Plate fin heat exchanger and repair method for plate fin heat exchanger

In a heat exchanger of the present invention, a release port for, in a case where a fluid flows into an internal space, releasing the fluid to an exterior is provided in a protection unit main body of each of protection units arranged on both outer sides of a heat exchange unit, and a protection unit fin plate of the protection unit has such strength that a coupling state between an outer surface of an outermost-layer partition plate and a bonding plate of the protection unit main body facing the outer surface is maintained even in a case where an inner pressure set as a design pressure for a part of the heat exchange unit constituting an outermost-layer flow passage adjacent to the protection unit is applied to the internal space of the protection unit main body of the protection unit.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a so-called plate fin heat exchanger in which a fin plate is installed, and a repair method for the same.

Description of the Related Art

Conventionally, there is a known plate fin heat exchanger (hereinafter, also simply referred to as the “heat exchanger”) described in Japanese Unexamined Patent Application Publication No. H7-167580. This heat exchanger is provided with a heat exchange unit in which a number of flow passages are aligned in laminated blocks called a core. Specifically, as shown inFIGS.15and16, a heat exchange unit100is provided with a plurality of flat plate shape tube plates102arranged in parallel at intervals, a corrugated plate shape fin plate104arranged between the tube plates102, and side bars106respectively arranged on both sides of the fin plate104so as to sandwich this fin plate104from both sides in the width direction. The side bars106arranged on both the sides of the fin plate104and the pair of tube plates102sandwiching the fin plate104and the side bare106from the upper and lower sides enclose a flow passage r accommodating the fin plate104between the side bare and the tube plate. The fin plate104is combined to the tube plates102at a plurality of positions placed at predetermined intervals between the side bare106(refer toFIG.16). Thereby, heat of a fluid flowing in the flow passage r is transmitted from the fin plate104to the tube plates102. In such a way, the heat exchange unit100has a configuration that a number of flow passages r are layered inside. A header for supplying the fluid (not shown) is welded so as to be connected to an inlet of the flow passage r.

In the heat exchanger, by letting respectively different types of fluids (such as a high-temperature fluid and a low-temperature fluid) flow in two flow passages r arranged on both sides of a predetermined tube plate102in the heat exchange unit100, heat exchange is performed between the fluids flowing through the flow passages r via the tube plate102. At this time, the fin plate104transmits heat of the fluid flowing through the flow passage r to the tube plate102, and thereby efficiency of the heat exchange is improved.

The heat exchanger is generally provided with protection units110for protecting the heat exchange unit100from impact and external force applied at the time of installation of the heat exchanger or the like. The protection units110are respectively provided on both outer sides of the heat exchange unit100in the layering direction of the flow passages r (up and down direction inFIG.16), and have internal spaces r1. Even when the impact and the external force are applied to the heat exchanger from both the outer sides in the layering direction of the flow passages r, the protection units110are only dented but prevent the inside heat exchange unit100from being dented. Each of the protection units110is formed by for example, side bars112which is the same as the side bars106of the heat exchange unit100, an outer plate114bonded to the side bars112so as to face the outermost-layer tube plate102of the heat exchange unit100, the outer plate forming the internal space r1of the protection unit110together with the side bars112and the outermost-layer tube plate102of the heat exchange unit100, and a corrugated plate shape plate (not shown) provided in the internal space r1, the plate for coupling the outermost-layer tube plate102of the heat exchange unit100and the outer plate114.

In such a heat exchanger, when a radical temperature change is generated in the fluid flowing through the flow passage r in the heat exchange unit100, the tube plates102, the fin plate104, and the side bars106are expanded or contracted. For example, in a case where a high-temperature fluid flows through the flow passage r with the heat exchange unit100in a low temperature state, the thick side bars106having large heat capacity are slowly expanded whereas the thin tube plates102and fin plate104having small heat capacity are quickly expanded in the vicinity of center in the width direction of the flow passage r. As a result, in the vicinity of the center in the width direction of the flow passage r, a gap between the tube plates102is extended more than vicinities of both ends in the width direction. Meanwhile, in a case where a low-temperature fluid flows through the flow passage r with the heat exchange unit100in a high temperature state, the tube plates102and the fin plate104are adversely quickly contracted in the vicinity of the center in the width direction of the flow passage r. Thus, the gap between the tube plates102is narrowed in comparison to the vicinities of both the ends in the width direction.

Generally, a number of (for example, hundreds of) flow passages r are layered in the heat exchange unit100. Thus, on the outer side (on the upper side and the lower side inFIG.16) from a center portion in the layering direction of the flow passages r, a deformation amount of the tube plate102from an initial state is increased. This is because deformation amounts of layers (flow passages r) are added up from the center portion to the outer side. For example, in a case where the above heat exchanger is used in a chemical plant, a radical temperature change in the fluid where the heat exchange is performed and plant start-up/stop are frequently repeatedly performed. In this case, the above deformation is repeatedly generated, and fatigue due to this repeated deformation is accumulated most in the outermost-layer tube plate102whose deformation amount is the largest. As a result, a probability that damage such as a hole or cracking is generated in the outermost-layer tube plate102is increased.

When damage such a hole or cracking is generated in the outermost-layer tube plate102, the fluid flowing through the outermost-layer flow passage r flows into the internal space r1of the protection unit110through this damaged part. For example, in a case where a liquefied gas flows into the internal space r1of the protection unit110during a low-temperature operation, a radical pressure increase is generated the internal space r1of the protection unit110at the time of heating after that and there is a fear that the protection unit110bursts. Therefore, a release hole is formed in the protection unit110and the internal space r1is open to the atmosphere so as to release the gas flowing into the internal space r1of the protection unit110.

However, in the heat exchanger with the above configuration, when damage is generated in the outermost-layer tube plate102of the heat exchange unit100, the fluid flows out from the release hole formed in the protection unit110to an exterior. Therefore, in order to continuously use this heat exchanger after that, there is a need for repair for stopping the fluid from flowing out to the exterior. For example, repair for sealing the outermost-layer flow passage r is performed in such a manner that the fluid does not flow into the outermost-layer flow passage r of the heat exchange unit100. Thereby, the fluid can be prevented from flowing into the internal space r1of the protection unit110, and as a result, the fluid can be prevented from flowing out to the exterior.

However, such repair requires a considerably long working time. Thus, a stop period of the plant or the like where the heat exchanger is used is increased, so that a production loss becomes serious.

Specifically, at the time of this repair, tasks including detaching the header by cutting a welded part of the header for supplying the fluid which is welded to the heat exchange unit100, sealing the exposed inlet of the outermost-layer flow passage r by welding, so that no fluid flows into the outermost layer flow passage r, and then welding the header for supplying the fluid again are performed. The tasks generally require as a long time as two to four weeks.

SUMMARY OF THE INVENTION

The present invention is achieved in order to solve the problems described above, and an object thereof is to, even in a case where a partition wall partitioning an outermost-layer flow passage of a heat exchange unit and an internal space of a protection unit adjacent to the flow passage is damaged and a fluid flows out from a release portion provided in the protection unit to an exterior, restore a heat exchanger into a state that no fluid flows out to the exterior and the heat exchanger has a sufficient pressure resistance performance for a short time.

