Heater core with a film heater soldered to a heat exchanger, and a method of making a heater core

Abstract

A heater core is made by providing a heat exchanger having a plurality of flow plates. Peripheral edges of the flow plates define a heat exchanger peripheral surface. Flux is provided between a solder material and the heat exchanger peripheral surface, and between the solder material and a film heater positioned to heat flow paths of the heat exchanger. The film heater, solder material and inner and outer quantities of flux are pressed together to form an intermediate assembly. The intermediate assembly is heated by exposure to heated air or by supplying electrical power to the film heater, to heat the solder material and the flux, and thereby solder the film heater to the heat exchanger peripheral surface, without melting the heat exchanger or damaging the film heater. The intermediate assembly is cooled to solidify the solder material and the inner and outer quantities of flux.

Description

HEATER CORE WITH A FILM HEATER SOLDERED TO A HEAT EXCHANGER, AND A METHOD OF MAKING A HEATER CORECROSS-REFERENCES TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Provisional Patent Application 63 / 619,014, filed November January 9, 2024, and titled "SOLDERING PROCESS FOR HEATER TO HEAT EXCHANGER", the contents of which are incorporated herein by reference in their entirety, where permitted.FIELD OF THE DISCLOSURE

[0002] The present disclosure relates to a heater core having a heat exchanger and a film heater that is joined, in a mechanical and thermally conductive manner, to flow plates of the heat exchanger. The disclosure also relates to a method of making such a heater core.BACKGROUND

[0003] Electric vehicles and power systems with battery packs are known to have a thermal management system to control the operating temperature of the battery pack. Such a thermal management system may include a coolant-refrigerant heat exchanger to transfer heat between a coolant fluid used to cool the battery pack, and a refrigerant fluid. International patent application publication WO 2023 / 060352 A1 (Litens Automotive Partnership; 20 April 2023) discloses such a coolant-refrigerant heat exchanger that also includes a heater that is positioned to heat the coolant and the refrigerant therein. The coolant-refrigerant heat exchanger is made by disposing flow plates in a stack to define a coolant flow path and a refrigerant flow path between mutually facing adjacent flow pates. Flange portions of the adjacent flow pates are mated to one another and brazed together in a sealed manner. The joined flow plates are processed (e.g., by grinding, machining or milling) to remove portions of their outermost edges and generate a contiguous heat exchanger surface. A peripheral edge heater is then applied to the heat exchanger surface, by use of double-sided tape on the mating surface of the peripheral edge heater, or by printing the peripheral edge heater as a film on the heat exchanger surface.SUMMARY OF THE DISCLOSURE

[0004] There remains a need in the art for an economical, efficient, and convenient method of making of a heater core having a heat exchanger and a film heater that is joined, in a mechanically robust and thermally conductive manner, to flow plates of the heat exchanger.

[0005] In one aspect, the present disclosure relates to a method of making a heater core. The method comprises: providing a heat exchanger including a plurality of flow plates each having a plurality of faces and a peripheral edge, wherein the plurality of flow plates are sealingly joined together to define a first flow path for a first fluid through the heat exchanger and a second flow path for a second fluid through the heat exchanger, wherein the first flow path and the second flow path are positioned in order to transfer heat from one of the first fluid and the second fluid to the other of the first fluid and the second fluid, wherein the peripheral edges of the plurality of flow plates together define a heat exchanger peripheral surface, wherein the heat exchanger has a heat exchanger melting temperature; providing a film heater that is positioned to heat both the first flow path and the second flow path of the heat exchanger, wherein the film heater has a film heater damage threshold temperature; providing at least one intermediate layer between the film heater and the heat exchanger peripheral surface, wherein the at least one intermediate layer comprises a solder material; pressing the film heater, and the at least one intermediate layer against the heat exchanger peripheral surface, so as to form an intermediate assembly; heating the at least one intermediate layer so as to solder the film heater to the heat exchanger peripheral surface at a soldering temperature that is lower than the heat exchanger melting temperature and lower than the film heater damage threshold temperature; and cooling the intermediate assembly after reaching the soldering temperature so as to solidify the at least one intermediate layer.

[0006] In embodiments of the method, the solder material is provided by a solder member in the form of a plate .

[0007] In embodiments of the method, the at least one intermediate layer further comprises at least one quantity of flux comprising at least one of: an inner quantity of flux at an interface of the solder material and the heat exchanger peripheral surface; and an outer quantity of flux at an interface of the solder material and the film heater.In embodiments of the method, the at least one quantity of flux comprises potassium tetrafluoro aluminate, or cesium tetrafluoro aluminate, or a mixture of potassium tetrafluoro aluminate and cesium tetrafluoro aluminate.

[0008] In embodiments of the method, the method further comprises: removing oxygen from an ambient environment of the intermediate assembly prior to and / or during the heating of the at least one intermediate layer step. In embodiments of the method, the removing oxygen step includes supplying an inert gas and / or a reducing gas to an enclosure in which the intermediate assembly is positioned. In embodiments of the method, the film heater has a first heater terminal and a second heater terminal. The method further comprises connecting a first power source terminal to the first heater terminal, and connecting a second power source terminal to the second heater terminal. The method further comprises positioning a first inert and / or reducing gas outlet so as to direct the inert gas and / or the reducing gas towards the first power source terminal and the first heater terminal, and positioning a second inert and / or reducing gas outlet so as to direct the inert gas and / or the reducing gas towards the second power source terminal and the second heater terminal. The supplying step includes supplying the inert gas and / or the reducing gas to the first and second inert and / or reducing gas outlets so as to cool the first power source terminal and the first heater terminal, and the second power source terminal and the second heater terminal during the heating step. The heating of the at least one intermediate layer step includes supplying electrical power, via the first and second power source terminals, to the film heater to heat the film heater.

[0009] In embodiments of the method, the heating of the at least one intermediate layer step includes exposing the intermediate assembly to heated air.

[0010] In embodiments of the method, the heating of the at least one intermediate layer step includes supplying electrical power to the film heater to heat the film heater.

[0011] In embodiments of the method, the heating of the at least one intermediate layer step includes: a preheat phase that includes heating the intermediate assembly to a preheat phase temperature for a preheat phase duration, wherein the preheat phase temperature is sufficient to melt the at least one quantity of flux; and after the preheat phase, a peak phase that includes heating the intermediate assembly to a peak phase temperature for a peak phase duration, wherein the peak phasetemperature is greater than the preheat phase temperature and is sufficient to melt the solder material and the at least one quantity of flux. In embodiments of the method, the heating of the at least one intermediate layer step further includes: before the preheat phase, a plateau phase that includes heating the intermediate assembly to a plateau phase temperature for a plateau phase duration, wherein the plateau phase temperature is less than the preheat phase temperature and insufficient to melt the solder material and the at least one quantity of flux.

[0012] In embodiments of the method, the pressing step is performed to apply between about 25 kPa to about 150 kPa of pressure to the intermediate assembly.

[0013] In embodiments of the method, the pressing step includes compressing the film heater, the at least one intermediate layer, and the heat exchanger peripheral surface between at least a first clamp jaw and a second clamp jaw. In embodiments of the method, the compressing the film heater comprises at least one biasing member that biases the first clamp jaw toward the second clamp jaw. In embodiments of the method, at least one of the first clamp jaw and the second clamp jaw comprises a retaining member and a plurality of platens that are movable, independently of each other, relative to the retaining member to apply compressive forces to the film heater, the at least one intermediate layer and the heat exchanger peripheral surface. In embodiments of the method, the compressing the film heater comprises, for each one of the plurality of platens, an associated biasing member biasing the one of the platens toward the film heater, the at least one intermediate layer and the heat exchanger peripheral surface. In embodiments of the method, the method further comprises providing at least one protective member between the intermediate assembly and at least one of the first and second clamp jaws. In embodiments of the method, the at least one protective member comprises a silica fabric sheet.

