CN114127503A - Heat exchanger and system thereof - Google Patents

Abstract

Improved heat exchangers and methods of making heat exchangers are provided. These methods include modifying the surface of the heat exchanger in an integrated manner during manufacture to impart desired properties such as reduced corrosion, pressure drop, and water retention, as well as increased anti-frost properties.

Description

Heat exchanger and system thereof

Cross Reference to Related Applications

This application claims priority to PCT application number PCT/US2019/065978 filed on 12.12.2019 and claims the benefit of US provisional application number 62/876,632 filed on 20.7.2019 and US provisional application number 63/038,693 filed on 12.6.2020, all of which are incorporated herein by reference in their entirety.

Technical Field

The present invention relates to heat exchangers, and in particular to microchannel heat exchangers for cooling and refrigeration made by aluminum brazing techniques.

Background

Demand for air conditioning and refrigeration is also increasing due to population growth, expansion of the world's mid-range steps with ever-increasing purchasing power, and the abnormal growth of cities or regions with high average air temperatures. Furthermore, there is a need for a more efficient, less costly and more environmentally friendly system. Several different systems are available on site for providing cooling services. Heat exchangers are the primary components of most of these systems.

There are two main types of heat exchangers in use, finned tube heat exchangers and recently developed microchannel heat exchangers (MCHEs). With lower production costs and lower refrigerant usage, microchannel heat exchangers are better able to meet the increasing production and environmental demands than finned tube heat exchangers. However, microchannel heat exchangers degrade over time due to water collecting in the heat exchanger body. In addition, the proximity to corrosive environments (e.g., oceans, industrial environments, or polluted air) can increase corrosion rates and reduce component life.

Typically, up to 3km from shore and pollution levels > 50 micrograms/m³The system of (1), taking into account the coating to reduce corrosion. Corrosive coatings that do not adversely affect energy efficiency by increasing pressure drop, reducing airflow, or increasing thermal resistance between the heat exchange surface and the air are also highly desirable.

Microchannel heat exchangers are typically manufactured by a brazing process. The components are assembled and clamped together and then flux (flux) is applied to remove oxides from the heat exchanger surfaces to be brazed in order to improve the strength of the joint. Controlled atmosphere furnaces are used to form joints for heat exchangers. After cooling, the fluid interconnect is brazed to the heat exchanger body, then the unit is leak tested, and finally packaged for shipment to a coating facility for applying a coating, or to a location for assembling the heat exchanger into a system.

Disclosure of Invention

In one aspect, an integrated method for manufacturing a heat exchanger is provided. In some embodiments, the method comprises integrating the modification of one or more substrate surfaces of the heat exchanger with the fabrication of the heat exchanger, wherein the substrate surfaces are modified with a surface modifying material, and wherein the surface modification is performed prior to completing the fabrication of the entire heat exchanger structure. In one embodiment, the method comprises: (a) depositing a surface modifying material on a substrate surface of a heat exchanger; (b) treating the deposited surface-modifying material to remove moisture, anionic compounds, binders and/or solvents; (c) a second layer of material is deposited onto the surface modifying material to provide one or more functional properties to the surface. The functional properties provided by the second deposited material layer may include, but are not limited to, wettability, Ultraviolet (UV) protection, corrosion resistance, surface energy modification, and/or aesthetic modification.

In some embodiments, the heat exchanger is a microchannel heat exchanger (MCHE). In some embodiments, the substrate surface comprises a manifold, fin, tube, and/or microchannel surface.

In some embodiments, the surface modification comprises an additive barrier coating process.

In some embodiments, the method of manufacturing comprises a step of brazing and a step for connecting the fluid interconnect, and the surface modification is performed after brazing and before connecting the fluid interconnect. In some embodiments, the surface need not be prepared prior to surface modification. In some embodiments, the method of manufacture includes a brazing step and the surface modification is performed prior to brazing. In some embodiments, the manufacturing method includes a brazing step, applying a flux material to the surface prior to brazing, and performing the surface modification and the flux brazing simultaneously. In some embodiments, the flux material interacts with the substrate surface to remove native surface oxides and interacts with the surface modification material to remove metal oxides of the surface modification layer during brazing. In some embodiments, the flux braze interacts with the substrate surface to remove surface oxides and does not interact with the surface modifying material during brazing.

In some embodiments, the surface modifying material is an inorganic material. For example, the inorganic material may include one or more elements that form an alloy with aluminum, such as an aluminum alloy that melts at a temperature of less than about 660 ℃. For example, the one or more elements may include, but are not limited to, silicon, zinc, magnesium, indium, copper, germanium, calcium, or combinations thereof. In some embodiments, the elements may include metals and/or metalloids. In some embodiments, the elements may include transition metals, post-transition metals, lanthanides, actinides, alkaline earth metals, and/or alkali metals.

In some embodiments, the surface modifying material forms a nanostructured material on the surface of the substrate.

In some embodiments, the surface modifying material acts as a braze (braze), a flux, a barrier coating, a functional coating, or a combination thereof during the manufacture of the heat exchanger. In some embodiments, the surface modifying material participates in the bonding of parts of the heat exchanger. In some embodiments, the parts are adhered by brazing, ceramic bonding, or a combination thereof. In some embodiments, the parts are bonded at a temperature of less than 660 ℃. In some embodiments, the surface modified material provides improved brazing performance compared to a standard controlled atmosphere brazing process (CAB).

In another aspect, a heat exchanger manufactured according to the integrated manufacturing method as disclosed herein is provided. In some embodiments, the heat exchanger is a microchannel heat exchanger (MCHE). In some embodiments, the heat exchanger is used in an air conditioning system, a refrigeration system, a filter element, or a heat pump.

In some embodiments, the surface modification material affects condensate droplet adhesion and, in turn, wettability of the surface of the heat exchanger. In some embodiments, the surface modification material provides improved heat exchanger performance compared to an uncoated heat exchanger surface. In some embodiments, the surface modification material provides improved corrosion resistance compared to an uncoated heat exchanger surface. In some embodiments, the surface modification material provides a reduced amount of stagnant liquid in the heat exchanger as compared to an uncoated heat exchanger surface. In some embodiments, the surface modification material reduces the amount of water, condensate, frost, or ice that remains within the heat exchanger body during operation as compared to an uncoated heat exchanger surface. In some embodiments, the surface modification material reduces the amount of debris or fouling material that remains within the heat exchanger body during operation as compared to an uncoated heat exchanger surface.

In some embodiments, the surface modification material in the heat exchanger is an inorganic material. For example, the inorganic material may include one or more elements that form an alloy with aluminum, such as an aluminum alloy that melts at a temperature of less than about 660 ℃. For example, the one or more elements may include, but are not limited to, silicon, zinc, magnesium, indium, manganese, copper, germanium, calcium, or combinations thereof.

In some embodiments, the surface modification material forms a nanostructured material on the surface of the substrate of the heat exchanger.

In another aspect, a refrigeration unit is provided. In some embodiments, a refrigeration unit comprises: a compressor; a microchannel evaporator coil; a microchannel condenser coil; a working fluid expansion device; and an outer shell (enclosure), wherein the microchannel evaporator coil comprises a coating of a surface modifying material comprising a metal oxide and/or metal hydroxide, and wherein the outer shell comprises a shell (housing) capable of maintaining a predetermined temperature range across all variable seasonal temperature conditions. In some embodiments, the working fluid expansion device is a thermostatic expansion valve. For example, the enclosure may include a housing that, for example, protects the refrigeration unit and maintains a desired temperature range (e.g., a predetermined temperature range) within an area (e.g., space, area, volume) where temperature control is desired. The output of the system controls the temperature of the area of interest (e.g., a room, house, refrigerator, etc.). In the case of a house, the casing separates the inside from the outside environment, in the case of a refrigerator, the casing separates the inside from the outside environment, and the outdoor casing protects the device and accommodates a duct or the like that introduces outdoor air.

In some embodiments, the coating has a thickness of less than about 20 microns or less than about 10 microns. In some embodiments, the coating increases the air-side heat transfer coefficient of the microchannel evaporator coil. In some embodiments, the microchannel evaporator coils are brazed.

In some embodiments, the surface modification results in a contact angle of greater than about 120 °, which significantly reduces the accumulation of water on the surface of the microchannel evaporator coil. In some embodiments, the surface modification results in a contact angle of less than about 45 ° or less than about 30 °, which distributes water significantly over the surface of the microchannel evaporator coil to reduce the accumulation and pooling of water.

In another aspect, a method for coating a microchannel heat exchanger is provided. In some embodiments, the method comprises: (a) immersing the heat exchanger in a bath comprising a metal salt; (b) immersing the heat exchanger in a solution of a fluorinated end-capping or alkyl end-capping compound; and (c) allowing the heat exchanger to dry. In other embodiments, the method comprises: (a) etching a surface of the heat exchanger; (b) immersing the heat exchanger in a bath comprising a metal salt; (c) immersing the heat exchanger in a solution of a fluorinated end-capping or alkyl end-capping compound; and (d) allowing the heat exchanger to dry. In other embodiments, the method comprises (a) etching a surface of the heat exchanger; (b) immersing the heat exchanger in a bath comprising a metal salt; and (c) allowing the heat exchanger to dry.

In another aspect, a heat pump system is provided. In some embodiments, the heat pump comprises: a compressor; a first microchannel evaporator coil; a second microchannel evaporator coil; a working fluid expansion device; and a housing comprising a heating mode and a cooling mode, wherein the first microchannel coil and the second microchannel coil comprise a coating of a surface modifying material comprising a metal oxide and/or a metal hydroxide, and wherein the housing comprises a shell capable of maintaining a predetermined temperature range across all seasonal temperature conditions. For example, the enclosure may include a housing that, for example, protects the heat pump system and maintains a desired temperature range (e.g., a predetermined temperature range) within an area (e.g., space, area, volume) where temperature control is desired. The output of the system controls the temperature of the region of interest. In some embodiments, the working fluid expansion device is a thermostatic expansion valve.

In some embodiments, the coating has a thickness of less than about 20 microns or less than about 10 microns. In some embodiments, the coating increases the air-side heat transfer coefficient of the first and second micro-channel evaporator coils. In some embodiments, the first and second microchannel evaporator coils are brazed.

In some embodiments, the direction of operation of the heat pump system may be reversed.

In some embodiments, the surface modification results in a contact angle of greater than about 120 °, which significantly reduces the accumulation of water on the surface of the microchannel evaporator coil. In some embodiments, the surface modification results in a contact angle of less than about 45 ° or less than about 30 °, which distributes water significantly over the surface of the microchannel evaporator coil to reduce the accumulation and pooling of water.

Drawings

Fig. 1 illustrates several design integration embodiments of a method for producing an improved heat exchanger, as described herein. The "part" or "clad part (clad part)" is used. "clamping (jigs)" refers to the step of securing a loose set of parts of a heat exchanger assembly in place. "flux" means the addition of flux material to a part from an external source. "heating" refers to a heat treatment step designed to activate the flux and promote brazing. "200" refers to surface preparation. "300" refers to the deposition of the surface modifying material. "400" refers to the heat treatment of the surface modified material. "500" refers to further processing of the deposited surface modifying material. "600" refers to a final surface treatment that provides various functional properties. "finishing" refers to adding fluid interconnects and fittings. "testing" means pressure testing the device to ensure that the unit can maintain the desired pressure level. "shipping" refers to transporting the assembled heat exchanger unit to the next destination, such as an assembly site or for a conventional surface coating procedure.