In order to achieve the above object, a plate fin heat exchanger according to the present invention includes a heat exchange unit inside which a plurality of flow passages is provided so as to be layered and heat exchange is performed between fluids flowing through the flow passages, and a pair of protection units arranged on both outer sides of the heat exchange unit in the layering direction of the flow passages, the protection units for protecting the heat exchange unit, wherein the heat exchange unit has a plurality of partition walls aligned at intervals in such a manner that the flow passage is formed between the adjacent partition walls, and a heat exchange unit fin plate which is arranged in the flow passage for coupling the partition walls facing each other across the flow passage, the protection unit has a protection unit main body attached to the outermost partition wall so as to form an internal space between the protection unit main body and the outermost partition wall, and a protection unit fin plate arranged in the internal space of the protection unit main body, the protection unit fin plate for coupling an outer surface of the outermost partition wall and an inner surface of the protection unit main body facing the outer surface, a release portion for, in a case where the fluid flows into the internal space, releasing the fluid to an exterior is provided in the protection unit main body of the protection unit, and the protection unit fin plate of the protection unit has such strength that a coupling state between the outer surface of the outermost partition wall and the inner surface of the protection unit main body facing the outer surface is maintained even in a case where an inner pressure set as a design pressure for a part of the heat exchange unit constituting the outermost-layer flow passage adjacent to the protection unit is applied to the internal space of the protection unit main body of the protection unit. It should be noted that the strength of the protection unit fin plate is the concept including pressure-resistance strength of the protection unit fin plate (tensile strength in the layering direction of the flow passages), strength of a bonding portion of the protection unit fin plate to the outer surface of the outermost partition wall (bonding strength), and strength of a bonding portion of the protection unit fin plate to the inner surface of the protection unit main body (bonding strength).

In this plate fin heat exchanger, the protection unit fin plate of the protection unit has such strength that the coupling state between the outer surface of the outermost partition wall which is in contact with the protection unit fin plate and the inner surface of the protection unit main body facing the outer surface (bonding plate to be described later) is maintained even in a case where the inner pressure set as the design pressure for the part of the heat exchange unit constituting the outermost-layer flow passage adjacent to the protection unit is applied to the internal space of the protection unit. Thus, even when the inner pressure corresponding to the design pressure is applied to the internal space of the protection unit, the strength resistant against the inner pressure can be given to the protection unit. Therefore, even when the fluid flowing through the outermost-layer flow passage of the heat exchange unit flows into the internal space of the protection unit, the protection unit can be resistant against pressure of the fluid. As a result, the internal space of the protection unit can be used as part of the outermost layer flow passage of the heat exchange unit adjacent to the protection unit. Therefore, in a case where the heat exchanger is continuously used even after the outermost partition wall is damaged in the heat exchanger and the fluid flows into the internal space of the protection unit from the outermost-layer flow passage, only by bringing the release portion of the protection unit into a sealed state, the heat exchanger can be brought into a state that the heat exchanger has a sufficient pressure resistance performance while preventing the fluid from flowing out from the heat exchanger to the exterior. That is, the protection unit can be utilized as the heat exchange unit. Therefore, in this heat exchanger, the heat exchanger can be restored into a state that no fluid flows out to the exterior and the heat exchanger has a sufficient pressure resistance performance for a short time in comparison to the conventional plate fin heat exchanger requiring repair tasks of detaching the header for supplying the fluid by cutting the welded part, sealing the inlet of the outermost-layer flow passage, and welding the header for supplying the fluid again.

In the above plate fin heat exchanger, preferably, the protection unit fin plate of the protection unit has pressure-resistance strength which is not less than pressure-resistance strength of the heat exchange unit fin plate arranged in the outermost-layer flow passage adjacent to the protection unit.

With this configuration, the heat exchanger having a sufficiently safe pressure resistance performance can be formed after the repair. Specifically, the heat exchange unit fin plate generally has greater pressure-resistance strength than minimum pressure-resistance strength to resist against the design pressure in the part where the heat exchange unit fin plate is provided. Thus, according to the configuration, the protection unit fin plate has pressure-resistance strength which is not less than the heat exchange unit fin plate thereof. Therefore, with the configuration, the protection unit has a pressure resistance performance which is not less than a pressure resistance performance of the part of the heat exchange unit constituting the outermost-layer flow passage adjacent to the protection unit. As a result, the pressure resistance performance of the protection unit is a pressure resistance performance with sufficiently extra room for resisting against the inner pressure set as the design pressure for the part of the heat exchange unit constituting the outermost-layer flow passage adjacent to the protection unit. Therefore, in a case where the outermost partition wall is damaged and even in a case where the release portion of the protection unit is brought into a sealed state and the internal space of the protection unit is utilized as part of the outermost-layer flow passage of the heat exchange unit, the heat exchanger in which the protection unit exerts a sufficiently safe performance in terms of a pressure resistance performance can be formed.

In the above plate fin heat exchanger, preferably, a pressure resistance test already confirms that the protection unit has such a pressure resistance performance that the protection unit is not broken even when the inner pressure set as the design pressure for the part of the heat exchange unit constituting the outermost-layer flow passage adjacent to the protection unit is applied to the internal space of the protection unit main body of the protection unit.

With this configuration, the pressure resistance test already confirms the pressure resistance performance of the protection unit. Thus, even in a case where the fluid flows into the internal space of the protection unit from the outermost-layer flow passage and the release portion of the protection unit is brought into a sealed state, the internal space of the protection unit can be utilized as part of the outermost-layer flow passage adjacent to the protection unit at ease.

In the above plate fin heat exchanger, the release portion may include a release port formed in the protection unit main body, and a sealing material for sealing the release port in a state that the inner pressure of the internal space of the protection unit main body is not more than a predetermined pressure, whereas opening the release port in a case where the inner pressure of the internal space of the protection unit main body exceeds the predetermined pressure.

With this configuration, since the release port is sealed by the sealing material in a state that the fluid does not flow into the internal space of the protection unit main body, foreign substances, rainwater, and the like can be prevented from invading the internal space of the protection unit main body through the release port. In addition, in a case where the fluid flows into the internal space of the protection unit main body from the outermost-layer flow passage and the inner pressure of the internal space of the protection unit main body is increased, the release port can be opened so as to release the fluid from the internal space to the exterior.

It should be noted that in the above plate fin heat exchanger, preferably, a material of the heat exchange unit and the protection units is an aluminum alloy.

A repair method for a plate fin heat exchanger according to the present invention is a method for repairing the plate fin heat exchanger including a sealing step of bringing the release portion into a scaled state in a case where the outermost partition wall is damaged and a damage portion providing communication between the outermost-layer flow passage and the internal space of the protection unit main body is formed.

With this repair method for the plate fin heat exchanger, even in a case where the outermost partition wall is damaged and the fluid flows into the internal space of the protection unit from the outermost-layer flow passage of the heat exchange unit, only by performing the sealing step of bringing the release portion into a sealed state, the heat exchanger can be repaired into a state that no fluid flows out to the exterior and the heat exchanger has a sufficient pressure resistance performance. Therefore, the heat exchanger can be repaired into a continuously usable state for a short time.

In the above repair method for the plate fin heat exchanger preferably further includes an opening formation step of forming an opening for providing communication between the internal space of the protection unit main body and the outermost-layer flow passage adjacent to the internal space on the outermost partition wall.

With this configuration, in a case where the outermost partition wall is damaged, and the internal space of the protection unit is to be used as part of the outermost-layer flow passage of the heat exchange unit, the opening can be formed on the outermost partition wall so as to smoothen fluid distribution between the outermost-layer flow passage and the internal space of the protection unit.

As described above, according to the present invention, even in a case where the partition wall partitioning the outermost-layer flow passage of the heat exchange unit and the internal space of the protection unit adjacent to the flow passage is damaged and the fluid flows out from the release portion provided in the protection unit to the exterior, the heat exchanger can be restored into a state that no fluid flows out to the exterior and the heat exchanger has a sufficient pressure resistance performance for a short time.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Firstly, with reference toFIGS.1to10, a configuration of a plate fin heat exchanger according to one embodiment of the present invention will be described.