[0014] In embodiments of the method, the providing the heat exchanger step comprises forming the heat exchanger by: arranging the plurality of flow plates in a stack and pressing the plurality of flow plates against each other in the stack to define the first flow path for the first fluid, the second flow path for the second fluid, and the peripheral heat exchanger surface of the heat exchanger to be formed; providing a braze material at junctions of the plurality of flow plates with one another; during the heating of the at least one intermediate layer step, heating the braze material so as tobraze the brazing material to each other at a brazing temperature that is lower than the heat exchanger melting temperature and lower than the film heater damage threshold temperature; and cooling the braze material after reaching the brazing temperature so as to solidify the braze material, whereupon the plurality of flow plates are sealingly joined together to form the heat exchanger. In embodiments of the method, the braze material forms at least part of each of the plurality of flow plates. In embodiments of the method, the braze material forms a cladding layer material of each of the plurality of flow plates that covers a core layer material of each of the plurality of flow plates, wherein a melting temperature of cladding layer material is lower than a melting temperature of the core layer material. In embodiments of the method, the braze material partly or wholly comprises a material of the at least one intermediate layer. In embodiments of the method, the heating of the at least one intermediate layer step is performed by exposing the intermediate assembly to the heated air, and the heating of the braze material step is performed, at least partly, by exposing the braze material to the heated air. In embodiments of the method, the heating of the at least one intermediate layer step is performed by supplying electrical power to the film heater to heat the film heater, and the heating of the braze material step is performed, at least partly, by exposing the braze material to the heat of the film heater.

[0015] In another aspect, the present disclosure relates to a heater core. The heater core comprises: a heat exchanger including a plurality of flow plates each having a plurality of faces and a peripheral edge, wherein the plurality of flow plates are sealingly joined together to define a first flow path for a first fluid through the heat exchanger and a second flow path for a second fluid through the heat exchanger, wherein the first flow path and the second flow path are positioned in order to transfer heat from one of the first fluid and the second fluid to the other of the first fluid and the second fluid, wherein the peripheral edges of the plurality of flow plates together define a heat exchanger peripheral surface, wherein the heat exchanger has a heat exchanger melting temperature; a film heater that is positioned to heat both the first flow path and the flow path of the heat exchanger, wherein the film heater has a film heater damage threshold temperature; at least one intermediate layer comprising a solder material; wherein the film heater is soldered to the heat exchanger peripheral surface by the at least one intermediate layer, and wherein the at least one intermediate layer has at least one intermediate layer melting temperature that is lowerthan the heat exchanger melting temperature and lower than the film heater damage threshold temperature.

[0016] In embodiments of the heater core, when electrical power is supplied to the film heater, the film heater has an operating temperature that is greater than the at least one intermediate layer melting temperature.

[0017] In embodiments of the heater core, the at least one intermediate layer further comprises at least one quantity of flux comprising at least one of: an inner quantity of flux at an interface of the solder material and the heat exchanger peripheral surface; and an outer quantity of flux at an interface of the solder material and the film heater.BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The foregoing and other aspects of the invention will be better appreciated with reference to the attached drawings, as follows.

[0019] Figures 1 to 6 are views of an embodiment of a heater core of the present disclosure, in which Figure 1 is a front-left perspective view, Figure 2 is a rear-right perspective view, Figure 3 is a front view, Figure 4 is a left-side view, Figure 5 is an exploded perspective view, and Figure 6 is a schematic sectional view of a portion of the heater core.

[0020] Figure 7 is a perspective view of an embodiment of a flow plate of the heat exchanger of the heater core shown in Figures 1 to 6.

[0021] Figure 8 is a sectional side view of a portion of a plurality of flow plates of the heat exchanger of the heater core shown in Figures 1 to 6.

[0022] Figure 9 is a phase diagram of embodiments of zinc-aluminum alloys that may be used to make the solder material of the heater core of the present disclosure 6.

[0023] Figures 10A and 10B are collectively a flow chart showing an embodiment of a method of the present disclosure for making a heater core of the present disclosure. Figure 10C is a flow chart showing the forming of a heat exchanger whichmay be used in an embodiment of the step of providing a heat exchanger in the method shown in Figures 10A and 10B.

[0024] Figures 11 to 13 show stages of an embodiment of a method of the present disclosure for making a heater core. Figure 11 shows the heat exchanger and the film heater before being pressed in a jig. Figure 12 shows the jig pressing the heat exchanger, the film heater and other components together to form an intermediate assembly. Figure 13 shows the intermediate assembly being heated in a furnace.

[0025] Figure 14 is a chart showing an example of a temperature profile over time of an intermediate assembly, the atmosphere internal to a furnace, and an ambient environment external to the furnace, during heating and cooling of an intermediate assembly in the furnace to make a heater core.

[0026] Figure 15 is a chart showing another example of the temperature profile over time of the intermediate assembly, during heating and cooling of an intermediate assembly in a furnace to make a heater core.

[0027] Figures 16 to 19 show stages of another embodiment of a method of the present disclosure for making a heater core. Figure 16 shows the heat exchanger and the film heater before being pressed in a jig with a header attached thereto. Figure 17 shows a jig pressing the heat exchanger, the film heater and other components together to form an intermediate assembly. Figure 18 shows a portion of Figure 17 at an enlarged scale with a cut-away view of the header. Figure 19 shows the intermediate assembly being heated in an enclosure by supply of electrical power to the first and second power source terminals, while supplying an inert and / or reducing gas to the enclosure.

[0028] Figure 20 is a chart showing an example of power, voltage and current over time of electrical power supplied to a film heater to heat the intermediate assembly in an enclosure, and temperature profiles overtime of an intermediate assembly, an inert and / or reducing gas, and an ambient environment external to the enclosure while the intermediate assembly is heated to make a heater core.

[0029] Figures 21 to 23 show views of another embodiment of a jig of the present disclosure used to press together the heat exchanger, film heater and other components of the heater core to form an intermediate assembly thereof. Figure 21 isa perspective view. Figure 22 is an exploded perspective view of a portion of Figure 21 . Figure 23 is another exploded perspective view of a portion of Figure 21 .DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0030] INTERPRETATION

[0031] For simplicity and clarity of illustration, where considered appropriate, reference numerals may be repeated among the Figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the embodiment or embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein may be practiced without these specific details. In other instances, well-known methods, procedures and components have not been described in detail so as not to obscure the embodiments described herein. It should be understood at the outset that, although exemplary embodiments are illustrated in the figures and described below, the principles of the present disclosure may be implemented using any number of techniques, whether currently known or not. The present disclosure should in no way be limited to the exemplary implementations and techniques illustrated in the drawings and described below.

[0032] Various terms used throughout the present description may be read and understood as follows, unless the context indicates otherwise: "or" as used throughout is inclusive, as though written "and / or"; singular articles and pronouns as used throughout include their plural forms, and vice versa; similarly, gendered pronouns include their counterpart pronouns so that pronouns should not be understood as limiting anything described herein to use, implementation, performance, etc. by a single gender; "exemplary" should be understood as "illustrative" or "exemplifying" and not necessarily as "preferred" over other embodiments. Further definitions for terms may be set out herein; these may apply to prior and subsequent instances of those terms, as will be understood from a reading of the present description.

[0033] It will also be noted that the use of the term "a" or "an" will be understood to denote "at least one" in all instances unless explicitly stated otherwise or unless it would be understood to be obvious that it must mean "one". The phrase "at least one of" is understood to be one or more. The phrase "at least one of... and..." is understoodto mean at least one of the elements listed or a combination thereof, if not explicitly listed. For example, "at least one of A, B, and C" is understood to mean A alone or B alone or C alone or a combination of A and B or a combination of A and C or a combination of B and C or a combination of A, B, and C.

[0034] The term "comprising" and its derivatives, as used herein, are intended to be open ended terms that specify the presence of the stated features, elements, components, groups, integers, and / or steps, but do not exclude the presence of other unstated features, elements, components, groups, integers and / or steps. The foregoing also applies to words having similar meanings such as the terms, "including", "having" and their derivatives. It will be understood that any embodiments described as "comprising" certain components may also "consist of' or "consist essentially of" these components, wherein "consisting of" has a closed-ended or restrictive meaning and "consisting essentially of" means including the components specified but excluding other components except for components added for a purpose other than achieving the technical effects described herein.