Figure 2 shows a series of images when water is sprayed on the coated and uncoated surfaces for removing paperboard lint, as described in example 6. The image in the upper left corner represents time zero. The images are arranged in chronological order from top to bottom, and the bottom right image represents the last point in time.

Detailed Description

The present invention provides methods and applications for improving microchannel heat exchangers (MCHEs) in terms of parameters such as corrosion, pressure drop, water retention, and frost protection performance. In contrast to conventional continuous processing methods, an integrated manufacturing process is disclosed herein. Also described herein are improved coating compositions for heat exchangers.

Modern heat exchangers, such as microchannel heat exchangers (MCHEs), can be improved by the application of surface modifications. Previously, surface modification was performed after the heat exchanger was manufactured, and therefore, surface modification was limited by manufacturing/brazing by-products (e.g., flux residue and surface roughness from reflow of clad material). However, in the processes described herein, the surface modification is integrated with and performed during the manufacture of the heat exchanger, which allows for surface treatments and processes that are not limited by brazing conditions, can be applied on more uniform surfaces, result in higher quality parts, and/or can be machined in a side-by-side rather than sequential manner, reducing costs and potential damage from additional packaging and handling. The heat exchanger component may be machined in whole or in part in this manner.

For example, the surfaces of the heat exchanger, such as manifolds, fins and/or tubes (microchannels), may be modified during the preparation and processing of the loose parts, and/or the surfaces of the heat exchanger itself may be modified during brazing. Surface modification may include applying a coating composition to these surfaces in an integrated manufacturing process (e.g., in a multi-step coating process integrated with the manufacture of a heat exchanger).

The coating compositions used for surface modification herein may provide one or more benefits compared to uncoated surfaces in the same heat exchanger, including but not limited to reduction of corrosion, improved heat transfer (which may allow for the manufacture of smaller units), improved frost resistance/faster defrosting, and reduced water retention (which may also increase service life through surface wettability changes).

The process of manufacturing a MCHE typically includes sizing the materials, loose assembly of the parts, adding flux to remove oxides and promote adhesion, multiple heating steps to braze the loose parts together, cooling, and adding fluid interconnects. Surface coatings may be applied to these heat exchangers after manufacture to reduce corrosion or provide other benefits. However, the improved process disclosed herein integrates surface modification processing and heat exchanger production into a single production process. Rather than completing the manufacture of the heat exchanger and then applying the coating composition, the method disclosed herein includes applying the coating in a processing step within a conventional heat exchanger manufacturing process, a non-limiting example of which is shown in FIG. 1 and described below.

Referring to fig. 1, as described herein, surface modification includes the following processing steps or a subset thereof: (a) cleaning to ensure that the substrate material to be coated is free of debris and oil that may be present in the testing, packaging and/or shipping operations (100) (not shown in fig. 1), which may limit the quality of the coating and reduce the life of the production bath; (b) optional surface preparation to prepare the surface and promote adhesion of the surface to the functional surface modifying material (coating composition) (200); (c) additive deposition (300) of functional material, for example by immersion in a bath comprising a metal salt; (d) heat treating the functional material (400); (e) optionally a secondary surface treatment, such as etching, or providing or enhancing functionality, such as for (c) or (f) or the material deposited in the optional step, to further prepare the surface (500) for the final surface treatment in (f); and (f) an optional final surface treatment providing functional properties such as UV protection, wettability, surface energy modulation, improved corrosion resistance and/or aesthetic finish (600). In some embodiments, step (a) (100) is not explicitly performed, for example, relying on a remote cleaning process or an alternative process step (e.g., a brazing process). In some embodiments, step (b) (200) is not performed. In some embodiments, step (e) (500) is not performed. In some embodiments, steps (c) (300), (d) (400), and (f) (600) are performed, and one or more or all of steps (a), (b), and (e) are not performed. In some embodiments, steps (c) (300) and (d) (400) are performed and one or more or all of steps (a), (b), (e) and (f) are not performed.

Functional surface modifying materials may include, but are not limited to: metal oxide barrier coatings or other ceramic coatings, such as metal oxides, hydroxides, carbonates and/or phosphates, for example for corrosion resistance; metal oxides and/or phosphates, e.g., for adhesion; silanes, for example, for wetting; and/or urethanes, for example, for UV protection. In one embodiment, step (c) comprises depositing a layer of metal oxide and/or hydroxide and then immersing in a solution of a fluorinated terminated, alkyl terminated or other compound that affects wettability (e.g., is functionalized to make the surface hydrophobic).

Functional surface modification can be used to enhance the manufacturing process. In one non-limiting example, some or all of the individual components are treated with a hydrophilic wicking material prior to the clamping and brazing process, the primary purpose of which is to enhance wicking and distribution of the flux material to and around the joint.

Functional surface modifications can be used to enhance the performance of the resulting part. In one non-limiting example, tube materials that are typically treated with zinc to alter corrosion behavior are surface modified to alter the electrochemical potential.

Functional surface modification can be used to enhance the manufacturing process. In one non-limiting example, some or all of the individual components are treated with a hydrophilic wicking material prior to the clamping and brazing process, the primary purpose of which is to enhance the mechanical strength of the folded coil material.

The integration of heat exchanger production processes and surface modification has several potential benefits, including functional modification due to surface energy changes over hours, lower production costs, and reduced shipping and packaging costs. In some embodiments, the surface preparation places the heat exchanger surfaces in a low energy state suitable for additional processing. For example, after heat treatment, if the surface energy is low, water will readily wet the surface immediately after processing with a contact angle of less than about 20 °. The contact angle on the same material may be about 40 ° at about 6 hours, about 65 ° at about 24 hours, and about 80 ° at about 72 hours. Since the previous machining, the energy state of the surface is a function of the surrounding environment and time. The surface preparation described herein may render the surface suitable for subsequent processing such that the contact angle is less than about 20 °. This state can be confirmed by soaking and removing in the cleaning water step and observing the wetting property. The tested parts do not need to be dried prior to subsequent processing steps. In some embodiments, the surface preparation step (e.g., step (b) above or (200) in fig. 1) may be eliminated by integrating the surface modification with the remaining fabrication steps.

In some embodiments, the integrated surface modification as described herein allows for the application of a thin layer of coating material, for example less than about 1 mil (25 microns) in thickness, or less than any of about 20 microns, 10 microns, 5 microns, or 1 micron in thickness. The coating methods disclosed herein can provide benefits not found with thick (e.g., greater than about 25 microns) coatings, such as low thermal resistance and low surface stress, while providing properties required for longevity and durability, such as corrosion resistance, when compared to a single process step method alone (e.g., spray or dip coating (e.g., paint, polymer)).

In some embodiments, the integrated surface modification includes machining a surface modifying material on top of the flux material. In some embodiments, the surface modification material eliminates the need for a flux material. In some embodiments, the integrated surface modification comprises ceramic bonding of parts of the heat exchanger.

Furthermore, the proposed integrated method eliminates the need for continuous processing, in which the almost finished parts require additional processing steps, such as conventionally applied coatings. Such continuous processing requires two discrete facilities and provides an opportunity for damage after QA/QC testing in the primary production facility.

In addition to optimization through process integration, additional manufacturing methods are disclosed that can be used to alter the heat exchanger manufacturing process, providing additional benefits. One such example is alternative processing methods such as ceramic bonding.

Ceramic bonding can be used to make a variety of useful components. The metal oxide and/or hydroxide allows for high temperature operation, much higher than typical aluminum to which the metal oxide and/or hydroxide is bonded. For example, the metal oxide and/or hydroxide may include an oxide and/or hydroxide of an alkaline earth metal, such as, but not limited to, an oxide and/or hydroxide of magnesium. For example, the metal oxide and/or hydroxide may include an oxide and/or hydroxide of a transition metal, such as, but not limited to, an oxide and/or hydroxide of manganese or zinc. For example, the metal oxides and/or hydroxides may include oxides and/or hydroxides of other metals, such as, but not limited to, oxides and/or hydroxides of aluminum. For example, ceramic bonding may be performed with more than one metal, resulting in mixed metal oxides and/or hydroxides. In one embodiment, the metal oxide is ZnO. In addition, the metal-based ceramic layer may create a strong bond between the two metal parts, thereby creating a ceramic bond having a strength that approximates the strength of the weld, as well as a number of other advantageous properties, such as uniformity and conformality. The metal oxide and/or hydroxide deposition processes disclosed herein provide thin, uniform layers that provide benefits over spray-type applications.

In certain embodiments, the ceramic bonding process may bond separate oxides on adjacent parts, resulting in a mechanically strong but resistive joint. For example, two discrete parts or components (each comprising an oxide and/or hydroxide) that may be the same (e.g., MgO/MgO in a non-limiting example) or different (e.g., MgO/ZnO in a non-limiting example) are fused or joined together with a common oxide and/or hydroxide (e.g., MgO) or mixed metal oxide and/or hydroxide (e.g., MgZnO) to create a single part. "MO" (in a non-limiting example, MgO or ZnO) in which "M" is a metal means herein a metal oxide and/or hydroxide, including different oxidation and/or hydration states, if applicable. For example, MgO may refer to Mg_xO_yH_zWherein x, y and z are present in different combinations, such as, for example, 1-1-0 for MgO, 1-1-1 for Mg (OH), and 1-1-1 for Mg₆O₆*H₂O is 6-7-2.

The process also includes conformally coating the desired features, providing the designer with additional design freedom. In addition, the ceramic bonding process temperature may be lower than typical brazing temperatures. Brazing requires melting of the flux and/or the material of the braze, while ceramic joining does not require melting of the flux and/or the material of the braze; thus, lower temperatures may be deployed.

The use of ceramic bonding provides processing benefits including lower processing temperatures and ambient heating environments. Controlled Atmosphere Brazing (CAB), the most common for MCHE, occurs at temperatures no lower than 585 ℃, while ceramic bonding may occur at temperatures as low as 250 ℃. Such lower processing temperatures may provide additional benefits to the underlying structure and/or allowable materials of construction. In some embodiments, such lower bonding temperatures may allow ceramic bonding to occur with the flux binder removal process. In some embodiments, such lower bonding temperatures may allow ceramic bonding to occur with the application of polymers and other organic materials. Ceramic structures may be used to promote uniform coverage of polymers, glues, paints, organic materials, and other lower temperature materials, such as, for example, wicking of adhesives or glues to ensure good contact.

