Dual manifold thermoelectric heat exchanger

Abstract

A heat transfer device having a housing and a manifold. The manifold has a first channel that transfers a first medium at a first temperature from a first input to a first output, and a second channel that transfers a second medium at a second temperature from a second input to a second output. The manifold is formed of a thermoelectric material that pumps heat between the first and second mediums or generates electricity based on the temperature differential between the first and second mediums. An electrically conductive material layer is formed about the thermoelectric material to receive or supply the electricity. And a sealing layer is formed about the electrically conductive material layer.

Description

DUAL MANIFOLD THERMOELECTRIC HEAT EXCHANGERRelated Application

[0001] This application claims the benefit of priority of U.S. Provisional Application No. 63 / 663,232, filed on June 24, 2024, including the references cited therein, the entire content of which is relied upon and incorporated herein by reference in its entirety.Government License Rights

[0002] This invention was made with Government support under Grant No. N00014-20- 1 -2365 177047 awarded by the Office of Naval Research. The Government has certain rights in this invention.Background

[0003] Thermoelectrics are a form of solid-state energy devices that produce an electrical potential (i.e., voltage) when a temperature gradient is imposed across them, or they can pump heat when a voltage is applied to them. They have been utilized across a broad spectrum of applications, serving as both a load and a source in various scenarios. These applications span from their use as heat pump devices within common heater / cooler systems such as automobile seat coolers to their deployment as power generators aboard space satellites. Thermoelectrics are attractive because they have no moving parts, require little maintenance, and are silent. Bulk, macroscale thermoelectric devices are typically constructed by hot pressing, sintering, or growing the material into large ingots from powder or crystals. The ingots are then diced into the thermoelectric legs which are attached to an insulator and with contacts making up a module. This construction allows for the legs to be electrically in series while thermally in parallel. The manufacturing cost of thermoelectrics can be cost prohibitive due to material waste in the manufacturing process and inefficiencies from the device shapes and components. Since thermoelectric devices provide small amounts of power, they are often not integrated into applications because the process and device become cost prohibitive.

[0004] There is prior work that discusses additive manufacturing of thermoelectric materials and devices with methods such as laser powder bed fusion or selective laser sintering / melting, fused deposition modeling, ink printing, and binder jetting. Additive manufacturing allows for theability to change the thermoelectric leg and device shapes. It has been shown that changing the thermoelectric legs shape increases the thermal resistance and increases the power output. US20190229252 relates to additive manufacturing of thermoelectric devices including the sintering of powder and the basis for powder bed fusion while also discussing the sintering of powder layer by layer to construct a 3D part. TW201627256A describes an additive manufacturing technique in which thermoelectric powder is placed in select locations in a membrane to form electrically isolated columns of thermoelectric material; the powder is then sintered and fused to form thermoelectric components. US20130218241, US9419197, CN114655936A, US6942728B2, WO2018143598A1 relate to thermoelectric powder or heat treatment of traditionally manufactured thermoelectric materials. These systems conform to traditionally manufactured thermoelectric designs and shapes.

[0005] Periodic minimal surface heat exchangers are heat exchangers that use periodic minimal surfaces and their properties to help increase heat exchange between two fluids. Prior art shows triply periodic minimal surfaces in a heat exchanger because these surfaces have good mass transfer properties or because the lattice structure induces turbulence. There was also an investigation into the strength properties that triply periodic minimal surfaceshave and how they could be integrated into heat exchangers. There is also prior art related to how the triply periodic minimal surface heat exchangers compared to traditional heat exchangers with comparisons using computational models. There were also investigations of the effect of constructing a heat exchanger out of triply periodic minimal surfaces because of their effect on the thermal conductivity. There are also investigations of other types of structures that have bi-manifold symmetry and their potential application to heat exchangers.

[0006] US20220196337, US20220003503, US11389765, US20200033070, US20190145298 are concerned with a device that uses the triply periodic minimal surface to increase their efficiency or capabilities by taking advantage of the bi-manifold symmetry, or the high heat transfer. US20210216683 andUS7866377 focus on controlling the thermal conductivity of the device by using triply periodic minimal surfaces. US20210180885 focuses on the method for construing bi- manifold devices.

[0007] Thermoelectric heat exchangers include the implementation of thermoelectric devices into devices that have wasted heat such as car mufflers, carburetors, and plane heat. Other work focused on different methods for optimizing thermoelectric devices by optimizing thethermoelectric component size, material, and boundary conditions. There is also prior art discussing using thermoelectric heat exchangers on a large scale. US8001794, US7650757, US4306426 add thermoelectric devices to heat exchanger systems to assist in cooling down a fluid. US20180031285 and US20150128614 add thermoelectrics to heat exchangers to take advantage of the wasted heat. Lastly, US8378205 shows a new way to construct thermoelectric heat exchangers. However, all of the prior art is for traditional thermoelectric devices that are constructed in rectangular shapes with the thermoelectric device attached to the heat exchanger. There was no mention of heat exchangers with integrated thermoelectric materials and functionality. There is also no mention of changing the shape of the thermoelectric heat exchanger with bi-manifold symmetry.