[0035] It will be understood that any component defined herein as being included may be explicitly excluded from the claimed invention by way of proviso or negative limitation, such as any specific components or method steps, whether implicitly or explicitly defined herein.

[0036] In addition, all ranges given herein include the end of the ranges and also any intermediate range points, whether explicitly stated or not.

[0037] Terms of degree such as "substantially", "about" and "approximately" as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. These terms of degree should be construed as including a deviation of at least ±5% of the modified term if this deviation would not negate the meaning of the word it modifies.

[0038] The abbreviation, "e.g." is derived from the Latin exempli gratia, and is used herein to indicate a non-limiting example. Thus, the abbreviation "e.g." is synonymous with the term "for example." The word "or" is intended to include "and" unless the context clearly indicates otherwise.

[0039] "Attached", as used herein, in describing the relationship between two connected parts includes the case in which the two connected parts are "directly attached" with the two connected parts being in contact with each other, and the case in which the connected parts are "indirectly attached" and not in contact with each other but connected by one or more intervening other part(s) between.

[0040] Any reference to upper, lower, top, bottom or the like is intended to refer to an orientation of a particular element during use of the claimed subject matter and not necessarily to its orientation during shipping or manufacture. The upper surface of an element, for example, can still be considered its upper surface even when the element is lying on its side.

[0041] Modifications, additions, or omissions may be made to the systems, apparatuses, and methods described herein without departing from the scope of the disclosure. For example, the components of the systems and apparatuses may be integrated or separated. Moreover, the operations of the systems and apparatuses disclosed herein may be performed by more, fewer, or other components and the methods described may include more, fewer, or other steps. Additionally, steps may be performed in any suitable order. As used in this document, "each" refers to each member of a set or each member of a subset of a set.

[0042] The embodiments of the disclosures described herein are exemplary (e.g., in terms of materials, shapes, dimensions, and constructional details) and do not limit by the claims appended hereto and any amendments made thereto. Persons skilled in the art will appreciate that there are yet more alternative implementations and modifications possible, and that the following examples are only illustrations of one or more implementations. The scope of the invention, therefore, is only to be limited by the claims appended hereto and any amendments made thereto.

[0043] Unless otherwise explained, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0044] HEATER CORE

[0045] Figures 1 to 6 show an embodiment of a heater core 2 that includes a heat exchanger 4, film heaters 40a, 40b, and solder members 50a, 50b.

[0046] The heat exchanger 4 may be used to transfer heat between a first fluid and a second fluid that flow through the heat exchanger 4, while the film heaters 50a, 50b may be used to heat the first fluid and the second fluid in the heat exchanger. In a non-limiting example, the first fluid may be a coolant, and the second fluid may be a refrigerant in a thermal management system for a battery pack of an electric vehicle ora power system. For illustrative purposes, Table I sets out non-limiting specifications of a heater core 2 for such applications. The width (W), depth (D) and height (H) dimensions of the heat exchanger 4, excluding the end cover plate 20 thereof, are shown in Figures 3 and 4.

[0047] The heat exchanger 4 includes a plurality of flow plates 6. Figure 7 shows one of the flow plates 6 in isolation. Each flow plate 6 has a first face 8 and a second face 10. Each of the first face 6 and the second face 10 has a plurality of ridges 12 thereon, which define grooves which act as channels for the flow of a first fluid and a second fluid, as the case may be. Each flow plate 6 also has a peripheral edge 14, first fluid pass-through apertures 16, and second fluid pass-through apertures 18.

[0048] Figure 8 shows a sectional side view of a portion of a plurality of flow plates 6 of the heat exchanger 4. The plurality of flow plates 6 are stacked together and sealingly joined together to define a first flow path for a first fluid through the heat exchanger 4, and to define a second flow path for a second fluid through the heat exchanger 4. The first flow path includes spaces between first and second adjacent flow plates 6, third and fourth flow plates 6 and so on, which spaces are in fluid communication with the first fluid pass-through apertures 16. Meanwhile, the second flow path includes spaces between second and third flow plates 6, and fourth and fifthflow plates 6, and so on, which spaces are in fluid communication with the second fluid pass-through apertures 18. Accordingly, the first flow path and the second flow path are positioned in order to transfer heat from one of the first fluid and the second fluid to the other of the first fluid and the second fluid. Referring to Figure 5, the heat exchanger 4 has an end cover plate 20 that defines a first fluid inlet 22 and a first fluid outlet 24 in fluid communication with the first flow path, and that defines a second fluid inlet 26 and a second fluid outlet 28 in fluid communication with the second flow path.

[0049] As shown in Figure 8, the flow plates 6 each have a flange portion 30 that is used for joining the flow plates 6 together. The flange portions 30 of the flow plates 6 mate with one another. Braze material may be provided between the flange portions 30 and the flow plates 6 may then be heated to melt the braze material so as to sealingly join the flow plates 6 together. The outermost edges of the flange portions 30 form the peripheral edges 14 of the flow plates 6. In some embodiments, the peripheral edges 14 have a shape that creates a valley 32 between successive ones of the flow plates 6 when they are sealingly joined together. The peripheral edges 14 of the flow plates 6 together form a heat exchanger peripheral surface 34. In the embodiment shown, the heat exchanger peripheral surface 34 has a ridged texture in profile, on account of the peripheral edges 14 of the flow plates 6 having a sloped surface.

[0050] The heat exchanger 4 has a heat exchanger melting temperature, the magnitude of which depends on various parameters including the material of manufacture (e.g., aluminum or stainless steel) of the flow plates 6, and the braze material used to join the flow plates 6 together.

[0051] In the embodiment shown in Figures 1 to 6, the heater core 2 has two film heaters 40a, 40b. In other embodiments, the heater core 2 may have only one film heater, or more than two film heaters (e.g., three or more film heaters). Each of the film heaters 40a, 40b may be a thin film heater, a thick film heater or any other suitable kind of film heater. Film heaters are known in the art. As a non-limiting example, the film heater may comprise a substrate (e.g., made of materials such as aluminium, stainless steel, ceramics, and / or glass mica), a resistive trace printed or otherwise applied onto the substrate, and an electrically-conductive trace (e.g., of metallic material) printed or otherwise applied to the substrate layer to conduct electricalenergy to the resistive trace to generate heat. The electrically conductive traces terminate at first and second heater terminals 42, 42a (see Figure 5).

[0052] The film heaters 40a, 40b have a film heater damaging threshold temperature. In the present disclosure, the "film heater damaging threshold temperature" refers to any temperature that causes damage of any kind to the functionality of the film heater.

[0053] In the embodiment shown in Figures 1 to 6, the heater core 2 has two solder members 50a, 50b (generally 50), each of which is associated with a different one of the film heaters 40a, 40b, respectively. In other embodiments, the heater core 2 may have only one solder member, or more than two solder members (e.g. three or more solder members) so as to correspond in number with the number of film heater(s). In the embodiment shown in Figures 1 to 6, each of the solder members 50a, 50b is in the form a solder plate - i.e., a member having first and second surfaces that are substantially planar and substantially parallel to each other. In other embodiments not shown, the solder member 50 may have shapes other than a plate. As non-limiting examples, the solder member 50 may be "preformed" (e.g., by molding, pressing, or other operation) to have a non-planar surface that is complementary to the ridged texture of the heat exchanger peripheral surface 34.

