Method for manufacturing an exchanger comprising passages provided with at least one support member and exchanger manufactured by such a method
Patent Information
- Application Number
- FR2023007531
- Authority / Receiving Office
- FR · FR
- Patent Type
- Utility models
- Current Assignee / Owner
- Filing Date
- 2023-07-13
- Publication Date
- 2025-07-18
- Estimated Expiration
- 2033-07-13
AI Technical Summary
Existing methods for texturing heat exchange structures in brazed plate heat exchangers face challenges such as difficulty in deposition due to wave geometry, material loss, and reduced mechanical resistance, leading to inefficient thermal performance and high costs.
A method involving the use of elongated support members, such as springs or twisted metal strips, arranged in the passages between plates to ensure mechanical resistance during brazing while minimizing loss of textured surface area, allowing for efficient fluid flow and easy removal post-brazing.
The method maintains mechanical integrity and maximizes thermal performance by preserving textured surface area, reducing material waste, and lowering production costs.
Abstract
Description
Title of the invention: Method for manufacturing an exchanger comprising passages provided with at least one support member and exchanger manufactured by such a method
[0001] The present invention relates to a method of manufacturing a brazed plate and fin type heat exchanger comprising passages provided with at least one support member as well as to a heat exchanger manufactured by such a method.
[0002] The present invention finds application in particular in the field of gas separation by cryogenics, in particular air separation by cryogenics known by the English acronym "ASU" for air separation unit. In particular, the present invention can be applied to the manufacture of a heat exchanger which vaporizes a liquid flow, for example liquid oxygen, nitrogen and / or argon by heat exchange with a gaseous flow, for example air or nitrogen.
[0003] The present invention also finds application in the field of natural gas liquefaction. The invention can in particular be applied to a heat exchanger which vaporizes at least one flow of liquid-gas mixture, in particular a flow of mixture with several constituents, for example a mixture of hydrocarbons, by heat exchange with at least one other fluid, for example natural gas.
[0004] An exchanger according to the invention can also find application in a unit for the cryogenic separation of CO from a synthesis gas flow.
[0005] Plate heat exchangers generally consist of a stack of parallel plates, between which are inserted heat exchange structures, in particular corrugated or wave structures delimiting passages for different fluids to be brought into thermal relation.
[0006] The heat exchange structures of brazed plate exchangers not only serve to increase the heat exchange surface of the exchanger but also act as spacers between the plates. Indeed, during the manufacture of the exchanger, a compression device is used to press the stack of plates, the intermediate elements and the other constituent elements of the exchanger against each other. These elements are then bonded together by brazing in a vacuum furnace at temperatures between 550 and 650°C, with the application of a compressive force typically ranging from 20,000 to 40,000N / m2.
[0007] Plate heat exchangers can be made of aluminum or aluminum alloy to ensure good thermal conductivity and good mechanical strength.
[0008] The performance of an exchanger is linked to the heat exchange coefficient of the heat exchange structures in contact with fluids. The heat exchange coefficient of a structure depends in particular on the nature of the material constituting it, the porosity of this material and the fluid flow regime.
[0009] Documents US 2005 / 121181 A1, EP 3 098 554 A1, US 5 514 248 A and CN 102 322 765 A are known to disclose different configurations of heat exchange structures.
[0010] It is known that the heat exchange coefficient can be greatly improved by texturing the exchange surface (particularly in condensation and boiling), and commercial solutions also exist in tubes.
[0011] Document WO-A-2005 / 075920 discloses various techniques for depositing texturing on the surface of a wave for a heat exchanger.
[0012] One problem concerns the difficulty of carrying out texturing in the context of vacuum brazing of aluminum exchangers. Indeed, the shape and geometric dimensions of the waves make it difficult to implement texturing carried out either by a porous deposit or by direct mechanical action on the surface of the wave. The porous deposit can be made by projection on both faces of the wave. However, the difficulties linked to the geometry of the wave, which has horizontal and vertical surfaces, as well as the reduced size of the channels make the deposition technique much longer to carry out and much more expensive than on a flat surface; it requires several projection passes and more losses of materials to be projected due to the low efficiency of the process.
[0013] It is possible to carry out the texturing of the heat exchange structures after brazing these structures in the exchanger. However, it is then difficult to access the channels formed by the exchange structures in the passages of the exchanger and it is impossible to use mechanical texturing techniques. Other surface treatment techniques are difficult to implement. For example, for techniques involving preliminary steps of heat treatment or deposition of an impregnation layer to ensure adhesion of the coating, it is the entire exchanger that must be treated. There are then risks of blocking the channels, of debrazing parts of the exchanger or of creating fragile metallurgical phases and damaging the brazed matrix.
[0014] Furthermore, it has been proposed to carry out surface texturing on the separating plates before brazing but this leads to removing the fins and reducing the mechanical resistance of the exchange passage.
