Heat exchanger with leak detection system

Abstract

The invention relates to a brazed plate heat exchanger comprising a stack (1) of plates (2) arranged parallel to one another so as to define a plurality of channels (3) between said plates (2) for the flow of one or more fluids, each plate (2) comprises at least one first edge (4) extending parallel to a first direction (z), at least one sealing strip (6) is arranged in at least one channel (3) between two consecutive plates (2) so as to at least partially define one or more internal spaces in the channel (3), the sealing strip (6) comprises at least one longitudinal groove (12), the sealing strip (6) and the longitudinal groove (12) extend parallel to the first direction (z) in the length direction thereof. According to the invention, at least one measuring element (14) is mounted in the longitudinal recess (12) for measuring at least one physical quantity, in particular at least one temperature, in the longitudinal recess (12).

Description

[0001] The present invention relates to a brazed plate heat exchanger which is provided with at least one measuring device for detecting leaks in the heat exchanger.

[0002] The present invention is particularly applicable to the field of low-temperature gas separation, especially to cryogenic air separation units (ASUs) for the production of pressurized gaseous oxygen. In particular, the present invention can be applied to heat exchangers for cooling or liquefying a gaseous oxygen stream from an ASU by heat exchange with a liquid nitrogen stream, or to heat exchangers for heating or vaporizing a liquid oxygen stream by heat exchange with a gaseous nitrogen stream. Additionally, the present invention can also be used in heat exchangers for cooling or liquefying an oxygen gas stream from an ASU by heat exchange with a heated or vaporized liquid argon stream.

[0003] The present invention can also be applied to a heat exchanger for heating or vaporizing at least one liquid-gas mixture stream, especially a multi-component mixture stream such as a hydrocarbon mixture, by heat exchange with at least one other fluid (such as natural gas or nitrogen). According to the present invention, the exchanger can also be used for vaporizing or heating liquefied natural gas by cooling or liquefying nitrogen.

[0004] More generally, the present invention can be applied to heat exchangers in which at least one fluid circulates at a pressure of at least 20 bar.

[0005] According to the present invention, the exchanger can also be a reactor exchanger or a catalytic exchanger configured for a chemical reaction with the circulating fluid in the exchanger.

[0006] Brazed plate heat exchangers are a commonly used heat exchanger technology. Such heat exchangers are compact in structure, have a large heat exchange area, and a small pressure drop. These heat exchangers consist of a set of parallel plates, and intermediate elements such as corrugated or wavy structures can be inserted between the plates to form a finned heat exchange structure. A stack of planar channels is formed between the stacked plates for different fluids to enter into a heat exchange relationship.

[0007] During the manufacturing process of the exchanger, the plates, fin spacers, and other exchanger components are first pressed together and then brazed together in a vacuum furnace at a temperature of 550 to 900 °C.

[0008] Due to the compact integral design of plate heat exchangers, it is difficult to measure the physical quantities inside them, especially temperature. Therefore, in most processes where plate heat exchangers are installed, operators can only obtain the total heat energy exchanged between fluids through the energy balance conducted between the inlets and outlets of each fluid. This makes the characteristic analysis and operation monitoring of these exchangers very complex. For example, it is impossible to separately measure the physical quantities related to the circulating fluid in each channel.

[0009] During use, the lack of local data limits the possibilities of process control. In particular, certain physical phenomena that may occur within the exchanger, such as phase changes or chemical reactions, can cause local temperature variations, which also depend on the position within the exchanger.

[0010] Local temperature measurements can be used to detect on-site poor operating conditions of the heat exchanger, for example, poor fluid distribution or performance degradation in certain areas of the heat exchanger due to blockages or local distillation. Local temperature or heat flux measurements also help to monitor the performance of plate-fin heat exchangers during their service life.

[0011] On-site "temperature measurement methods do exist, but they are relatively invasive as they change the fluid flow within the heat exchanger channels. Moreover, since this method was not foreseen during the construction of the heat exchanger, its implementation is relatively complex, costly, and less robust.

[0012] In addition, in a brazed plate heat exchanger, due to the geometry and microstructure of the brazing material connecting the exchanger components, the brazed area is prone to fatigue damage, the appearance and propagation of cracks, which can lead to the risk of fluid leakage. This risk increases if the exchanger operates in a cyclic mode, i.e., the pressure of the circulating fluid in the exchanger changes periodically, and / or the pressure of the circulating fluid in the exchanger is high, usually exceeding 30 bar, and even exceeding 50 bar.

[0013] In certain processes, leakage can cause local high concentrations of certain fluids, which represents a risk inherent in the fluid properties or a change in the quality of the fluid leaving the exchanger. Leakage also reduces the operating conditions and performance of the exchanger and related processes.

[0014] Document FR-A-2929369 describes a plate heat exchanger with a double-layer channel seal strip. Thus, the space between the seal strips forms a dead zone that opens to the atmosphere through a vent, and any liquid leakage can be discharged through this dead zone. However, this solution cannot detect the occurrence of leakage, especially cannot adjust or stop the operation of the heat exchanger when necessary, nor can it determine the location of the leakage, especially cannot facilitate future inspection of the heat exchanger.

[0015] Another way to limit these risks is to use a coil heat exchanger. However, the efficiency of this heat exchanger is still far lower than that of a plate heat exchanger because the plate heat exchanger has a large exchange surface area, a small pressure drop, and higher thermal efficiency.

[0016] One of the objectives of the present invention is to solve some or all of the above problems by providing a plate heat exchanger that can accurately and quickly detect and locate fluid leakage without affecting the operation of the exchanger or the fluid flow, nor increasing its volume.