[0008] Other thermoelectric heat exchangers are shown in the following papers. [4.1] Webb, R.L., M. D. Gilley, and V. Zarnescu. “Advanced Heat Exchange Technology for Thermoelectric Cooling Devices.” Journal of Electronic Packaging 120, no. 1 (March 1, 1998): 98-105. Karri,M.A., E.F. Thacher, and B.T. Helenbrook. “Exhaust Energy Conversion by Thermoelectric Generator: Two Case Studies.” Energy Conversion and Management 52, no. 3 (March 2011): 1596-1611. Lu, Hongliang, Ting Wu, Shengqiang Bai, Kangcong Xu, Yingjie Huang, Weimin Gao, Xianglin Yin, and Lidong Chen. “Experiment on Thermal Uniformity and Pressure Drop of Exhaust Heat Exchanger for Automotive Thermoelectric Generator.” Energy 54 (June 2013): 372-77. Liu, Yan, Zhaochun Shi, Guohua Wang, YuYing Yan, and Yingchao Zhang.“Experimental Investigation for a Novel Prototype of a Thermoelectric Power Generator With Heat Pipes.” Frontiers in Energy Research 9 (September 20, 2021): 744366. Liu, X., Y.D. Deng, K. Zhang, M. Xu, Y. Xu, and C.Q. Su. “Experiments and Simulations on Heat Exchangers in Thermoelectric Generator for Automotive Application.” Applied Thermal Engineering 71 , no. 1 (October2014): 364-70. Wang, Yiping, Shuai Li, Yifeng Zhang, Xue Yang, Yadong Deng, and Chuqi Su. “The Influence of Inner Topology of Exhaust Heat Exchanger and Thermoelectric Module Distribution on the Performance of Automotive Thermoelectric Generator.” Energy Conversion and Management 126 (October 2016): 266-77. Ahammed, Nizar, Lazarus Godson Asirvatham, and Somchai Wongwises. “Thermoelectric Cooling of Electronic Devices with Nanofluid in a Multiport Minichannel Heat Exchanger.” Experimental Thermal and Fluid Science 74 (June 2016): 81-90. Hasebe, M., Y. Kamikawa, and S. Meiarashi. “Thermoelectric Generators Using Solar Thermal Energy in Heated Road Pavement.” In 2006 25th InternationalConference on Thermoelectrics, 697-700. Vienna, Austria: IEEE, 2006. Wang, Tongcai, Weiling Luan, Wei Wang, and Shan-Tung Tu. “Waste Heat Recovery through Plate Heat Exchanger Based Thermoelectric Generator System.” Applied Energy 136 (December 2014): 860-65. Zhu, Lin, Hongbo Tan, and Jianlin Yu. “Analysis on Optimal Heat Exchanger Size of Thermoelectric Cooler for Electronic Cooling Applications.” Energy Conversion and Management 76 (December 2013): 685-90. Astrain, David, Juliana Jaramillo-Fernandez, Miguel Araiz, Achille Francone, Leyre Catalan, Alejandra Jacobo-Martin, Patricia Alegria, and Clivia M. Sotomayor-Torres. “Enhanced Behaviour of a Passive Thermoelectric Generator with Phase Change Heat Exchangers and Radiative Cooling.” Applied Thermal Engineering 225 (May 2023): 120162. Riffat, S. B., and Xiaoli Ma. “Improving the Coefficient of Performance of Thermoelectric Cooling Systems: AReview.” International Journal of Energy Research 28, no. 9 (July 2004): 753-68. Esarte, J., G. Min, and D.M. Rowe. “Modelling Heat Exchangers for Thermoelectric Generators.” Journal of Power Sources 93, no. 1-2 (February 2001): 72-76. David, Benjamin, Julien Ramousse, and Lingai Luo. “Optimization of Thermoelectric Heat Pumps by Operating Condition Management and Heat Exchanger Design.” Energy Conversion and Management 60 (August 2012): 125-33. Astrain, D., J.G. Vian, A. Martinez, and A. Rodriguez. “Study of the Influence of Heat Exchangers’ Thermal Resistances on a Thermoelectric Generation System.” Energy 35, no. 2 (February 2010): 602-10. Panya Yodovard, Joseph Khedari, Jon. “The Potential of Waste Heat Thermoelectric Power Generation From Diesel Cycle and Gas Turbine Cogeneration Plants.” Energy Sources 23, no. 3 (April 2001): 213-24. Ahammed, Nizar, Lazarus Godson Asirvatham, and Somchai Wongwises. “Thermoelectric Cooling of Electronic Devices with Nanofluid in a Multiport Minichannel Heat Exchanger.” Experimental Thermal and Fluid Science 74 (June 2016): 81-90. All the references mentioned herein are incorporated by reference in their entireties.SUMMARY

[0009] To use thermoelectrics more universally, a multifunctional design is needed so that thermoelectrics can be integrated into other functional components. Additive manufacturing can facilitate this by printing thermoelectrics in unique geometry so that it can have both thermoelectric properties as well structural, thermal, or electrical functionality. Additiveprocessing allows the device to be fabricated in a freeform manner, layer by layer, by simultaneously printing the different layers (thermoelectric, electric contact, and electric insulating). However, additive manufacturing a device out of thermoelectric materials is one possible method. Other manufacturing methods, perhaps not developed yet, could also be used to create unique device shapes. There are several methods to produce additive manufactured thermoelectrics. Some attempts have involved fused deposition methods, stereolithography, direct ink writing, and laser powder bed fusion.