A plate fin heat exchanger1according to the present embodiment (hereinafter, also simply referred to as the “heat exchanger1”) is a heat exchanger in which heat exchange is performed between a plurality of fluids flowing inside. Specifically, as shown inFIGS.1to3, the plate fin heat exchanger1is provided with a heat exchanger main body4, a first supply header6, a first collection header8, a second supply header10, and a second collection header12.

The heat exchanger main body4is formed by a heat exchange unit22and two protection units24. In the present embodiment, a material of the heat exchange unit22and the protection units24is an aluminum alloy.

The heat exchange unit22is to perform the heat exchange between the fluids respectively flowing through a number of flow passages30(refer toFIG.3) provided inside. The heat exchange unit22has a heat exchange unit main body22aand a plurality of heat exchange unit fin plates22h.

In the heat exchange unit main body22a, a number of flow passages30are provided so as to be layered. In the present embodiment, these flow passages30are formed by a plurality of first flow passages30athrough which a first fluid F1flows and a plurality of second flow passages30bthrough which a second fluid F2flows. The first flow passages30aand the second flow passages30bare arranged so as to be alternately aligned. The heat exchange unit main body22ahas a plurality of partition plates22c, a plurality of first enclosing portions22d, and a plurality of second enclosing portions22e. It should be noted that the partition plates22care included in the concept of the “partition wall” of the present invention.

The partition plate22cis a rectangular flat plate member capable of transmitting heat between one surface and the other surface in the thickness direction thereof. The plurality of partition plates22care aligned at intervals in the same direction as the layering direction of the flow passages30in such a manner that a flow passage30is formed between the adjacent partition plates22c. The partition plates22care arranged in parallel to each other. The heat exchange is performed between the fluids flowing through the flow passages30which sandwich the partition plate22con both sides via the partition plate22c. The partition plate22chas thickness of about 1.6 mm. It should be noted that a plate having predetermined thickness within a range from 1.0 mm to 3.0 mm can be used as the partition plate22c. The partition plate22chas a configuration that thin layers of a brazing filler material are respectively formed on both surfaces of a flat plate shape base material. A material of the base material of the partition plate22cis an aluminum alloy such as A3003 in the present embodiment. However, the material is not limited to this but may be titanium, copper, stainless steel, or the like.

The plurality of first enclosing portions22dis to seal both end portions in the width direction of the plurality of first flow passages30a. The first enclosing portion22dis arranged between the adjacent partition plates22cforming the first flow passage30a. The first enclosing portion22dis formed by two first side bars22f. The two first side bars22fare arranged separately on both ends in the width direction of the pair of partition plates22csandwiching the first side bars22f, and extend in the up and down direction along both edges in the width direction of the pair of partition plates22cso as to couple the corresponding edges in the width direction of the pair of partition plates22c. Thereby, the two first side bars22fclose and enclose corresponding end portions in the width direction of the pair of partition plates22csandwiching the first side bars. It should be noted that in the present specification, the “width direction” indicates the direction which is parallel to a surface and a back surface of the partition plate22cand orthogonal to the fluid distribution direction in the first flow passage30a. The first side bar22fis bonded to the pair of partition plates22csandwiching the first side bar22fby brazing with using the brazing filler material of the partition plates22c. A material of the first side bar22fis an aluminum alloy such as A3003 in the present embodiment. However, the material is not limited to this but may be titanium, copper, stainless steel, or the like. A part between lower end portions of the two first side bars22fforming the first enclosing portion22dserves as a first introduction port30cfor introducing the first fluid F1to the first flow passage30a. A part between upper end portions of the two first side bars22fforming the first enclosing portion22dserves as a first discharge port30dfor discharging the first fluid F1from the first flow passage30a. That is, the first introduction port30cof the first flow passage30ais opened on a lower end surface of the heat exchanger main body4(heat exchange unit22), and the first discharge port30dof the first flow passage30ais opened on an upper end surface of the heat exchanger main body4(heat exchange unit22).

The plurality of second enclosing portions22eis to seal peripheries of the plurality of second flow passages30b. The second enclosing portion22eis arranged between the adjacent partition plates22cforming the second flow passage30b. The second enclosing portion22eis formed by two end bars22gand two second side bars22h.

The two end bars22gare arranged separately on upper and lower ends of the pair of partition plates22csandwiching the end bars22g, and extend in the width direction along upper and lower edges of the pair of partition plates22c. One of the end bars22garranged on the upper ends of the pair of partition plates22ccouples upper end portions of the pair of partition plates22cand closes and encloses the upper end portions. The other end bar22garranged on the lower ends of the pair of partition plates22ccouples lower end portions of the pair of partition plates22cand closes and encloses the lower end portions. The two second side bars22hare arranged separately on both the ends in the width direction of the pair of partition plates22csandwiching the second side bars22h, and extend in the up and down direction along both the edges in the width direction of the pair of partition plates22cso as to couple the corresponding ends in the width direction of the pair of partition plates22c. It should be noted that one second side bar22hamong the two second side bars22his provided so as to range from a position downward away from the upper end bar22gat a predetermined interval to a position reaching the lower end bar22g, and the other second side bar22his provided so as to range from a position upward away from the lower end bar22gat a predetermined interval to a position reaching the upper end bar22g. The end bars22gand the second side bars22hforming the second enclosing portion22eare bonded to the pair of partition plates22csandwiching the end bars22gand the second side bars22hby brazing with using the brazing filler material of the partition plates22c. A material of the end bars22gand the second side bars22his the same as the material of the first side bars22f. A space formed between an upper end of the one second side bar22hand the upper end bar22gserves as a second introduction port30cfor introducing the second fluid F2to the second flow passage30b. A space formed between a lower end of the other second side bar22hand the lower end bar22gserves as a second discharge port30ffor discharging the second fluid F2from the second flow passage30. That is, the second introduction port30eof the second flow passage30bis opened in the vicinity of an upper end portion on one side surface in the width direction of the heat exchanger main body4(heat exchange unit22), and the second discharge port30fof the second flow passage30bis opened in the vicinity of a lower end portion on the other side surface in the width direction of the heat exchanger main body4(heat exchange unit22).

The plurality of heat exchange unit fin plates22bis provided in order to improve heat exchange efficiency in the heat exchange unit22. In the present embodiment, the plurality of heat exchange unit fin plates22bincludes a plurality of heat exchange unit first fin plates22iarranged in the first flow passages30aand a plurality of heat exchange unit second fin plates22jarranged in the second flow passages30b.

The heat exchange unit first fin plate22icouples the partition plates22c(adjacent partition plates22c) facing each other across the first flow passage30ain which the heat exchange unit first fin plate is arranged. The heat exchange unit first fin plate22itransmits heat of the first fluid F1flowing through the first flow passage30ain which the heat exchange unit first fin plate is arranged respectively to the partition plates22cfacing each other across the first flow passage30a. That is, the heat exchange unit first fin plate22iensures a contact area with the first fluid F1flowing in the first flow passage30ain which the heat exchange unit first fin plate is arranged so as to improve the heat exchange efficiency of the heat exchange unit22. The heat exchange unit first fin plate22iis formed by a heat exchange unit first center fin plate22k, a heat exchange unit first supply-side fin plate (not shown), and a heat exchange unit first discharge-side fin plate (not shown).