[0017] To this end, the object of the present invention is a brazed plate heat exchanger, which comprises a stack of plates arranged in parallel with each other so as to define a plurality of channels between said plates. Each plate comprises at least one first edge extending parallel to a first direction. At least one channel defined between two consecutive plates comprises at least one sealing strip, which is arranged in such a way as to at least partially define one or more internal spaces for one or more fluids to flow in said channels. The sealing strip comprises at least one longitudinal groove, and the sealing strip and the longitudinal groove extend parallel to the first direction (z) in their length direction. It is characterized in that at least one measuring component is arranged in the longitudinal groove for measuring at least one physical quantity in said longitudinal groove, in particular at least one temperature.

[0018] According to specific circumstances, the exchanger of the present invention may comprise one or more of the following features.

[0019] Said at least one sealing strip is arranged at the first edge so as to at least partially separate an internal space from the outside of the stack structure, or said at least one sealing strip is arranged at a predetermined distance from the first edge so as to at least partially separate an internal space from another internal space in the channel.

[0020] Said at least one measuring component is elongated and parallel to the first direction of the longitudinal groove in its length direction. Preferably, the measuring component can measure a plurality of values of said physical quantity along the first direction.

[0021] Said at least one measuring device comprises at least one optical waveguide, in particular at least one optical fiber.

[0022] The sealing strip comprises a first strip portion and a physically independent second strip portion. Each strip portion extends parallel to the first direction and is spaced apart in a second direction orthogonal to the first direction and parallel to the plate. In this way, the longitudinal groove is formed by the space between the first strip portion and the second strip portion, or the longitudinal groove is formed by a groove in an integral sealing strip. The integral sealing strip comprises two side faces facing each adjacent plate, and the groove opens to one or the other side face of the strip portion.

[0023] The exchanger comprises at least two sealing strips arranged opposite each other between two adjacent plates. Each sealing strip extends parallel to the first direction in its length direction and comprises at least one longitudinal groove. The length direction of the groove is parallel to the first direction, and there is at least one measuring component in the groove.

[0024] The longitudinal groove and the measuring component extend at least 50% of the length of the sealing strip, preferably at least 75%, and more preferably the entire length.

[0025] The sealing strip includes at least one longitudinal face parallel to a first direction and at least one transverse face orthogonal to the first direction. The longitudinal groove opens to the outside of the stacking structure through at least one opening located on the transverse face of the sealing strip. Preferably, the sealing strip includes two opposite transverse faces, and the longitudinal groove opens to the outside of the stacking structure through two openings located on each of the opposite transverse faces.

[0026] The exchanger includes at least one set of sealing strips that extend parallel to the first direction in the length direction and are arranged one above the other in the stacking direction orthogonal to the plate. Each sealing strip in the set includes at least one longitudinal groove that extends parallel to the first direction in the length direction and is provided with at least one measuring component.

[0027] The sealing strips of the assembly each include at least one longitudinal face parallel to the first direction, at least one transverse face orthogonal to the first direction, and at least one longitudinal groove that extends parallel to the first direction in the longitudinal direction and is provided with at least one measuring component. The longitudinal groove of each sealing strip opens to the outside of the stacking structure through respective openings located on the transverse face of each sealing strip, and at least one measuring component extends outside a longitudinal groove through one opening and then re-enters the interior of an adjacent longitudinal groove through another opening.

[0028] The measuring component includes at least two inner portions, each inner portion being located within the longitudinal groove of the sealing strip and integrally connected by a curved outer portion located outside the stacking structure. The radius of curvature of the outer portion is preferably at least 10 cm, and preferably at least 20 cm.

[0029] The plate has two opposite second edges parallel to a second direction orthogonal to the first direction. The measuring component includes a plurality of inner portions connected by outer portions alternately located on one or the other side of the opposite second edges.

[0030] The stacking structure has a total height measured in the stacking direction. The sealing strips of the assembly are spaced apart at an intermediate height measured in the stacking direction. The ratio between the intermediate height and the total height is from 5% to 50%.

[0031] The at least one longitudinal groove and the at least one measuring component respectively have an inner dimension and an outer dimension along at least one direction orthogonal to the first direction when the sealing strip is arranged parallel to the first direction, or along at least one direction parallel to the first direction when the sealing strip is arranged orthogonal to the second direction. The ratio between the outer dimension of the measuring component and the inner dimension of the longitudinal groove is at most 95%, and preferably between 70% and 90%.

[0032] Furthermore, the present invention also relates to a heat exchange device, which comprises an exchanger according to one of the foregoing claims, and includes at least one distribution pipe configured to distribute one or more fluids in one or more internal spaces of at least one channel; at least one fluid control device configured to allow, modify, and / or stop the distribution of at least one fluid through the distribution pipe; a measuring device configured to generate at least one leakage signal according to a change in the physical quantity, and a control device configured to modify or stop the distribution of the fluid through the distribution pipe according to the leakage signal.

[0033] According to another aspect, the present invention relates to an exchanger or device used according to the present invention for heat exchange between at least one fluid and at least another fluid, wherein the fluid and / or the other fluid includes: one of neon, krypton, xenon, nitrogen, argon, oxygen, hydrogen, helium, carbon monoxide, carbon dioxide, methane, and in particular, gaseous oxygen is liquefied or cooled by heat exchange with liquid nitrogen or liquid argon.

[0034] The present invention also relates to a cryogenic air separation device, which comprises at least one exchanger designed according to the present invention or a device designed according to the present invention, in which the exchanger liquefies or cools a gaseous oxygen stream from the cryogenic air separation device with liquid nitrogen or liquid argon, and the liquid nitrogen or liquid argon is heated or vaporized.