Higher temperature processing can lead to mechanical grain growth and potential corrosion and stress-induced problems at grain boundaries. The lower temperature for ceramic bonding provides greater and easier control of the heating profile with fewer processing limitations. This increased machining tolerance maximizes part-to-part consistency, improves product yield, and minimizes QA/QC challenges in heat exchanger production in terms of maintaining temperature and time profiles for part adhesion. As disclosed herein, ceramic bonding may be deployed as an alternative to CAB processes. In some embodiments, the ceramic bond is lighter, stronger, and is accomplished at lower temperatures than standard CAB conditions. For example, the ceramic bonding may be performed at a temperature about 100 ℃ lower than CAB. In various embodiments, the ceramic bonding is performed at a temperature that is about any of 100 ℃, 150 ℃, 200 ℃, 250 ℃, 300 ℃, 350 ℃, or 400 ℃ lower than CAB (e.g., 250 ℃ versus 650 ℃ CAB temperature). For example, ceramic bonding can be performed at any one of a temperature of about 250 ℃, 300 ℃, 350 ℃, 400 ℃, 450 ℃, 500 ℃, or 550 ℃, or about 250 ℃ to about 300 ℃, about 275 ℃ to about 325 ℃, about 300 ℃ to about 350 ℃, about 325 ℃ to about 375 ℃, about 350 ℃ to about 400 ℃, about 375 ℃ to about 425 ℃, about 400 ℃ to about 450 ℃, about 425 ℃ to about 475 ℃, about 450 ℃ to about 500 ℃, about 475 ℃ to about 525 ℃, or about 500 ℃ to about 550 ℃, about 250 ℃ to about 350 ℃, about 300 ℃ to about 400 ℃, about 350 ℃ to about 450 ℃, about 400 ℃ to about 500 ℃, about 450 ℃ to about 550 ℃, about 250 ℃ to about 400 ℃, about 300 ℃ to about 450 ℃, about 400 ℃ to about 550 ℃, about 250 ℃ to about 450 ℃, about 300 ℃ to about 500 ℃, about 350 ℃ to about 550 ℃, or about 250 ℃ to about 550 ℃.

Ceramics that may be formed using the techniques described herein include, but are not limited to, metal oxide and/or hydroxide (e.g., oxides and/or hydroxides of zinc, magnesium, manganese, or aluminum) alloys and structures, such as, but not limited to, Zn-XO alloys and structures including zinc-aluminum-oxygen spinel (X ═ a1), zinc silicate (X ═ Si), zinc-manganese-oxide (X ═ Mn), zinc-manganese-aluminum-oxide (X ═ Mn, a1), or any combination thereof. Ceramics (e.g., M-X-O, where M ═ metal) are considered additional non-limiting examples. Other non-limiting examples include Y-X-O, where Y ═ Mg and X ═ a1, Si, Mn, Ce, Zn, etc., or Y ═ Mn and X ═ Al, Si, Mg, Ce, Zn, etc.

As described herein, surface modification techniques can be applied to MCHE designs to reduce the amount of water, condensate, frost, or ice retained within the heat exchanger body. This trapped water can cause ice formation when frozen and can cause damage to the heat exchanger as the volume expands. Surface modifications resulting in contact angles greater than about 150 ° or greater than about 120 ° (which significantly mitigate the accumulation of water on heat exchanger surfaces under condensing conditions) can prevent damage due to water retention, such as frost/ice accumulation, fouling, corrosion, and/or microbial growth. Surface modification is important because it enables applications that have heretofore been unattainable, including refrigeration heat exchangers and outdoor coils for heat pump applications.

As described herein, surface modification techniques can be applied to MCHE designs to reduce the amount of debris and fouling materials retained within the heat exchanger body. Such materials result in reduced performance of the heat exchanger, may result in reduced component life, may serve as a source of microbial activity, may increase the pressure drop of the working fluid, and may accelerate degradation of performance.

Unless defined otherwise herein, 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 invention belongs. Any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention.

Numerical ranges provided herein include the numbers defining the range.

Definition of

The terms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise.

Reference herein to an "additive" in a surface modifying (coating) material means that the material is added to a substrate, as opposed to a conversion coating.

"ambient heating environment" means a heating environment, e.g., in a furnace, which is not conditioned, e.g., nitrogen is not added to replace air; or no vacuum is applied.

The "barrier coating" forms at least a portion of a physical barrier to minimize contact with undesired elements (e.g., water (as a "moisture barrier"); e.g., electrolyte (as a "corrosion barrier")).

"brazing" refers to a metal joining process in which two or more metal articles are joined together by melting a filler metal and flowing the filler metal into a joint, wherein the filler material has a lower melting point than the adjoining metals of the joint.

As used herein in the specification and claims, the phrase "and/or" should be understood to mean "either or both" of the elements so combined, i.e., the elements exist in combination in some cases and exist separately in other cases. In addition to the elements specifically identified by the "and/or" phrase, other elements may optionally be present, whether related or unrelated to those elements specifically identified unless clearly indicated to the contrary. Thus, as a non-limiting example, when used in conjunction with open-ended language such as "comprising," a reference to "a and/or B" may refer in one embodiment to a without B (optionally including elements other than B); in another embodiment, B is referred to without a (optionally including elements other than a); in yet another embodiment, reference is made to both a and B (optionally including other elements); and so on.

"Binder" or binding agent is any material or substance that mechanically, chemically, by adhesion or cohesion, secures or pulls other materials together to form a cohesive whole.

By "binderless" is meant the absence of a binder that can be exogenously added to the host material to improve structural integrity, particularly with respect to organic binders or resins (e.g., polymers, glues, adhesives, asphalt) or inorganic binders (e.g., lime, cement glass, gypsum, etc.).

"capillary climb" refers to the upward flow of liquid along the sample driven by surface tension when the porous substrate is in contact with the free surface of the liquid (capillary climb is parallel and opposite to the direction of the force (vector) due to gravity).

"ceramic" or "ceramic material" refers to a solid material comprising inorganic compounds of metals or metalloids and non-metals having ionic or covalent bonds. The "non-metal" may include oxygen (oxide ceramics), or carbon (carbides) or nitrogen (nitrides) (non-oxide ceramics). "Metal" may include non-hydrogen elements from group 1 of the periodic Table, elements from groups 2-12 of the periodic Table, or elements from the p-block (groups 12-17 of the periodic Table), for example, Al, Ga, In, Tl, Sn, Pb, Bi, or combinations thereof. The "metalloid" may comprise B, Si, Ge, As, Sb, Se, Te or Po, or a combination thereof.

"ceramic bonding" means the simultaneous deposition of a ceramic coating composition onto two metal parts. The coating fills the spaces between the parts and, after heat treatment, fuses the parts and ceramic together into a bond.

By "complete heat exchanger structure" is meant a structure in which a working fluid (e.g., refrigerant) is at least partially or completely contained and a fluid to be conditioned (e.g., air) is at least partially or completely isolated from the working fluid, resulting in an exchange of thermal energy between the working fluid and the fluid to be conditioned. In one embodiment, the working fluid is partially contained water, the fluid to be conditioned is air, and some leakage of the working fluid is used to further treat the airflow.

"conformal" refers to a deposited composition that is uniform or substantially uniform in thickness. "conformality" refers to the degree to which the deposited coating material has a uniform thickness, e.g., even in pores and in hard-to-reach spots. "conformal coating" refers to a coating composition, such as a film, that conforms to the contours of a substrate.

"contact angle" refers to the angle measured by a liquid between a surface and the liquid-vapor interface at the contacting surface.

"contiguous" or "adjacency" refers to pores and structures that contain walls and features that are in direct contact with each other, or that share a common wall across a large area or dimension relative to the individual pores or structures.

By "controlled atmosphere" is meant a heated environment, e.g., in a furnace, in which the composition, pressure and/or temperature is controlled, e.g., by adding nitrogen to displace air or applying a vacuum.

"conversion coating" refers to a surface layer in which a reactant chemically reacts with the surface to be treated, which converts the substrate into a different compound. This process is usually not additive or deposition but may result in small mass variations. In a non-limiting embodiment, the conversion coating may be a ceramic non-barrier (e.g., porous ceramic) coating.

"fluid interconnect" refers to a fluid connection that connects the MCHE fluid manifold to a desired system connection. In one embodiment, the fluid interconnect involves a small tube (e.g., copper tube) that is brazed to a manifold (e.g., aluminum manifold). In other embodiments, the fluid interconnect involves other types of fittings that allow a system integrator to assemble an air conditioning or refrigeration system of which the MCHE is a component.

"flux" refers to chemical cleaners, flowables, or scavengers used for extractive metallurgy and metal joining. In a particular application, the flux may have more than one function. As a cleaning agent, flux facilitates soldering (soldering), brazing and welding by removing oxidation from the metals to be joined. In high temperature metal joining processes (e.g., welding, brazing, and soldering), the flux prevents oxidation of the matrix and filler materials. Fluxes are generally inert at room temperature, but absorb and prevent the formation of metal oxides at high temperatures. In metal joining processes, the flux typically has the dual purpose of dissolving oxides on the metal surfaces and promoting wetting of the molten metal, thereby acting as an oxygen barrier by coating the hot surfaces and preventing their oxidation.

The "fouling material" herein may include, but is not limited to, salts (such as, but not limited to, salt residues deposited from air near salt water (e.g., ocean air)), bird droppings (bird excrements) or other solid deposition materials from the surrounding environment, or microbial (e.g., bacterial, fungal) materials, such as biofilms.

"grain growth" refers to an increase in the size of grains (e.g., crystallites) in a material at elevated temperatures. This occurs when recovery and recrystallization are complete and a further reduction in internal energy is achieved by reducing the total area of the grain boundaries.

"stagnant liquid" refers to condensate or other liquid remaining in the body of the heat exchanger that does not freely (e.g., by gravity or by air flow through the heat exchanger) leave the body of the heat exchanger.

"hydrophilic" refers to a surface having a high affinity for water. The contact angle may be very low (e.g., less than 30 degrees when measured through liquid water from a surface in the presence of air) and/or not measurable.

"layered double hydroxide" refers to a class of ionic solids characterized by a layered structure, the general sequence of which is [ AcB ZAcB]_nWherein c represents a metal cation layer, a and B are hydroxide anion layers, and Z is an other layer anion and/or neutral molecule (e.g. water) layer. Layered double hydroxides are also described in PCT application number PCT/US2017/052120, which is incorporated herein by reference in its entirety.

"macroscopic voids" refers to geometric spaces within a solid that have a characteristic dimension that is significantly greater than the characteristic dimension (e.g., thickness) of the pores or features alone, e.g., at least about 5 times to about 10 times or about 10 times to about 100 times greater than the characteristic dimension.

"average" means the arithmetic mean or average.

The "average pore diameter" was calculated as 4 times the total pore volume divided by the total surface area (4V/a) using total surface area and total volume measurements from Barrett-Joyner-halenda (bjh) adsorption/desorption method, assuming cylindrical pores.

"multimodal" refers to a distribution comprising more than one distinct mode, which appear as more than one distinct peak.

"permeability" in hydrodynamics is a measure of the ability of a porous material to allow fluid to pass through it. The permeability of the media is related to the porosity, but also to the shape of the pores in the media and their level of connectivity.

"pore size distribution" refers to the relative abundance of each pore size or range or pore size, as determined by Mercury Intrusion Porosimetry (MIP) and Washburn equations.