The heat exchange unit first center fin plate22kis arranged in a center portion in the first flow passage30ain the direction in which the first flow passage30aextends (up and down direction). The heat exchange unit first supply side fin plate (not shown) is arranged on the lower side of the heat exchange unit first center fin plate22kin the first flow passage30a. The heat exchange unit first discharge-side fin plate (not shown) is arranged on the upper side of the heat exchange unit first center fin plate22kin the first flow passage30a.

The heat exchange unit first center fin plate22kis a plate member in which concave and convex parts are repeated in the width direction (arrow a direction inFIG.2) in alternate contact with the pair of partition plates22cfacing each other so as to sandwich the heat exchange unit first center fin plate22k, in other words, a corrugated plate shape member. The heat exchange unit first supply-side fin plate and the heat exchange unit first discharge-side fin plate are respectively corrugated plate shape members in which concave and convex parts are repeated in the width direction as well as the heat exchange unit first enter fin plate22k. The repetition numbers of the concave and convex parts of the fin plates forming the heat exchange unit first fin plate22iare equal to each other. The fin plates are arranged in such a manner that positions of the concave and convex parts match with each other in the width direction and the concave and convex parts extend along the flow direction of the first fluid F1(up and down direction) in the first flow passage30a.

The fin plates forming the heat exchange unit first fin plate22iare respectively formed by processing thin metal plates into a corrugated plate shape. A material of these fin plates is an aluminum alloy such as A3003 in the present embodiment. However, the material is not limited to this but may be titanium, copper, stainless steel, or the like. These fin plates are respectively combined to the pair of partition plates22cat parts which are in contact with the pair of partition plates22csandwiching these fin plates. That is, these fin plates are combined to the partition plates22cat the plurality of parts placed at intervals in the width direction in which the concave and convex parts are aligned. The fin plates and the partition plates22care combined by brazing with using the brazing filler material of the partition plates22c. Since the fin plates are thinner than the first side bars22f, the fin plates have smaller heat capacity and are easily thermally deformed.

The fin plates forming the heat exchange unit first fin plate22ialso contribute to a pressure resistance performance of a part of the heat exchange unit22constituting the first flow passage30a. Specifically, these fin plates couple and hold the pair of partition plates22csandwiching the fin plates. Thus, even when an inner pressure is applied to the first flow passage30abetween the pair of partition plates22c, the fin plates prevent the part of the heat exchange unit22constituting the first flow passage30afrom bursting, so as to improve the pressure resistance performance of the part. In detail, tensile strength of these fin plates in the layering direction of the flow passages30contributes to holding force of the adjacent partition plates22cforming the first flow passage30a, and as a result, contributes to the pressure resistance performance of the part of the heat exchange unit22constituting the first flow passage30a. The part of the heat exchange unit22constituting the first flow passage30ais designed to resist against a predetermined inner pressure set as a design pressure. That is, the part of the heat exchange unit22constituting the first flow passage30ahas such strength that the part does not burst or is not damaged even when the inner pressure set as the design pressure for the part is applied to the first flow passage30a.

The heat exchange unit second fin plate22jcouples the partition plates22cfacing each other across the second flow passage30bin which the heat exchange unit second fin plate is arranged. The heat exchange unit second fin plate22jtransmits heat of the second fluid F2flowing through the second flow passage30bin which the heat exchange unit second fin plate is arranged respectively to the partition plates22cfacing each other across the second flow passage30b. That is, the heat exchange unit second fin plate22jensures a contact area with the second fluid F2flowing in the second flow passage30bin which the heat exchange unit second fin plate is arranged so as to improve the heat exchange efficiency of the heat exchange unit22. The heat exchange unit second fin plate22jis formed by a heat exchange unit second center fin plate22p, a heat exchange unit second supply-side fin plate (not shown), and a heat exchange unit second discharge-side fin plate22r.

The heat exchange unit second center fin plate22pis arranged in a center portion in the second flow passage30bin the direction in which the second flow passage30bextends (up and down direction). The heat exchange unit second supply-side fin plate (not shown) is arranged on the upper side of the heat exchange unit second center fin plate22pin the second flow passage30b. The heat exchange unit second discharge-side fin plate22ris arranged on lower side of the heat exchange unit second center fin plate22pin the second flow passage30b.

The heat exchange unit second center fin plate22pis a corrugated plate shape member as well as the heat exchange unit first center fin plate22k. The heat exchange unit second supply-side fin plate is a corrugated plate shape member in which concave and convex parts are repeated, and is arranged in such a manner that the concave and convex parts obliquely extend toward lower end portions of corresponding concave and convex parts of the heat exchange unit second center fin plate22pfrom the second introduction port30e. The heat exchange unit second discharge-side fin plate22ris also a corrugated plate shape member in which concave and convex parts are repeated, and is arranged in such a manner that the concave and convex parts obliquely extend toward upper end portions of the corresponding concave and convex parts of the heat exchange unit second center fin plate22pfrom the second discharge port30f. Other configurations of the heat exchange unit second center fin plate22p, the heat exchange unit second supply-side fin plate, and the heat exchange unit second discharge-side fin plate22rare the same as the configurations of the heat exchange unit first center fin plate22k, the heat exchange unit first supply-side fin plate, and the heat exchange unit first discharge side fin plate.

The two protection units24are to protect the heat exchange unit22from impact and external force applied to the heat exchanger1at the time of installation of the heat exchanger1or the like. Specifically, the two protection units24are arranged separately on both outer sides of the heat exchange unit22in the layering direction of the flow passages30as shown inFIG.3. When the impact and the external force are applied, the protection unit24is dented and prevents the dent from influencing the inside heat exchange unit22. The protection unit24has a protection unit main body24aand a protection unit fin plate24b.

The protection unit main body24ais attached to the partition plate22con the outermost side in the layering direction of the flow passages30among the plurality of partition plates22cof the heat exchange unit22(hereinafter, referred to as the outermost-layer partition plate22c) so as to form an internal space32between the protection unit main body and the outermost-layer partition plate22c. The protection unit main body24ahas a bonding plate24c, four protection unit side bars24d, and an outer plate24.

The bonding plate24cis a flat plate shape member having the same structure as the partition plate22cof the heat exchange unit22. The bonding plate24cis arranged on the outer side of the outermost-layer partition plate22cof the heat exchange unit22in the layering direction of the flow passages30at an interval so as to be parallel to the outermost-layer partition plate22c.

Two protection unit side bars24damong the four protection unit side bars24dof the protection unit24are arranged separately on both ends in the width direction of both the plates22c,24cbetween the outermost-layer partition plate22cof the heat exchange unit22and the bonding plate24c, so as to couple corresponding end portions in the width direction of both the plates22c,24c. The two protection unit side bars24dextend in the up and down direction along edges in the width direction of the bonding plate24c. The remaining two protection unit side bars24dare arranged separately on the upper ends and lower ends of both the plates22c,24cbetween the outermost-layer partition plate22cof the heat exchange unit22and the bonding plate24c, so as to couple the upper ends and the lower ends of both the plates22c,24c. The remaining two protection unit side bars24dextend in the width direction along the upper end and the lower end of the bonding plate24c. The four protection unit side bars24dare respectively bonded to the outermost-layer partition plate22cand the bonding plate24cby brazing as well as the first side bars22fand the second side bars22hof the heat exchange unit22. Parts between the corresponding end portions in the width direction of the outermost-layer partition plate22cand the bonding plate24c, upper end portions, and lower end portions are closed by the protection unit side bars24drespectively provided between the portions. Thereby, the internal space32of the protection unit main body24asurrounded by both the plates22c,24cand the four protection unit side bars24dis formed between the outermost-layer partition plate22cand the bonding plate24cfacing the partition plate22c.