[0035] Through the following description, we will better understand the present invention. The following description is only a non-limiting example and refers to the accompanying drawings, in which:

[0036] Figure 1 is a three-dimensional view of an exchanger made according to an embodiment of the present invention,

[0037] Figure 2 is a longitudinal sectional view of an exchanger channel in an embodiment of the present invention,

[0038] Figure 3 is another longitudinal sectional view of an exchanger channel in an embodiment of the present invention,

[0039] Figure 4 is another longitudinal sectional view of an exchanger channel according to an embodiment of the present invention, and the sectional plane is orthogonal to the sectional planes of Figure 2 and Figure 3 .

[0040] Figure 5 is a sectional view of a measuring device in an embodiment of the present invention,

[0041] Figure 6 is a longitudinal sectional view of a measuring device in an embodiment of the present invention.

[0042] ​​​​​​Figure 1 Shows an example of a brazed plate - fin heat exchanger, which is composed of a set of plates 2 that extend along a first Z - direction and a second X - direction respectively in terms of length and width. The shape of the stacked structure 1 is preferably a parallelepiped. The plates 2 are arranged one above the other, parallel to each other and spaced apart. Thus, several groups of channels 3 are formed between them, some of which are for the flow of a first fluid F1, and the other channels are for the flow of at least one other fluid F2, F3, and these fluids form an indirect heat - exchange relationship with F1 through the plates 2. The second direction x is preferably perpendicular to the first direction z and parallel to the plates 2. The fluids preferably flow along the length direction of the exchanger, and the length is greater than the width. In the illustrated case, the first Z - direction corresponds to the longitudinal extension of the exchanger, and the fluids generally flow parallel to the first Z - direction. Of course, within the scope of the present invention, there can also be other flow directions, especially the fluid flow direction substantially parallel to the first x - direction.

[0043] Each channel is preferably in the shape of a flat parallelepiped. Measured along the stacking direction y of the plates 2, the distance between two consecutive plates 2 (equivalent to the height of the channel) is less than the length and width of each consecutive plate. The stacking direction y is orthogonal to the plates 2.

[0044] Each of the plates 2 includes at least one first edge 4 that extends parallel to the first direction z. Preferably, each of the plates 2 includes a pair of first edges 4 that are parallel to the first direction z and are arranged opposite to each other. According to Figure 1 the illustrated embodiment, the plates 2 are also defined by a pair of second edges 5 that are parallel to the second direction x and are opposite to each other.

[0045] The channels 3 are defined by sealing strips 6 that are arranged between the plates 2 on the periphery of the channels 3. These sealing strips 6 ensure the spacing between the plates 2, delimit the internal space suitable for the flow of one or more fluids within each channel 3, and ensure the sealing of the channels 3 relative to the outside of the stacked structure. Preferably, at least one sealing strip 6 extends along the first direction z, and more preferably, the channel 3 is delimited between a pair of sealing strips 6 that are parallel to the first direction z. The channel 3 can be further defined by at least one sealing strip 6 that extends along the second direction x, and preferably, the channel 3 is delimited between a pair of sealing strips 6 that are parallel to the second direction x.

[0046] Depending on the positions of the fluid inlet and outlet regions of the exchanger, the sealing strips 6 may not completely seal the channels, but leave gaps for the corresponding fluids to enter or exit. The exchanger 1 includes semi - tubular manifolds 7 and 9 with inlets and outlets 10 for introducing fluids into the exchanger and discharging fluids from the exchanger. A distribution area is arranged downstream of the inlet manifold and upstream of the outlet manifold for uniformly introducing or discharging fluids across the entire width of the channels.

[0047] In addition, at least some of the channels 3 may also include at least one sealing strip 6, which is arranged in such a way as to at least partially define several internal spaces in the channel 3. Different fluids can flow through these internal spaces, and the role of the sealing strip is to prevent these fluids from circulating from one internal space to another.

[0048] Preferably, at least some of the channels 3 include fin spacing elements 8, which extend along the width and length of the exchange channel and are parallel to the plate 2. In the illustrated example, the spacing element 8 includes a corrugated sheet-like heat exchange wave. In this case, the wave feet connecting the consecutive vertices and base points of the wave are referred to as "fins". The spacing element 8 can also adopt other special shapes according to the required fluid flow characteristics. Generally speaking, the term "fin" includes blades or other secondary heat exchange surfaces extending from the main heat exchange surface (i.e., the exchange plate) into the exchange channel.

[0049] Preferably, corrugations are used as the spacing element 8. In particular, for the wave, its fins extend parallel to the first Z direction, and the general direction of the corrugation is perpendicular to the first Z direction and parallel to the plate 2.

[0050] When manufacturing the exchanger 1, it is preferable to provide a set of plates 2 and stack them parallel to each other in the first Z direction. The plates 2 are spaced apart by the sealing strips 6. Once the other components of the heat exchanger, especially the exchange waves, distribution waves, etc. are assembled, the stack is brazed to fix the heat exchanger components together. The brazing filler metal is arranged between the exchange elements. The plates and some or all of the other exchange elements are preferably made of aluminum or aluminum alloy.

[0051] Within the stacked structure, adjacent plates 2 are separated by the sealing strips 6 arranged between each pair of adjacent plates. These sealing strips 6, together with the adjacent plates 2, define at least one internal space in which at least one fluid can flow. The role of the sealing strip 6 is to prevent the fluid from leaking from one internal space of the channel 3 to the outside of the stacked structure, and / or to prevent the fluid from flowing between multiple internal spaces of the same channel 3 (as the case may be). A sealed connection area is formed between the sealing strip and the adjacent plate, especially by brazing the sealing strip to the plate. However, due to the heat stress and mechanical stress that the exchanger endures for a long time, the sealing performance of the channel may be reduced, and the first fluid may penetrate between the sealing strip and the adjacent plate.