"porosity" is a measure of the space of voids (i.e., "empty") in a material, and is the fraction of the volume of voids (i.e., macroscopic voids) in the total volume, which is between 0 and 1, or as a percentage between 0% and 100%. Porosity as disclosed herein is measured by mercury intrusion porosimetry.

"porous" refers to a space, pore, or void within a solid material.

"Superhydrophobic" refers to surfaces that are extremely difficult to wet. Contact angle of a water droplet on a superhydrophobic material a superhydrophobic surface here means a sessile drop contact angle > 150 °. The contact angle for high hydrophobicity is more than 120 degrees. The contact angle referred to herein is the angle formed between surfaces by a liquid.

"surface area per square meter of projected substrate area" refers to the actual measured surface area (which is typically measured in square meters) divided by the surface area of the substrate (if the substrate is atomically smooth (no surface roughness)) (which is also typically measured in square meters).

"thickness" refers to the length between the surface of the substrate and the top of the surface modified (e.g., ceramic) material.

"third quartile pore size" refers to a pore size value at which the cumulative pore surface area measured in the direction of pore size increase corresponds to 75% of the total cumulative pore surface area as determined by BJH gas adsorption/desorption measurements.

"tortuosity" refers to the fraction Δ l of the shortest path through a porous structure and the euclidean distance Δ x between the start and end points of that path.

"tunable" refers to the ability of a material to have its function, characteristic, or quality changed or modified.

Exemplary embodiments

Referring to FIG. 1, several exemplary but non-limiting embodiments and scenarios of heat exchanger processing are provided.

A. In one embodiment, the surface modification process (including multiple process steps) is performed in-situ and prior to application of the fluidic interconnect. Benefits of such integration include reduced shipping, removal of cleaning requirements, and prevention of damage to fluid interconnects. A surface coating is applied on top of the heated flux material, which facilitates the brazing process.

In another embodiment, the process is the same as a except that no flux is applied in the process.

B. In another embodiment, the surface modification process (including multiple process steps) is performed in-situ immediately after the heat treatment step and before the application of the fluid interconnect. Benefits of such integration include removal of surface preparation processing steps, reduced shipping, removal of cleaning requirements, and prevention of damage to fluid interconnects. A surface coating is applied on top of the heated flux material, which facilitates the brazing process. To be effective, the heat treatment and surface preparation steps should be performed in a minimum time (about 5 minutes, up to about 12-24 hours) as determined by local environmental conditions. Such time constraints will avoid surface fouling between steps, which may be facilitated by co-location or close geographic proximity of equipment/processes.

C. In another embodiment, the surface modification process (including multiple process steps) is performed in-situ and prior to the heat treatment. Benefits of such integration include furnace co-usage, reduced transportation, removal of cleaning requirements, and prevention of damage to fluid interconnects. Prior to the brazing process, a surface coating is applied on top of the flux. The surface modification may interact with the flux material during the combined heating process.

In another embodiment, the surface modification process (including multiple process steps) is performed in-situ and prior to the heat treatment. Benefits of such integration include furnace co-usage, reduced shipping, removal of cleaning requirements, removal of surface preparation steps, and prevention of damage to fluid interconnects. Prior to the brazing process, a surface coating is applied on top of the flux. The flux acts as a surface modifier in this capacity, eliminating the need for the surface preparation step (200).

C "(not shown in fig. 1). In another embodiment, the process is the same as C or C' except that no secondary surface treatment (500) is performed.

D. In another embodiment, the surface modification process (including multiple process steps) is performed in-situ and prior to the heat treatment. Benefits of such integration include the co-utilization of heating furnaces, reduced transportation, removal of cleaning requirements, co-curing of flux and surface modifying materials to avoid damage due to shrinkage, and to prevent damage to fluid interconnects. Prior to the brazing process, a surface coating is applied on top of the flux. In this example, the flux formulation is modified to preferentially remove alumina rather than the surface modifying material. The surface modification material interacts with the flux material to a lesser extent than in certain other embodiments, such as C, C' or C "as described above, or does not interact with the flux material during the combined heating process.

E. In another embodiment, no flux is used and the surface modifying material is applied to the clamped part by a conventional heating step, such as by ceramic bonding. Cladding materials that do not contain additional flux can be brazed, which will result in ceramic bonding and brazing, with the surface modifying material acting as a flux. The temperature used for the ceramic joining process is typically lower than the temperature required for brazing.

F. In another embodiment, no flux is used and the surface modifying material is applied to the loose part (pre-clamped) by a common heating step.

G. In another embodiment, the unclad part is processed. The surface modifying material is applied to the loose or clamped (G' -not shown) part. The flux (i.e., either the flux that interacts with the surface modifying material or the flux that does not interact with the surface modifying material) is added by ordinary heat treatment after deposition of the surface modifying material. In this case, the surface modifying material acts as a binder (rather than the existing encapsulated parts, solder, etc.).

H. In another embodiment, the process is the same as G except that no flux is added. The surface-modifying material serves as a binder and, if desired, also as a fluxing agent.

Structured ceramic material

The coating or surface modifying material as described herein can be a structured ceramic, such as a binderless (e.g., surface-fixed) ceramic, for example, a binderless ceramic having a crystallinity of greater than about 20%. In some embodiments, the structured ceramic is porous. Non-limiting examples of ceramic materials are provided in PCT/US19/65978, which is incorporated herein by reference in its entirety.

The ceramic material may comprise a metal oxide and/or hydroxide ceramic, for example, a single metal or mixed metal oxide and/or hydroxide ceramic. In some embodiments, the ceramic material comprises a metal hydroxide and/or hydroxide ceramic, e.g., a single metal or mixed metal oxide and/or hydroxide ceramic. In some embodiments, the ceramic material comprises a metal oxide and metal hydroxide ceramic, wherein the metal oxide and metal hydroxide comprise the same or different single or mixed metals. In some embodiments, the ceramic material comprises a metal oxide and/or metal hydroxide ceramic, wherein the substrate is hydrated by water or other compounds, resulting in a change in the surface energy and potentially the ratio of metal oxide to metal hydroxide composition of the ceramic. In some embodiments, the ceramic material comprises a metal hydroxide, wherein at least a portion of the metal hydroxide is in the form of a layered double hydroxide, e.g., at least about 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95% of the metal hydroxide is a layered double hydroxide.

In some embodiments, the "metal oxide" or "metal hydroxide" may be in the form of a hydrate of the metal oxide or metal hydroxide, respectively, or a portion of the metal oxide or metal hydroxide may be in the form of a hydrate of the metal oxide or metal hydroxide, respectively.

The mixed metal oxide or mixed metal hydroxide may include, for example, oxides or hydroxides of more than one metal, such as, but not limited to, iron, cobalt, nickel, copper, manganese, chromium, titanium, vanadium, zirconium, molybdenum, tantalum, zinc, lead, tin, tungsten, cerium, praseodymium, samarium, gadolinium, lanthanum, magnesium, aluminum, or calcium, respectively.

In some embodiments, the ceramic material is a binderless ceramic material, i.e., it is deposited onto the substrate without a binder. In some embodiments, the ceramic material is fixed on the substrate.

In some embodiments, the ceramic material has an open porous structure (open ce)ll pore structure), for example, characterized by one or more of the following: the ability to achieve capillary rise of a liquid with low surface tension (e.g., less than about 25mN/m, such as isopropyl alcohol) over a surface of greater than about 5mm against gravity in a closed container within 1 hour; about 0.1m²A/g to about 10,000m²Surface area per gram; an average pore size of about 10nm to about 1000nm or about 1nm to about 1000 nm; a pore volume of about 0 to about 1cc/g as measured by mercury intrusion (Hg) porosimetry; and a tortuosity of about 1 to about 1000, as defined by the length of the fluid path to the shortest distance, i.e., the "arc-to-chord ratio"; and/or a permeability of about 1 to about 10,000 millidarcies.

In some embodiments, the ceramic material is porous with a porosity of about 5% to about 95%. In some embodiments, the porosity may be at least about or greater than about 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95%. In some embodiments, the porosity is from about 10% to about 90%, from about 30% to about 90%, from about 40% to about 80%, or from about 50% to about 70%.

In some embodiments, the porous ceramic material has a permeability of about 1 to 10,000 millidarcies. In some embodiments, the permeability may be at least about any one of 1, 10, 100, 500, 1000, 5000, or 10,000 millidarcies. In some embodiments, the permeability is about 1 to about 100, about 50 to about 250, about 100 to about 500, about 250 to about 750, about 500 to about 1000, about 750 to about 2000, about 1000 to about 2500, about 2000 to about 5000, about 3000 to about 7500, about 5000 to about 10,000, about 1 to about 1000, about 1000 to about 5000, or about 5000 to about 10,000 millidarcies.

In some embodiments, the porous ceramic material comprises about 100mm³G to about 7500mm³Void volume in g, as determined by mercury intrusion porosimetry. In some embodiments, the void volume is at least about 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, 5000, 5500, 6000, 6500, 7000, or 7500mm³Any one of the values/g. In some embodimentsA void volume of about 100 to about 500, about 200 to about 1000, about 400 to about 800, about 500 to about 1000, about 800 to about 1500, about 1000 to about 2000, about 1500 to about 3000, about 2000 to about 5000, about 3000 to about 7500, about 250 to about 5000, about 350 to about 4000, about 400 to about 3000, about 250 to about 1000, about 250 to about 2500, about 2500 to about 5000, or about 500 to about 4000mm³Any one of the values/g.

The porous ceramic material as disclosed herein may be characterized by its interaction with a liquid material. As previously mentioned, the ceramic material may be characterized by the ability to achieve capillary rise of a low surface tension liquid (e.g., less than about 25mN/m, such as isopropyl alcohol) on a surface greater than about 5mm against gravity in a closed container within 1 hour. Other solvents having a surface tension of less than about 25mN/M at 20 ℃ may be used, including but not limited to perfluorohexane, perfluoroheptane, perfluorooctane, n-Hexane (HEX), polydimethylsiloxane (Baysilone M5), t-butyl chloride, n-heptane, n-Octane (OCT), isobutyryl chloride, ethanol, methanol, isopropanol, 1-chlorobutane, isovaleryl chloride, propanol, n-Decane (DEC), ethyl bromide, Methyl Ethyl Ketone (MEK), n-undecane, cyclohexane. Other solvents with surface tensions > 25mN/m at 20 ℃ may be used, including: acetone (2-propanone), N-dodecane (DDEC), isopentonitrile, Tetrahydrofuran (THF), dichloromethane, N-Tetradecane (TDEC), sym-tetrachloromethane, N-Hexadecane (HDEC), chloroform, 1-octanol, butyronitrile, p-cymene, cumene, toluene, dipropylene glycol monomethyl ether, 1-decanol, ethylene glycol monoethyl ether (ethylcellosolve), 1, 3, 5-trimethylbenzene (mesitylene), benzene, m-xylene, N-propylbenzene, ethylbenzene, N-butylbenzene, 1-nitropropane, o-xylene, dodecylbenzene, diethyl fumarate, decalin, nitroethane, carbon disulfide, cyclopentanol, 1, 4-dioxane, 1, 2-dichloroethane, chlorobenzene, dipropylene glycol, cyclohexanol, hexachlorobutadiene, bromobenzene, Pyrrole (PY), N-Dimethylacetamide (DMA), Nitromethane, diethyl phthalate, N-Dimethylformamide (DMF), pyridine, methylnaphthalene, benzyl alcohol, ethyl anthranilate, iodobenzene, N-methyl-2-pyrrolidone, tricresyl phosphate (TCP), m-nitrotoluene, bromobenzene, o-nitrotoluene, phenylisothiocyanate, alpha-chloronaphthalene, furfural (2-furfural), quinoline, 1, 5-pentanediol, Aniline (AN), polyethylene glycol 200(PEG), methyl anthranilate, nitrobenzene, a-Bromonaphthalene (BN), diethylene glycol (DEG), 1, 2, 3-tribromopropane, benzyl benzoate (BNBZ), 1, 3-diiodopropane, 3-Pyridinemethanol (PYC), Ethylene Glycol (EG), 2-aminoethanol, sym-tetrabromoethane, Diiodomethane (DI) Thiodiglycol (2, 2' -Thiodiethanol) (TDG), Formamide (FA), Glycerol (GLY), Water (WA) and mercury.