[0010] The present disclosure manufactures thermoelectric material in any shape that has a bimanifold symmetry.

[0011] These and other objects of the disclosure, as well as many of the intended advantages thereof, will become more readily apparent when reference is made to the following description, taken in conjunction with the accompanying drawings. This summary is not intended to identify all essential features of the claimed subject matter, nor is it intended for use in determining the scope of the claimed subject matter. It is to be understood that both the foregoing general description and the following detailed description are exemplary and are intended to provide an overview or framework to understand the nature and character of the disclosure.BRIEF DESCRIPTION OF THE FIGURES

[0012] The accompanying drawings are incorporated in and constitute a part of this specification. It is to be understood that the drawings illustrate only some examples of the disclosure and other examples or combinations of various examples that are not specifically illustrated in the figures may still fall within the scope of this disclosure. Examples will now be described with additional detail through the use of the drawings, in which:

[0013] FIGS. 1 A and IB shows a triply periodic minimal surface gyroid as it is produced in accordance with an example embodiment of the disclosure.

[0014] FIGS. 1C shows a triply periodic minimal surface gyroid with two manifolds, each manifold having a different color for illustrative purposes.

[0015] FIG. 2A is an example of a simple heat exchanger design that has two inlets and two outlets one for each manifold.

[0016] FIG. 2B is a cross section of the simple heat exchanger showing the two manifold triply periodic minimal surface gyroid interwoven into the device.

[0017] FIG. 3 A is a 3D view showing the two manifold triply periodic minimal surface gyroid thermoelectric material (gray), coated with a contacting material (gold), and an insulating plastic (red).

[0018] FIG. 3B is a view of a heat exchanger showing the multi layered gyroid on the right and the multilayered gyroid inside a box with inlet and outlet ports. The black would be the thermoelectric material, the green the contacting material, and the red an electrically insulating material such as plastic.

[0019] FIG. 3C, 3D is a 3D printed layered gyroid inserted into the heat exchanger body with cap removed, rendering shown in (B).

[0020] FIG. 3E is a 3D printed layered gyroid structure inserted into the heat exchanger body with a top.

[0021] FIG. 4 is the gyroid structure inserted into the heat exchanger body with the top removed and the hot and cold manifolds colored for clarity.

[0022] FIG. 5A is a chart showing the electric potential distribution across the device.

[0023] FIG. 5B is a chart showing temperature distribution within the heat exchanger.

[0024] FIG. 5C is a chart showing fluid flow pressure drop through the structure.

[0025] FIG. 5D is a chart showing fluid flow velocity and temperature within the heat exchanger.

[0026] FIG. 6A is a chart showing heat transfer rate of the thermoelectric heat exchanger over the heat transfer rate of copper vs. various thermoelectric thermal conductivities.

[0027] FIG. 6B is a chart showing power and power per area of the heat exchanger for various thermoelectric thermal conductivities.

[0028] FIG. 6C is a chart of the power and power per area for a range of thermoelectric material Seebeck coefficients.

[0029] FIGS. 7A, 7B are perspective views of a compartmentalized heat exchanger, n-type and p-type materials are shaded with light and gray material respectively. The thermoelectric materials are electrically insulated from the fluids. The two manifolds are colored to illustrate the hot and cold fluid manifolds.

[0030] FIGS. 8 A, 8B show the smallest repeating periodic structure of the heat exchanger of FIGS. 1-4.

[0031] FIGS. 9 and 10 show additional embodiments of the disclosure.DETAILED DESCRIPTION

[0032] In describing the illustrative, non-limiting embodiments illustrated in the drawings, specific terminology will be resorted to for the sake of clarity. However, the disclosure is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes all technical equivalents that operate in similar manner to accomplish a similar purpose. Several embodiments are de scribed for illustrative purposes, it being understood that the description and claims are not limited to the illustrated embodiments and other embodiments not specifically shown in the drawings may also be within the scope of this disclosure.

[0033] Thermoelectric devices need to have a thermal gradient to produce voltage, so they have been used in plate heat exchangers, sandwiched between flow plates. However, this structure is cumbersome and adds complexity to heat exchangers, a technology in which fabrication costs are paramount, and profit margins are low. The present disclosure provides the heat exchangers with thermoelectric functionality; it manufactures part of the heat exchanger itself out of thermoelectric material.

[0034] Thus, in one example embodiment, the present disclosure provides a thermoelectric heat exchanger having a wall made of thermoelectric material that separates a hot fluid from a cold fluid. In an alternative embodiment, a wall has two non-intersecting manifolds (structures that, when looking at each point, have Euclidean space around them, but when, looking at the entire domain, have a much different structure).

[0035] The simplest of these dual manifold systems is that of a plane. This plane separates hot and cold liquid which allow them to thermally interact with each other without mixing. A group of shapes that can generate this phenomenon are minimal surfaces. Minimal surfaces are the result of an energy minimization of a material given specific boundaries. This is done by minimizing the surface area and producing zero mean curvature at every point on the surface (i.e., the sum of the principal curvatures is zero). Some of these surfaces can repeat periodicallyin unit cell structures that take the shape of lattice structures, and these are known as triply periodic minimal surfaces. These surfaces are described by a level set function which can be manipulated and tuned so that the lattice parameters can be altered.