[0054] The heater core 2 also includes an inner quantity of flux at an interface of the solder members 50a, 50b and the heat exchanger peripheral surface 34. Referring to Figure 5 (and as further described below with reference to Figure 6), in one embodiment, it will be understood that there is a first inner quantity of flux between the first solder member 50a and a first portion 34a of the heat exchanger peripheral surface 34, and a second inner quantity of flux between the second solder member 50b and a second portion 34b of the heat exchanger peripheral surface 34. The inner quantities of flux are not shown in Figure 5, but it will be understood that they are applied to the inward facing surfaces of the solder members 50a, 50b and / or the outward facing surfaces of the heat exchanger peripheral surface 34. The heater core 2 also includes an outer quantity of flux at an interface of the solder members 50a, 50b and the film heaters 40a, 40b, respectively. Referring to Figure 5 (and as further described below with reference to Figure 6), it will be understood that there is a first outer quantity of flux between the first solder member 50a and the first film heater 40a,and a second outer quantity of flux between the second solder member 50b and the second film heater 40b. The outer quantities of flux are not shown in Figure 5, but it will be understood that they are applied to the outward facing surfaces of solder members 50a, 50b and / or the inward facing surfaces of the film heaters 40a, 40b. The first and second film heaters 40a, 40b are soldered to the first and second portions 34a, 34b of the heat exchanger peripheral surface 34, respectively, by the first and second solder members 50a, 50b, respectively, and the first and second inner and outer quantities of flux, respectively.

[0055] Each of the solder members 50a, 50b has a solder member melting temperature. By selection of the material forming the solder members 50a, 50b, the solder member melting temperature is selected to be lower than the heat exchanger melting temperature and the film heater damage threshold temperature. As a nonlimiting example, the material forming the flow plates 6 of the heat exchanger 4 and the film heaters 40a, 40b may comprise aluminum or stainless steel, while the material forming the solder members 50a, 50b may be a zinc-aluminum alloy. Figure 9 shows a phase diagram for a zinc-aluminum alloy. Whereas the melting point of zinc (419.53 degrees Celsius) is lower than the melting point of aluminum (660.32 degrees Celsius), solder members 50a, 50b made of a zinc-aluminum (Zn-AI) alloy may have solder member melting temperature (e.g. in the range of 380 degrees Celsius to 500 degrees Celsius) that is suitably lower than the heat exchanger melting temperature and the film heater damage threshold temperature. As other non-limiting examples, the material forming the solder members 50a, 60b may be a zinc-coper (Zn-Cu) alloy with a melting temperature in the range of about 350 degrees Celsius to 420 degrees Celsius, a zinc-tin (Zn-Sn) alloy with a melting temperature in the range of about 200 degrees Celsius to 400 degrees Celsius, or a zinc-magnesium (Zn-Mg) alloy with a melting temperature in the range of about 350 degrees Celsius to 400 degrees Celsius.

[0056] The inner and outer quantities of flux have a flux melting temperature. By selection of the flux material, the flux melting temperature is selected to be lower than the heat exchanger melting temperature and the film heater damage threshold temperature. As non-limiting example, the flux material may be provided in a powder or paste form with a concentration in the range of about 5 g / m2to about 150 g / m2. As a non-limiting example, the flux material may be a mixture in a ratio from 1 :0 to 0:1 ofpotassium tetrafluoro aluminate, K1-3AIF4-6, and cesium tetrafluoro aluminate, CSAIF . As another non-limiting example, the flux material may be a corrosive type of flux such as zinc chloride. Further embodiments of the heater core 2 may use different flux materials, which may be selected by the person skilled in the art having regard to factors such as compatibility with the solder material used to form the solder members 50a, 50b, and the heating temperatures used to make the heater core 2. Additional additives may be included in the flux material to promote flux application behavior and efficacy. As another non-limiting example, the quantities of flux may be provided as a solid embedded in the solder member, which is within the meaning of the quantities of flux being provided at an interface of the solder member with the heat exchanger peripheral surface 34 or the film heaters 40a, 40b, as the case may be. In the latter regard, reference herein is made to the TRILLIUM Lean (TM) and TRILLIUM Solid (TM) brazing materials (Granges AB; Stockholm, Sweden) as possible materials for forming the solder members with embedded flux material.

[0057] Figure 6 shows a schematic depiction of one of the solder members 50, one of the inner quantities of flux 52 and one of the outer quantities of flux 54 in relation to one of the portions of the heat exchanger peripheral surface 34 and one of the film heaters 40 in accordance with the foregoing description. The solder member 50, the inner quantity of flux 52 and the outer quantity of flux may each individually be considered to be an "intermediate layer", and collectively referred to as "at least one intermediate layer". Stated generally, the the film heater 40 is soldered to the heat exchanger peripheral surface 34 by at least one intermediate layer comprising a solder material, which may be provided by at least the solder member 50 comprising the solder material. In embodiments, the at least one intermediate layer may consist of only of the solder member 50, without any other intermediate layer. In embodiments, the intermediate layers may include the solder member 50 and the inner quantity of flux 52, but omit the outer quantity of flux 54. In embodiments, the intermediate layers may include the solder member 50 and the outer quantity of flux 54, but omit the inner quantity of flux 52. Thus, it will be understood that by suitable selection of the solder material, in embodiments of the heater core: the inner quantity of flux 52 may be omitted such that the solder member 50 is soldered directly to the heat exchanger peripheral surface 34; and / or the outer quantity of flux 54 may be omitted such that the solder member 50 is soldered directly to the film heater 40. Further, it will beunderstood that the at least intermediate layer (i.e., the solder member 50, and, if present, the inner quantity of flux 52 and the outer quantity of flux 54) has at least one "intermediate layer melting temperature". The at least one intermediate layer melting temperature (i.e., the solder member melting temperature, and the flux melting temperature of the inner and / or outer quantities of flux, if present) is or are lower than the heat exchanger melting temperature, and lower than the film heater damage threshold temperature. The at least one intermediate layer melting temperature may also be equal to or lower than an operating temperature of the film heater 40 during operation thereof to generate heat to make the heater core in embodiments of the method 60 as described below.

[0058] METHOD OF MAKING HEATER CORE

[0059] Figures 10A and 10B together are a flow chart showing steps of an embodiment of a method 60 of the present disclosure. The method 60 is described below with reference to Figures 11 to 23 showing aspects of the method 60 or equipment used in the method 60, for making the embodiment of the heater core 2 shown in Figures 1 to 6. It will be understood that the described method 60 may be adapted to making other embodiments of a heater core 2, including those having a different number of film heater(s) and associated solder member(s).

[0060] At step 62, the method 60 involves providing a heat exchanger 4 in accordance with the foregoing description. Broadly stated, the heat exchanger 4 includes a plurality of flow plates 6 each having a plurality of faces 8, 10 and a peripheral edge 14, wherein the plurality of flow plates 6 are sealingly joined together to define a first flow path for a first fluid through the heat exchanger 4 and a second flow path for a second fluid through the heat exchanger 4, wherein the first flow path and the second flow path are positioned in order to transfer heat from one of the first fluid and the second fluid to the other of the first fluid and the second fluid, wherein the peripheral edges 14 of the plurality of flow plates together define a heat exchanger peripheral surface 34, and wherein the heat exchanger 4 has a heat exchanger melting temperature. Figures 1 to 8, as described above, show how flow plates 6 may be configured and sealingly joined together to provide such a heat exchanger 4.

[0061] At step 64, the method 60 further includes providing a film heater 40a, 40b that is positioned to heat both the first flow path and the second flow path in the heatexchanger 4, wherein the film heater 40a, 40b has a film heater damage threshold temperature. Figures 1 to 6, as described above, show how film heaters 40a, 40b may be positioned with respect to the heat exchanger 4 to achieve this functionality.

[0062] At step 66, the method 60 further includes providing a solder member 50a, 50b made from a solder material. Figure 5, as described above, shows how solder members 50a, 50b may be positioned relative to the heat exchanger 4 and the film heaters 40a, 40b.

[0063] A step 68, the method 60 further includes providing an inner quantity of flux between the solder member and the heat exchanger peripheral surface 34. As described above, the inner quantity of flux may be applied to the solder members 50a, 50b and / or the heat exchanger peripheral surface 34. At step 68, the method 60 further includes providing an outer quantity of flux between the solder members 50a, 50b and the film heaters 40a, 40b. As described above, the outer quantity of flux may be applied to the solder members 50a, 50b and / or the film heaters 40a, 40b. As described above, in some embodiments, the heater core 2 may omit the outer quantities of flux and / or the inner quantities of flux. Thus, it will be understood that in some embodiments of the method 60, step 68 as shown in Figure 10A may be omitted entirely, or modified to include providing only the inner quantity of flux, or only the outer quantity of flux.