The porous ceramic surface modifying material may have the ability to affect the capillary rise of water at various temperatures. These materials may have the ability to separate miscible materials from binary azeotropes (e.g., ethanol-water, ethyl acetate-ethanol, or butanol-water) to break the ternary azeotrope or remove pentanol from a mixture comprising ethanol and water.

The pores of the porous ceramic surface modification material may comprise open pores filled with one or more gases, may comprise partially filled pores (e.g., partially filled with one or more solid materials), or may comprise fully or substantially filled pores (e.g., fully or substantially filled with one or more liquid and/or solid materials). In some embodiments, the pores are partially, substantially, or completely filled with a gas, liquid, or solid substance, or a combination thereof.

In some embodiments, the pores are partially filled with a first material and then partially or completely filled with a second material. In some embodiments, the second material is added as a layer of material over the partially filled holes. In some embodiments, the first material is a gas, a solid, or a liquid, or a combination of gas, liquid, and/or solid substances. In some embodiments, the second material is a gas, solid and/or liquid substance, or an environment (e.g., air). Examples include and functions imparted thereby include changes in porosity, wicking, repellency, and/or wetting behavior; changes in the composite material (including the porous material and the second material) to alter electrical/dielectric properties, to alter mechanical properties such as abrasion resistance, hardness, toughness, feel, elastic modulus, yield strength, yield stress, young's modulus, surface (compressive or tensile) stress, and/or elasticity; changes in thermal properties, such as thermal diffusivity, electrical conductivity, coefficient of thermal expansion, thermal interface stress, and/or thermal anisotropy; changes in optical properties, such as emissivity, color, reflectivity, and/or absorption coefficient; a change in chemical properties, such as corrosion, catalysis, reactivity, inertness, compatibility, fouling resistance, ion pump blockage, microbial resistance, and/or microbial compatibility; and/or as a substrate for biocatalysis.

In some embodiments, the first material interacts with the second material in a positive or negative synergistic manner to alter one or more functional properties of the ceramic material, such as, but not limited to, wettability, hardness, elasticity, mechanical, electrical, piezoelectric, optical, adhesion or thermal properties, microbial affinity or resistance, alteration of biofilm growth, catalytic activity, permeability, aesthetic appearance, liquid repellency, and/or corrosion resistance.

Non-limiting materials that can be used to partially or completely fill the pores include molecules that are capable of binding to the surface, such as molecules having a head group and a tail group, where the head group is a silane, phosphonate or phosphonic acid, carboxylic acid, vinyl, hydroxide, thiol, or ammonium compound. The tail group may include any functional group, such as a hydrocarbon, fluorocarbon, vinyl group, phenyl group, and/or quaternary ammonium group. Other ceramic materials may also be partially or completely deposited into the pores. The polymer may also be partially or completely deposited into the pores. The ceramic material may comprise, for example, one or more oxides of zinc, aluminum, manganese, magnesium, cerium, gadolinium and cobalt. Further, the ceramic material may comprise any solid material that may be added to the surface-modified material, including inorganic compounds of metal, non-metal, or metalloid atoms that are primarily held in ionic and covalent bonds, such as, for example, clays, silica, and glass. Polymers may include, for example, natural polymeric materials such as hemp, shellac, amber, wool, silk, natural rubber, cellulose and other natural fibers, sugars, hemicellulose and holocellulose, polysaccharides and biologically derived materials such as extracellular proteins, DNA, chitin. Synthetic polymers include, for example, polymers and copolymers comprising polyethylene, polypropylene, polystyrene, polyvinyl chloride, synthetic rubber, phenolic (or bakelite), neoprene, nylon, polyacrylonitrile, PVB, silicone, polyisobutylene, PEEK, PMMA, and PTFE.

In some embodiments, the pores are partially filled with a thin composite polymer layer to produce a surface-modified material having the porosity and functionality provided by the polymer. In other embodiments, the pores are completely filled with a thick polymer layer to produce a surface modifying material having a thick polymer layer with composite properties of the porous base material and the polymer layer. Polymers as described in the compositions herein include copolymers.

In some embodiments, the pores are partially or completely filled with a layer of material deposited on the surface of the surface modifying material. In some embodiments, a layer of material is deposited that adds one or more functional groups to the surface modifying material, such as, but not limited to, ammonium groups (e.g., quaternary ammonium groups), alkyl groups, perfluoroalkyl groups, fluoroalkyl groups. In some embodiments, a polymer or ceramic layer is deposited. In one embodiment, a ceramic top surface layer is deposited that is the same or different ceramic as the ceramic of the binderless porous ceramic material on the substrate. Examples of functional groups and the functions imparted thereby include quaternary ammonium groups for antimicrobial functions, alkyl chains for water and hydrocarbon affinity, perfluoroalkyl groups for water and oil repellency functions, polymers for mechanical performance functions, other ceramics for aesthetic, opto-electronic or anti-corrosion functions.

In some embodiments, the pores are partially or completely filled with a gas, liquid, or solid substance, or a combination thereof, and the composition further comprises a top surface material layer on the ceramic material, and the top surface material imparts one or more functions, such as, but not limited to, wettability with the liquid and/or selective separation of compounds in the liquid. In certain embodiments, the top surface material is a material that is separate from the substance with which the hole is partially, substantially, or completely filled, and does not itself fill or intrude into the hole. In some embodiments, the top surface material interacts with the substance in the well. For example, the top surface material may interact with the substance in the pores to provide one or more functionalities such as, but not limited to, thermal management, electrochemical reactivity modulation, and/or mechanical property modulation. In certain embodiments, the top surface material is the ambient environment with which the binderless porous ceramic material is in contact.

In some embodiments, the pores are substantially or completely filled with a polymeric or ceramic material.

In some embodiments, the material in the pores interacts with the ceramic material. Examples of such materials and the functions imparted thereby include oxidation of the surface-modifying material by surrounding liquids or vapors, condensation of minor components (e.g., environmental pollutants), hazardous environmental materials (e.g., CO or H from ambient air)₂S), capture or oxidation, and/or collection and retention of materials in the environment.

In some embodiments, moisture in the environment or added to the pores interacts with the material in the pores to modify the material in the pores or surface modifying material. Examples of such materials and the functions imparted thereby include changes in wetting behavior, changes in optical properties, changes in oxidation state or reactivity, changes in the rate of evaporation, frosting, icing or condensation.

In some embodiments, the material in the pores may be designed to interact with the ceramic material to "tune" the properties of the entire surface. Examples of properties that can be tuned include, but are not limited to, wettability, hardness, antimicrobial properties, catalytic activity, corrosion resistance, color, and/or photochemical activity.

In some embodiments, the ceramic surface modifying material and the material in the pores interact in a synergistic manner, e.g., enhancing or reducing at least one functionality of the surface modifying material and/or the material in the pores as compared to the functionality of the surface modifying material and/or the material in the pores alone. In some embodiments, two or more materials in a pore interact in a synergistic manner, e.g., to enhance or reduce at least one functionality of at least one material in the pore as compared to the functionality of the materials alone.

In some embodiments, the ceramic surface modifying material is asymmetric, e.g., not spherical, cylindrical, cubic, or otherwise ordered into a pore morphology having a well-defined, relatively constant normal distribution of surface area to volume, as characterized by the ratio of pore size at the first quartile to pore size at the third quartile as a function of the thickness of the binderless ceramic surface modification. In particular, the pore morphology is asymmetric about its center when compared to spherical, cylindrical or cubic shaped structures. Non-limiting examples of asymmetric pores are described in PCT application No. PCT/US 19/397643, which is incorporated herein by reference in its entirety.

The porous ceramic surface modifying material may be characterized by a wide pore size distribution that varies with distance from the substrate. In particular, the pore structure at a given distance from the substrate may be characterized locally, e.g., as described herein, and have different characterizations at different distances. The resulting asymmetry is determined in situ by a combination of substrate, ion mobility, processing conditions (e.g., temperature, pressure, and concentration). The degree of asymmetry can be further varied by integral means such as mixing, agitation, electric field modulation, and tank filtration, or by surface-oriented process means such as shear rate, impinging stream, or surface charge modification and modulation. The asymmetry can be determined ex situ by various means such as etching, track etching, ion beam milling, oxidation, photocatalysis, or by additional means. These methods refer to materials having a narrow or symmetrical pore structure, having a thickness and/or pore depth, such as zeolites, orbital etched membranes, or expanded PTFE membranes.

In some embodiments, the porous ceramic surface modifying material comprises a mesoporous average pore size in a range of about 2nm to about 50 nm. In other embodiments, the average pore size is in the range of about 50nm to about 1000 nm. In some embodiments, the binderless porous ceramic material comprises an average pore size of about 2nm to about 20 nm. In some embodiments, the average pore size is at least about any one of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 nm. In some embodiments, the average pore size is any one of about 2 to about 5, about 4 to about 9, about 5 to about 10, about 7 to about 12, about 9 to about 15, about 12 to about 18, about 15 to about 20, about 4 to about 11, about 5 to about 9, about 4 to about 8, or about 7 to about 11 nm.

The ceramic surface modifying material may comprise one or more metal oxides and/or metal hydroxides (and/or hydrates thereof). Non-limiting examples of metals that may be included in the ceramic compositions disclosed herein include: zinc, aluminum, manganese, magnesium, cerium, copper, gadolinium, tungsten, tin, lead, and cobalt. In some embodiments, the ceramic material comprises a transition metal, a group II element, a rare earth element (e.g., lanthanum, cerium, gadolinium, praseodymium, scandium, yttrium, samarium, or neodymium), aluminum, tin, or lead. In some embodiments, the ceramic material comprises two or more metal oxides (e.g., mixed metal oxides), including but not limited to zinc, aluminum, manganese, magnesium, cerium, praseodymium, and cobalt.