[0036] Turning to the drawings, FIGS. 1-4, a heat exchanger system 10 is shown in accordance with one non-limiting illustrative embodiment of the current disclosure. The heat exchanger 10 includes an otional housing 100 and a manifold assembly 200. The manifold assembly 200 can be provided alone or can formed integrally with the housing 100 (FIG. 2B), for example by extrusion molding or 3D printing, or as a separate device that is placed inside the interior space of the housing 100 (FIG. 3B). The housing 100 includes a housing body 102, one or more input ports, and one or more output ports. In the example embodiment shown, the housing body 102 has the shape of a cube or cuboid with six walls including four side walls, a bottom wall, and a top wall, that together define the housing interior space and a housing exterior. The housing body 102 protects the manifold assembly 200 and encloses the manifold assembly 200. A first input port 110, a second input port 112, a first output port 120, and a second output port 122 are positioned about the housing walls. Here, the first input port 110 is shown on a first side wall, and the first output port 120 is shown on a second side wall opposite the first side wall; the second input port 112 is shown on the second side wall separated from the first output port 120, and the second output port 122 is shown on the first side wall separated from the second input port 112.

[0037] The manifold assembly 200 includes a manifold body 202 formed by one or more channel walls forming one or more flow channels. The manifold assembly 200 can be formed, for example, by extrusion molding or 3D printing. In the embodiment shown, the manifold body 202 has a manifold channel wall 250 that forms a first manifold with a first manifold channel 260, and a second manifold with a second manifold channel 262 (as best shown in FIGS. 1C, 4). In the embodiment shown, there is a single channel wall 250 that defines two channels 260, 262. However, in other embodiments, a first wall (or walls) can define the first channel 260 and a second wall (or walls) can define the second channel 262. The wall 250 is shown as having a curved shape, and certain portions may have a repeating pattern such as a sinusoidal shape (see the faces shown in FIGS. 2B, 3B). In other embodiments, the wall 250 can be linear.

[0038] The manifold assembly 200 has the same shape (cube or cuboid) as the housing 100, though the housing and manifold assembly can have any suitable shape. Thus, the manifoldassembly 200 has four sides or lateral faces (left side face, right side face, front side face, and back side face), a top side or top face, and a bottom side or bottom face, as well as 12 edges and 8 vertexes. As shown, a portion of each face, edge and vertex may be open, and portion of each face, edge and vertex may be closed by the manifold channel wall 250. Where the face, edge and vertex are open, the inner surface of the channel wall 250 forms a wall of the channel. The channel wall 250 comes into contact with the housing wall at the respective housing sides and manifold faces. In other embodiments, the faces of the manifold assembly 200 can be fully closed.

[0039] The first channel 260 has a first end that aligns and is in flow communication with the first input port 110, and a second end that aligns and is in flow communication with the first output port 120. The second channel 262 has a first end that aligns and is in fluid flow communication with the second input port 112, and a second end that aligns and is in fluid flow communication with the second output port 122. The first input port 110 receives a first material, which travels from the first input port 110 through the first channel 260 to the first output port 120. The second input port 112 receives a second material, which travels from the second input port 112 through the first channel 262 to the first output port 122. The first channel 260 is completely isolated from the second channel 262, so that the first material in the first channel 260 does not mix with the second material in the second channel 262. It will be recognized that the input and output ports can be positioned at any side of the housing. For example, the first input port 1 10 and first output port 120 can be located on the same side or adjacent sides, and not on opposite sides. The first and second material can be, for example, a fluid, gel, gas, or solid, and the first material can be the same (e.g., both can be water) as, or different than, the second material (e.g., one can be water and one can be gas, or one can be a first liquid and the other can be a second liquid).

[0040] Three of the most widely known triply periodic minimal surfaces are the gyroid, Schwarz P, and the diamond. The thermoelectric heat exchanger 10 can have the shape of a periodic minimal surface (example shown in FIGS. 1-4). In one embodiment, the heat exchanger 10 has a relatively cold fluid traveling through the first manifold channel 260 and a relatively hot fluid traveling through the second manifold channel 262. As used here, relatively refers to the temperature of the hot fluid is greater than the temperature of the cold fluid, though the hot and cold temperatures can be “equal to” each other, for instance, when one or both of the fluids areundergoing a phase change. The greater the temperature differential the greater the electrical power that is generated. The manifold wall 250 is made of a material that separates the two channels 260, 262 that is made from a thermoelectric material. This allows for the multifunctionality of both heat exchange as well as the production of electrical power and localized heating or cooling.