[0052] According to the present invention, at least one longitudinal groove 12 is provided on at least one sealing strip 6 extending in the first direction z, so as to collect the first fluid when leakage occurs in the channel 3 defined by the sealing strip 6. The sealing strip 6 and the longitudinal groove 12 extend along the length direction parallel to the first z direction. A measuring device 14 is installed in the longitudinal groove 12 for detecting a change in at least one physical quantity in the longitudinal groove 12, especially a change in temperature.

[0053] Therefore, the present invention can detect whether there is fluid leakage from the adjacent internal space at the sealing strip 6 by detecting the change in the physical quantity caused by the fluid entering the longitudinal groove 12 in the longitudinal groove 12. According to the position of the sealing strip, the present invention can detect leakage from the channel 3 to the outside of the stacked structure or leakage between the internal spaces of the channels separated by the sealing strip 6. If leakage is detected, the operation of the exchanger can be stopped to ensure the safety of the operator and reduce the risk of contamination of the fluid used. As a physical quantity representing the leakage of the loop 12, the temperature in the longitudinal groove 12 can be measured. Advantageously, the measuring device can be used to detect the change in temperature in the longitudinal groove 12 or measure the temporal change in the temperature in the longitudinal groove 12. By measuring the temperature, a sudden change in temperature can be detected, which is characteristic of leakage.

[0054] Mounting the measuring element 14 in the sealing strip 6 does not increase the overall size of the heat exchanger. The measuring element can be positioned as required for in-situ temperature measurement. More importantly, the measuring element can be inserted after the formation stage of the stacked structure, thereby reducing the risk of probe damage and allowing the use of more techniques without being limited to high-temperature-resistant probes.

[0055] The present invention can also measure the fluid properties, such as temperature, of the fluid flowing through the channel 3 defined by the sealing strip 6 including the longitudinal groove without affecting the fluid flow. Such measurements can be used to detect any faults in the exchanger or for dynamic monitoring of fluid properties, especially for evaluating the thermal shock to the exchanger.

[0056] Figure 2 An example is shown where a longitudinal groove 12 is formed in the sealing strip 6 extending parallel to the first direction z, and the groove determines the overall direction F1 of fluid flow. In addition to leakage detection, such a structure can also perform local measurements of the temperature of the fluid and its changes at different positions along the length of the exchanger when the fluid exchanges heat with another fluid flowing in an adjacent channel. This provides information about the physical phenomena that may occur within the exchanger, including phase changes and chemical reactions, and their locations within the exchanger.

[0057] In the present invention, one or more sealing strips 6 can carry one or more longitudinal grooves 12, and each groove 12 is equipped with a measuring element 14. Conceivably, one or more longitudinal grooves 12 can also be provided on other sealing strips, especially the sealing strips 6 parallel to the second direction x.

[0058] Referring to Figure 3 , each plate 2 may also include at least one second edge 5 extending perpendicular to the first direction z, at least one sealing strip 6 is arranged longitudinally parallel to the second edge 5 and includes at least one longitudinal groove 12 extending longitudinally parallel to the second edge 5, and at least one measuring component 14 is provided on the groove 12.

[0059] In the present invention, at least one sealing strip 6 can be arranged on the first edge 4 or the second edge 5 to form a peripheral strip that at least separates the internal space from the external part of the stacking structure. Thus, the sealing strip at least partially defines the periphery of the channel 3. At least one sealing strip 6 can also be arranged at a predetermined distance from the first edge 4 or the second edge 5 to form a separating strip that separates one internal space within the channel 3 from another internal space. In this way, the sealing strip at least partially separates one internal space 3A from another volume 3B within the stacking structure. Combinations of these embodiments can be envisioned, in particular that at least one channel 3 can include at least one peripheral strip and at least one separating strip.

[0060] According to one embodiment, at least two sealing strips 6 are arranged opposite each other between two adjacent plates 2, parallel to the first direction z or the second direction x, so as to delimit the same channel 3. Each of the two opposite sealing strips 6 includes at least one measuring element 14 mounted in the fluid circuit 12.

[0061] Mounting the measuring device 14 on the sealing strips on both sides of the channel 3 can more effectively detect leaks. This can also check whether the fluid is evenly distributed across the width of the channel, in particular verifying whether the physical quantities measured on both sides are the same. In particular, by measuring the temperature on both sides of the channel, we can effectively detect any uneven distribution. The heat exchange in the channel (the fluid and rod temperatures depend on the heat exchange) is related to the fluid flow rate near the probe. Therefore, the temperature difference between each side will indicate a flow difference. In addition, the probe can also be used to dynamically monitor the transient temperature over a period of time and evaluate the thermal shock received by the heat exchanger.

[0062] The longitudinal groove 12 and the measuring component 14 preferably extend at least 50%, preferably at least 75%, or even more of the length of the sealing strip 6. It should be noted that the length of the sealing strip 6 is measured along its longitudinal extension, particularly in the case where the sealing strip extends along the first Z direction. In this way, one or more measuring devices can be arranged along most of the length or width of the channel 3, thereby improving the efficiency and accuracy of leak detection. By arranging multiple grooves, the change in physical quantities at different positions along the length and / or width direction of the exchanger can be measured, thereby determining the leak location.

[0063] In one embodiment, the exchanger includes at least a set of sealing strips 6 that are arranged parallel to the first direction z and arranged one above the other along the stacking direction y. At least one measuring element 14 is mounted in the longitudinal groove 12 of each sealing strip 6 in the assembly. In this way, fluid leaks at different positions in the stacking height can be detected and the relevant channels can be identified. Each groove 12 in the sealing strip 6 can be used to detect the leak of the channel 3 opposite the sealing strip 6.