In some embodiments, the ceramic surface modifying material comprises: mixtures of zinc and aluminum oxides and/or hydroxides; ZnO and Al₂O₃And mixtures of Zn-aluminates; mixtures of materials including any/all phases comprising Zn, Al and oxygen; mixtures of manganese and magnesium oxides and/or hydroxides; manganese oxide; alumina; mixed metal manganese oxides and/or hydroxides; mixtures of oxides and/or hydroxides of magnesium and aluminum; mixtures of oxides and/or hydroxides of magnesium, cerium and aluminum; mixtures of oxides and/or hydroxides of zinc, gadolinium and aluminium; mixtures of cobalt and aluminum oxides and/or hydroxides; mixtures of manganese and aluminum oxides and/or hydroxides; a mixture of cerium and aluminum oxides and/or hydroxides; mixtures of iron and aluminum oxides and/or hydroxides; mixtures of tungsten and aluminum oxides and/or hydroxides; a mixture of tin and aluminum oxides; oxides and/or hydroxides of tungsten; oxides and/or hydroxides of magnesium; oxides and/or hydroxides of manganese; oxides and/or hydroxides of tin; or zinc oxide and/or hydroxide.

In some embodiments, at least one metal in the ceramic material is at 2⁺Oxidation state.

In some embodiments, the ceramic surface modifying material comprises one or more oxides and/or hydroxides of zinc, aluminum, manganese, magnesium, cerium, gadolinium, and cobalt, and the substrate is aluminum or an aluminum alloy.

In some embodiments, the ceramic surface modifying material is superhydrophobic. In some embodiments, the surface modifying material is highly hydrophobic. In some embodiments, the surface modifying material comprises one or more functional properties selected from wettability, hardness, elasticity, mechanical, electrical, piezoelectric, electromagnetic, optical, adhesive or thermal properties, microbial affinity or resistance, alteration of biofilm growth, catalytic activity, permeability, aesthetic appearance, and corrosion resistance, as compared to a substrate that does not comprise a ceramic material.

In some embodiments, a layer of functional material (e.g., a top layer of material) is deposited onto the ceramic material. Examples of such materials include, but are not limited to, quaternary ammonium groups for antimicrobial functions, alkyl chains for water and hydrocarbon affinity, perfluoroalkyl groups for water and oil repellency functions, polymers for mechanical performance functions, other ceramics for aesthetic, opto-electrical, or anti-corrosion functions. Examples of functionalities imparted by such materials include, but are not limited to, changes in porosity, wicking, repellency, and/or wetting behavior; modifying the composite material (including the porous material and the second material) to modify electrical/dielectric properties, to modify mechanical properties such as abrasion resistance, hardness, toughness, feel, elastic modulus, yield strength, yield stress, young's modulus, surface (compressive or tensile) stress, tensile strength, compressive strength, and/or elasticity; thermal properties, such as thermal diffusivity, electrical conductivity, coefficient of thermal expansion, thermal interface stress, thermal anisotropy, to alter optical properties, such as emissivity, color, reflectivity, and/or absorption coefficient, to alter chemical properties, such as corrosion, catalysis, reactivity, inertness, compatibility, stain resistance, ion pump blocking, antimicrobial, and/or microbial compatibility, to promote adhesion of subsequent layers of material, and/or as a biocatalytic substrate.

In some embodiments, the ceramic surface modifying material is resistant to degradation by ultraviolet radiation as compared to a substrate material, such as a polymer or any substrate material disclosed herein.

In some embodiments, the ceramic surface modifying material comprises a thickness of about 0.5 microns to about 20 microns. In some embodiments, the ceramic material comprises a thickness of about 0.2 microns to about 25 microns. In some embodiments, the thickness is at least about any one of 0.2, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 microns. In some embodiments, the thickness is any one of about 0.2 to about 0.5, about 0.5 to about 1, about 1 to about 5, about 3 to about 7, about 5 to about 10, about 7 to about 15, about 10 to about 15, about 12 to about 18, about 15 to about 20, about 18 to about 25, about 0.5 to about 15, about 2 to about 10, about 1 to about 10, about 3 to about 13, about 0.5 to about 15, about 0.5 to about 5, about 0.5 to about 10, or about 5 to about 15 microns.

In some embodiments, the surface modifying material of the ceramic is characterized by a water contact angle of about 0 ° to about 180 °. In other embodiments, the water contact angle is less than about 30 degrees. In other embodiments, the water contact angle is greater than about 150 degrees.

In some embodiments, the ceramic surface modifying material comprises a surface area of about 1.1m2 to about 100m2 per square meter of projected substrate area. In some embodiments, the ceramic material comprises a surface area of about 10m2 to about 1500m2 per square meter of projected substrate area. In some embodiments, the surface area is at least about any one of 10, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000, 1050, 1100, 1150, 1200, 1250, 1300, 1350, 1400, 1450, or 1500m2 per square meter of projected base area. In some embodiments, the surface area is about 10 to about 100, about 50 to about 250, about 150 to about 500, about 250 to about 750, about 500 to about 1000, about 750 to about 1200, about 1000 to about 1500, about 70 to about 1000, about 150 to about 800, about 500 to about 900, or about 500 to about 1000m per square meter of projected base area²Any one of the above.

In some embodiments, the ceramic material comprises about 15m per gram of ceramic material²To about 1500m²Watch (A)Area. In some embodiments, the surface area is at least about 15, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000, 1050, 1100, 1150, 1200, 1250, 1300, 1350, 1400, 1450, or 1500m per gram of ceramic material²Any one of the above. In some embodiments, the surface area is from about 15 to about 100, from about 50 to about 250, from about 150 to about 500, from about 250 to about 750, from about 500 to about 1000, from about 750 to about 1200, from about 1000 to about 1500, from about 50 to about 700, from about 75 to about 600, from about 150 to about 650, or from about 250 to about 700m per gram of ceramic material²Any one of the above.

Substrate

The substrate (e.g., heat exchanger component) on which the one or more coatings or surface modifying materials as described herein are applied or deposited may be comprised of any material suitable for structural or functional properties or functional applications, for example, for use in devices such as heat exchangers. In some embodiments, the substrate is aluminum or comprises aluminum (e.g., an aluminum alloy), an iron alloy, zinc, a zinc alloy, copper, a copper alloy, a nickel alloy, nickel, a titanium alloy, titanium, a cobalt-chromium containing alloy, glass, a polymer, a copolymer, a natural material (e.g., a natural material comprising cellulose), or a plastic.

In some embodiments, the substrate comprises a metal, and the predominant metal in the ceramic surface modifying material as described herein is different from the predominant metal in the substrate. The primary metal is a metal that comprises at least about 50%, 60%, 70%, 80%, 90%, or 95% of the total metal in the substrate or ceramic material, for example, as determined by atomic metal-based x-ray diffraction. Examples of base primary metals include, but are not limited to, aluminum, iron, copper, zinc, nickel, titanium, and magnesium. Examples of ceramic primary metals include, but are not limited to, zinc, aluminum, manganese, magnesium, cerium, copper, gadolinium, tungsten, tin, lead, and cobalt.

In some embodiments, the substrate comprises a metal capable of reacting (e.g., dissolving) under reaction conditions that allow for localized dissolution of the substrate metal, and the substrate metal is incorporated into a substrate-modifying material (e.g., a ceramic material, such as a binderless porous ceramic material). For example, aluminum substratesAluminum (e.g., Al) may be provided²⁺) Aluminum is incorporated into the ceramic material when the ceramic material is deposited on the substrate.

In some embodiments, the substrate comprises more than one class or type of material, for example, a substrate of more than two different types of materials joined by a ceramic as described herein, a metal and a ceramic joined by a ceramic as described herein, a polymer and a ceramic joined by a ceramic as described herein, or a ceramic as described herein.

Selective coating of surface modifying materials

In certain embodiments, selective application of a coating composition (surface modifying material) as described herein may be used to provide protection against environmental damage. Furthermore, over time, the conditions to be prevented or treated may change, which may be addressed by layered coating structures that provide different protection when the layers are changed (e.g., during the useful life of the device).

Coating compositions and substrate modifications are provided herein to minimize environmental wear or degradation (e.g., corrosion) in areas where environmental exposure and damage is particularly challenging (e.g., edges, material or composite interfaces, low velocity areas, areas of high electrochemical corrosion potential, or areas exposed to or susceptible to excessive moisture, salt, debris accumulation, biofouling, or abrasion).

The coating material or surface modification can be used to apply a more corrosion resistant material or to facilitate or enhance the movement of a liquid (e.g., water) away from the substrate in areas of high environmental exposure or stress, or stress due to operational factors during use of the device or system as described herein, to partially coat the component without the need to coat the entire surface or device, to protect the material differently over time, for example, by thickness differences of the coating material or surface modification across the substrate surface or by a surface normal gradient (e.g., a gradient of one or more chemical or physical properties from the top or surface modification of the coating material to the bottom in contact with the substrate surface) and/or as a brand or cost cut-down measure.

Selective application of coating materials or surface modification can also be used to achieve complementary benefits such as corrosion resistance while minimizing potential negative effects (e.g., heat transfer loss due to thermal resistance of the coating).

Some outdoor heat exchangers can corrode and fail in very specific locations due to water accumulation after rain, sprinkler devices, use near or in marine environments, or animal (e.g., cat) urination. Other environmental stresses that may be reduced or eliminated by application of the compositions and surface modifications described herein include exhaust gas pollution, municipal pollution, dust/debris, fertilizers, road salt, sand, marine aerosols, industrial emissions (e.g., refineries, water treatment, manufacturing), or microbial, bacterial, fungal, or viral exposure and/or degradation, including biofilm formation (i.e., antimicrobial, antibacterial, antifungal, or antiviral coatings or surface modifications). The spatial gradient of performance may be used to create a gradient effect. For example, a spatial gradient of porosity that directionally wicks and "pumps" fluid (e.g., water) from one direction to another may be used for corrosion protection and other purposes, such as enhanced drying or fluid transport.

In some embodiments, the coating or surface modification can make the heat exchanger or components thereof or components of the system as described herein resistant to impact contaminants (e.g., slaughterhouse particles, corrosive aerosols, etc.) and increase thermal resistance to reduce frost formation by reducing thermal conductivity and thereby increasing surface temperature. Downstream of the fin sets, the coating may be different to reduce the corrosion rate and improve heat transfer/anti-frost performance.

The coating or surface modification may be applied to the entire substrate surface or selectively (to one or more portions of the substrate surface, e.g., to one or more regions exposed to adverse environmental conditions or subjected to environmental or operational stresses). In certain embodiments described herein, the coating or surface modification is configured as a gradient (i.e., spatial variability) in one or more dimensions across the surface of the substrate or across the device or a portion or component of the device. Exemplary material parameters may include material density, pore size distribution, pore filling (i.e., fractional filling, or spatial gradient of material filling the pores of the porous material), or gradient in material thickness.