[0041] The configuration shown in FIGS. 1-4 has a desirable shape because it: (1) keeps the hot and cold fluids separated and (2) provides for large surface area in a small volume to enable more heat transfer between the fluids. It maximizes the amount of surface area for the fluids in a given space. Triply periodic minimal surfaces (TPMSs) are a family of three-dimensional level set equations that define a surface with a mean curvature of zero everywhere on the surface. Minimal surface means that the two principal curvature directions, when averaged, are zero. The principal curvature directions are orthogonal to each other and lie on the surface.K, +K.Mathematically, the mean curvature H can be described as ~ 2 , where K i K 2 are the principle curvatures in two orthogonal directions on the surface. Every point on the surface bends equally in orthogonal directions, which is similar to a saddle shape, so the curvatures cancel each other out. Minimal surface is often formed in nature because it is the shape that forms when a system has minimized its shapes. The exact shape that is formed depends on the boundary conditions that are holding the surface. The unit gyroid minimal surface shape is formed if the surface is bound to the points that form four vertices on a cube as shown in FIGS. 8 A and 8B. This shape can then be moved and rotated to form the gyroid unit cell, which is also a minimal surface (since it is made up of minimal surfaces) but with more complex pinning boundary conditions. This unit cell can then be expanded and manipulated in all directions by controlling the domain of the minimal surface and by manipulating the terms in the level set equation as well. Critically, these minimal surfaces have two domains that do not interact throughout any defined number of unit cells or volumes, making them advantageous for heat exchangers. This minimal surface is extremely complex with high tortuosity that creates a very high surface area for its given volume. If the porosity of this gyroid (or any TPMS) is increased, then the surface area to volume ratio also increases. This is beneficial for a heat exchanger because it allows for more heat to be exchanged between the two fluids, increasing the efficiency of the heat exchanger. The high tortuosity also promotes fluid mixing as it travels through theheat exchanger, improving its performance. This increased heat exchange also allows for heat exchangers to be much more compact.

[0042] Thus, the thermoelectric heat exchanger comprises a thermoelectric device that is constructed with a two manifold symmetry allowing for the passage of two fluids, one fluid and one solid, or two solids to interact thermally without mixing. As best shown in FIG. 3 A, the manifold wall 250 has three layers, a first inner or center layer 252, a second middle layer 254, and a third outer layer 256. The first center layer 252 is a thermoelectric material, which makes up the bulk of the wall 250. The thickness of the various layers 252, 254, 256 can be varied, whereas in some embodiments the first layer 252 is thicker than the middle layer 254 and the outer layer 256, and in other embodiments the first layer 252 is thinner than the middle layer 254 and / or the outer layer 256. And the middle layer 254 and outer layer 256 can have a same thickness or one can be thicker than the other. The second middle layer 254 is a contact coating of a conducting material. This contacting material does not cover the whole thermoelectric material, but only covers manifolds, leaving the edges of the shape uncovered. This means that both manifolds are electrically isolated from each other, and electrical current flows through the thermoelectric material. The third outer layer 256 is an electrically insulating material that separates the fluid from the electrical conducting material of the second middle layer 254. This insulating material of the outer layer 256 can also make up the housing 100 that holds the manifold assembly 200.

[0043] This housing 100 forms the external structure of the heat exchanger 10 and the shape is dictated by the geometry of the device is in which it is implemented. For example, the heat exchanger 10 can be in the shape of a tube around a pipe or thin rectangular plates for a plate heat exchanger. The thermoelectric material then generates a current from the imposed temperature gradient; the current is transferred to the electrical contacts via the conductor layer 254 that is attached to the surface 256 of each manifold. The device has sealed wires that make contact to the device (e.g., at the housing input / output ports 110, 112, 120, 122) to allow for the electrical current to be moved out of the device. An electrical wire 50 is shown, for example, in FIG. 3C to conduct electricity into and out of the device and is in electrical contact with the conductor layer 254. A second contact wire exits the box on the other side of the device. Each contact is to the conductor layer 254 on either side of the thermoelectric material 252, though the wires can be connected at the same side of the housing. For power to be pulled from the device, aload can be placed between these contacts and connected with wires. The insulating material layer 256 is added to prevent electrical shorting of the device with the fluid as well as to reduce corrosion of the contacts and the thermoelectric material.

[0044] Thus, the disclosure is a heat exchanger having a body made from thermoelectric material. The heat exchanger allows two fluids to thermally interact without mixing. This device uses the thermoelectric material itself to separate the two materials, creating a multi-functional material. This device being additively manufactured allows for the device to be created with unique geometry that can be tuned to match the required application conditions. This multifunctionality and ability to tailor this multifunctional device to the specific boundary conditions is unique to this disclosure. The difference in the temperature between the two fluids creates a temperature gradient across the thermoelectric material that results in electrical power generation or localized heat pumping.

[0045] The application is a heat exchanger that has the multifunctional capability of conventional heat exchangers coupled with power generation or heat pumping from thermoelectric components. The heat exchanger 10 canbe used as a multifunctional device both as a heat exchanger and to generate electricity or locally heat / cool fluids and solids. This device has many applications such as in aircraft to efficiently preheat fuel, in petroleum refining, or in wastewater treatment. Any application where heat transfer between materials, waste heat recovery (heat-to-power conversion), or localized thermal control between materials is beneficial is a potential application of this disclosure.

[0046] Current technology uses thermoelectric devices in heat exchangers but only as ancillary devices. Thermoelectric modules are attached to heat exchangers where they harvest some of the waste heat or increase the cooling of the heat exchanger. The heat exchanger system 10 disclosed here uses 3D printing to make thermoelectric materials into shapes that have a two manifold symmetry, like a triply periodic minimal surface although any suitable manufacturing process can be utilized. The thermoelectric material separates the two fluids allowing them to thermally interact without mixing. This creates a multi-functional device that provides both electricity / heat pumping in tandem with heat exchange. This provides additional power generation or heating pumping without sacrificing heat transfer requirements, and can be implemented in a large range of heat exchangers.