[0064] In particular, the total height of the stacked structure in the stacking direction y is H, and the intermediate height h at which the sealing strip 6 with the groove 12 and the measuring element 14 are spaced apart from each other in the stacking direction y is such that the ratio of the intermediate height h to the total height H is between 5 and 50%.

[0065] In the case where the measuring element includes an optical fiber, the intermediate height h is greater than twice the minimum radius of curvature of the optical fiber or the protective sleeve in which the optical fiber is located.

[0066] In particular, the intermediate height h is at least 5 cm, preferably at least 10 cm, and even more preferably at least 20 cm.

[0067] In one embodiment, the ratio of the total number of channels 3 in the stacked structure to the number of channels 3 in which at least one sealing strip is installed according to the invention is between 1 and 10, preferably greater than or equal to 5.

[0068] It should be noted that the sealing strips 6 can be arranged equidistantly in the stacking height, but this is not necessarily the case.

[0069] Preferably, the longitudinal groove 12 opens to the outside of the stacked structure 1 through at least one opening 11. Thus, the first fluid that leaks can escape to the outside of the stacked structure. The opening 11 can be connected to the atmosphere through a vent or a leakage recovery circuit. The opening 11 can also be used for inserting and / or removing the measuring element 14. In particular, the longitudinal groove is continuous and communicates with two holes 11 located on both sides of the length of the sealing strip 6, thereby making the arrangement of the measuring element more flexible. The measuring element 14 preferably protrudes from the stacked structure 1 through at least one opening 11.

[0070] In particular, the sealing strip 6 includes at least one longitudinal face 64 parallel to the first Z-axis direction and at least one transverse face 65 orthogonal to the first Z-axis direction.

[0071] In one embodiment, at least one sealing strip 6 is in the shape of a parallelepiped. The cross-section of the sealing strip can be square or rectangular. The sealing strip 6 includes two opposite longitudinal faces 64 that are parallel to the first direction z and the stacking direction y. Depending on the position of the bar in the exchanger, one longitudinal face 64 faces the internal fluid circulation space, the other longitudinal face 64 faces the outside of the stacked structure, or each longitudinal face 64 faces its respective internal fluid circulation space. The sealing strip 6 includes two opposite side surfaces 63 that are parallel to the first direction z and orthogonal to the stacking direction y. The opposite side surfaces 63 face the adjacent plates 2.

[0072] As Figure 2As shown, the sealing strip 6 may include a first strip portion 61 and a second strip portion 62 that are physically different from each other. The first strip portion 61 and the second strip portion 62 extend parallel to the longitudinal direction z and the plate 2, respectively. The longitudinal groove 12 is formed by the space formed between the first strip portion 61 and the second strip portion 62 along the second direction x. If one or the other of the first and second strip portions loses its sealing function at least partially, fluid will flow into the groove 12 and accumulate in the groove 12.

[0073] Alternatively, the longitudinal groove 12 is formed by a groove on the integral sealing strip 6. In particular, the groove may have any suitable cross-sectional shape, including square, rectangular, or semi-circular. The groove is preferably formed on one or more side surfaces 63 of the sealing strip 6 facing the adjacent plate 2. The second width of the groove, measured along the second direction x, is less than the total width of the sealing strip. In the case where the sealing strip loses its sealing function at least partially, liquid will seep out and accumulate in the groove 12.

[0074] Preferably, the longitudinal groove 12 opens outwards through at least one opening 11 located on the transverse surface 65. As Figure 2 shown, the sealing strip 6 preferably includes two opposite transverse surfaces 65, and the longitudinal groove 12 opens outwards from the stacked structure 1 through two openings 11 located on each of the opposite transverse surfaces.

[0075] According to a specific embodiment, the sealing strip 6 includes an outer longitudinal surface 64e parallel to the first direction z and aligned with the first edge 4 of the adjacent plate 2. In this structure, the outer longitudinal surface 64e forms part of the peripheral surface of the stacked structure.

[0076] In particular, the sealing strip 6 may include at least one transverse surface 65 parallel to the second direction x and aligned with the second edge 5 of the adjacent plate 2. In this structure, the transverse surface 65 forms part of the peripheral surface of the stacked structure.

[0077] The stacked structure 1 preferably has at least one first surface parallel to the first direction z, on which the first edge 4 of the plate 2 and the outer longitudinal surface 64e of the sealing strip 6 are located. In addition, the stacked structure 1 may also have at least one second surface parallel to the second direction x, on which the second edge 5 of the plate 2 and the transverse surface 65 of the sealing strip 6 are located.

[0078] Figure 4 An embodiment is illustrated in which the exchanger includes at least a set of sealing strips 6 arranged one above the other and parallel to the first direction z, each set of sealing strips 6 having at least one longitudinal groove 12 and at least one measuring component 14 on the groove 12. In particular, each of the sealing strips 6 of the assembly includes at least one transverse surface 65 provided with an opening 11 through which the longitudinal groove 12 leads to the outside of the stacked structure 1.

[0079] Alternatively, the exchanger may include at least a pair of first strip-shaped components oppositely arranged on both sides of the channel 3.

[0080] Preferably, at least one measuring element 14 extends outward from the longitudinal groove 12 through a hole 11 and then re-enters the adjacent longitudinal groove 12 through another hole 11. In this way, the same measuring device can be installed in different grooves 12 to detect the leakage of different channels 3.

[0081] In particular, the measuring member 14 includes at least two internal portions 14a, each internal portion 14a being disposed in the longitudinal groove 12 of the sealing strip 6 and integrally connected by a curved external portion 14b disposed outside the stacked structure. The radius of the external portion 14b is preferably greater than 5 cm, preferably greater than 10 cm.

