Hybrid Heat Exchanger

Abstract

In one aspect, a hybrid heat exchanger includes a metallic serpentine tube having an inlet end portion for receiving a process fluid, an outlet end portion, and a series of extensions and return bends that direct the process fluid from the inlet end portion to the outlet end portion of the metallic serpentine tube. The hybrid heat exchanger further includes a thermally conductive polymer body thermally integrated with the serpentine tube. The thermally conductive polymer body has an outer surface in contact with a fluid, e.g., air and / or water. The thermally conductive polymer body is configured to transfer heat between the metallic serpentine tube and a fluid in contact with the outer surface of the thermally conductive polymer body. The outer surface of the thermally conductive polymer body includes surface enhancement features that affect the flow of a fluid across the outer surface of the thermally conductive polymer body.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 129,796, filed December 23, 2020.

[0002] Field This disclosure relates to heat exchangers, and more specifically to indirect heat exchangers. [Background technology]

[0003] background

[0003] Various types of indirect heat exchangers are known. Plate-frame heat exchangers, pillow plate heat exchangers, and plate-coil heat exchangers all use formed metal plates that are welded together and then either hydraulically expanded or pressed together with a gasket to form a liquid-tight cassette. These indirect heat exchangers are collectively referred to as plate heat exchangers. Similarly, serpentine coil indirect heat exchangers are also often used.

[0004]

[0004] Direct heat exchangers that can be used in combination with indirect heat exchangers, such as thermoformed polyvinyl chloride (PVC) packing, are also known. For example, the packing can be positioned above or below the serpentine coil to provide an area for the evaporating fluid to interact with air before or after it contacts the serpentine coil.

[0005]

[0005] Plate heat exchangers can be relatively expensive and difficult to manufacture, sometimes resulting in a higher cost per ton of cooling than the market will bear. Serpentine coil heat exchangers, on the other hand, can be less expensive, but cannot match the surface area density and therefore heat exchange efficiency of plate heat exchangers. Stainless steel (SST) plate heat exchangers are typically up to three or four times more expensive and less conductive than their hot-dip galvanized black steel (HDG) equivalents, but SST plate heat exchangers are often specified to allow for higher corrosion resistance. Summary of the Invention [Problem to be solved by the invention]

[0006]

[0006] Thermally conductive polymers are used in low pressure heat exchangers and may be more desirable than metallic materials from a material cost perspective. However, these heat exchangers are not strong enough to resist the internal pressures required for certification in many areas, such as refrigerant coils. For example, some applications of plate heat exchangers require the plate heat exchanger to withstand more than 150 psig, such as 300 psig or even 1000 psig. Making plate heat exchangers from thermally conductive polymers for these high pressure applications is therefore impractical using known thermally conductive polymers. [Brief description of the drawings]

[0007] BRIEF DESCRIPTION OF THE DRAWINGS [Figure 1] FIG. 1 is a perspective view of a hybrid heat exchanger having a metallic serpentine tube and a thermally conductive polymer body thermally integrated therewith. [Diagram 2]

[0008] FIG. 2 is a perspective view of a hybrid heat exchanger assembly including a plurality of the hybrid heat exchangers of FIG. 1 connected to inlet and outlet headers. [Diagram 3]

[0009] 3 is a cooling tower including the hybrid heat exchanger assembly of FIG. 2. [Figure 4]

[0010] 4 is a cross-sectional view taken along line 4-4 in FIG. 1 showing the sheath portion of the body receiving the serpentine tube extension. [Diagram 5]

[0011] FIG. 13 is a cross-sectional view of another hybrid heat exchanger having a thermally conductive polymer body including two sheets bonded together using a thermally conductive paste around two fluid conduits. [Figure 6]

[0012] 1 is a cross-sectional view of a hybrid heat exchanger having a thermally conductive polymer body including a sheet and cover portion connected around a fluid conduit. [Figure 7A]

[0013] FIG. 1 is a schematic diagram of a method for forming a hybrid heat exchanger using additive manufacturing. [Figure 7B]

[0013] FIG. 1 is a schematic diagram of a method for forming a hybrid heat exchanger using additive manufacturing. [Figure 7C]

[0013] FIG. 1 is a schematic diagram of a method for forming a hybrid heat exchanger using additive manufacturing. [Figure 7D]

[0014] FIG. 8 is a schematic diagram of a thermally conductive polymer filament that may be used in the method of FIGS. 7A-7C. [Figure 7E] FIG. 1 is a schematic diagram of a thermally conductive polymer filament that may be used in the method of FIGS. [Figure 7F] FIG. 1 is a schematic diagram of a thermally conductive polymer filament that may be used in the method of FIGS. [Figure 8A]

[0015] FIG. 1 is a schematic diagram of a method for forming a hybrid heat exchanger using injection molding. [Figure 8B] FIG. 1 is a schematic diagram of a method for forming a hybrid heat exchanger using injection molding. [Figure 8C] FIG. 1 is a schematic diagram of a method for forming a hybrid heat exchanger using injection molding. [Figure 9]

[0016] FIG. 2 is a perspective view of a hybrid heat exchanger assembly having a frame that maintains the hybrid heat exchangers in a fixed position relative to each other. [Figure 10]

[0017] FIG. 1 is a perspective view of a single thermally conductive polymer body that may be integrated with multiple fluid conduits. [Figure 11]

