clause 12, further comprising applying a protective coating to a predetermined area on a plate.

[0042] 14. The method of any preceding clause, further comprising applying a protective coating, which is a coating comprising at least one of titanium, nickel, and chromium.

[0043] 15. The method of any preceding clause, further comprising applying a protective coating which is a coating comprising iron and at least one of carbon, silicon, manganese, nitrogen, phosphorus, and sulfur.

[0044] 16. The method of any preceding clause, further comprising applying a protective coating to each plate with a thickness of approximately 0.1 to approximately 50 micrometers.

[0045] 17. The method of any preceding clause, further comprising using at least one of the following processes for applying a protective coating: physical vapor deposition (PVD), liquid metal coating, chemical vapor deposition (CVD), electroplating, and electrolytic deposition.

[0046] 18. The method of any preceding clause, further comprising ensuring that each plate to be coated is masked in order to ensure that the coating is applied only to a predetermined area of ​​the plate.

[0047] 19. In yet another embodiment, a printed circuit heat exchanger (PCHE) is provided comprising a plurality of plates bonded to each other via a diffusion bonding process, each of the plates comprising a plurality of channels defined thereon via a chemical etching process, and each of the plates also comprising a protective coating applied only to a predetermined area of ​​each plate, and the plates are bonded to each other such that a fluid flowing through the channels during use of the PCHE results in heat transfer within the PCHE.

[0048] Although the present invention has been described in relation to various specific embodiments, those skilled in the art will recognize that the present invention can be implemented with modifications within the spirit and scope of the claims. [Explanation of Symbols]

[0049] 100 Printed Circuit Heat Exchangers (PCHE), PCHE 110 Heat exchange surface, heat exchanger surface 112 A substantially flat metal plate 120 Fluid Flow Channels 130 Etched channel 120 portion, crack or pitting corrosion region, sensitized channel region, sensitized region, sensitized area 150 protective coating, protective corrosion-resistant coating 400 ways

Claims

1. A method for manufacturing a printed circuit heat exchanger (PCHE) (100) for use in facilitating heat transfer, wherein the method is: The system includes a plurality of plates (112) each containing a plurality of closely spaced channels (120) configured to guide fluid through the PCHE (100), Applying (402) a protective coating (150) to a predetermined area identified on at least one of the plurality of plates (112), wherein the protective coating (150) facilitates extending the service life of the PCHE (100), To create the PCHE (100), at least two of the plurality of plates (112) are joined together (410) Methods that include...

2. The method according to claim 1, further comprising inspecting each of the plurality of plates (112) (404) to determine whether the masking applied for use in creating the channel (120) remains intact after the channel (120) has been defined.

3. The method of claim 2, further comprising masking (406) at least one of the plurality of plates (112) which is identified to have one of the following after the channel (120) has been defined: masking (406)

4. The method according to claim 1, further comprising applying a protective coating (150) (402) such that a thin film of the coating extends only over the predetermined area of ​​each of the plurality of coated plates (112).

5. The method according to claim 1, further comprising applying a protective coating (150) (402) using at least one of a physical vapor deposition (PVD) process, a liquid metal coating process, a chemical vapor deposition (CVD) process, an electroplating process, and an electrolytic deposition process.

6. The method according to claim 1, further comprising applying a protective coating (150) (402) which is a coating comprising at least one of titanium, nickel, and chromium.

7. The method according to claim 1, further comprising applying a protective coating (150) to a predetermined area (402) to at least one of the plurality of plates (112) after the plate (112) has been chemically etched.

8. The method according to claim 1, wherein applying a protective coating (150) (402) to a predetermined area identified on at least one of the plurality of plates (112) includes applying a protective coating to a predetermined area on each of the plurality of plates, the protective coating (150) applied to each of the plurality of plates facilitates extending the service life of the PCHE (100).

9. The method according to claim 1, further comprising using diffusion bonding to bond at least two of the plurality of plates (112) to each other (410).

10. The method according to claim 9, wherein joining at least two of the plurality of plates (112) together (410) further comprises removing masking from each of the plates (112) before joining the plates (112) together (408).

11. The method according to claim 1, further comprising applying a protective coating (150) (402) which is a coating comprising iron and at least one of carbon, silicon, manganese, nitrogen, phosphorus and sulfur.

12. Multiple plates (112) bonded to each other via a diffusion bonding process A printed circuit heat exchanger (PCHE) (100) comprising, each of the plates (112) includes a plurality of channels (120) defined thereon via a chemical etching process, and each of the plates (112) also includes a protective coating (150) applied only to a predetermined area of ​​each plate (112), and the plates (112) are coupled to one another such that a fluid flowing through the channels (120) during use of the PCHE (100) results in heat transfer within the PCHE (100).

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