[0082] In particular, the plate 2 has two opposite second edges 5 arranged parallel to the second direction x. The measuring member 14 includes a plurality of internal portions 14a connected by external portions 14b alternately located on one or the other side of the second edge 5. In this way, the same measuring element can meander through the stacked structure. With this arrangement, only one measuring element is required, and thus only one signal transmission and acquisition system is required. This not only simplifies the operation but also facilitates the maintenance of the exchanger. The associated investment costs are also reduced accordingly.

[0083] In addition, the exchanger may further include at least a second set of sealing strips parallel to the second direction x and arranged one above the other in the stacking direction y. Each set of sealing strips has at least one longitudinal groove, and at least one measuring member is disposed in the groove. In particular, each of the second set of sealing strips includes at least one opening, and the longitudinal groove leads to the outside of the stacked structure through the opening. The above-mentioned second set of sealing strips may have all or part of the features of the above-mentioned first set of sealing strips, but the longitudinal surface of the sealing strip 6 is parallel to the second direction x, and the opening 11 is opened on one side of the first edge 4 and disposed on the transverse plane of the sealing strip 6 parallel to the first direction z.

[0084] Preferably with reference to Figure 5 the example shown, the measuring member 14 includes an internal member 15 sensitive to changes in the at least one physical quantity in the longitudinal groove 12 and a protective sleeve 16 surrounding the internal member 15.

[0085] The measuring element is preferably slender, so that it can be conveniently inserted into the groove without increasing the size of the heat exchanger.

[0086] As described above, it is preferable to dispose a measuring member in the groove of one strip-shaped component, or even in the grooves of multiple strip-shaped components, regardless of whether they are arranged parallel to the first Z direction or the second X direction.

[0087] Preferably, the at least one measuring member 14 includes a plurality of sensitive areas arranged along the measuring member 14, and physical quantities are measured in these sensitive areas. The sensitive areas may be arranged equidistantly from each other, but not necessarily. In particular, the distance between the sensitive areas may be between 5 and 100 mm, preferably between 10 and 50 mm.

[0088] According to an advantageous embodiment, the at least one measuring member 14 includes at least one optical waveguide, in particular at least one optical fiber. It should be noted that the term "optical fiber" can refer to both a single optical fiber and a network of multiple optical fibers connected in series or in parallel.

[0089] An optical waveguide is a structure for confining and guiding light. The waveguide consists of two or more layers of transparent dielectric materials with different refractive indices (such as silica glass or plastic) to ensure that the light is confined near the center. An optical fiber is a circularly symmetric optical waveguide. An optical fiber generally consists of a dielectric called the core and a material called the cladding, and the refractive index of the cladding is lower than that of the core. There is a coating, usually made of plastic, around the entire assembly, which has a dual function: mechanically protecting the optical fiber and capturing the unwanted light propagating through the cladding. Optical fiber measurement devices are both sensors and optical signal transmission channels. They are very sensitive to changes in physical quantities in the surrounding environment, such as temperature, deformation...

[0090] The advantages of optical fibers are that only limited instruments and little or no power supply are required, and the structure is very compact, so there is less interference, it is easier to implement, and it complies with the regulations regarding explosive gas environments (ATEX regulations).

[0091] In the case of the optical fiber 14, the protective sheath 16 can be an optical fiber sheath or a tubular sleeve around the sheath, preferably made of a metallic material.

[0092] The optical fiber measurement element is preferably connected to a system for measuring the range of physical quantities (especially temperature) measured along the optical fiber. In particular, the principle of the measurement system can be based on the Raman spectrum, Rayleigh spectrum or Brillouin spectrum of at least one optical pulse and the influence of physical quantities on light absorption. After digital processing, the intensity change and acquisition time of the reflected signal can record the change of physical quantities at different points along the optical fiber and be converted into a detailed temperature curve along the optical fiber. This temperature curve can be used to identify in real time the areas where changes occur on the sealing strip, indicating whether there is a leak. Figure 6 An example is shown in which a measuring device 14 including at least one optical fiber is connected to a device for emitting at least one optical pulse 23, and the device is configured to determine the physical quantities at different points or sensitive areas 22a, 22b... along the optical fiber.

[0093] The temperature curve measured along the optical fiber is usually discontinuous, i.e., it consists of a series of temperatures, each of which corresponds to a finite element of the optical fiber.

[0094] Two types of optical waveguide measurement devices 14 can be used. The first type includes distributed (i.e., continuously sensitive) sensors based on the Raman effect, Brillouin effect, or Rayleigh effect, as well as distributed (i.e., locally sensitive) sensors with a lithographic Bragg grating in the optical fiber core. The second type is extrinsic measurement devices that employ several techniques for connecting micro-sensors to the optical fiber. Whether it is a semiconductor, Fabry - Perot interferometric cavity, or phosphorescent compound, their function is to make a certain parameter of the guided optical wave - intensity, spectrum, phase, etc. - vary with temperature. - By measuring the change in this optical parameter, the induced thermal change can be traced. In the case of distributed sensors, the principle of optical fiber measurement is based on the interaction between light and matter. When an optical fiber material is traversed by an optical pulse, a backscattered spectrum consisting of three components is emitted: Raman backscattering, Rayleigh backscattering, and Brillouin backscattering. At least one of these components can be used.

[0095] In particular, Rayleigh backscattering can be used, which is the result of the interaction between impurities in the optical fiber and the electromagnetic field. Local changes in the refractive index related to temperature and / or deformation changes will alter the intensity of the backscattered wave, thus enabling the tracking of the required information.