[0018] FIG. 1 is a schematic diagram of a hybrid heat exchanger having straight extensions and return bends of the hybrid heat exchanger tubes thermally integrated with the thermally conductive polymer body of the hybrid heat exchanger. [Figure 12]

[0019] FIG. 12 is a partial view of a hybrid heat exchanger having a fluid conduit and a thermally conductive polymer body, showing chevrons on the exterior surface of the body. [Figure 13]

[0020] 13 is a cross-sectional view taken along line 13-13 in FIG. 12 showing the chevron ridges and grooves of the body. [Figure 14]

[0021] FIG. 1 is a perspective view of a hybrid heat exchanger having fluid conduits extending through a body of thermally conductive polymer. [Figure 15]

[0022] FIG. 15 is a partial perspective view of the hybrid heat exchanger of FIG. 14 showing the straight extensions and return bends of the tubes of the hybrid heat exchanger. [Figure 16]

[0023] FIG. 16 is a perspective view of a hybrid heat exchanger having tubes extending into a thermally conductive polymer body, and shows fins in the thermally conductive polymer body. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Detailed Description

[0024] According to one aspect of the disclosure, a hybrid heat exchanger is provided that includes a metallic serpentine tube having an inlet end portion for receiving a process fluid, an outlet end portion, and a series of extensions and return bends that direct the process fluid from the inlet end portion to the outlet end portion of the metallic serpentine tube. The hybrid heat exchanger further includes a thermally conductive polymer body thermally integrated with the serpentine tube. The thermally conductive polymer body includes an outer surface in contact with a fluid, such as air and / or an evaporating liquid, such as water. The thermally conductive polymer body is configured to transfer heat between the metallic serpentine tube and a fluid in contact with the outer surface of the thermally conductive polymer body. The outer surface of the thermally conductive polymer body includes surface enhancement features that affect fluid flow across the outer surface of the thermally conductive polymer body.

[0009]

[0025] A hybrid heat exchanger having metallic tubes and a thermally integrated thermally conductive polymer body combines the strength of metallic tubes with the ease of fabrication of a thermally conductive polymer body to withstand high process fluid operating pressures, which can be at least 150 psig for process fluids such as water, glycol, and brine, up to 410 psig for refrigerants such as ammonia or HCFC-22, or 1200 psi or more for refrigerants such as CO2. Additionally, the surface enhancement features on the outer surface of the thermally conductive polymer body improve the ability of the thermally conductive polymer body to facilitate heat transfer between the process fluid in the metallic serpentine tubes and the fluid on the outer surface of the thermally conductive polymer body.

[0010]

[0026] According to another aspect of the disclosure, a heat exchanger system is provided that includes an inlet header for receiving a process fluid, an outlet header, and a plurality of fluid conduits of a first thermally conductive material. The first thermally conductive material can be a metal, such as stainless steel or copper, a non-metallic material, such as a ceramic, a composite material, or a conductive polymer. The fluid conduits each have an inlet end portion connected to the inlet header, an outlet end portion connected to the outlet header, and an intermediate portion along the fluid conduit between the inlet and outlet end portions. The fluid conduits are configured to allow a process fluid to flow from the inlet header to the outlet header.

[0011]

[0027] The heat exchanger system includes a body of a thermally conductive polymer having an outer surface different from a first thermally conductive material. The thermally conductive polymer body is in thermal contact with an intermediate portion of the fluid conduit and is configured to facilitate heat transfer between the process fluid and a fluid on the outer surface of the thermally conductive polymer body as the process fluid moves through the intermediate portion of the fluid conduit. Because the thermally conductive polymer body is of a different material from the first thermally conductive material of the fluid conduit, the first thermally conductive material may be selected to provide sufficient strength to resist high pressure process fluid, while the material of the thermally conductive polymer body may be selected without being limited by pressure processing requirements.

[0012]

[0028] The present disclosure also provides a method of forming a hybrid heat exchanger including providing a metallic tube for receiving a process fluid and fabricating a thermally conductive polymer body. The body has an exterior surface with surface enhancement features to affect fluid flow at the exterior surface of the body. The method further includes thermally integrating the thermally conductive polymer body and the metallic tube. In one embodiment, fabricating includes making the body using additive manufacturing, and integrating the thermally conductive polymer body and the metallic tube includes forming the body using additive manufacturing around the metallic tube. In another approach, fabricating includes using additive manufacturing to form the body, and integrating the thermally conductive polymer body and the metallic tube includes assembling a portion of the body around the metallic tube.

[0013]

[0029] In one aspect of the present disclosure, a method is provided that includes additive manufacturing, e.g., three-dimensional (3D) printing, molding, and / or attaching a thermally conductive polymer to one or more fluid conduits, e.g., one or more metal tubes, to create a lower-cost yet highly efficient hybrid plate heat exchanger. In some examples, air and water handling features are formed into the polymer sheet of the hybrid plate heat exchanger via molding or 3D printing techniques, which can be used to avoid bypasses, optimize water distribution on the heat exchanger, promote water / air mixing, and / or provide thermally conductive polymer or polymer / metal hybrid surface area to enable heat transfer from the tubes. Thermally conductive polymers typically have electrical conductivity properties comparable to SST metals and 10 times higher than conventional polymers, while being less expensive per unit weight. Thus, thermally conductive polymers allow for lower-cost construction materials while maintaining thermal performance.