[0047] Our design takes advantage of triply periodic minimal surfaces dual manifold structure. These two manifolds allow for two fluids to interact thermally without mixing. Others have implemented thermoelectric devices into heat exchangers. Our system 10 makes the heat exchanger itself out the thermoelectric materials, forcing the thermal interaction through the thermoelectric material. This approach enables heat exchange as well electricity production and / or targeted, localized heating / cooling. The manufacturing of the concept must address three challenges: (1) makingthe thermoelectric material into any form factor required for the design; (2) minimizing waste of thermoelectric material; (3) making the complex periodic structure. Any suitable additive manufacturing of thermoelectric materials can be utilized, such as shown in US20190229252, which can be used in fused filament fabrication (FFF) and laser powder bed fusion (LPBF).

[0048] The basic design of the heat exchanger includes a thermoelectric material layer 252 constructed in the shape of a periodic minimal surface; as an illustration we will use a gyroid structure. The structure is first coated with an electrical conductor layer 254, such as copper, to enable the generated current to flow with minimal resistance. Next, this conductive layer 254 is covered with an electrically insulating material layer 256, like plastic. The entire assembly is then housed inside a box 100 equipped with four ports: one port 110 for hot fluid entry, one port 120 for hot fluid exit, one port 112 for cold fluid entry, and one port for cold fluid exit 122. This setup functions as a heat exchanger, whereby heat transfers from the hot fluid to the cold fluid as the fluids pass through the heat exchanger. Electrical contacts are positioned on the exterior of the structure to extract / supply current from / to the device.

[0049] FIGS. 3-4 show manufacturing a proof of concept of the heat exchanger using multimaterial fused filament fabrication printing and the synthesis of thermoelectric filament. FIGS. 5A and 5B show that computer simulations verify the design would both exchange heat and produce electricity. In some embodiments, water is used as the first and second fluids. The temperature of the water at the hot inlet was 400 K, and the temperature of the cold water was 275 K. These conditions generated an open circuit voltage of 4.20 mV that is evenly distributed across the volume of the thermoelectric gyroid. A short circuit voltage of 26.7A was also produced as well as a power output of 28.1 mW. Given the area of the thermoelectric, 0.019 m2, the power generated per area is 1.51 W / m2. FIG. 5C shows the pressure drop across the device was 445 Pa / cm. The heat transfer rate across the device was 144 W.

[0050] These values are exemplary only for a triply periodic minimal surface configuration of the heat exchanger having material: Thermoelectric Gyroid Volume: 16,609.17 mm3; Thermoelectric Gyroid Surface Area: 181,407.58 mm2; Thermoelectric Gyroid Thickness: 1.00 mm; High Electrical Conductivity Gyroid Volume: 3,794.62 mm3x2 (two sides); High Electrical Conductivity Gyroid Surface Area: 15,840.74 mm2x2 (two sides); High Electrical Conductivity Gyroid Thickness: 0.50 mm (both sides); Electrical Insulation Gyroid Volume: 3,343.1 1 mm3x2 (two sides); Electrical Insulation Gyroid Surface Area: 15840.13880.59 mm2x2 (two sides); Electrical Insulation Gyroid Thickness: 0.5 mm (both sides); Overall Container Volume: 63, 161.05 mm3; Overall Container Surface Area: 31,292.78 mm2From this, the hot fluid started at 400 K and dropped to 398.6 K at the end of the heat exchanger. The cold fluid temperature started at275.15 K and reached 276.3 K at the end of the heat exchanger. The average inlet and outlet temperature difference was 1.29K. Assuming that the water density was 997 kg / mA3, and the fluid velocity shown in FIG. 5D was 1 m / s, the volumetric flow rate was 0.0000214788, the mass flow rate was 0.021722 kg / s, and the heat capacity was 4182 J / kgC. The heat transfer rate was calculated to be 117 W. The thermoelectric materials utilized will depend on the specific application and fluid temperatures, to maximize the power generation.

[0051] The device 10 also works with thermoelectric materials that have different properties. FIGS. 6A and 6B showthe first comparison was madeto thermoelectric materials with different thermal conductivity values because the thermal conductivity would impact the amount of heat transferred in the heat exchanger. To compare the ability of the dual manifold thermoelectric heat exchanger to perform heat exchange, the geometry of the heat exchanger was kept the same, and the thermoelectric material was replaced with a common heat exchanger material, copper, and the heat transfer rates were compared. To examine how the heat exchanger might perform with different thermoelectric materials, we first changed the thermal conductivity of the thermoelectric material and calculated the heat transfer rate compared to non-thermoelectric copper (thermal conductivity of 400 W / mK) for a known range of thermoelectric thermal conductivities: from 0.2 W / mK to 2.0 W / mK. The heat transfer rate when compared to copper increased as the thermal conductivity increased because more heat can be exchanged between the two materials. The power output also decreased as the thermal conductivity increased because the temperature difference across the thermoelectric decreased

[0052] To further investigate the impact of different thermoelectric materials / properties, FIG. 6C shows the power output was calculated for a range of Seebeck coefficient values, -0.9 mV / K to 0.9mV / K. As expected, there was zero power generated with a Seebeck coefficient of zero and a maximum of 0.37 W or 19.65 W / m2at 0.9mV / K.