[0064] At step 70, the method 60 further includes pressing the film heaters 40a, 40b, and the intermediate layer(s) (i.e., the solder members 50a, 50b, and, if present, the outer quantity of flux and the inner quantity of flux) against the heat exchanger peripheral surface 34, so as to form an intermediate assembly 80.

[0065] In addition to securing the film heaters 40a, 40b and the solder sheets 50a, 50b to the heat exchanger, the pressing step 70 may be performed to flatten the film heaters 40a, 40b in cases where the film heaters 40a, 40b have any curvature. The pressing step 70 may also be performed to ensure good contact between the film heaters 40a, 40b and the solder members 50a, 50b, mediated by the outer quantity of flux 54 if present. The pressing step 70 may also be performed to ensure good contact between the solder members 50a, 50b and the heat exchanger peripheral surface 34, mediated by the inner quantity of flux 52 if present. The pressing step 70 may be useful where the heat exchanger peripheral surface 34 has a ridged texture in profile, such as in the embodiment shown in Figure 8, so as to at least partly or fully fill the valleys32 (see Figure 6) with the inner quantity of flux 52, if present, as consistently as possible to avoid hot spots when the film heaters 40a, 40b are operated. As a nonlimiting, the pressing step 70 may be used to apply between about 25 kPa to about 150 kPa of contact pressure to the intermediate assembly 80. The pressing step 70 may be performed by any suitable means, such as by application of a load (e.g., weight-based loading) or by use of devices such as jigs described below.

[0066] For example, Figure 11 (for one embodiment of the method) and Figure 16 (for another embodiment of the method) show a jig 90 with a first clamp jaw 92a and a second clamp jaw 92a. Other embodiments of the jig, not shown, may have additional clamp jaws. In Figures 11 and 16, the jig 90 is an open configuration, before pressing the heat exchanger 4, the film heaters 40a, 40b, the solder members 50a, 50b and the inner and outer quantities of flux together. Threaded fasteners in the form of bolts 94 extend between the first and second clamp jaws 92a, 92b and through threaded nuts 96. In Figure 12 (for one embodiment of the method) and Figure 17 (for another embodiment of the method 60), the jig 90 is in a closed configuration, with the first clamp jaw 92a is positioned to engage the first film heater 4a and urge the first film heater 40a, the outer quantity of flux (if present), the first solder member 50a and the inner quantity of flux (if present) against a first portion 34a of the heat exchanger peripheral surface 34. The second clamp jaw 92b is engaged with a second portion 34b of the heat exchanger peripheral surface 34 that is opposite the first portion 34a of the heat exchanger peripheral surface 34. Resilient biasing members 98, which in this embodiment are in in the form of coil springs 98 as shown in Figures 12 and 17, are disposed around the bolts 94 and between the outer face of the first clamp jaw 92a and the heads of the bolts 94 so as to urge or pre-load (i.e., bias) the first clamp jaw 92a toward the second clamp jaw 92b, and thus apply a compressive force to the first clamp jaw 92a. In other embodiments, the resilient biasing members 98 may be in the form of other types of springs (e.g., a conical or volute spring, a leaf spring, or a conical spring washer) or a piece of resiliently elastic material. Rotating the bolts 94 relative to the nuts 96 urges the first and second clamp jaws 92a, 92b towards each other. Thus, the first and second clamp jaws 92a, 92b apply a compressive force, denoted by the arrow lines labeled "F", to the intermediate assembly 80.

[0067] As another example, Figures 21 to 23 show views of another embodiment of a jig 100 that may be used to press together the heat exchanger 4, film heaters 40a, 40b and other components of the heater core 2 to form an intermediate assembly 80 thereof. The general operating principle of the jig 100 shown in Figure 21 is similar to that of the jig 90 shown in Figure 11 . That is, threaded fasteners in the form of bolts 104 and nuts 106 are used to urge first and second clamp jaws 102a, 102b toward each other so as to apply a compressive force to the intermediate assembly 80. The jig 100 shown in Figure 21 differs in that each of the first and second clamp jaws 102a, 102b comprises a plurality of pressure pins 108 and associated platens 112 (e.g., in this embodiment, a four-by-two array of eight pressure pins 108 and eight associated platens 112) that extend toward the intermediate assembly 80. Each pressure pin 108 is attached at one end by a retaining ring 110 to a retaining member 103a, 103b so as to able to move axially relative to the one of the retaining members 103a, 103b. Each pressure pin 108 is attached at another end to an associated one of the platens 112. As a non-limiting example, the retaining members 103a, 103b, the pressure pins 108 and the platens 112 may be made of metal (e.g., stainless steel) or carbon composite material. In embodiments where the pressure pins 108 and the platens 112 are made of metal, they may be made integrally as a single piece. In embodiments where the pressure pins 108 and the platens 112 are made of a composite material, they may be made as separate parts. Resilient biasing members 114, which in this embodiment are in the form of coil springs 114, are attached at one end by the retaining ring 110 to the retaining members 103a, 103b. As a non-limiting example, the biasing members 114 in the form of coil springs may be made of Inconel X-750 alloy, which can function with a maximum relaxation resistance at up 649 degrees Celsius. The retaining ring 110 may be used to set a spring pre-load. The biasing members 114 in the form of coil springs are disposed around the pressure pins 108 and bear against the retaining members 103a or 103b and the platens 112 such that the platens 112 apply compressive forces to the intermediate assembly 80. In other embodiments, the biasing members 114 may be in the form of other types of springs (e.g., a conical or volute spring, a leaf spring, or a conical spring washer) or a piece of resiliently elastic material. The pressure pins 108 and their associated platens 112 are spaced apart to allow for individual movement and pressure application to the intermediate assembly80. This may allow for application of more homogenous pressure to the intermediate assembly 80.

[0068] In the embodiment shown in Figures 16 to 19, protective members 140 in the form of silica fabric sheets are disposed between the intermediate assembly 80 and each of the clamp jaws 92a, 92b of the jig 90. Similarly, in the embodiment shown in Figures 21 and 22, protective members 140 in the form of silica fabric sheets are disposed between the platens 112 and the intermediate assembly 80. In a non-limiting example, the silica fabric sheet is made of a material that has at least 96% silicon dioxide (SiC>2), withstands temperatures up to about 983 degrees Celsius, and is fireproof. In other embodiments, the protective members may be made of other high- temperature resistant materials, such as fabrics impregnated with ceramic material (e.g., silicon carbide, boron nitride, or boron carbide), a flexible graphite sheet, or a polyimide polymer sheet. The material of the thermally insulative sheet should withstand temperatures in excess of the melting temperature of the solder material and the flux material. For the embodiment shown in Figures 16 to 19, the protective members 140 serve as thermal insulation to protect the power source terminals 124a, 124b and the header 130 from damage by excessive heat. The protective members 140 may be used to protect a relatively fragile surface of the film heaters 40a, 40b from cracking or other damage that might otherwise occur by direct contact with the clamp jaws 92a, 92b (Figures 16 to 19) or the platens 112 (Figures 21 and 22) and stress concentrations arising from irregularities or debris between the clamp jaws 92a, 92b (Figures 16 to 19) or the platens 112 (Figures 21 and 22) and film heaters 40a, 40b. The protective members 140 may also be used to prevent excess solder material and / or flux material, if present, from splattering on to and adhering to the jig 90 (Figures 16 to 19) or the jig 100 (Figures 21 and 22), which may result in inadvertent soldering of the film heaters 40a, 40b to the clamp jaws 92a, 92b (Figures 16 to 19) or the platens 112 (Figures 21 and 22). In other embodiments (not shown), each of the platens 112 may have an individualized silica fabric cushion attached thereto so that the silica fabric cushion, rather than the platen 112, directly contacts the film heaters 40a, 40b.

[0069] At optional step 72, the method 60 may further include removing oxygen from an ambient environment of the intermediate assembly 80 prior to and / or during the heating step 74. In one embodiment, the removing oxygen step 72 includessupplying an inert gas and / or a reducing gas to an enclosure 120 in which the intermediate assembly 80 is positioned.