[0014]

[0030] Generally, a thermally conductive polymer refers to a polymer that has a thermal conductivity of more than 2 W / mK, e.g., between 2 and 100 W / mK, e.g., more than 5 W / mK, e.g., 10 W / mK. The table below compares the approximate thermal conductivities for various materials measured at 20°C.

[0015] [Table 1]

[0016]

[0031] In one embodiment, metallic tubes may be used for process fluid handling to meet the pressure requirements for the hybrid heat exchanger. Examples of metals that may be used for the tubes include aluminum, copper, stainless steel, and carbon steel. Alternative materials of construction such as ceramics and conductive polymers may also be considered for the tubes.

[0017]

[0032] Some described examples include the combination of dissimilar materials and manufacturing processes (e.g., thermally conductive polymer and metallic tubes) to create a hybrid heat exchanger. At least one hybrid heat exchanger presented herein uses metallic tube construction to contain the internal pressure of high pressure process fluid, which may be provided at greater than 150 psig, e.g., greater than 200 psig or greater than 300 psig, while a thermally conductive polymer is used to extend the surface area of ​​the hybrid heat exchanger at a lower material cost than a typical single material metallic plate heat exchanger.

[0018]

[0033] In one aspect of the present disclosure, a low-cost plate heat exchanger is provided that is easily manufactured and can be configured for a variety of applications (different sizes, dimensions, patterns for use in a particular unit type) without extensive tooling or equipment modifications. The plate heat exchanger addresses the pressure handling issues of welded metal plates, where the welds are the weak link. The plate heat exchanger is adapted to maintain the surface area density of the heat exchanger while improving cost, manufacturability, and adaptability. The use of highly conductive polymeric material bonded to the tubes containing the pressurized process fluid allows for excellent heat transfer with high corrosion and fouling resistance and reduced weight at a lower cost than SST heat exchangers.

[0019]

[0034] Using a first material for the process fluid-operation fluid conduits and a second material connected to the fluid conduits allows for a heat exchanger that can meet pressure handling requirements while being engineering flexible (i.e., designs that are adaptable to a particular application but are not constrained by traditional manufacturing considerations) and cost effective. There are a variety of different tube circuits and polymer sheet configurations (e.g., surface patterns) that can be used with this approach. Additionally, it is also envisioned that the infill can be printed or shaped as a continuous part of the plate to combine both features into one plate heat exchanger. This technology can be applied in any field where heat transfer into and out of pressurized fluid channels is required (e.g., automotive / aerospace, battery cooling, engine cooling, power engineering cooling, consumer HVAC, high performance computing cooling).

[0020]

[0035] The examples shown in the figures are meant to be illustrative, and it is envisioned that they may be modified or redesigned in a manner that optimizes the design for mass production and balances cost versus thermal performance, for example.

[0021]

[0036] 1, a hybrid heat exchanger 10 is provided in which a process fluid, such as water, glycol, brine, ammonia, or CO2, passes through the hybrid heat exchanger 10 to be cooled. The hybrid heat exchanger 10 includes a fluid conduit, e.g., tube 11, and a body 12 of a thermally conductive polymeric material. The tube 11 is configured to withstand high internal operating pressures, e.g., at least 150 psig, exerted on the interior of the tube 11 by the process fluid therein. The body 12 facilitates heat transfer between the high pressure process fluid traveling through the tube 11 and a fluid, e.g., air and / or water, in contact with an exterior surface 15 of the body 12.

[0022]

[0037] The tube 11 has an inlet end portion 11A, an outlet end portion 11B, and an intermediate portion 9 intermediate the inlet and outlet end portions 11A, 11B along the tube 11. In one embodiment, the tube 11 is a serpentine tube, and the intermediate portion 9 includes an extension, such as a straight extension 11C, and a return bend 11D. The straight extension 11C is arranged as a vertical array of tube portions. The tube 11 may have a unitary configuration and may be formed, for example, by extruding a tube having a desired cross-section over its length. Another approach to forming the tube 11 includes rolling a strip of material into a desired cross-sectional configuration and welding the longitudinal edges of the strip together. In yet another embodiment, the tube 11 may be an assembly of components. For example, the straight extension 11C may be made of a first material and the return bend 11D is made of a second material, such as different first and second metals, and the straight extension 11C and the return bend 11D are connected together, for example, via welding.

[0023]

[0038] Tube 11 has an overall length and a cross-section perpendicular to the length. The cross-section of tube 11 may be uniform throughout its length or may vary throughout its length. For example, straight extension 11C may have a different cross-section than return bend 11D. The cross-section of tube 11 may include a cross-section that is, for example, at least one of circular, elliptical, oblong, and transversely elongated.

[0024]

[0039] The body 12 has a sleeve portion, e.g., sheath 13, that receives the linear extension 11C of the tube 11. The body 12 also has an exterior surface 15 that includes surface features 14, such as a three-dimensional surface pattern, to guide fluid flowing across the exterior surface 15 and / or enhance heat transfer between the fluid flowing across the exterior surface 15 and the body 12. Examples of surface features 14 include protrusions, e.g., chevrons, peaks and valleys, ridges, etc., and the surface features 15 may be formed in a variety of different patterns or configurations to control fluid distribution throughout the assembly and enhance heat transfer between the process fluid in the tube 11 and a fluid, e.g., water and / or air, that contacts the exterior surface 15 of the body 12.