The outer plate24eis a rectangular flat plate member, which is overlapped on the further outer side of the bonding plate24cin the layering direction of the flow passages30, and bonded to the bonding plate24cin the above state. The outer plate24eis brazed to the bonding plate24cwith a brazing filler material on the outer surface side of the bonding plate24c. The outer plate24ehas more thickness than thickness of the partition plate22cand thickness of the bonding plate24c. Specifically, the outer plate24ehas thickness of about 5 mm. The same material as the material of the base material of the bonding plate24cand the partition plate22cis used as a material of the outer plate24e.

The protection unit fin plate24bis arranged in the internal space32of the protection unit main body24a. The protection unit fin plate24bis formed by a protection unit center fin plate24f, a protection unit upper fin plate24g, and a protection unit lower fin plate24h.

The protection unit center fin plate24fis arranged in a center portion in the up and down direction in the internal space32of the protection unit main body24a. The protection unit upper fin plate24gis arranged on the upper side of the protection unit center fin plate24fin the internal space32. The protection unit lower fin plate24his arranged on the lower side of the protection unit center fin plate24fin the internal space32.

A configuration of the protection unit center fin plate24fis the same as the configuration of the heat exchange unit first center fin plate22kin the first flow passage30a. The protection unit upper fin plate24gis a corrugated plate shape member in which concave and convex parts are repeated, and is arranged in such a manner that the concave and convex parts extend toward an upper end of the protection unit center fin plate24ffrom a lower surface of the upper protection unit side bar24d. The protection unit lower fin plate24his also a corrugated plate shape member in which concave and convex parts are repeated, and is arranged in such a manner that the concave and convex parts extend toward a lower end of the protection unit center fin plate24ffrom an upper surface of the lower protection unit side bar24d. Other configurations of the protection unit upper fin plate24gare the same as the configuration of the heat exchange unit first discharge-side fin plate, and other configurations of the protection unit lower fin plate24hare the same as the configuration of the heat exchange unit first supply-side fin plate. The protection unit center fin plate24f, the protection unit upper fin plate24g, and the protection unit lower fin plate24hare combined to the plates22c,24cat parts which are in contact with the outermost-layer partition plate22cand the bonding plate24csandwiching the fin plates. That is, the fin plates24f,24g,24hare combined to the outermost-layer partition plate22cand the bonding plate24cat the plurality of parts placed at intervals in the width direction. The fin plates and the plates are combined by brazing with using the brazing filler material of the outermost-layer partition plate22cand brazing with using the brazing filler material of the bonding plate24c.

The protection unit fin plate24hgives rigidity against the impact and the external force to the protection unit24. Specifically, when the impact and the external force are applied to the outer plate24efrom the outer side to the inner side in the layering direction of the flow passages30, the protection unit fin plate24bsupports the bonding plate24cand the outer plate24ein the internal space32, so as to reduce dents of the bonding plate24cand the outer plate24eand prevent the dents from influencing the heat exchange unit22.

The protection unit fin plate24bgives the pressure resistance performance to the protection unit24. Specifically, the protection unit fin plate24bcouples and holds the outermost-layer partition plate22cof the heat exchange unit22and the bonding plate24csandwiching the protection unit fin plate. Thus, even when an inner pressure is applied to the internal space32between the outermost-layer partition plate22cand the bonding plate24c, the protection unit fin plate prevents the protection unit main body24afrom bursting, so as to give the pressure resistance performance to the protection unit24.

Specifically, the protection unit fin plate24bof the protection unit24has pressure-resistance strength which is not less than pressure-resistance strength of the heat exchange unit fin plate22barranged in the outermost-layer flow passage30adjacent to the protection unit24. The pressure-resistance strength of a fin plate is indicated by an inner pressure applied to a space (flow passage) in which the fin plate is arranged, the maximum inner pressure with which the fin plate is not broken. Tensile strength of the protection unit fin plate24bin the layering direction of the flow passages30is set to be such strength that the protection unit fin plate24bdoes not burst or is not damaged even in a case where the inner pressure set as the design pressure is applied to the internal space32of the protection unit main body24a. In the present embodiment, as the tensile strength in the layering direction of the flow passages30, the protection unit fin plate24hof the protection unit24has strength which is not less than the tensile strength in the same direction of the heat exchange unit fin plate22barranged in the outermost-layer flow passage30adjacent to the protection unit24.

The pressure-resistance strength and the tensile strength of the protection unit fin plate24bare varied by thickness and a material of a thin plate forming the protection unit fin plate24b, an arrangement interval of a plurality of fins of the protection unit fin plate24b(parts extending in the layering direction of the flow passages30, in other words, extending substantially perpendicularly to the outermost-layer partition plate22cand the bonding plate24c), or the like. That is, with more thickness of the thin plate used for forming the protection unit fin plate24bthan thickness of a thin plate used for forming the heat exchange unit fin plate22bwhich is arranged in the outermost-layer flow passage30, the pressure-resistance strength and the tensile strength of the protection unit fin plate24bmay be made greater than the pressure-resistance strength and the tensile strength of the heat exchange unit fin plate22bwhich is arranged in the outermost-layer flow passage30. With a material of the protection unit fin plate24bhaving higher strength than a material of the heat exchange unit fin plate22b, the pressure-resistance strength and the tensile strength of the protection unit fin plate24bmay be made greater than the pressure-resistance strength and the tensile strength of the heat exchange unit fin plate22bwhich is arranged in the outermost-layer flow passage30. With a closer arrangement interval of the plurality of fins of the protection unit fin plate24bthan an arrangement interval of a plurality of fins of the heat exchange unit fin plate22b, the pressure-resistance strength and the tensile strength of the protection unit fin plate24bmay be made greater than the pressure-resistance strength and the tensile strength of the heat exchange unit fin plate22bwhich is arranged in the outermost-layer flow passage30.

The protection unit fin plate24bof the protection unit24and an outer surface of the outermost-layer partition plate22care bonded with such bonding strength that a bonding state between the protection unit fin plate24band the outer surface of the outermost-layer partition plate22cis maintained even in a case where the inner pressure set as the design pressure for the part of the heat exchange unit22constituting the outermost-layer flow passage30adjacent to the protection unit24is applied to the internal space32of the protection unit main body24aof the protection unit24. The protection unit fin plate24bof the protection unit24and an inner surface of the bonding plate24cfacing the outer surface of the outermost-layer partition plate22care bonded with such bonding strength that a bonding state between the protection unit fin plate24band the inner surface of the bonding plate24cis maintained even in a case where the inner pressure set as the design pressure for the part of the heat exchange unit22constituting the outermost-layer flow passage30adjacent to the protection unit24is applied to the internal space32of the protection unit main body24aof the protection unit24.

With the above configuration of the protection unit fin plate24b, the pressure resistance performance is given to the protection unit24. It should be noted that in order to prevent an increase in a type of members, the protection unit fin plate24b1may be a fin plate with the same configuration as the heat exchange unit fin plate22barranged in the outermost-layer flow passage30.

A plurality of release ports24m(refer toFIG.4) for, in a case where the fluid flows into the internal space32from the outermost-layer flow passage30, releasing the fluid to an exterior is provided in the protection unit main body24aof the protection unit24. The release ports24mare included in the concept of the “release portion” of the present invention. The release ports24mare formed in the protection unit main body24aso as to make the internal space32of the protection unit main body24aopen to the atmosphere. In the present embodiment, the release ports24mare through holes formed in the protection unit side bars24dof the protection unit24so as to provide communication between the internal space32of the protection unit main body24aand an external space of the heat exchanger1. In the present embodiment, the release ports24mare respectively formed in the protection unit side bar24darranged in one end portion of the protection unit main body24ain the direction in which the flow passage30of the heat exchange unit22extends, and the protection unit side bar24darranged in the other end portion.