[0070] In one embodiment shown in Figure 13, the removing oxygen step 72 may include providing the enclosure 120 in the form of a furnace with one or more associated heat source(s) 122, positioning the intermediate assembly 80 in the furnace, and supplying an inert gas such as nitrogen (N2) to the furnace and / or a reducing gas such as hydrogen (H2) to the furnace. In the embodiment shown in Figure 13, the heat sources 122 are in the form of electrically-resistive radiative plates provided in a two-by-two array on two sides of the enclosure 120. It will be appreciated that, in other embodiments, the heat sources 122 may be powered by non-electrical sources, differ in configuration, differ in number, and / or may be provided at different locations of the enclosure 120 such as on the front and rear sides or the top and bottom thereof. In the embodiment shown in Figure 13, the enclosure 120 is provided with a venting port 123 to allow for purging of excess gas (e.g. , air and / or the inert gas and / or the reducing gas) from the enclosure 120. (In Figure 13, the furnace enclosure 120 and the heat sources (in dashed line) are shown as transparent, so as not to obscure the intermediate assembly 80 positioned within it.) The intermediate assembly 80 may be introduced into the furnace by means of a conveyor belt or some other suitable way. Thus, more than one intermediate assembly 80 may be processed by the furnace, either sequentially or in batches. By supplying the inert and / or the reducing gas to the furnace, oxygen in the furnace is flushed out and is therefore removed from the furnace and therefore from the ambient environment of the intermediate assembly 80. Supplying a reducing gas may also prevent the production of metallic oxides that may interfere with bonding of the solder members 50a, 50b with the heat exchanger peripheral surface 34 and the film heaters 40a, 40b.

[0071] In another embodiment shown in Figure 19, the enclosure 120 may be a small enclosure that fits around the intermediate assembly 80 but which does not have its own heat source. In the embodiment shown in Figure 19, the enclosure 120 is provided with a venting port 123 to allow for purging of excess gas (e.g., air and / orthe inert gas and / or the reducing gas) from the enclosure 120. (In Figure 19, the enclosure 120 is shown as transparent, so as not to obscure the intermediate assembly positioned within it.) In the embodiment, the film heaters 40a, 40b themselves are usedto melt the solder members 50a, 50b and the flux (if present) to solder the film heaters 40a, 40b to the heat exchanger peripheral surface 34 of the heat exchanger 4, as discussed below with respect to the heating step 74. Referring to Figure 18, the method 60 further comprises connecting a first power source terminal 124a to the first heater terminal 42a, and connecting a second power source terminal 124b to the second heater terminal 42b. In Figures 18 and 19, electrical conduits lead from the first and second power source terminals 124a, 124b to a power source 126. The power source 126 is shown symbolically and may be any suitable electrical power source, such as grid power or a battery. The method 60 further includes positioning a first inert and / or reducing gas outlet 128a so as to direct the inert and / or reducing gas towards the first power source terminal 124a and the first heater terminal 42a, and positioning a second inert and / or reducing gas outlet 128b so as to direct the inert and / or reducing gas towards the second power source terminal 124b and the second heater terminal 42b. As shown in Figures 18 and 19, the first and second inert gas outlets 128a, 128b may together be connected to or defined by a common header 130 (i.e., a manifold), which is fluidically connected to an inert and / or reducing gas supply conduit 132. The header 130 may define channels for through passage of the first and second power source terminals 124a, 124b. The supplying step noted above may thus include supplying the inert and / or reducing gas to the first and second inert and / or gas outlets 128a, 128b, so as to cool the first power source terminal 124a and the first heater terminal 42a, and the second power source terminal 124b and the second heater terminal 42b during operation of the film heaters 40a, 40b during the heating step 74 as discussed below. This prevents excessive heat from being transmitted to the first and second power source terminals 124a, 124b and their associated electrical conduits.

[0072] At step 74, the method 60 further includes heating the intermediate layer(s) (i.e., the solder members 50a, 50b and, if present, the inner and outer quantities of flux) to melt the intermediate layer(s) (i.e., the solder members 50a, 50b, and, if present, the inner and outer quantities of flux) so as to solder the film heaters 40a, 40b to the heat exchanger peripheral surface 34 at a soldering temperature that is lower than the heat exchanger melting temperature and lower than the film heater damage threshold temperature. At step 76, the method 60 further includes cooling the intermediate assembly 80 after reaching the soldering temperature so as to solidifythe intermediate layer(s) (i.e., the solder material of the solder members 50a, 50b, and, if present, the inner and outer quantities of flux).

[0073] In one embodiment shown in Figure 13, the heating step 74 includes exposing the intermediate assembly 80 to air heated in a furnace. This embodiment may be referred to herein as a "furnace soldering approach". Figure 14 is a chart showing a non-limiting example of the temperature profile overtime of the intermediate assembly, the atmosphere internal to the furnace, and an ambient environment external to the furnace, while the intermediate assembly 80 is heated in a furnace. As a non-limiting example, the intermediate assembly may be heated to a maximum temperature between about 488 degrees Celsius and about 515 degrees Celsius (e.g., 488.9 degrees Celsius after about 44 minutes of heating as shown in Figure 14) to reliably melt the solder members 50a, 50b and activate the inner and outer quantities of flux if present. Once this temperature is reached, the cooling step 76 starts immediately. When the temperature of the produced heater core 2 has decreased to below about 350 degrees Celsius, the supply of inert and / or reducing gas to the furnace may be stopped. When the temperature of the produced heater core 2 has decreased to below about 100 degrees Celsius, the produced heater core may be removed from the jig 90.

[0074] Figure 15 is a chart showing another example of the temperature profile over time of the intermediate assembly 80, while the intermediate assembly 80 is heated in the furnace as shown in Figure 13. Table II below summarizes examples of time durations (phase durations) and temperature ranges (phase temperatures) for phases of the heating step 74 and cooling step 76 shown in Figure 15. Figure 15 shows a distinct plateau phase and a preheat phase before the peak phase. The plateau phase has a plateau phase temperature that is insufficient to melt the solder material and the flux material if present. The plateau phase may help to promote temperature uniformity throughout the intermediate assembly 80. The preheat phase has a preheat phase temperature that is between the plateau phase temperature and the peak phase temperature, and that is sufficient to melt (promote activation of) the inner and outer quantities of flux if present. In other examples, the temperature of the intermediate assembly may be increased directly to the peak phase temperature - i.e., the plateau and preheat phases may have zero duration.

[0075] In another embodiment shown in Figure 19, the heating step 72 includes operating the film heater by supplying electrical power from the power source 126 to the film heaters 40a, 40b to heat the film heaters 40a, 40b. This embodiment may be referred to herein as a "self-soldering approach". Figure 20 is a chart showing a nonlimiting example of power, voltage and current profiles over time of electrical power supplied to the film heaters 40a, 40b to heat the intermediate assembly in the enclosure 120, and temperature profiles over time of the intermediate assembly 80, an inert and / or reducing gas, and an ambient environment external to the enclosure 120 while the intermediate assembly 80 is heated in the enclosure 120 as shown in Figure 19. In this example, electrical power at up to about 1000 W is supplied to the film heaters 40a, 40b until the intermediate assembly 80 reaches a temperature of about 488 degrees Celsius to about 515 degrees Celsius. Once this temperature is reached, the cooling step 76 starts immediately. When the temperature of the produced heater core 2 has decreased to below about 350 degrees Celsius, the supply of inert and / or reducing gas to the enclosure 120 may be stopped. When the temperature of the produced heater core 2 has decreased to below about 100 degrees Celsius, the produced heater core 2 may be removed from the jig 100. In other embodiments, the self-soldering approach may be performed by controlling the electrical power supplied from the power source 126 to the film heaters 40a, 40b so that the film heaters 40a, 40b exhibit heating phases analogous to those described above with reference to Figure 15 and Table II for the furnace soldering approach.