[0025]

[0040] The body 12 may be made of one or more thermally conductive polymeric materials, which may provide increased strength and improved thermal performance compared to conventional heat exchanger materials. In one embodiment, the thermally conductive polymer comprises an elastomer, such as a plastic, synthetic rubber, or natural rubber. The elastomer is infused with graphite or metal particles to provide thermal conductivity. In another embodiment, the thermally conductive material comprises a polymer and continuous fibers or wires of metal in the polymer.

[0026]

[0041] The thermally conductive polymer of the body 12 may be a polymeric material doped with a metallic material. For example, the thermally conductive polymer of the body 12 may be a thermoplastic polyurethane (TPU) doped with a thermally conductive material. As another example, the thermally conductive polymeric elastomer of the body 12 may include polylactic acid (PLA), acrylonitrile butadiene styrene (ABS), or a nylon-based material. The thermally conductive doping material may include, for example, graphite fibers, aluminum fibers, or copper fibers.

[0027]

[0042] In one embodiment, body 12 is a shell for tube 11, with inlet end portion 11A, outlet end portion 11B, and return bend 11D outside the shell. Body 12 has a perimeter 8 that includes vertical edges 8A, 8B and horizontal edges 8C, 8D. Note that the terms vertical and horizontal are used to describe relative positioning, rather than describing an orientation with respect to, for example, the Earth.

[0028]

[0043] 1, the body 12 may have an upper filler portion 5A extending above the topmost of the linear extensions 11C of the tubes 11 and a lower filler portion 5B extending below the bottommost of the linear extensions 11C. The upper and lower filler portions 5A, 5B provide additional surface area for a fluid, such as an evaporative liquid, to move along the body 12 and transfer heat to and from the body 12. Additionally, in an embodiment in which an evaporative liquid, such as water, is distributed onto the hybrid heat exchanger 10 and an airflow is directed along the evaporative heat exchanger 10 against or across the evaporative liquid, the upper and lower filler portions 5A, 5B provide additional area for potential and detectable heat transfer between the air and the evaporative liquid. The upper and lower filler portions 5A, 5B may include surface enhancing features, such as protrusion patterns, chevrons, ridges, grooves, male / female members, and the like.

[0029]

[0044] 2, a hybrid heat exchanger assembly 16 is provided having a plurality of hybrid heat exchangers 10 connected in parallel to an inlet header 17 and an outlet header 18. The tubes 11 of each hybrid heat exchanger 10 define a separate flow path or circuit for the process fluid from the inlet header 17 to the outlet header 18. The inlet and outlet headers 17, 18 may be reversed for a given embodiment.

[0030]

[0045] The bodies 12 have spacing 19 therebetween that allows fluid to travel along the exterior surface 15 of the bodies 12. In one embodiment, each tube 11 has a respective body 12 integral therewith, with spacing between the bodies 12. In another embodiment, a unitary body 12 may be integral (e.g., molded, 3D printed, assembled) with two, three, or more tubes 11. The unitary body 12 may have through openings therein that allow air and evaporative fluid to pass through the hybrid heat exchanger assembly 16. An exemplary unitary body configuration is discussed in more detail below with respect to FIG. 10.

[0031]

[0046] With reference to FIG. 2, the number of hybrid heat exchangers 10 and the configuration of tubes 11 and body 12 can be customized for a particular application. The body 12 of each hybrid heat exchanger 10 is integrated, laminated, molded, and / or mechanically secured to the tubes 11 using, for example, additive manufacturing, to form a continuous plate-type heat exchanger that helps distribute heat from the process fluid in the tubes 11 and enhances interaction with the fluid, e.g., air and / or evaporative cooling water, contacting the exterior surface 15 of the body 12. To this end, surface features 14 are formed in the body 12 in an application-specific manner. Additionally, the body 12 can extend above, below, or above and below the tubes 11 to create a filler portion (see 5A, 5B in FIG. 1) for the fluid contacting the exterior surface 15 and to enhance the heat transfer characteristics of the hybrid heat exchanger assembly 16.

[0032]

[0047] 3, a thermal rejection device, such as a cooling tower 24, is provided that includes one or more direct and / or indirect heat exchangers, such as a hybrid heat exchanger assembly 16, and packing 34. The cooling tower 24 has an outer structure 26 and one or more fans 28 including fan blades 30 and a motor 32. The cooling tower 24 may be an evaporative condenser, a closed circuit cooling tower, or a dry cooler heat exchanger, as some examples. Although the packing 34 is shown below the hybrid heat exchanger assembly 16, in other embodiments, the packing 34 is above and / or to the side of the hybrid heat exchanger assembly 16.

[0033]

[0048] 3, the cooling tower 24 has an evaporative liquid distribution system 43 including a spray assembly 44 having spray nozzles or orifices 46 that distribute an evaporative fluid, such as water, over the hybrid heat exchanger assembly 16. The evaporative liquid distribution system 43 includes a sump 50 for collecting the evaporative fluid from the packing 34 and the hybrid heat exchanger assembly 16, and a pump 52 for pumping the collected evaporative fluid through a pipe 54 to the spray assembly 44.