[0096] The Raman effect can also be used to determine the temperature of the optical fiber at different points (regular spatial discretization of the optical fiber). The Raman effect is a non - linear effect based on the principle of energy exchange between optical waves and material vibrations. This effect shifts the lines representing the spectrum. The shifted low - frequency and high - frequency can be observed. Since temperature only affects the higher offset frequency, this spectrum can be used as a temperature sensor.

[0097] These phenomena are best realized by an OTDR - type device (abbreviation in English: Optical Time Domain Reflectometry), which includes sending a long optical pulse and tracking the position of the measurement point or sensitive area by knowing the propagation speed of the optical wave in the material. The spatial resolution depends on the length of the sent pulse.

[0098] Alternatively, a measuring element 14 consisting of at least one fiber Bragg grating can also be used. A fiber Bragg grating is a type of optical fiber in which the refractive index of the core varies alternately between relatively high and relatively low values along the length of the fiber. This variation enables the fiber to reflect certain wavelengths while allowing other wavelengths to pass through. The reflected wavelength depends on the distance between the high-refractive-index portions and the low-refractive-index portions. The distance between two high-refractive-index portions is called the Bragg grating period. Due to the "pattern printed on the optical fiber", each measurement point or sensitive area can reflect a wavelength. The reflected wavelength varies with temperature and strain.

[0099] Note that a resistive temperature measuring element 14, such as a resistance thermometer, especially a PT100 type platinum resistance thermometer, or a thermocouple or a thermistor temperature measuring element 14 can also be used. In particular, the measuring element 14 can include a protective sheath 16, in which a plurality of resistance, thermocouple or thermistor measuring elements are dispersed along the protective sheath, so that measurements can be made at different positions of the measuring element, and thus also at different positions of the exchanger.

[0100] The transverse dimension of the longitudinal groove 12 can match the transverse dimension of the sealing strip 6 and / or the measuring element 14.

[0101] In particular, the at least one longitudinal groove 12 and the at least one measuring component 14, when the sealing strip 6 is parallel to the longitudinal edge 4, have an inner dimension and an outer dimension in at least one direction parallel to the second direction x, or when the sealing strip 6 is parallel to the transverse edge 5, in a direction parallel to the first direction z. The ratio of the outer dimension of the measuring component 14 to the inner dimension of the longitudinal groove 12 is at most 95%, preferably between 70% and 90%. These values are determined so that the measuring element can slide in the groove and deviate slightly from its overall extension direction in the groove to avoid the measuring element being subjected to tensile forces due to the expansion difference between the measuring element and the material around the groove. This can reduce the risk of the measuring element breaking. The outer dimensions of the measuring element 14 include the outer dimensions of the protective sheath (if applicable).

[0102] If the longitudinal groove 12 is formed by the space between two independent strip portions 61, 62, the depth of the longitudinal groove 12 is measured in the stacking direction y and corresponds to the height of the channel 3 in which the sealing strip 6 is located. The inner dimension of the longitudinal groove 12 is preferably equal to the height of the channel, and the ratio of the outer dimension of the measuring component 14 to the channel height is at most 95%, preferably between 70% and 90%.

[0103] If the longitudinal groove 12 is formed by a groove in the integral sealing strip 6, the depth of the longitudinal groove 12 (measured in the stacking direction y) is less than the height of the channel 3 in which the sealing strip is located. The internal dimensions of the longitudinal groove 12 are preferably equal to the groove depth, and the ratio of the external dimensions of the measuring member 14 to the groove depth is at most 95%, preferably between 70% and 90%.

[0104] When measuring leakage, the outer surface of the measuring element 14 is preferably not in contact with the surface of the inner wall of the groove 12. By contact we mean direct or indirect thermal contact, in particular through a material that enables heat transfer between the outer surface of the measuring element 14 and the inner wall of the groove 12. This non-contact approach can avoid the thermal inertia of the material, thereby improving the system response speed.

[0105] Alternatively, the outer surface of the measuring element 14 is at least in thermal contact with at least a part of the inner wall surface of the groove 12. This configuration can be used in particular to measure the characteristics of a fluid flowing through a heat exchanger in order to monitor or describe its operation.

[0106] If necessary, the measuring element can be fixed in the groove, on the sealing strip 6 or on a part of the stacking structure 1, for example using a cement or an adhesive with good thermal conductivity.

[0107] Preferably with reference to Figure 5 the partial schematic view in, the exchanger according to the invention comprises a cold box formed by a wall 20 which forms a closed outer shell around the stacking structure 1. The measuring member 14 extends between a first end 14c and a second end 14d located outside the cold box and circulates inside the cold box through a hole in at least one wall of the cold box. In this way, the instrumentation required for detecting and processing the measurement signals and the control system (if applicable) for the supply of the exchange fluid can be placed outside the cold box in order to reduce the constraints on such equipment and thus place it in the equipment control area.

[0108] Of course, the present invention is not limited to the specific embodiments described and illustrated in the present application. Without departing from the scope of the present invention as defined by the following claims, those skilled in the art can also envision other variations or embodiments.

Claims

1. A brazed plate heat exchanger, comprising a stack (1) of plates (2) arranged parallel to one another so as to define a plurality of channels (3) between the plates (2), the plates (2) each comprising at least one first edge (4) extending parallel to a first direction (z), at least one channel (3) defined between two consecutive plates (2) comprising at least one sealing strip (6), the sealing strip (6) being arranged to at least partially define one or more internal spaces for one or more fluids to flow in the channel (3), the sealing strip (6) comprising at least one longitudinal groove (12), the sealing strip (6) and the longitudinal groove (12) extending parallel to the first direction (z) in their length direction, characterized in that At least one measuring component (14) is arranged in the longitudinal groove (12) for measuring at least one physical quantity, in particular at least one temperature, in the longitudinal groove (12).