A pressure resistance test already confirms that the protection unit24having the configuration as described above has such a pressure resistance performance that the protection unit is not broken even when the inner pressure set as the design pressure for the part of the heat exchange unit22constituting the outermost-layer flow passage30adjacent to the protection unit24is applied to the internal space32of the protection unit main body24aof the protection unit24.

Specifically, in this pressure resistance test, a connection member50a(refer toFIG.5) is attached onto an outer surface of the protection unit side bar24din which the release ports24mare formed so as to cover the release ports24m, a pipe (not shown) is connected to the connection member50a, and a fluid (a gas or a liquid) for a pressure test is introduced from this pipe into the internal space32of the protection unit main body24athrough the connection member50aand the release port24m. The connection member50ahas for example a bowl shape part formed so as to cover all the plurality of release ports24mwhich is formed in one protection unit side bar24d, and a threaded connection portion attached on the outer side of the part and connected to the pipe. It should be noted that the connection member50ais not limited to such a connection member but the threaded connection portion ofFIG.5may be replaced with a flanged connection portion as shown inFIG.6, the bowl shape part may be replaced with a plate body in which a through hole is formed as shown inFIG.7, or various other modes may be used.

After the liquid is introduced into the internal space32of the protection unit main body24a, the release ports24mother than the release port24mfrom which the liquid is introduced are closed. While confirming a supply pressure of the fluid, that is, a pressure applied to the internal space32of the protection unit main body24aby a pressure gauge on the supply side of the fluid, the pressure is boosted until the pressure reaches a set pressure of the pressure resistance test. This set pressure of the pressure resistance test is a pressure which is not less than the inner pressure set as the design pressure. In order to enhance safety, the set pressure is set to be for example a pressure which is about 1.3 to 1.5 times more than the inner pressure set as the design pressure.

When the pressure applied to the internal space32reaches the set pressure, by retaining the pressure for a fixed time, it is confirmed that the protection unit24has such a pressure resistance performance that the protection unit can resist against the set pressure. After that, the pressure is released, and in a case where the liquid is used as the fluid for the pressure test, an interior of the protection unit main body24ais dried. Finally, all the release ports24mare sealed. For example, in a case where the connection member50aprovided with the threaded connection portion is used (refer toFIG.8) or in a case where the connection member50aprovided with the flanged connection portion is used (refer toFIG.9), the release ports24mmay be sealed by closing a hole of the connection member50athrough which the fluid passes with a sealing material51such as an aluminum tape. The release ports24mmay also be scaled by cutting the threaded connection portion or the flanged connection portion in the middle and the attaching the sealing material such as an aluminum tape onto the cut surface so as to close the hole of the connection member50athrough which the fluid passes. As shown inFIG.10, the release ports24mmay also be sealed by cutting the entire connection member50aso as to expose an outer surface of a part of the protection unit side bar24dwhere the release ports24mare formed, and attaching the sealing materials51such as an aluminum tape to the outer surface so as to close the release ports24m. It should be noted that when the fluid flowing into the internal space32of the protection unit main body24ais expanded, the pressure of the internal space32is increased, and the inner pressure of the internal space32exceeds a predetermined pressure, the sealing material51may be attached with such attachment force that the sealing material is detached by the pressure so as to open the release ports24m. It should be noted that the predetermined pressure is a small pressure in comparison to the design pressure, and the attachment force of the sealing material51is such small attachment force that the sealing material51is detached by such small pressure.

The first supply header6(refer toFIG.1) is attached to the lower end surface of the heat exchanger main body4in such a manner that an internal space thereof communicates with the first introduction port30cof the first flow passage30a. A first supply pipe6afor supplying the first fluid F1is connected to the first supply header6.

The first collection header8is attached to the upper end surface of the heat exchanger main body4in such a manner that an internal space thereof communicates with the first discharge port30dof the first flow passage30a. A first discharge pipe8afor discharging the first fluid F1from the heat exchanger1is connected to the first collection header8.

The second supply header10is attached to one side surface in the width direction in an upper part of the heat exchanger main body4in such a manner that an internal space thereof communicates with the second introduction port30eof the second flow passage30b. A second supply pipe10afor supplying the second fluid F2is connected to the second supply header10.

The second collection header12is attached to a side surface on the opposite side of the one side surface in the width direction in a lower part of the heat exchanger main body4in such a manner that an internal space thereof communicates with the second discharge port30fof the second flow passage30b. A second discharge pipe12afor discharging the second fluid F2from the heat exchanger1is connected to the second collection header12. It should be noted that the internal spaces of the headers6,8,10,12do not communicate with the internal space32of the protection unit main body24a.

In the heat exchanger1of the present embodiment formed as above, for example the relatively high-temperature first fluid F1passes from the first supply pipe6ato the first supply header6and the first introduction port30cin this order and is introduced into the first flow passage30a, while for example the highly low-temperature second fluid F2passes from the second supply pipe10ato the second supply header10and the second introduction port30ein this order and is introduced into the second flow passage30b. Thereby, while the first fluid F1and the second fluid F2flow oppositely (the first fluid F1flows upward and the second fluid F2flows downward inFIG.1) in the heat exchange unit22, the heat exchange is performed between the first fluid F1in the first flow passage30aand the second fluid F2in the adjacent second flow passage30bvia the partition plate22c. The first fluid F1flowing through the first flow passage30ais discharged from the first flow passage30athrough the first discharge port30d, then collected in the first collection header8, and discharged to the exterior through the first discharge pipe8a. The second fluid F2flowing through the second flow passage30bis discharged from the second flow passage30bthrough the second discharge port30f, then collected in the second collection header12, and discharged to the exterior through the second discharge pipe12a.

During the heat exchange in the heat exchanger1, a radical temperature change may sometimes be generated in the fluid flowing through the flow passage30of the heat exchange unit22. In this case, the partition plate22cand the heat exchange unit fin plate22bwhich are thin members are quickly expanded or contracted. However, since the side bars22fwhich are thick members have large heat capacity, the side bars are expanded or contracted later than the partition plate22cand the heat exchange unit fin plate22b. For example, in a case where a high-temperature fluid abruptly flows through the flow passage30, the partition plate22cand the heat exchange unit fin plate22bare held by the side bars22f,22hand hence not easily expanded in the vicinity of the side bars22f.22hbut greatly expanded in the vicinity of center in the width direction of the flow passage30. As a result, in the vicinity of the center in the width direction of the flow passage30, a gap between the adjacent partition plates22cis extended more than vicinities of both ends in the width direction. Meanwhile, in a case where a low-temperature fluid abruptly flows through the flow passage30, the partition plate22cand the heat exchange unit fin plate22bare greatly contracted in the vicinity of the center in the width direction of the flow passage30, and the gap between the adjacent partition plates22cis narrowed in comparison to the vicinities of both the ends in the width direction.

In a case where the heat exchanger1is used for an unstable operation, supply of the fluid to the heat exchanger1and stop of the supply are repeatedly performed. In this case, the same thermal deformation as above is also repeatedly generated in the heat exchange unit22.