[0076] The self-soldering approach may be advantageous over the furnace soldering approach by avoiding the need for expensive furnace equipment. Further, the self-soldering approach may be more energy efficient than the furnace soldering approach. In the self-soldering approach, the heat generated by the film heaters 40a, 40b is focused near the solder members 50a, 50b to be soldered to the heat exchanger 4 and the film heaters 40a, 40b. In contrast, the furnace soldering approach may use significant amounts of energy to heat large volumes of air that do not contact the intermediate assembly 80. The self-soldering approach may also be more time efficient than the furnace soldering approach. In the self-soldering approach, with sufficient supply of electrical power, the film heaters 40a, 40b can be increased to the peak temperature in a relatively short time, such as less than 15 minutes (e.g., in about 11 minutes as shown in Figure 20), less than 10 minutes, less than 5 minutes or less than 3 minutes. In contrast, it may take a relatively longer time (e.g., about 40 minutes in Figure 14) to heat air in a furnace sufficiently to heat the intermediate assembly 80 to the peak temperature.

[0077] METHOD OF MAKING HEATER CORE: BRAZING OF FLOW PLATES CONCURRENTLY WITH SOLDERING OF FILM HEATER

[0078] In the foregoing description of the embodiment of the method 60 shown in Figures 10A and 10B, it is presumed that step 62 of providing the heat exchanger 4 is performed before steps 64 to 76. In another embodiment of the method 60, step 62 of providing the heat exchanger 4 comprises forming the heat exchanger 4 by steps shown in Figure 10C, some of which steps are performed concurrently with steps 64 to 76 shown in Figures 10A and 10B such that the flow plates 6 of the heat exchanger 4 are brazed together during step 74 of heating the intermediate layer(s).

[0079] At step 62a, the plurality of flow plates 6 are arranged in a stack and pressed against each other in the stack to define the first flow path for the first fluid through the heat exchanger 4 to be formed, the second flow path for the second fluid through the heat exchanger 4 to be formed, and the heat exchanger peripheral surface 34 of the heat exchanger 4 to be formed. Accordingly, it will be understood that the term "heat exchanger peripheral surface" as used herein includes reference to the surface formed by the peripheral edges 14 (see Figure 8) of the flow plates 6 either before or after the flow plates are sealingly joined together to form the heat exchanger.Therefore, in steps 66 through 74, reference to performing steps in respect to the heat exchanger peripheral surface includes performing steps in respect to the surface formed by the peripheral edges 14 (see Figure 8) of the flow plates 6 either before or after the flow plates are sealingly joined together to form the heat exchanger. Figures 6 and 8 show an embodiment of a stack of flow plates 6 arranged in this manner. The pressing of the flow plates against each other may be performed by any suitable means, such as by application of a load (e.g., weight-based loading) or by use of devices such as a jig, which may be similar to the jig 90 described above with reference to Figs. 11 to 13 and Figs. 16 to 19, or similar to the jig 100 described above with reference to Figs. 21 to 23 above, except that the jig is modified to apply compress the flow plates 6 against one another.

[0080] At step 62b, a braze material is provided at junctions of the plurality of flow plates 6 with one another.

[0081] In some embodiments, providing the braze material may involve providing the flow plates 6 formed at least in part by the braze material. More particular, in one embodiment, as shown in the embodiment of the Figure 6, each of the plurality of flow plates 6 may be formed from a core layer 6a covered by a cladding layer 6b of braze material. The core layer 6a and the cladding layer 6b are made of different materials, with the melting point of the core layer 6a material being higher than the melting point of the cladding layer 6b material. As a non-limiting example, the core layer 6a may comprise a 3000 series aluminum-manganese (Al-Mn) alloy, while the cladding layer 6b material may comprise a 4000series aluminum-silicon (Al-Si) alloy, which serves as the braze material. Stock material having such core layer and cladding layer is commercially available (e.g., automobile 3003+4045 aluminum brazing plate; Henan Mingtai Al Industrial Co., Ltd.; Zhengzhou, China). Optionally, flux material may be applied to the cladding layer 6b (e.g., in power, paste or liquid form, such as by electrostatic coating processes).

[0082] In other embodiments, providing the braze material may involve providing the flow plates 6 formed from a brazing material having flux provided as a solid embedded in the material forming the flow plates 6. Reference herein is made to the TRILLIUM Lean (TM) and TRILLIUM Solid (TM) brazing materials (Granges AB;Stockholm, Sweden) as possible materials for forming the flow plates 6 from brazing material with embedded flux material.

[0083] In other embodiments, providing the braze material involve applying a braze material as a coating to the overlapping portions of the flow plates 6, and / or in the valleys 32 at the junctions of successive ones of the flow plates 6 shown in Figure 6.

[0084] In other embodiments, the braze material provided may be a material of the intermediate layer(s) that is or are provided as the solder material at step 66 and / or as the inner quantity of flux 52, if present, at step 68 of the method 60. As a non-limiting example, referring to Figure 6, the at least one intermediate layer includes the inner quantity of flux 52 and the solder member 50. When these materials are melted and thereby fluidized, these materials may migrate into the valleys 32 between successive ones of the flow plates 6 so as to contact the junctions between successive ones of the flow plates 6, and serve as the braze material that is provided in step 62b.

[0085] At step 62c, during the heating of the intermediate layer(s) at step 74, the braze material is heated so as to braze the braze material at a brazing temperature that is lower than the heat exchanger melting temperature and lower than the film heater damage threshold temperature. Since step 62c is performed during (i.e., concurrently with step 74), the heat source that is used for step 74 may also be used for step 62c. For example, in embodiments in which the intermediate layer(s) are heated in step 74 by exposing them to air heated in a furnace according to the "furnace soldering approach" described above, the heating of the braze material in step 62c may also be performed by exposure to the air heated in the furnace. As another example, in embodiments in which the intermediate layer(s) are heated in step 74 by heat generated by operation of the film heaters 40a, 40b according to the "selfsoldering approach" described above, the heating of the braze material in step 62 may also be performed by exposure to the heat generated by the operation of the film heaters 40a, 40b. In comparison to performing steps 62c and 74 sequentially, performing steps 62c and 74 concurrently with each other may reduce the overall time required to make the heater core 2 and more efficiently utilize the energy required to heat the air in the furnace or to operate the film heaters 40a, 40b.

[0086] At step 62d, the braze material is cooled after reaching the brazing temperature so as to solidify the braze material, whereupon the plurality of flow plates6 are sealingly joined together to form the heat exchanger 4. The cooling of the braze material in step 62d may be performed concurrently with the cooling of the intermediate assembly 80 in step 76.

[0087] While the description contained herein constitutes a plurality of embodiments of the present invention, it will be appreciated that the present invention is susceptible to further modification and change without departing from the fair meaning of the accompanying claims.

[0088] LIST OF ITEMS

Claims

CLAIMSWhat is claimed is:1 . A method of making a heater core, the method comprising: providing a heat exchanger including a plurality of flow plates each having a plurality of faces and a peripheral edge, wherein the plurality of flow plates are sealingly joined together to define a first flow path for a first fluid through the heat exchanger and a second flow path for a second fluid through the heat exchanger, wherein the first flow path and the second flow path are positioned in order to transfer heat from one of the first fluid and the second fluid to the other of the first fluid and the second fluid, wherein the peripheral edges of the plurality of flow plates together define a heat exchanger peripheral surface, wherein the heat exchanger has a heat exchanger melting temperature; providing a film heater that is positioned to heat both the first flow path and the second flow path of the heat exchanger, wherein the film heater has a film heater damage threshold temperature; providing at least one intermediate layer between the film heater and the heat exchanger peripheral surface, wherein the at least one intermediate layer comprises a solder material; pressing the film heater, and the at least one intermediate layer against the heat exchanger peripheral surface, so as to form an intermediate assembly; heating the at least one intermediate layer so as to solder the film heater to the heat exchanger peripheral surface at a soldering temperature that is lower than the heat exchanger melting temperature and lower than the film heater damage threshold temperature; and cooling the intermediate assembly after reaching the soldering temperature so as to solidify the at least one intermediate layer.

2. The method as claimed in claim 1 , wherein the solder material is provided by a solder member in the form of a plate .