[0034]

[0049] The cooling tower 24 further includes one or more air inlets 35, an inlet louver 58 to prevent evaporative liquid from exiting the cooling tower 24, an air outlet 59, and an eliminator 56 to collect water mist from the air before it exits the air outlet 59. The fan 28 is operable to generate or direct an airflow upwardly over the hybrid heat exchanger assembly 16 and the fill 34. In other embodiments, the cooling tower 24 may have one or more fans configured to direct airflow downward or in cross flow over the indirect and / or direct heat exchangers of the cooling tower 24.

[0035]

[0050] With reference to FIG. 4, a cross-sectional view of a portion of the hybrid heat exchanger 10 is provided. The straight extension 11C of the tube 11 is received in the sheath portion 13 of the body 12. The sheath portion 13 extends around the entire cross section of the straight extension 11C for at least a portion of the length 79 (see FIG. 1) of the extension 11C. In one embodiment, the hybrid heat exchanger 10 has a thermally conductive paste 80 intermediate the body 12 and the extension 11C to improve thermal contact between the body 12 and the extension 11C. In other embodiments, the thermally conductive paste 80 is not used. For example, direct printing / molding of the body 12 onto the extension 11C, expanding the extension 11C to engage the body 12C (e.g., by advancing a ball bearing through the tube 11 to increase the outer diameter of the tube 11 or by applying a pressurized liquid into the tube 11), a mechanical connection to secure the body 12 and the tube 11, such as a snap-fit ​​or clamping mechanism, or a baked-on paint method to achieve surface contact between the body 12 and the tube 11 may be used. In some cases, the thermally conductive paste 80 may be a binder or adhesive to provide mechanical stability, such as a non-slip configuration of the tube 11 and the body 12. In one embodiment, the thermally conductive paste 80 may be a coating to protect the tube 11.

[0036]

[0051] With reference to FIG. 5, a hybrid heat exchanger 100 similar to the hybrid heat exchanger 10 discussed above with reference to FIG. 4 is provided. The hybrid heat exchanger 100 has a body 102 of a thermally conductive polymer. The body 102 includes two sheets 104, 106 assembled around an extension 108 of a tube 110. The sheets 104, 106 may include mating portions, e.g., snap fittings, that engage to connect the sheets 104, 106 to the tube 110. The body 102 has a sheath 112 formed by sheath portions 112A, 112B of the sheets 104, 106. The hybrid heat exchanger 100 further includes a thermally conductive paste 114, e.g., an epoxy. The thermally conductive paste 114 may be used to facilitate heat transfer and / or ensure mechanical stability. In one embodiment, the body 102 is heated to bond the sheets 104, 106 to each other and to the tube 110.

[0037]

[0052] With reference to Fig. 6, a hybrid heat exchanger 150 similar to the hybrid heat exchanger 10 discussed above with reference to Fig. 4 is provided. The hybrid heat exchanger 150 includes a tube 152 and a body 154 of a thermally conductive polymer. The body 154 has a sheet 154A and covers 154B, 154C. The sheet 154A has a different size and shape than the covers 154B, 154C. The sheet 154A and covers 154B, 154C cooperate to form a sheath portion 156 of the body 154. The sheath portion 156 has an opening 158 for receiving the tube 152. The sheet 154A and covers 154B, 154C each have a collar portion 160, 162 configured to accommodate an outer surface of the tube 152. In one embodiment, the collar portion 160 of the sheet 154A extends around a majority of the cross-section of the tube 152, and the collar portion 162 of the covers 154B, 154C extends around a smaller portion of the cross-section of the tube 152. In other embodiments, the collar portion 160 may extend around a smaller portion of the cross-section, the collar portion 162 may extend around a majority of the cross-section, or the collar portions 160, 162 may have a similar extent around the cross-section. In one embodiment, the hybrid heat exchanger 150 includes paste 164 in the openings 158 between the body 154 and the tubes 11. The paste 164 may be used to facilitate heat transfer and / or ensure mechanical stability.

[0038]

[0053] 7A-7C, an exemplary method for forming a hybrid heat exchanger is provided. The method includes forming a body 200 of a thermally conductive polymer using an additive manufacturing apparatus 202 and integrating the body 200 with a tube 204. The tube 204 can be, for example, a continuously formed metal tube or a tube made of another thermally conductive pressure-treated material.

[0039]

[0054] The apparatus 202 includes a thermally conductive polymer filament 206, gears 208 for threading the filament 206 through a heating chamber 210 used to melt the filament to a nozzle 212. The nozzle 212 deposits the molten filament 214. After deposition, the molten filament 214 becomes a solidified filament 216. In some embodiments, a removable support material, such as a mold plate 218, is provided. The mold plate 218 can be removed, for example, by being crushed or dissolved in a liquid. Removal of the mold plate 218 leaves a corresponding shape in the solidified filament 216, for example, the protrusion 221 in FIG. 7A is removed leaving a recess 220 in the solidified filament 216. In some embodiments, a build plate 222 can be provided onto which the molten filament 214 is initially deposited. The solidified filament 216 can be removed from the mold plate 218 once the body 200 is completed.

[0040]

[0055] 7A-7C includes that the body 200 is formed using a fused deposition modeling (FDM) 3D printing process. Other additive manufacturing processes such as selective laser sintering, stereolithography (SLA) 3D printing, and / or binder jetting may also be used.