In the heat exchange unit22, a number of flow passages30are layered. Thus, from a center portion toward the outer side in the layering direction of the flow passages30(toward the upper side and the lower side inFIG.3), deformation amounts of the partition plates22cin layers are added up, so that a deformation amount of the partition plate22cfrom an initial state is increased. In a case where the heat exchanger1is used for an unstable operation, the above thermal deformation is repeatedly generated. Thus, metal fatigue due to the above deformation is accumulated in the partition plate22c, and this metal fatigue is accumulated most in the outermost-layer partition plate22cwhose deformation amount is the largest. As a result, a possibility that damage such as breaking or cracking is generated in the outermost-layer partition plate22cis high. Particularly, since large bending deformation is generated in parts of the outermost-layer partition plate22cin the vicinity of the side bars22f,22hin comparison to other parts, damage is easily generated. In a case where damage such as breaking or cracking is generated in the outermost-layer partition plate22c, the fluid flows into the internal space32of the protection unit main body24afrom the outermost-layer flow passage30through the damaged parts. This fluid flowing into the internal space32of the protection unit main body24acan be emitted to the exterior through the release ports24m. For example, even in a case where a low-temperature liquefied gas flows into the internal space32of the protection unit main body24afrom the outermost-layer flow passage30, then the heat exchanger1is heated, and the liquefied gas is gasified and abruptly expanded, the sealing material51closing the release ports24mis pushed away by a pressure of the gas and the release ports24mare opened. Thus, the gas is emitted from the internal space32of the protection unit main body24ato the exterior through the release ports24m. As a result, burst or damage of the protection unit main body24ais avoided.

However, in this state, the fluid flowing through the outermost-layer flow passage30always flows into the internal space32of the protection unit main body24athrough the damaged parts of the outermost-layer partition plate22c, and flows out from the internal space32to the exterior through the release ports24m. Therefore, in order to continuously use the heat exchanger1, there is a need for repairing the heat exchanger1for stopping the fluid from flowing out from the internal space32of the protection unit main body24ato the exterior. It should be noted that a state that the outermost-layer partition plate22cis damaged and the fluid flows out from the internal space32of the protection unit main body24ato the exterior through the release ports24mcan be detected by for example a gas detector. In a case where the fluid has a highly low temperature, ice coating is generated on an outer surface of the heat exchanger main body4. Thus, the above state can also be detected by the ice coating.

Next, a repair method for the heat exchanger1will be described.

Firstly, the supply of the fluid to the flow passage30of the heat exchange unit22is stopped. The release ports24mfrom which the fluid flows out are sealed (sealing step). In the present embodiment, the release ports24mare sealed by welding.

Further, in the repair method, an opening34(refer toFIG.12) is formed on the outermost-layer partition plate22con the side of the protection unit24where the closed release ports24mare formed (opening formation step). In this opening formation step, firstly, a hole34a(refer toFIG.11) is formed on the heat exchanger main body4by a drill. At this time, the hole34aranges over the outermost-layer partition plate22con the side of the protection unit24where the sealed release ports24mare formed and the protection unit side bar24dand the second side bar22hsandwiching the partition plate22cin the heat exchange main body4, and the hole34ais formed so as to pass through the side bars24d,22hfrom the outer side of the partition plate22cand the side bars24d,22htoward the inner side in the width direction of the flow passage30. By welding and sealing a part of this hole34aopened on the outer side of the heat exchanger main body4, the opening34providing communication between the outermost-layer flow passage30and the internal space32of the protection unit main body24ainside the heat exchanger main body4is formed. It should be noted that the opening34has a section area which is the same as or more than a section area of a flow passage in a supply pipe (the second supply pipe10ain the present embodiment) connected to the outermost-layer flow passage30.

In the heat exchanger1repaired in such a way, even when the fluid supplied to the outermost-layer flow passage30flows out to the internal space32of the protection unit main body24a, due to the sealed release ports24mprovided in the protection unit main body24a, the fluid is prevented from flowing out from the internal space32of the protection unit main body24ato the exterior. In this repaired heat exchanger1, the opening34providing communication between the outermost-layer flow passage30and the internal space32of the protection unit main body24ais formed. Thus, fluid distribution between the outermost-layer flow passage30and the internal space32of the protection unit main body24ais smoothened.

In the present embodiment, the protection unit fin plate24bof the protection unit24has such strength that the coupling state between the outermost-layer partition plate22cand the bonding plate24cis maintained even in a case where the inner pressure set as the design pressure for the part of the heat exchange unit22constituting the outermost-layer flow passage30adjacent to the protection unit24is applied to the internal space32of the protection unit main body24aof the protection unit24. Therefore, even when the inner pressure corresponding to the design pressure is applied to the internal space32of the protection unit main body24aof the protection unit24, the strength resistant against the inner pressure can be given to the protection unit24. That is, even when the fluid flowing through the outermost-layer flow passage30of the heat exchange unit22flows into the internal space32of the protection unit24, the protection unit24has strength resistant against the pressure of the fluid. Thus, the internal space32of the protection unit24can be used as part of the outermost-layer flow passage30adjacent to the protection unit24. Therefore, after the outermost-layer partition plate22cis damaged in the heat exchanger1and the fluid flows into the internal space32of the protection unit24from the outermost-layer flow passage30, only by sealing the release ports24mof the protection unit24, the heat exchanger1can be brought into a state that the heat exchanger has a sufficient pressure resistance performance while preventing the fluid from flowing out from the heat exchanger1to the exterior. Accordingly, in the present embodiment, the heat exchanger1can be restored into a state that no fluid flows out to the exterior and the heat exchanger has a sufficient pressure resistance performance for a short time in comparison to the conventional plate fin heat exchanger requiring repair tasks of detaching the header for supplying the fluid by cutting the welded part, sealing the inlet of the outermost-layer flow passage, and welding the header for supplying the fluid again. It should be noted that the opening34for providing communication between the internal space32of the protection unit main body24aand the outermost-layer flow passage30adjacent to the internal space32is formed upon the repair of the heat exchanger1in the present embodiment. However, even when a time required for forming this opening34is added, the heat exchanger1can be restored for a short time in comparison to the repair tasks of the conventional plate fin heat exchanger.

In the present embodiment, the protection unit fin plate24bof the protection unit24and the outer surface of the outermost-layer partition plate22care bonded with such bonding strength that the bonding state between the protection unit fin plate24hand the outer surface of the outermost-layer partition plate22cis maintained even in a case where the inner pressure set as the design pressure for the part of the heat exchange unit22constituting the outermost-layer flow passage30adjacent to the protection unit24is applied to the internal space32of the protection unit main body24aof the protection unit24, and the protection unit fin plate24bof the protection unit24and the inner surface of the bonding plate24cfacing the outer surface of the outermost-layer partition plate22care bonded with such bonding strength that the bonding state between the protection unit fin plate24band the inner surface of the bonding plate24cis maintained even in a case where the inner pressure set as the design pressure is applied to the internal space32of the protection unit main body24aof the protection unit24. Therefore, sufficient bonding strength is respectively given to a bonding portion between the protection unit fin plate24band the outer surface of the outermost-layer partition plate22cand a bonding portion between the protection unit fin plate24band the inner surface of the bonding plate24c, so that the coupling state of the protection unit fin plate24bwith the outer surface of the outermost-layer partition plate22cand the inner surface of the bonding plate24ccan be more reliably maintained.