[0015] Furthermore, it is possible to carry out texturing on a flat sheet which serves as a separator. In this case, the absence of a wave inside the passages makes it difficult to ensure resistance to compressive forces during brazing. In addition, the use of waves, even of low density or intermediate bars to reinforce the mechanical resistance during brazing of the exchanger, masks part of the textured surface and therefore results in a loss of potential thermal performance gain. This significant loss of treated surface area, combined with additional labor and material costs, results in a ratio of thermal performance gain to additional cost that is of no interest. As for the use of removable shims, the difficulty lies in being able to remove them after compression of the passages during brazing of the exchanger.
[0016] It is also possible to carry out texturing on an aluminum strip before shaping the wave. This technique has poor compatibility with stamping the waves. In fact, it is impossible to completely preserve the texturing if it is carried out before stamping the waves. In addition, part of the texturing can tear off and damage the stamping mechanism, particularly for a porous deposit.
[0017] The present invention aims to solve all or part of the problems mentioned above, by proposing a method of manufacturing a heat exchanger of the brazed plate and fin type making it possible both to ensure mechanical resistance to compression forces during brazing and to minimize the loss of part of the textured surface.
[0018] The invention therefore relates to a method of manufacturing a heat exchanger of the brazed plate and fin type comprising the following steps:
[0019] a) Arranging with space several plates parallel to each other so as to define between said plates a plurality of passages adapted for the flow of at least one fluid in a longitudinal direction, said passages having a length measured parallel to the longitudinal direction and a width, less than said length, measured in a lateral direction orthogonal to the longitudinal direction;
[0020] b) Arranging at least one support member in at least one of the passages formed between two adjacent plates so as to form a stack;
[0021] c) Forming at least one contact zone between the at least one support member and each of the two adjacent plates;
[0022] d) Arranging a surface texturing in the form of a porous structure or reliefs formed on the adjacent plates and / or on the support;
[0023] e) Braze the stack;
[0024] Characterized in that said at least one support member is of elongated shape and extends parallel to the longitudinal direction.
[0025] Depending on the case, the exchanger according to the invention may comprise one or more of the following characteristics: - Said at least one support member is shaped so as to have several contact zones following one another discreetly along the Ion- direction gitudinal. - Several support members are arranged in said at least one passage and follow one another in the lateral direction. - Said at least one support member is shaped to allow the flow of fluid inside the passages. - Said at least one support member comprises a spring, or a twisted metal strip or at least two twisted wires.
[0026] The invention further relates to a heat exchanger manufactured by a method according to the invention.
[0027] The invention will be better understood upon reading the following description and examining the accompanying figures. These figures are given only for illustrative purposes but in no way limit the invention.
[0028] [Fig.l] [Fig.l] is a three-dimensional view of a brazed plate exchanger which can be manufactured by a method according to the invention;
[0029] [Fig.2] [Fig.2] is a view along the axis of the fluid flow of an exchanger passage comprising a support member according to a first embodiment;
[0030] [Fig.3] [Fig.3] is a view perpendicular to the axis of the fluid flow of the first embodiment according to [Fig.2]
[0031] [Fig.4] [Fig.4] is a view along the axis of the fluid flow of an exchanger passage comprising a support member according to a second and a third embodiment;
[0032] [Fig.5] [Fig.5] is a view perpendicular to the axis of fluid flow of the second embodiment of [Fig.4];
[0033] [Fig.6] [Fig.6] is a view perpendicular to the axis of fluid flow of the third embodiment of [Fig.4];
[0034] [Fig.7] [Fig.7] is a partial isometric view of a support member of the second embodiment.
[0035] [Fig.l] represents a heat exchanger 1 of the brazed plate type comprising a stack of plates 2 which extend in two dimensions, length and width, respectively in the longitudinal direction z and the lateral direction x. The plates 2 are arranged parallel to one another with spacing and thus form several sets of passages 3 for a fluid F1, and at least one other fluid F2, F3 to be put into indirect heat exchange relation via the plates 2. The lateral direction x is orthogonal to the longitudinal direction z and parallel to the plates 2.
[0036] Preferably, each passage has a parallelepiped and flat shape. The passages extend in length along the longitudinal direction z and in width along the lateral direction x. The gap between two successive plates 2, corresponding to the height of the passage, measured along the stacking direction y of the plates 2, is small compared to the length and width of each successive plate.
[0037] The passages 3 are bordered by closing bars 6 which do not completely close the passages but leave free openings for the entry or exit of the corresponding fluids.
[0038] The exchanger 1 comprises semi-tubular shaped collectors 7, 8 provided with openings 9 for introducing fluids into the exchanger 1 and discharging fluids from the exchanger 1. These collectors have openings that are narrower than the passages. Distribution zones arranged downstream of the inlet collectors and upstream of the outlet collectors serve to channel the fluids homogeneously to or from the entire width of the passages.