[0041]

[0056] The filament 206 is plasticized at the nozzle 212 and selectively deposited layer-by-layer to form the desired shape of the body 200. Multiple nozzles 212 can be used to speed up the process and / or print dissimilar materials (e.g., a soluble sacrificial support material in addition to the conductive polymer). The printed body 200 in FIG. 7A includes a collar portion, e.g., a channel 224, sized for the tube 204 to be positioned therein.

[0042]

[0057] The method includes positioning the tube 204 in the channel 224, as shown in Figure 7B. The method includes subsequently depositing the molten filament 214 to embed the tube 204 in the channel 224, as shown in Figure 7C. The method of Figures 7A-7C may be aided with a thermally conductive paste around the tube 204, bake-on paint techniques, and / or mechanical fastening methods to secure all components into a completed, thermally efficient assembly.

[0043]

[0058] 7D-7F, cross sections of various types of thermally conductive polymer filaments that may be used with the methods described herein are provided. With reference to FIG. 7D, a thermally conductive polymer filament 230 is provided having a matrix phase 231 of a polymer material that may or may not be thermally conductive. The thermally conductive polymer filament 230 further includes a particle phase 232 of an electrically conductive material such as graphite or a metal.

[0044]

[0059] 7E, a thermally conductive polymer filament 234 is provided having a thermally conductive matrix 235 and a continuous wire 236. The thermally conductive matrix 235 may be, for example, an elastomer, e.g., a plastic material doped with a thermally conductive material such as graphite, aluminum, and / or copper.

[0045]

[0060] The continuous wire 236 may be made of a metallic material, such as copper and / or nichrome, that acts as a thermally conductive material. In embodiments in which the continuous wire 236 includes nichrome, an electric current may be applied to the nichrome material to generate heat in the continuous wire 236. Referring to FIG. 3, in one embodiment, the cooling tower 24 may include a power source 99 operable to apply an electric current to the nichrome wire of the body 12 for an active heating cycle. The active heating cycle may be used as a defrosting, freeze protection method, or to force a phase change in a phase change material of the body 12, as discussed below.

[0046]

[0061] With reference to FIG. 7F, a thermally conductive polymer filament 240 is provided having a thermally conductive shell 241 made of, for example, TPU, ABS, or PLA plastic. The thermally conductive polymer filament 240 also has a phase change core 242 made of, for example, paraffin, non-paraffin organics, and / or hydrated salts. The phase change core 242 has the ability to undergo, for example, a solid-liquid phase change after the thermally conductive polymer filament 240 is laid down and cured. The phase change of the phase change core 242 allows the thermally conductive polymer body printing using the thermally conductive polymer filament 240 to absorb heat via the changing state of the phase change core 242. In this manner, the thermally conductive polymer body printing using the thermally conductive polymer filament 240 provides energy storage as well as energy transfer.

[0047]

[0062] 8A-8C, an exemplary method is provided for forming a hybrid heat exchanger 250 (see FIG. 8C) using injection molding and a mold 252. The hybrid heat exchanger 250 includes a fluid conduit, such as a tube 260, and a body 262 of a thermally conductive polymer.

[0048]

[0063] 8A, the mold 252 has a first mold portion, e.g., an upper pattern 254, a second mold portion, e.g., a lower pattern 256, and a cavity 258 therebetween. The method includes positioning a fluid conduit, e.g., a tube 260, in the mold 252 and closing the mold 252 so that the tube 260 is in the cavity 258. The tube 260 is positioned in the cavity 258 so that there is sufficient spacing between the tube 260 and the upper and lower patterns 254, 256 to form a desired thickness of the body 262. Injection molding the thermally conductive polymer onto the tube 260 allows the polymer to fuse with the tube 260, which fills the openings between the tube 260 and the thermally conductive polymer to improve thermal contact between the tube 260 and the body 262. Injection molding the thermally conductive polymer onto the tube 260 also provides structural rigidity for the hybrid heat exchanger 250.

[0049]

[0064] With reference to Figure 8B, the method includes injecting a thermally conductive polymer 270 into the cavity 258 of the mold 252 and filling a portion 272 of the cavity 258. As shown in Figure 8C, a molten front 274 of the polymer 270 advances throughout the cavity 258 until the cavity 258 is filled with the polymer 270.

[0050]

[0065] 8C shows the hybrid heat exchanger 250 after the thermally conductive polymer 270 has been injected and prior to removal or ejection of the hybrid heat exchanger 250 from the mold 252. In some approaches, post-molding or bake-on paint techniques may be applied after solidification of the polymer 270 to finish the assembly and provide the desired thermal contact and rigidity for a particular embodiment.

[0051]

[0066] With reference to Figure 9, a hybrid heat exchanger assembly 300 is provided that is similar in many respects to the hybrid heat exchanger assembly 16 of Figure 2. The hybrid heat exchanger assembly 300 includes a plurality of hybrid heat exchangers 302 connected in parallel to an inlet header 304 and an outlet header 306. The hybrid heat exchanger assembly 300 has a frame 308 that holds the hybrid heat exchangers 302 fixed relative to one another.

[0052]

[0067] 10, a body 350 of thermally conductive polymer is shown. Body 350 has an arrangement of sheets 352 formed as a single piece using, for example, additive manufacturing. Body 350 has openings 354 to allow airflow through body 350 and a sheath portion 356 for receiving a fluid conduit, such as an extension of a serpentine tube, connected via a return bend outside body 350. In one embodiment, sheets 350 are connected via struts in body 350 that extend between sheets 350.