In the present embodiment, the tensile strength of the protection unit fin plate24bof the protection unit24in the layering direction of the flow passages30is strength which is not less than the tensile strength in the same direction of the heat exchange unit fin plate22barranged in the outermost-layer flow passage30adjacent to the protection unit24. Thus, the protection unit24has a pressure resistance performance which is not less than the pressure resistance performance of the part of the heat exchange unit22constituting the outermost-layer flow passage30adjacent to the protection unit24. Therefore, the pressure resistance performance of the protection unit24is a pressure resistance performance with sufficiently extra room for resisting against the inner pressure set as the design pressure for the part of the heat exchange unit22constituting the outermost-layer flow passage30adjacent to the protection unit24. Accordingly, in a case where the outermost-layer partition plate22cof the heat exchange unit22is damaged and even in a case where the release ports24mof the protection unit24adjacent to the outermost-layer partition plate22care sealed and the internal space32of the protection unit24is utilized as part of the outermost-layer flow passage30of the heat exchange unit22, the heat exchanger1in which the protection unit24exerts a sufficiently safe pressure resistance performance can be formed.

In the present embodiment, the pressure resistance test already confirms that the protection unit24has such a pressure resistance performance that the protection unit is not broken even when the inner pressure set as the design pressure for the part of the heat exchange unit22constituting the outermost-layer flow passage30adjacent to the protection unit24is applied to the internal space32of the protection unit24. In the conventional plate fin heat exchanger, it is not supposed that in a case where the outermost-layer partition wall is damaged, repair of sealing the release ports is performed so as to utilize the internal space of the protection unit as part of the outermost-layer flow passage, and hence the pressure resistance performance of the protection unit is not confirmed by a test of an actual product. Meanwhile, in the present embodiment, the pressure resistance performance of the protection unit24is already confirmed as above. Thus, in a case where the release ports24mof the protection unit24are sealed after the outermost-layer partition plate22cis damaged, the internal space32of the protection unit24can be utilized as part of the outermost-layer flow passage30adjacent to the protection unit24at ease.

In the present embodiment, since the release ports24mare sealed by the scaling material51in a state that the fluid does not flow into the internal space32of the protection unit main body24a, foreign substances, rainwater, and the like can be prevented from invading the internal space32of the protection unit main body24athrough the release ports24m. In addition, in a case where the fluid flows into the internal space32of the protection unit main body24afrom the outermost-layer flow passage30and the inner pressure of the internal space32of the protection unit main body24ais increased, the release ports24mcan be opened so as to release the fluid from the internal space32to the exterior.

It should be noted that the embodiment disclosed herein is thought to be not restriction but only an example in all aspects. The scope of the present invention is indicated not by the above description of the embodiment but by the claims, and further includes equivalent meanings to the claims and all modifications within the scope.

For example, in the above embodiment, one layer of protection unit24is provided on the outermost-layer partition plate22cof the heat exchange unit22. However, two layers of protection units may be provided on the outermost-layer partition plate22c. Both the two layers of protection units are preferably formed as the same as the one layer of protection unit24of the above embodiment so as to have a pressure resistance performance.

The protection unit fin plate24bof the protection unit24may have at least such strength that the coupling state between the outermost-layer partition plate22cand the bonding plate24cof the protection unit main body24afacing the partition plate22cis maintained even in a case where the inner pressure set as the design pressure for the part of the heat exchange unit22constituting the outermost-layer flow passage30adjacent to the protection unit24is applied to the internal space32of the protection unit main body24aof the protection unit24. That is, the pressure-resistance strength of the protection unit fin plate24bof the protection unit24and the tensile strength of the protection unit fin plate24bof the protection unit24in the layering direction of the flow passages30are not necessarily not less than the pressure-resistance strength of the heat exchange unit fin plate22barranged in the outermost-layer flow passage30adjacent to the protection unit24and the tensile strength in the layering direction of the flow passages30. Specifically, the pressure-resistance strength and the tensile strength of the protection unit fin plate24bof the protection unit24may be pressure-resistance strength and tensile strength resistant against the inner pressure set as the design pressure for the part constituting the outermost-layer flow passage30adjacent to the protection unit24and may be smaller than the pressure-resistance strength and the tensile strength of the heat exchange unit fin plate22barranged in the outermost-layer flow passage30adjacent to the protection unit24.

In the above embodiment, the heat exchanger in which the heat exchange is performed between two types of fluids F1, F2is described as an example. However, the present invention can be applied to a heat exchanger in which heat exchange is performed between three or more types of fluids.

The release portion of the present invention is not limited to the release ports24msealed by the sealing material51as shown in the above embodiment. For example, as shown inFIG.13, a release portion46may be formed by a discharge pipe42connected to the internal space32of the protection unit main body24aand a safety valve44provided in the discharge pipe42. With this configuration, when the fluid flows into the internal space32of the protection unit main body24a, the heat exchanger1is heated, this fluid is expanded, and the inner pressure of the internal space32of the protection unit main body24abecomes not less than a fixed pressure, the fluid can be released from the internal space32of the protection unit main body24ato the exterior through the discharge pipe42and the safety valve46.

The release ports24mare not necessarily scaled by the sealing material51but may be always open to the atmosphere. The release ports may be respectively formed on the pair of protection unit side bars24dfacing each other in the width direction. One release port may be provided on each of the pair of protection unit side bars24dfacing each other.

The protection unit lower fin plate may be formed in such a manner that the concave and convex parts obliquely extend as well as the heat exchange unit second discharge-side fin plate22r, and the protection unit upper fin plate may be formed in such a manner that the concave and convex parts obliquely extend as well as the heat exchange unit second supply-side fin plate. In this case, preferably, the release ports are formed at a point facing an end portion of the protection unit lower fin plate in one protection unit side bar24damong the pair of protection unit side bars24dfacing each other in the width direction, and the release ports are formed at a point facing an end portion of the protection unit upper fin plate in the other protection unit side bar24d.

Positions where the release ports are provided in the protection unit main body24aare arbitrary as long as the fluid flowing into the internal space32of the protection unit main body24acan be efficiently released. For example, in the above embodiment, the release ports24mare respectively provided in the protection unit side bars24darranged in one end portion and the other end portion of the protection unit main body24ain the longitudinal direction of the flow passages30. However, the release ports may be respectively provided in the protection unit side bars24darranged in one end portion and the other end portion in the width direction of the protection unit main body24a. It should be noted that in order to efficiently release the fluid, the release ports are preferably arranged at two points of the protection unit main body24awhich are away from each other.

A shape of the release ports is arbitrary and appropriately set in accordance with the positions where the release ports are provided and various conditions. For example, a part of the protection unit side bar24dranging over a particular range in the longitudinal direction may be omitted all, and the omitted part may serve as a release port. Specifically, as shown inFIG.14, by making two protection unit side bars24dextending in the width direction of the protection unit24as short as not reaching the protection unit side bars24dextending in the longitudinal direction of the protection unit24, spaces may be formed between end portions of the protection unit side bars24dextending in the width direction and the protection unit side bars24dextending in the longitudinal direction, so that the spaces may serve as release ports24n. In this case, the release ports24nare preferably closed by the scaling materials51so that the outside of the release ports24nis covered.

In the above embodiment, the outer plate24eis attached to the protection unit side bars24dand the protection unit fin plate24bvia the bonding plate24cin the protection unit24. However, the outer plate may be directly attached to the protection unit side bars24dand the protection unit fin plate24b. In this case, a layer of brazing filler material is formed on one surface of the outer plate, and the outer plate may be brazed to the protection unit side bars24dand the protection unit fin plate24bwith using the brazing filler material.

In the above embodiment, the example that the protection unit fin plate24bis formed by the protection unit center fin plate24f, the protection unit upper fin plate24g, and the protection unit lower fin plate24his shown. However, the configuration of the protection unit fin plate is not limited to such an example. That is, the protection unit fin plate may be formed by a single fin plate or may be formed by two or four or more fin plates.