[0053] We doubled the volume of the heat exchanger to understand how an increase in volume (i.e., a larger heat exchanger) changes the power output of the device. An open circuit voltage of 0.0055 V, and a short circuit voltage of 32.5A was generated. This resulted in power of 44.23 mW and a pressure loss of 9279.75 Pa / cm. The larger volume also resulted in a much larger heat transfer rate of 1 197.32 W. The larger volume resulted in a much higher heat transfer rate but a much smaller power per volume.

[0054] FIGS. 7A, 7B show a compartmentalized or modular thermoelectric heat exchanger system 20 in accordance with another embodiment of the disclosure. The system 20 has one or more divider plates and multiple manifold assemblies 200. In the example embodiment shown, there is a first divider plate 70, second divider plate 72, and third divider plate 74, as well as first through eighth manifold assemblies 200a-200h. Each manifold assembly 200 has a first channel 260 that receives a first material and a second channel 262 receives a second material. For example, the second manifold assembly 200b has a first channel 260b and a second channel 262b, and the sixth manifold assembly 200fhas a first channel 260f and a second channel 262f. The manifold assemblies 200a-200h can be made of the same material, or different material. In one embodiment, the first manifold assemblies 200 can be made of alternating p-type material and n-type material. For example, the first manifold assembly 200a can be made of a first p-type material, and the neighboring manifold assemblies (namely the second, fourth, fifth manifold assemblies 200b, 200d, 200e, respectively) can each be made of an n-type material (either the same n-type material or different n-type materials). Accordingly, the third, sixth, and eighth manifold assemblies 200c, 200f, 200h are also p-type material, and the seventh manifold assembly 200g is n-type material.

[0055] The divider plates 70, 72, 74 are solid flat thin plates. In certain embodiments, some areas of the plates are electrically insulating and / or some areas of the plates are electrically conducting depending on what they are touching. For example, some of the faces that are touching the thermoelectric material have electrical contacts. This allows for electrical current to go from quadrant to quadrant. In all other locations, the plates are electrically insulating. The designcould work with the plates as thermally conductive or thermally insulating. Either option would work although thermally insulating would force the temperature difference across the thermoelectric materials to come from the difference in hot and cold fluid temperatures.

[0056] One or more openings are located in at least one of the plates 70, 72, 74 to permit the flow of the first or second material through the opening. The openings are each aligned with one channel in each of neighboring manifold assemblies 200 to allow material in the channel to pass between the two (or more) manifold assemblies 200. For example, an opening 76 is shown at one corner of the second manifold assembly 200b, and one corner of the sixth manifold assembly 200f. The opening 76 is aligned with a first channel 260b in the second manifold assembly 200b, and a first channel 260fin the sixth manifold assembly 200f. Thus, the first channel 260b and first channel 260f are in flow communication, so that the first material passes from the first channel 260b into the first channel 260f, or vice versa. In the example embodiment shown, the three divider plates 70, 72, 74 have two top rows (front and rear) of manifold assemblies 200, and two bottom rows of manifold assemblies 200, as well as two left (front and rear) and two right columns of manifold assemblies 200. If the material for each manifold differs, that could impact how the temperature of the fluid changes in each manifold. In certain embodiments, the current will only enter and leave from the plates 70, 72, 74.

[0057] A housing can also be provided, similar to the one of FIG. 3C, that receives the entire heat exchanger 20. The divider plates 70, 72, 74 are shown being longer than the rows and columns of manifold assemblies 200 so that the divider plates extend beyond the outer surfaces of the manifold assemblies 200. However, the divider plates can be flush with the outer surfaces of the manifold assemblies 200 and the housing walls can contact the outer surfaces of the manifold assemblies 200. The housing can have a first and second input port and a first and second output port. The first input port (e.g., carrying a hot fluid) can be at the same manifold assembly 200 (e.g., manifold assembly 200a) as the second input port (e.g., carrying a cold fluid), and the first and second output ports can also be at that same manifold assembly (e.g., 200a), so that the first and second materials travel sequentially through all the manifold assemblies. Or the first and second input ports and first and second output can all (or some) be at different manifold assemblies. In some embodiments, each manifold assembly can be in flow communication with each and every one of its neighbor manifold assemblies. However, in other embodiments, a manifold assembly need not be in flow communication with a neighboringmanifold assembly (or only one channel can be in flow communication). And there can be more than two channels, so for example a first hot fluid flows through the first hot channel of the top row of manifold assemblies, and a second hot fluid (e.g., different temperatures or different fluid types) flows through a second hot channel of the bottom row of manifold assemblies, while the cold fluid can flow through a same cold channel for all (top and bottom) manifolds or through a first and second cold channel of the top and bottom manifolds respectively.

[0058] The heat exchanger 20 allows the voltage to be stepped up each time as the electric current passes through from cube to cube. FIG. 7 shows the outside removed to show the slight difference in material color (light vs. dark gray), which represents the n- and p-type material. The modular system 20 provides a combination of n- and p-type thermoelectric materials to be placed electrically in series to increase the voltage and power output of the device without interrupting fluid flow. The openings 76 allow the material (e.g., fluid) to be directed from block to block, allowing for the increase in the voltage. As material passes from one manifold assembly to another, the electric power is generated in that manifold assembly. In the example given, material flows through the n-type second manifold assembly 200b and activates the n-type material. The material then flows through the opening 76 into the sixth manifold assembly 200f, which is a p-type material and activates the p-type material. Of course, other embodiments can be provided. In certain embodiments, the divider plate allows for electrical isolation in some locations and electrical conduction in other locations, so the n- and p-type materials can be electrically (e g., in series, though other embodiments can be provided).