[0053]

[0068] 11, a hybrid heat exchanger 400 is provided having an inlet tube 402, an outlet tube 404, and three tubes 406 connecting the inlet and outlet tubes 402, 404. The tubes 406 each include a straight extension 412 and a return bend 414 connecting the straight extensions 412. The hybrid heat exchanger 400 has a body 408 of a thermally conductive polymer that is thermally integrated with the tubes 406. The body 408 is thermally integrated with the straight extensions 412 as well as the return bend 414. The return bend 414 is within an outer periphery 420 of the body 408. In one embodiment, the straight extensions 412 and the return bend 414 are embedded in the body 408.

[0054]

[0069] The thermally conductive polymer body 410 has surface enhancement features such as chevrons 410. In one embodiment, the evaporating liquid is distributed onto the hybrid heat exchanger 400 in a direction 411 and the air moves across the hybrid heat exchanger 400 in a cross-flow or counter-flow across the hybrid heat exchanger 400. The surface enhancement features 410 create a tortuous path for the evaporating liquid to move across the hybrid heat exchanger 411 which limits air blow-by and improves heat transfer between the air and the evaporating liquid.

[0055]

[0070] 12, a portion of a hybrid heat exchanger 450 is provided. The hybrid heat exchanger 450 includes a fluid conduit, such as a tube 452, and a body 454 of a thermally conductive polymer integral with the tube 452. The tube 452 has a centerline 453 with a distance 455 therebetween.

[0056]

[0071] Body 454 has chevrons 456 for affecting fluid flow across an exterior surface 458 of body 454. The chevrons 456 are arranged in alternating rows, with a first row extending at a positive angle 460 to the vertical and an adjacent row extending at a negative angle 460 to the vertical. The angled orientation of the chevrons 456 causes the fluid to move in a direction 462 across the exterior surface 458 of body 454 in a zigzag path across the exterior surface 458, which improves heat exchange between the fluid and body 454.

[0057]

[0072] 13, the chevron 456 includes ridges 472 and grooves 474 formed by wall portions 476 of the body 454. The ridges 472 have peaks 480 and the grooves 474 include valleys 482. The body 454 has a peak-to-valley height 484, a peak-to-valley distance 486, and a distance 488 between sheath portions 490 of the body 454 that may be selected for a particular embodiment. The sheath portions 490 extend around the entire cross section of the tube 452 and are joined to a sidewall 492 of the tube 452. In other embodiments, the sheath portions 490 may extend around less than the entire cross section of the tube 452.

[0058]

[0073] With reference to Figure 14, a hybrid heat exchanger 500 is provided that includes an inlet tube 502, an outlet tube 504, a circuit tube 506, and a thermally conductive polymer body 508. In Figure 15, the inlet tube 502 and the outlet tube 504 have been removed to show that the circuit tube 506 includes a straight extension 510 and a return bend 512. The tube 506 extends through an opening 514 in a housing 516 for the body 508. The tube 506 may be, for example, a copper tube.

[0059]

[0074] With reference to FIG. 16 , a hybrid heat exchanger 550 is provided that includes a fluid conduit, e.g., a copper tube 552, and a body 554 of a thermally conductive polymer thermally integrated with the copper tube 552. The body 554 has a collar portion 556 and fins 560 that extend around an opening 558 in the body 554. The body 554 is 3D printed using a thermally conductive polymer filament. The copper tube 552 was advanced into the opening 558 after printing of the body 554 to assemble the hybrid heat exchanger 550. The outer diameter of the copper tube 552 was larger than the inner diameter of the opening 558 after 3D printing of the body 554. Advancing the copper tube 552 into the opening 558 deformed the collar portion 556 of the body 554 around the opening 558, creating an interference fit that secured the body 554 to the copper tube 552. In another approach, the copper tube 552 has an outer diameter smaller than the inner diameter of the opening 558 in the body 554, the copper tube 552 is advanced into the opening 558, and the copper tube 552 is expanded to engage the body 554 by applying high pressure fluid (e.g., water) to the interior of the copper tube 552.

[0060]

[0075] A variety of different materials can be used in additive manufacturing processes to form the hybrid heat exchangers described herein, with considerable possible variation in performance / functionality of the thermally conductive polymer materials. For example, adding continuous copper wire may increase thermal conductivity and / or adding continuous nichrome wire may provide heating properties to the hybrid heat exchanger. Embedding phase change material into the additively manufactured filament also allows for a variety of thermal energy storage designs to be used in accordance with these disclosures.

[0061]

[0076] Use of singular terms such as "a," "an," and the like are intended to cover both the singular and the plural, unless otherwise stated herein or clearly contradicted by context. The terms "comprising," "having," "including," and "containing" are to be construed as open-ended terms. The phrase "at least one of," as used herein, is intended to be construed in a disjunctive sense. For example, the phrase "at least one of A and B" is intended to encompass A, B, or both A and B.

[0062]

[0077] While particular embodiments of the present invention have been illustrated and described, it will be understood that numerous changes and modifications will occur to those skilled in the art, and it is intended that the present invention cover all such changes and modifications that fall within the scope of the appended claims.