The selective coating of a substrate (e.g., a surface of a heat exchanger or microchannel coil) can be performed in a variety of ways, such as: partial (selective) coating on a portion of the surface of the substrate, with some locations uncoated and some locations coated, based on local corrosion resistance requirements or other requirements, such as, but not limited to, limiting microbial growth (e.g., legionella) or movement of liquid (e.g., water) away from the substrate in areas of high moisture; completely coating the substrate with a first material a and partially coating a second material B on the first material (i.e. selectively coating the second material B on a portion (one or more regions) of the surface of the first material a), wherein the second material may be the same as or different from the first material; and gradients within the coating across the substrate based on the need to protect from environmental or operational stress conditions.

The gradient may be spatially variable with respect to the at least one chemical or physical property. For example, the coating or surface modifying material a may be a uniform material on the surface of the substrate, or may include a spatial gradient (variability) of one or more properties, such as, but not limited to, material density, pore size distribution, pore filling fraction, or thickness. In addition, the optional second material B may also be applied over material a, which may be a homogeneous material, or may have spatial variability in one or more properties such as, but not limited to, material density, pore size distribution, thickness, and/or filling fraction of pores of material a. In some embodiments, the optional third material C may also be selectively applied and may be a uniform material across the substrate or across the material directly below, or may have spatial variability in one or more properties such as, but not limited to, material density, pore size distribution, thickness, and/or filling fraction of pores of material B. In some embodiments, material C is applied over a stack of materials (such as, but not limited to, a-B-a) and may have spatial variability of one or more properties (such as, but not limited to, material density, pore size distribution, thickness, and/or fill fraction of pores of material (such as material a) directly beneath material C). Additional optional uniform or graded material layers may also be included. The coating or surface modifying material may be applied continuously on the substrate surface or in one or more discrete (selective) areas, such as areas of the substrate that are subjected to environmental or operational stresses in the application of the device or component in which the substrate is incorporated.

The gradient layer may comprise a gradient in one or more properties of the structural layer. For example, the gradient may include higher porosity near the joint, variations in the structural composite thickness on the panel, e.g., thicker near the bottom or edges due to drainage and drying of the immersion process at a particular temperature, selective spraying of material in selected areas, addition of additional material coatings in selected areas, configuration of the spray application resulting in more material addition at the leading edge, or compositional variations affecting the electrochemical potential.

Gradients may be formed during processing of the structural layer, for example, by changing the concentration level (drop) during processing (which results in a change in composition through the thickness of the coating), and/or changing the temperature during the processing bath to change the structure or change the part temperature during processing, or having hot and cold zones of the part to result in thicker, thinner, or different materials, such as structural ceramic materials. Changes in local chemical reactivity by mechanical part agitation, fluid advection, addition of local heat and light, pressure differentials, and/or gravity settling differentials may also be used to create gradient properties. The drying and curing process can also be used to create a gradient of properties by using selected temperature zones, drying directions and selective light addition.

In some embodiments, the one or more coatings or surface modifying materials (e.g., materials a-C) are structured ceramics, such as binderless ceramic surface modifying materials, e.g., having pores that can be filled, unfilled, or partially filled, optionally in a manner that creates a gradient relative to the partial filling of the pores with the second material. In one embodiment, the ceramic material comprises a contiguous network of pores filled with a second material (e.g., a polymeric material).

In some embodiments, the one or more surface modifying materials are a single layer of chemistry that can provide any of a range of properties, such as, but not limited to, wettability, encapsulant, optical properties, and the like.

Many heat exchangers have multiple metal parts (e.g., composite interfaces), such as copper-aluminum heat exchangers, steel-aluminum heat exchangers, and brazed aluminum heat exchangers. Selective protection in these composite scenarios can provide additional protection (e.g., selective anodic protection) for galvanic corrosion sensitive metal pairs in various environments and anode/cathode regions. The methods described herein can also be used to introduce electrically insulating materials or to disrupt the formation of the galvanic cell. Other substrates, whether homogeneous or heterogeneous in composition, contain localized areas of susceptibility to corrosion from the local environment, such as localized abrasion, stagnant liquid or gas flow gradients, which can be mitigated by selective surface modification as described herein.

The following examples are intended to illustrate the invention without limiting it.

Examples of the invention

The surface modification material on the substrate (e.g., heat exchanger component) was prepared according to the following general procedure. The substrate assembly was cleaned in place with isopropyl alcohol to remove any residual oil. Next, the part is immersed in an alkali caustic etching bath having a pH > 11 for about 5 minutes to about 20 minutes at a temperature of about 20 ℃ to about 60 ℃. The assembly is then rinsed in distilled or deionized water to remove any residual caustic or loosely adhered material. Next, the part is immersed in a solution of a non-coordinating oxidizing acid (e.g., nitric acid) having a pH of less than 2 and a temperature of from about 20 ℃ to about 60 ℃ to remove the black powder and/or reduce the substrate. The assembly is then placed in a production bath containing 20-250mM metal nitrate (e.g., manganese (II) nitrate or sulfate (e.g., manganese (II) sulfate) or mixed metal nitrate (e.g., manganese (II) nitrate and zinc nitrate, typically in a ratio of about 50: 1 to about 1: 50) or sulfate and similar molar amounts of diamine (e.g., urea or ethylenediamine), triamine or tetramine (e.g., hexamethylenetetramine), typically in a ratio of about 2: 1 to about 0.5: 1, which is heated to a reaction temperature of about 50-85 c.the assembly is held in the bath for a time in the range of about 5 minutes to about 3 hours.the assembly is removed, rinsed with distilled or deionized water, and placed in an oven to dry and/or calcined at 50-600 c for several minutes to several hours. Followed by another optional drying step. In some embodiments, the metal in the deposited coating may be from the substrate (e.g., aluminum in the deposit, including zinc and aluminum hydroxides/oxides). After cooling, the parts were further processed and/or tested as described in the examples below.

Example 1

Coated heat exchanger, no cleaning

Microchannel heat exchangers are manufactured by taking loose parts and assembling them together. The assembled parts are sprayed with brazing flux, excess flux is removed, and heated in a controlled atmosphere brazing furnace. The brazed heat exchanger is machined without cleaning after preliminary machining in a brazing furnace. Typically, debris or oil in the area of the surface subjected to the water treatment can result in areas of non-uniformity, as observed by non-uniform wetting behavior. In practice, this is known as the water burst test, and standard test methods (ASTM F22) are available. The heat exchanger is uniform and is directly processed in surface preparation, deposition, heat treatment, deposition treatment and surface finishing. As indicated by the water burst test, the uniformity and resulting surface treatment was uniform and conformal. This example corresponds to a non-limiting example of case a of fig. 1.

Example 2

Coated heat exchangers, without cleaning or surface preparation

Microchannel heat exchangers are manufactured by taking loose parts and assembling them together. The assembled parts are sprayed with brazing flux, excess flux is removed, and heated in a controlled atmosphere brazing furnace. The brazed heat exchanger is machined without cleaning after preliminary machining in a brazing furnace. Typically, debris or oil in the area of the surface subjected to the water treatment can result in areas of non-uniformity, as observed by non-uniform wetting behavior. In practice, this is known as the water burst test, and standard test methods (ASTM F22) are available. The heat exchanger is homogeneous and is directly processed in deposition, heat treatment, deposit treatment and surface finishing. Successful coatings require substrates with low and uniform surface energies. In this case, the hot working of the brazing furnace results in a uniform surface, which results in a uniform coating. The time between heat exchanger brazing surface preparation was 84 hours. As indicated by the water burst test, the uniformity and resulting surface treatment was uniform and conformal. This example corresponds to a non-limiting example of case B of fig. 1.

Example 3

Ceramic bonding (tube)

A0.5 inch 6061-T6 ring was placed onto a 0.5 inch outside diameter 6061-T6 aluminum tube which was securely held with 18-8 stainless steel set screws. There is an estimated gap of 0.005 inches between the ring and the tube. The assembly was then etched in aqueous sodium hydroxide to clean the surface and the stain removed in aqueous nitric acid. Then the assembly is put into a container 2⁺Warm water baths of metal anion salts were run for several hours. The resulting part was then baked for a period of 24 hours to remove water and organic components. Surprisingly, it was not possible to remove the ring from the tube with bare hands or hand tools after removal from the drying step. This process results in the material filling the gap, resulting in a very strong ceramic bond between the ring and the tube. This example corresponds to a non-limiting example of cases E, F and H of FIG. 1.

Example 4

Ceramic bonded-loose part relative to clamping part

Sections of 1 inch (in.) diameter, 4 inch long (pre-drilled) aluminum alloy manifolds and 6 inch long microchannel tubes were tested. In one case, the microchannels are bent into a U-shape and inserted into a manifold. In another kindIn this case, the microchannel tubes and manifolds are processed independently. The assembly and loose parts are treated with an alkaline etch followed by an acid treatment step. After this surface treatment, the part is then worked by placing it in a mold containing 2⁺The part is subjected to a surface treatment in a warm water bath of the metal anion salt for only more than one hour. The loose parts are then assembled by placing the microchannels into a manifold. The two assemblies were then baked for a period of 4 hours to remove water and organic components.

Both assemblies look the same and are subjected to mechanical testing. The estimated contact area at each joint of microchannel and manifold was 0.15 inches². The manifold assembly is mounted on a microchannel fitting that is suspended below the manifold. A weight is added to the microchannel to determine the weight that caused the microchannel to separate from the manifold. The preassembled assembly withstood a weight of 65 pounds (1bs) prior to separation. The assembled and processed separated parts were subjected to a weight of 55lbs prior to separation. This example corresponds to a non-limiting example of cases E, F and H of FIG. 1.

Example 5

Microchannel heat exchangers are manufactured by taking loose parts and assembling them together. The assembled parts are flux sprayed, excess flux removed, and the parts are then heated in a controlled atmosphere brazing furnace. The brazed heat exchanger is machined without cleaning after preliminary machining in a brazing furnace. Typically, debris or oil in the area of the surface subjected to the water treatment can result in areas of non-uniformity, as observed by non-uniform wetting behavior. In practice, this is known as the water burst test, and standard test methods (ASTM F22) are available. The surface of the heat exchanger is uniform and the surface is prepared by an alkaline working step and then subjected to an acid treatment to reduce the surface concentration of metals other than aluminum. After surface preparation, the heat exchanger is subjected to a deposition step, a heat treatment, a deposition treatment and surface finishing. The contact angle, which is a measure of the surface modification performance, is measured at various points in the process. Notably, the contact angles are measured at different points on the substrate and during the process over the area of excess brazing flux. The results are in table 1 below. This example corresponds to a non-limiting example of case a of fig. 1.

TABLE 1

	Contact angle on substrate material	Contact angle on excess flux
			As received, prior to surface preparation	About 60 °	About 50 °
After surface preparation, deposition and deposit heat treatment	＜20°	＜20°
			After deposition treatment and surface finishing	＞165°	＞165°

Example 6

The ability of surface modifying materials as described herein to provide self-cleaning functionality, reduce the amount of debris and fouling materials on the modified surface was investigated. Fine cardboard lint was applied to the 3 inch x3 inch samples coated with aluminum and uncoated with aluminum. Water was sprayed onto the samples using a small hand spray bottle filled with water, and the samples were mounted side-by-side at 10 ° to the vertical.