3. The method as claimed in claim 1 or claim 2, wherein the at least one intermediate layer further comprises at least one quantity of flux comprising at least one of: an inner quantity of flux at an interface of the solder material and the heat exchanger peripheral surface; and an outer quantity of flux at an interface of the solder material and the film heater.

4. The method as claimed in claim 3, wherein the at least one quantity of flux comprises the inner quantity of flux at the interface of the solder material and the heat exchanger peripheral surface.

5. The method as claimed in claim 3 or claim 4, wherein the at least one quantity of flux comprises the outer quantity of flux at the interface of the solder material and the film heater.

6. The method as claimed in any one of claims 3 to 5, wherein the at least one quantity of flux comprises potassium tetrafluoro aluminate, or cesium tetrafluoro aluminate, ora mixture of potassium tetrafluoro aluminate and cesium tetrafluoro aluminate.

7. The method as claimed in any one of claims 1 to 6, further comprising: removing oxygen from an ambient environment of the intermediate assembly prior to and / or during the heating of the at least one intermediate layer step.

8. The method as claimed in claim 7, wherein the removing oxygen step includes supplying an inert gas and / or a reducing gas to an enclosure in which the intermediate assembly is positioned.

9. The method as claimed in claim 8, wherein the film heater has a first heater terminal and a second heater terminal,wherein the method further comprises connecting a first power source terminal to the first heater terminal, and connecting a second power source terminal to the second heater terminal, wherein the method further comprises positioning a first inert and / or reducing gas outlet so as to direct the inert gas and / or the reducing gas towards the first power source terminal and the first heater terminal, and positioning a second inert and / or reducing gas outlet so as to direct the inert gas and / or the reducing gas towards the second power source terminal and the second heater terminal, wherein the supplying step includes supplying the inert gas and / or the reducing gas to the first and second inert and / or reducing gas outlets so as to cool the first power source terminal and the first heater terminal, and the second power source terminal and the second heater terminal during the heating step, and wherein the heating of the at least one intermediate layer step includes supplying electrical power, via the first and second power source terminals, to the film heater to heat the film heater.

10. The method as claimed in any one of claims 1 to 8, wherein the heating of the at least one intermediate layer step includes exposing the intermediate assembly to heated air.11 . The method as claimed in any one of claims 1 to 8, wherein the heating of the at least one intermediate layer step includes supplying electrical power to the film heater to heat the film heater.

12. The method as claimed in any one of claims 1 to 11 , wherein the heating of the at least one intermediate layer step includes: a preheat phase that includes heating the intermediate assembly to a preheat phase temperature for a preheat phase duration, wherein the preheat phase temperature is sufficient to melt the at least one quantity of flux; and after the preheat phase, a peak phase that includes heating the intermediate assembly to a peak phase temperature for a peak phase duration, whereinthe peak phase temperature is greater than the preheat phase temperature and is sufficient to melt the solder material and the at least one quantity of flux.

13. The method as claimed in claim 12, wherein the heating of the at least one intermediate layer step further includes: before the preheat phase, a plateau phase that includes heating the intermediate assembly to a plateau phase temperature for a plateau phase duration, wherein the plateau phase temperature is less than the preheat phase temperature and insufficient to melt the solder material and the at least one quantity of flux.

14. The method as claimed in any one of claims 1 to 13, wherein the pressing step is performed to apply between about 25 kPa to about 150 kPa of pressure to the intermediate assembly.

15. The method as claimed in any one of claims 1 to 14, wherein the pressing step includes compressing the film heater, the at least one intermediate layer, and the heat exchanger peripheral surface between at least a first clamp jaw and a second clamp jaw.

16. The method as claimed in claim 15, wherein the compressing the film heater comprises at least one biasing member that biases the first clamp jaw toward the second clamp jaw.

17. The method as claimed in claim 15, wherein at least one of the first clamp jaw and the second clamp jaw comprises a retaining member and a plurality of platens that are movable, independently of each other, relative to the retaining member to apply compressive forces to the film heater, the at least one intermediate layer and the heat exchanger peripheral surface.

18. The method as claimed in claim 17, wherein the compressing the film heater comprises, for each one of the plurality of platens, an associated biasing memberbiasing the one of the platens toward the film heater, the at least one intermediate layer and the heat exchanger peripheral surface.

19. The method as claimed in any one of claims 15 to 18, wherein the method further comprises providing at least one protective member between the intermediate assembly and at least one of the first and second clamp jaws.

20. The method as claimed in claim 19, wherein the at least one protective member comprises a silica fabric sheet.

21. The method as claimed in any one of claims 1 to 20, wherein the providing the heat exchanger step comprises forming the heat exchanger by: arranging the plurality of flow plates in a stack and pressing the plurality of flow plates against each other in the stack to define the first flow path for the first fluid, the second flow path for the second fluid, and the peripheral heat exchanger surface of the heat exchanger to be formed; providing a braze material at junctions of the plurality of flow plates with one another; during the heating of the at least one intermediate layer step, heating the braze material so as to braze the brazing material to each other at a brazing temperature that is lower than the heat exchanger melting temperature and lower than the film heater damage threshold temperature; and cooling the braze material after reaching the brazing temperature so as to solidify the braze material, whereupon the plurality of flow plates are sealingly joined together to form the heat exchanger.

22. The method as claimed in claim 21 , wherein the braze material forms at least part of each of the plurality of flow plates.

23. The method as claimed in claim 22, wherein the braze material forms a cladding layer material of each of the plurality of flow plates that covers a core layer material of each of the plurality of flow plates, wherein a melting temperature ofcladding layer material is lower than a melting temperature of the core layer material.

24. The method as claimed in any one of claims 21 to 23, wherein the braze material partly or wholly comprises a material of the at least one intermediate layer.

25. The method as claimed in any one of claims 21 to 24, wherein the heating of the at least one intermediate layer step is performed as claimed in claim 10 by exposing the intermediate assembly to the heated air, and wherein the heating of the braze material step is performed, at least partly, by exposing the braze material to the heated air.

26. The method as claimed in any one of claims 21 to 25, wherein the heating of the at least one intermediate layer step is performed as claimed in claim 11 by supplying electrical power to the film heater to heat the film heater, and wherein the heating of the braze material step is performed, at least partly, by exposing the braze material to the heat of the film heater.

27. A heater core, comprising: a heat exchanger including a plurality of flow plates each having a plurality of faces and a peripheral edge, wherein the plurality of flow plates are sealingly joined together to define a first flow path for a first fluid through the heat exchanger and a second flow path for a second fluid through the heat exchanger, wherein the first flow path and the second flow path are positioned in order to transfer heat from one of the first fluid and the second fluid to the other of the first fluid and the second fluid, wherein the peripheral edges of the plurality of flow plates together define a heat exchanger peripheral surface, wherein the heat exchanger has a heat exchanger melting temperature; a film heater that is positioned to heat both the first flow path and the flow path of the heat exchanger, wherein the film heater has a film heater damage threshold temperature; at least one intermediate layer comprising a solder material;wherein the film heater is soldered to the heat exchanger peripheral surface by the at least one intermediate layer, and wherein the at least one intermediate layer has at least one intermediate layer melting temperature that is lower than the heat exchanger melting temperature and lower than the film heater damage threshold temperature.

28. The heater core as claimed in claim 27, wherein, when electrical power is supplied to the film heater, the film heater has an operating temperature that is greater than the at least one intermediate layer melting temperature.

29. The heater core as claimed in claim 27 or claim 28, wherein the at least one intermediate layer further comprises at least one quantity of flux comprising at least one of: an inner quantity of flux at an interface of the solder material and the heat exchanger peripheral surface; and an outer quantity of flux at an interface of the solder material and the film heater.

30. The heater core as claimed in claim 29, wherein the at least one quantity of flux comprises the inner quantity of flux at the interface of the solder material and the heat exchanger peripheral surface.

31. The heater core as claimed in claim 29 or claim 30, wherein the at least one quantity of flux comprises the outer quantity of flux at the interface of the solder material and the film heater.

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