2. The heat exchanger according to claim 1, characterized in that The at least one sealing strip (6) is arranged on the first edge (4) so ​​as to at least partially separate an internal space from the outside of the stacking structure, or the at least one sealing strip (6) is arranged at a predetermined distance from the first edge (4) so ​​as to at least partially separate an internal space from another internal space in the channel (3).

3. The heat exchanger according to any one of claims 1 or 2, characterized in that: The at least one measuring component (14) is elongated and extends in parallel with the first direction (z) in the longitudinal groove (12) in its length direction. The measuring component is preferably configured to measure multiple values ​​of the physical quantity along the first direction (z).

4. Heat exchanger according to one of the preceding claims, characterized in that The at least one measuring component (14) comprises at least one optical waveguide, in particular at least one optical fiber.

5. Heat exchanger according to one of the preceding claims, characterized in that The sealing strip (6) comprises a first strip portion (61) and a second strip portion (62), which are physically different, each extending parallel to a first direction (z), and spaced apart from each other in a second direction (x) orthogonal to the first direction (z) and parallel to the plate (2), so that the longitudinal groove (12) is formed by the space between the first strip portion (61) and the second strip portion (62), or the longitudinal groove (12) is formed by a groove in a single sealing strip (6), the single sealing strip (6) comprising two side surfaces (63) facing each of the adjacent plates (2), the groove (12) opening at one or the other side surface (63) of the sealing strip (6).

6. Heat exchanger according to one of the preceding claims, characterized in that It comprises at least two sealing strips (6) arranged opposite to each other between two adjacent plates (2), each sealing strip extending in a length direction parallel to a first direction (z), and comprising at least one longitudinal groove (12) extending in a length direction parallel to the first direction (z), and at least one measuring component (14) is provided in the groove.

7. Heat exchanger according to one of the preceding claims, characterized in that The sealing strip (6) comprises at least one longitudinal surface (64) parallel to the first direction (z) and at least one transverse surface (65) orthogonal to the first direction (z), and the longitudinal groove (12) leads to the outside of the stacking structure (1) through at least one opening (11) located on the transverse surface (65) of the sealing strip (6). Preferably, the sealing strip (6) comprises two opposite transverse surfaces (65), and the longitudinal groove (12) leads to the outside of the stacking structure (1) through two openings (11) located on each opposite transverse surface.

8. Heat exchanger according to one of the preceding claims, characterized in that It comprises at least one set of sealing strips (6), which extend in a length direction parallel to a first direction (z) and are arranged one by one in a stacking direction (y) orthogonal to the plate (2), each sealing strip (6) of the assembly comprising at least one longitudinal groove (12), which extends in a length direction parallel to the first direction (z) and is provided with at least one measuring component (14).

9. The heat exchanger according to claim 8, characterized in that The sealing strips (6) of the assembly each include at least one longitudinal surface (64) parallel to a first direction (z), at least one transverse surface (65) orthogonal to the first direction (z), and at least one longitudinal groove (12) extending longitudinally parallel to the first direction (z) and having at least one measuring component (14); the longitudinal groove (12) of each sealing strip (6) opens toward the outside of the stacking structure (1) through an opening (11) located on each transverse surface (65) of the sealing strip, and at least one measuring component (14) extends outside a longitudinal groove (12) through one of the openings (11) and then re-enters an adjacent longitudinal groove (12) through another opening (11).

10. The heat exchanger according to claim 8 or 9, characterized in that: The measuring component (14) comprises at least two inner parts (14a), each inner part (14a) is arranged in the longitudinal groove (12) of the sealing strip (6) and is integrally connected by a curved outer part (14b) arranged outside the stacking structure (1), and the curvature radius of the outer part (14b) is preferably at least 10 cm, more preferably at least 20 cm.

11. The heat exchanger according to claim 10, characterized in that The plate (2) has two opposite second edges (5) parallel to the first direction (z) and orthogonal to the second direction (x), and the measuring component (14) comprises a plurality of inner parts (14a) connected by outer parts (14b) alternately located on both sides of the opposite second edges (5).

12. The heat exchanger according to any one of claims 9 to 11, characterized in that The stack has a total height (H) measured in the stacking direction (y), the sealing strips (6) of the assembly being separated from each other by an intermediate height (h) measured in the stacking direction (y), the ratio between the intermediate height (h) and the total height (H) being between 5 and 50%.

13. Heat exchanger according to one of the preceding claims, characterized in that If the sealing strip (6) is arranged parallel to the first direction (z), the at least one longitudinal groove (12) and the at least one measuring component (14) have inner and outer dimensions, respectively, along at least one direction orthogonal to the first direction (z), or if the sealing strip (6) is arranged orthogonal to the second direction (x), the at least one longitudinal groove (12) and the at least one measuring component (14) have inner and outer dimensions, respectively, along at least one direction parallel to the first direction (z), and the ratio between the outer dimension of the measuring component (14) and the inner dimension of the longitudinal groove (12) is at most 95%, preferably between 70% and 90%.

14. A heat exchange device, comprising an exchanger according to one of the preceding claims, and comprising at least one distribution pipe, which is configured to distribute one or more fluids in one or more internal spaces of at least one channel (3); at least one fluid control device, which is configured to allow, modify and / or stop the distribution of at least one fluid through the distribution pipe; a measuring device (14) configured to generate at least one leakage signal based on the change of the physical quantity; and a control device configured to modify or stop the distribution of the fluid through the distribution pipe based on the leakage signal.

15. Cryogenic air separation plant comprising at least one exchanger according to any one of claims 1 to 13 or a plant according to claim 14, in which the exchanger liquefies or cools a gaseous oxygen stream coming from the cryogenic air separation plant by heating or vaporizing liquid nitrogen or liquid argon.

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