The results are shown in fig. 2. There are two side by side plates, one uncoated and one coated. The image in the upper left corner is time zero. The images are then arranged in order from top to bottom.

In the first image, the cardboard lint can be seen inside the black oval. It was observed that the cardboard lint was easily removed from the coated sample and very little water remained on the surface.

In image No. 8, on the uncoated side, water droplets containing lint were observed to adhere to the substrate (white squares). Paperboard lint is not easily removed from the substrate.

The contact angle of the coating was > 120 °.

Example 7

A refrigeration system was constructed comprising an 1/4hp R-134 condensing unit, needle valves to control the throttling process, and a small microchannel heat exchanger having a surface area of about 200mm x 100mm and a depth of 25mm and installed in a plexiglas wind tunnel. The wind tunnel contains a fan that pulls air through the coil at a speed of 1-5m/s, cooling the air and producing condensate at a coil temperature below the dew point of the room. The inlet air comes from an air conditioned room at about 1000ft2 with a temperature in the range of 18-20 deg.C and a relative humidity in the range of 40-50%. The system is designed in such a way that the system can be evacuated, the coil isolated from the rest of the system, the coil replaced, and the system recharged with R-134. In addition to visual observation, the pressure drop across the coil and the refrigerant pressure were monitored throughout the system.

The refrigerant coil includes a refrigerant inlet distribution manifold, a series of vertically oriented microchannel tubes, and a series of fins spanning the space between the individual tubes and the refrigerant outlet manifold. Several microchannel coil configurations were tested, with two different louver configurations: (a) a non-louvered solid fin; and (b) louvered fins to increase the heat transfer efficiency of the air to the heat exchanger, and two different coating configurations: (1) as received from the manufacturing process; and (2) applying a surface modifying material and a fluorinated topcoat as described herein.

The test protocol includes installing a new coil and filling the system with refrigerant. The metering valve is closed to avoid any refrigerant flow. The fan was turned on to set the flow rate and initial pressure drop across the dry coil. Under dry conditions, the pressure drop of the (b) louvered coil is about 20% greater than that of the (a) non-louvered coil. In the configuration as manufactured, there was no significant difference in pressure drop for (2) the coated coil versus (1) the coil.

The refrigerant pressure is controlled by a metering valve and a condensing unit compressor. The high side pressure is 90-110psig and the evaporator inlet pressure is adjusted to about 30psig, which corresponds to a refrigerant temperature of about 1.1 ℃. The pressure drop of the refrigerant across the coil is in the range of 1-1.5 psig. During the test, the evaporator inlet pressure was adjusted from 30-24psig, resulting in a refrigerant temperature of 1.1 ℃ to-3.8 ℃. These conditions produce condensate on the coil under these conditions. It was observed that the condensate generated in (2) the coated coil remained more at the trailing edge than (1) the uncoated coil. (2) The coated coils appeared to produce a greater amount of condensate, however, the collection of all condensate from each test condition was uncertain because some condensate was retained in the coils (as indicated by the increased 0-5Pa pressure drop across the coils during the test), some drainage from outside the manifold, some condensate in the tunnel, and some condensate flowing to the fan. It was observed that (2) the coated coils and (1) the uncoated coils removed a significant amount of condensate from the ambient air, indicating efficient heat transfer, thereby dehumidifying and conditioning the air. Each test condition was run for about 120 minutes to ensure steady state was reached.

Although the foregoing invention has been described in some detail by way of illustration and example for purposes of clarity of understanding, it will be readily apparent to those of ordinary skill in the art that certain changes and modifications may be made thereto without departing from the spirit and scope of the invention as defined by the appended claims. Accordingly, the description should not be construed as limiting the scope of the invention.

All publications, patents, and patent applications cited herein are hereby incorporated by reference in their entirety and to the same extent as if each individual publication, patent, or patent application were specifically and individually indicated to be incorporated by reference.

Claims (41)

1. A method for manufacturing a heat exchanger comprising integrating modification of one or more substrate surfaces of the heat exchanger with the manufacture of the heat exchanger,

wherein one or more substrate surfaces of the heat exchanger are modified with a surface modifying material, and

wherein the surface modification is performed before the complete manufacture of the heat exchanger structure is completed.

2. The method of claim 1, wherein the modification of one or more substrate surfaces comprises:

(a) depositing the surface modifying material on the one or more substrate surfaces of the heat exchanger;

(b) treating the deposited surface-modifying material to remove moisture, anionic compounds, binders and/or solvents; and

(c) optionally, a second layer of material is deposited onto the surface modifying material to provide one or more functional properties to the surface.

3. The method of claim 2, wherein the surface modification alters wettability, Ultraviolet (UV) protection, corrosion resistance, surface energy modulation, and/or aesthetic modification compared to the same substrate surface that does not comprise the surface modification.

4. The method of claim 1, wherein the heat exchanger is a microchannel heat exchanger (MCHE).

5. The method of claim 1, wherein the substrate surface comprises a surface of a manifold, fin, tube, and/or microchannel.

6. The method of claim 1, wherein the modification of one or more substrate surfaces comprises an additive barrier coating process, a conversion coating process, or a combination thereof.

7. The method of claim 1, wherein the manufacturing method comprises a step of brazing and a step for connecting a fluid interconnect, and wherein the surface modification is performed after brazing and before connecting the fluid interconnect.

8. The method of claim 1, wherein the manufacturing method comprises a brazing step, and wherein the surface modification is performed prior to brazing.

9. The method of claim 1, wherein the manufacturing method comprises a brazing step, wherein a flux material is applied to the substrate surface prior to brazing, and wherein the surface modification and flux brazing are performed simultaneously.

10. The method of claim 9, wherein the surface modifying material comprises a metal oxide, and wherein, during brazing, the flux material interacts with the substrate surface to remove native surface oxide and interacts with the surface modifying material to remove at least a portion of the metal oxide contained in the surface modifying material.

11. The method of claim 9, wherein the flux material interacts with the substrate surface to remove native surface oxides and does not interact with the surface modification material during brazing.

12. The method of claim 1, wherein the surface modifying material is an inorganic material.

13. The method of claim 12, wherein the surface modifying material comprises a metal and/or a metalloid.

14. The method of claim 13, wherein the metal and/or metalloid comprises a transition metal, a post-transition metal, a lanthanide, an actinide, an alkaline earth metal, an alkali metal, and/or another metal.

15. The method of claim 12, wherein the inorganic material comprises one or more elements that form an alloy with aluminum.

16. The method of claim 15, wherein one or more elements comprise silicon, zinc, magnesium, manganese, indium, copper, germanium, calcium, cerium, or combinations thereof.

17. The method of claim 12, wherein the surface modifying material forms an alloy with aluminum that melts below 660 ℃.

18. The method of claim 1, wherein the surface modifying material forms a nanostructured material on the substrate surface.

19. The method of claim 1, wherein the surface modification material acts as a braze, a flux, a barrier coating, a functional coating, or a combination thereof during the manufacture of the heat exchanger.

20. The method of claim 1, wherein the surface modifying material participates in the bonding of parts of the heat exchanger.

21. The method of claim 20, wherein the parts are bonded by brazing, ceramic bonding, or a combination thereof.

22. The method of claim 21, wherein the parts are bonded at a temperature of less than 660 ℃.

23. The method of claim 22, wherein the substrate comprises a metal alloy, a ceramic, a polymer, or a combination thereof.

24. A heat exchanger made according to any of claims 1-23.

25. The heat exchanger of claim 24, wherein the heat exchanger is a microchannel heat exchanger (MCHE).

26. The heat exchanger of claim 24, wherein the surface modification material reduces condensate droplet adhesion and, in turn, reduces the wettability of the surface.

27. The heat exchanger of claim 24, wherein the surface modifying material provides improved heat exchanger performance compared to a heat exchanger comprising the same substrate surface that does not comprise the surface modifying material.

28. The heat exchanger of claim 24, wherein the surface modifying material provides improved corrosion resistance as compared to a heat exchanger comprising the same substrate surface that does not comprise the surface modifying material.

29. A system comprising the heat exchanger of claim 24, wherein the system comprises an air conditioning system, a refrigeration system, a filter element, or a heat pump.

30. The heat exchanger of claim 24, wherein the surface modification material provides a reduced amount of stagnant liquid in the heat exchanger as compared to a heat exchanger comprising the same substrate surface that does not contain the surface modification material.

31. The heat exchanger of claim 24, wherein the surface modifying material reduces an amount of water, condensate, frost, or ice retained within a body of the heat exchanger during operation as compared to a heat exchanger comprising the same substrate surface that does not contain the surface modifying material.

32. The heat exchanger of claim 24, wherein the surface modification material reduces the amount of debris or fouling material retained within the body of the heat exchanger during operation as compared to an uncoated heat exchanger surface.

33. A system comprising a refrigeration unit, the refrigeration unit comprising: a compressor; an evaporator coil; a condenser coil; a working fluid expansion device; and a housing, and a cover for the housing,

wherein at least one of the evaporator coil and the condenser coil comprises one or more microchannel coils,

wherein a surface of at least one of the microchannel coils comprises a coating of a surface modifying material comprising a metal oxide and/or a metal hydroxide, and

wherein the enclosure comprises a housing that protects the refrigeration unit and maintains a desired temperature range within the zone of system controlled temperature, wherein the temperature is controlled across variable seasonal temperature conditions in the ambient environment outside the zone of system controlled temperature.

34. A system comprising a heat pump system, the heat pump system comprising: a compressor; a first microchannel coil; a second microchannel coil; a working fluid expansion device; and a housing; including a heating mode and a cooling mode,

wherein the first microchannel coil and/or the second microchannel coil comprises a coating of a surface modifying material comprising a metal oxide, and

wherein the enclosure comprises a housing that protects the heat pump system and maintains a desired temperature range within an area of the system controlled temperature, wherein the temperature is controlled across variable seasonal temperature conditions in an ambient environment outside the area of the system controlled temperature.

35. The system of claim 33 or 34, wherein the working fluid expansion device comprises a thermostatic expansion valve.

36. The system of claim 33 or 34, wherein the coating of surface modifying material comprises a thickness of less than about 20 microns.

37. The system of claim 33 or 34, wherein the coating of surface modifying material comprises iron, manganese, magnesium, cerium, tin, zinc, or a combination thereof.

38. The system of claim 33 or 34, wherein at least one of the heat exchangers is brazed.

39. The system of claim 33 or 34, wherein the surface modification results in a contact angle on the microchannel coil surface of greater than 120 ° or less than 30 °, which reduces the accumulation of water, condensate, frost, or ice on the microchannel coil surface as compared to the same microchannel coil surface that does not include the surface modification.

40. A method of coating a microchannel heat exchanger with a surface modifying material, comprising:

(a) optionally, etching one or more surfaces of the heat exchanger;

(b) immersing the heat exchanger in a bath comprising a metal salt;

(c) optionally, immersing the heat exchanger in a solution of a fluorinated end-capped or alkyl end-capped compound or an alkane; and

(d) allowing the heat exchanger to dry.

41. The system of claim 34, wherein the direction of operation of the heat pump system can be reversed.

Images