Claims

1. 1. A heat exchanger system comprising: an inlet header for receiving a process fluid; An exit header; a plurality of fluid conduits of a first thermally conductive material, each of the fluid conduits having an inlet end portion connected to the inlet header, an outlet end portion connected to the outlet header, and an intermediate portion along the fluid conduit between the inlet and outlet end portions, the fluid conduits configured to allow a process fluid to flow from the inlet header to the outlet header; a body of a thermally conductive polymer having an outer surface different from the first thermally conductive material; Including, the thermally conductive polymer body is in thermal contact with the intermediate portion of the fluid conduit and is configured to facilitate heat transfer between the process fluid and a fluid on the exterior surface of the thermally conductive polymer body as the process fluid travels through the intermediate portion of the fluid conduit.

2. The heat exchanger system of claim 1 , wherein the thermally conductive polymer body is secured to the intermediate portion of the fluid conduit and spaced from the inlet and outlet headers.

3. the fluid conduits each have a length; The heat exchanger system of claim 1 , wherein at least one of the fluid conduits is embedded in the thermally conductive polymer body over at least a portion of the length of the at least one fluid conduit.

4. the fluid conduits each have a length; The heat exchanger system of claim 1 , wherein the thermally conductive polymer body is in thermal contact with the fluid conduit over at least a majority of the length of the fluid conduit.

5. each of the fluid conduits having an outer surface and a cross section perpendicular to said length; 24. The heat exchanger system of claim 23, wherein the thermally conductive polymer body is in thermal contact with the exterior surface of the fluid conduit around at least a majority of the cross-section of the fluid conduit.

6. The hybrid heat exchanger of claim 1 , further comprising a thermally conductive paste thermally connecting said thermally conductive polymer body and said fluid conduit.

7. The hybrid heat exchanger of claim 1 , wherein the thermally conductive polymer body has a thermal conductivity of at least 2 Watts per meter-Kelvin.

8. a fan operable to generate airflow across said thermally conductive polymer body; an evaporated liquid distribution system configured to distribute the fluid onto the exterior surface of the thermally conductive polymer body; and a sump for collecting said fluid from said exterior surface of said thermally conductive polymer body; The hybrid heat exchanger of claim 1 further comprising:

9. the thermally conductive polymer body comprising a polymeric material; Graphite particles, metal particles, Metal wire, and Phase change materials The hybrid heat exchanger of claim 1 , comprising at least one of:

10. The fluid conduit comprises: Stainless Steel Tube, Aluminum tube, Copper tubes, and Carbon Steel Tube The hybrid heat exchanger of claim 1 , comprising at least one of:

11. The hybrid heat exchanger of claim 1 , wherein the fluid conduits are microchannels.

12. 1. A method of forming a hybrid heat exchanger, the method comprising: providing a metallic tube having an interior for receiving a process fluid; manufacturing a body of thermally conductive polymer, the body having an exterior surface with surface enhancing features to affect fluid flow at the body exterior surface; Thermally integrating said thermally conductive polymer body and said metallic tube. The method includes:

13. The method of claim 12 , wherein the metallic tube includes an inlet end portion, an outlet end portion, an extension, and at least one bend connecting the extension.

14. the metallic tube having an exterior portion with a first surface area; thermally integrating the thermally conductive polymer body and the metallic tube includes fastening the thermally conductive polymer body and the outer surface portion of the metallic tube; The method of claim 12 , wherein the thermally conductive polymer body includes an exterior surface having a second surface area greater than the first surface area.

15. The method of claim 12 , wherein manufacturing the thermally conductive polymer body comprises manufacturing the thermally conductive polymer body using additive manufacturing.

16. 16. The method of claim 15, wherein thermally integrating the thermally conductive polymer body and the metallic tube comprises additively manufacturing the thermally conductive polymer in situ with the metallic tube.

17. manufacturing the thermally conductive polymer body includes manufacturing portions of the thermally conductive polymer body using additive manufacturing; The method of claim 12 , wherein thermally integrating the thermally conductive polymer body and the metallic tube comprises assembling the portion of the thermally conductive polymer body and the metallic tube.

18. The method of claim 12 , wherein manufacturing the thermally conductive polymer body comprises molding the thermally conductive polymer body.

19. 20. The method of claim 18, wherein thermally integrating the thermally conductive polymer body and the metallic tube comprises in-situ molding the thermally conductive polymer body with the metallic tube.

20. The method of claim 12 , wherein thermally integrating the thermally conductive polymer body comprises positioning a thermally conductive paste between the thermally conductive polymer body and the metallic tube.

21. 13. The method of claim 12, wherein thermally integrating the thermally conductive polymer body and the metallic tube comprises melting a portion of the thermally conductive polymer body, the melted portion of the thermally conductive polymer body melting to fill an opening between the thermally conductive polymer body and the metallic tube.

22. The method of claim 12 , wherein fabricating the thermally conductive polymer body comprises using additive manufacturing of a polymer material infused with discontinuous conductive particles.

23. 13. The method of claim 12, wherein manufacturing the thermally conductive polymer body comprises using additive manufacturing comprising forming a bead comprising a metal thread and a polymer annulus extending around the thread.

24. The metal tube is Stainless Steel Tube, Aluminum tube, Copper tubes, and Carbon Steel Tube The method of claim 12 , comprising at least one of:

25. providing the metallic tubes includes providing at least three metallic tubes; The method of claim 12 , wherein thermally integrating the thermally conductive polymer body and the metallic tube comprises integrating a unitary polymer body with the metallic tube.

Images