[0039] Preferably, at least one surface texturing in the form of a porous structure or reliefs, not shown in the figures, is arranged on at least one surface of the adjacent plates 2 and / or of the support member 10. It is specified that it could be envisaged to arrange one or more support members 10 in an exchanger without surface texturing.
[0040] According to the invention, before brazing the exchanger 1, at least one support member 10 is arranged in at least one of the passages 3. After brazing, the support member 10 can be removed or left in place.
[0041] Preferably, the exchanger passages are designed without a wave or exchange structure. For this, it is proposed to use specific geometric supports or support members which make it possible both to ensure mechanical resistance to the compressive forces during brazing and to minimize the loss of a portion of the textured surface. Indeed, the greater the total surface area of the contact points between the supports and the texturized-coated separating sheets, the less the potential gain in thermal performance.
[0042] These specific geometric supports can be springs, twisted bands or two twisted wires installed in the direction (parallel) to the length of the exchange passage (Figures 2 to 6). They can be made in a single continuous piece, or by assembling several pieces.
[0043] These specific geometric supports also make it possible, by virtue of their profile, to facilitate the flow of the fluid inside the exchange passage by minimizing and / or limiting the size in the section of the passage.
[0044] Furthermore, due to the reduced contact surface 11, but especially the deformability of these supports 10, the latter will be easier to remove after brazing and the risk of damaging or deforming the passage 3 in which they are inserted is reduced. This is not the case when using solid rods or shims to maintain passages without waves. This is an additional possibility which is not essential to their use being understood that the forms of support members which are the subject of the invention have the advantage of being able to be left in place in the passage without excessively harming the heat exchange.
[0045] The number of supports 10 over the width of the passage is defined according to the mechanical resistance necessary and sufficient for brazing the exchanger.
[0046] The nature of the material (stainless steel for example), the pitch (number of turns or twists per meter of length) and the thickness (of the wire or twisted strip) can be adapted in order to minimize the points of contact with the textured surface.
[0047] Note that the support member 10 can be arranged in the passage 3 during or after the step of stacking the plates 2.
[0048] According to an advantageous embodiment, the support member 10 is arranged in the passage during the step of stacking the plates 2. In particular, considering two plates 2 to be stacked on top of each other to define a passage 3 between them, the support member 10 is placed before one of the two plates is stacked on top of the other. Thus, intervention on the matrix resulting from the stacking is avoided and the risk of damaging the stack or moving an element of the stack when inserting the support member 10 into the passage 3 is limited, which would compromise the operation of the exchanger.
[0049] Figures 2 and 3 show an embodiment in which the support member 10 is a spring. A solid round tube 12 may be added inside the springs in order to increase the mechanical strength. This solid round tube 12 has the advantage of not increasing the contact points 11. In addition, it may be possible once the exchanger is brazed, to remove the solid round tubes 12 in order to free up more space for the circulation of the fluid.
[0050] [Fig.4] shows an embodiment in which the support member can be either a twisted flat strip or 2 twisted wires.
[0051] [Fig. 5] represents a view perpendicular to the axis of the fluid flow of the second embodiment in which the support member 10 consists of a twisted flat strip.
[0052] [Fig.6] represents a view perpendicular to the axis of the fluid flow of the third embodiment in which the support member 10 is made up of two twisted wires.
[0053] [Fig.7] represents a partial isometric view of a support member 10 of the second embodiment.
[0054] Of course, the invention is not limited to the particular examples described and illustrated in the present application. Other variants or embodiments within the reach of those skilled in the art may also be envisaged without departing from the scope of the invention defined by the claims below.
Claims
Claims
1. A method of manufacturing a brazed plate and fin heat exchanger (1), said method comprising the following steps: a) Arranging with space several plates (2) parallel to each other so as to define between said plates (2) a plurality of passages (3) adapted for the flow of at least one fluid in a longitudinal direction (z), said passages (3) having a length measured parallel to the longitudinal direction (z) and a width less than said length measured in a lateral direction (x) orthogonal to the longitudinal direction (z); b) Arranging at least one support member (10) in at least one of the passages (3) formed between two adjacent plates (2) so as to form a stack; c) Forming at least one contact zone (11) between the at least one support member (10) and each of the two adjacent plates (2);d) Arranging a surface texturing in the form of a porous structure or reliefs formed on the adjacent plates (2) and / or on the support (10); e) Brazing the stack; Characterized in that said at least one support member (10) is of elongated shape and extends parallel to the longitudinal direction (z).;
2. Method according to claim 1, characterized in that several support members (10) are arranged in said at least one passage (3) and follow one another in the lateral direction (x).
3. A method according to any one of the preceding claims, characterized in that the support member (10) is shaped to allow the flow of fluid inside the passages (3).
4. Method according to any one of the preceding claims, characterized in that said at least one support member (10) comprises a spring, or a twisted metal strip or at least two twisted wires.
5. A brazed plate and fin type heat exchanger (1) obtained by a method according to any one of claims 1 to 4.