[0059] The voltage increases when an n- and p-type materials are electrically in series; the voltages add due to the superposition principle which states that in a linear circuit the total voltage across the series of elements is the sum of the voltage contributed by each individual leg. Since each type of material has a different carriers they each add to the voltage in the same direction. Typically, this can be expressed with the equation: V = (Sp—n is the number of legs, Spis the Seebeck coefficient of the p-type material, Snis the Seebeck coefficient of the n-type material, and AT is the temperature difference across the legs. We can make an analogous prediction for our compartmentalized version which will have n = 8. For the same n- and p-type Seebeck coefficient and temperature difference, we could expect a fourfold voltage increase. If the short circuit current is the same, then there will be a fourfold increase in the power output in a heat exchanger with double the volume.

[0060] It is further noted that the assembly 20 of FIGS. 7 A, 7B is a 2x2x2 array of manifolds 200 that together form a cube shape. However, more or fewer manifolds can be provided and form other shapes, such as an elongated cuboid or rectangular shape.

[0061] FIGS. 8A, 8B show the periodic structure of the manifold assemblies 200 of FIGS. 1-4. The element on the left side of those figures shows the smallest repeating periodic structure. Here, it is a hexagonal shape having alternating concave and convex edges and is ergonomically curved to be a continuous curved structure without edges or points. Those smallest repeating periodic structures join together to form the more complex structure on the right side of FIGS. 8 A, 8B, such as a hexagonal pinwheel structure. This is a small minimal surface that is naturally created (if energy minimization is required) if a surface is suspended from 6 of the 8 comers of a three-dimensional structure. This structure is made of hyperbolas and is well defined mathematically by the three-dimensional level set equation. This surface can then be expanded to the unit cell of the gyroid, which is also a minimal surface. FIGS. 9, 10 show other non-limiting examples of the disclosure.

[0062] The system 10, 20 could be used in any heat exchanger application, any application in which heat is intentionally transferred. There are many industries and applications where this occurs. The general field is thermal management. Thermal management is used in power generation and propulsion systems (e.g., turbines for power generation), industrial processes (e.g., chemical processing, metal / ceramic manufacturing), vehicles (heat pumps, catalytic converters, internal combustion, radiator), home appliances (water heater, furnace, air conditioner), and power electronics (e.g., inverters).

[0063] In one example, illustrative, non-limiting embodiment of the disclosure, the heat exchanger can be an engine radiator, such as one used in a vehicle. The radiator has a radiator body such as a first closed channel that is arranged to form thin fins with a second open channel formed as one or more openings around the fins. A first material, such as water or radiator fluid, flows through the radiator body first channel including through the fins, and a second material, such as air, flows through the second channels and cools the first fluid. The radiator body is formed of a thermoelectric material layer, conductor layer, and insulating layer. Thus, as the first and second materials flow in the first and second channels, the thermoelectric material generates electrical power that is conveyed by the conductor layer. The insulating layer prevents damage to the thermoelectric and conductor layers. The shape of the radiator body can be linear / planar,non-linear, or any other suitable shape. In addition, a housing can partly cover the first and / or second channels. In other embodiments of the disclosure (including those shown in the figures), a frame can be attached to the housing to hold the housing body in position. In certain embodiments, the insulatinglayer 256 is optional. And, in certain embodiments, the conducting material can be the center or inner layer and the thermoelectric material layer can be the middle layer between the conducting material and the insulating outer layer. Though the manifold and housing body are shown as a cube in the figures, it can have any suitable shape, including that the manifold can have a circular elongated shape and the housing can form a tube around the manifold. And, the housing wall need not contact the outer surface of the manifold, or can only partly contact the outer surface of the manifold, to form an interior space between the manifold and the housing wall, for example to provide condensation of a gas. Thus, the structure of the heat exchanger and / or manifold is not limited by the examples shown and described.

[0064] The systems 10, 20 could be used in applications where large surfaces areas are required for chemical processes. For example, in catalysis applications, there may be a need for localized heating or cooling to control the chemical mechanisms taking place. Example applications include carbon capture and gas synthesis / treatment.

[0065] The initial target customer segment could include natural gas baseload energy generation facilities and operators. For natural gas power generation plants, depending on the installed generation capacity, fuel costs represent $18 - 32 / MWh of the Levelized Cost of Electricity, second only to capital costs. Over a representative 30-40-year productive life cycle, the ability to recover waste heat extracts additional incremental electricity per unit of feedstock input, which improves profitability for installed capacity. Application-specific implementations for the innovation benefit baseload energy generation and industrial waste heat recovery processes. These sectors frequently operate continuously for years with limited system -wide downtime for maintenance. Downtime incurs significant revenue opportunity costs. As a result, reliability, predictability, and operational efficiency are essential characteristics for target market segments.

[0066] The thermoelectric layer can have one or more compounds selected from the group comprising bismuth chalcogenides, lead chalcogenides, tin chalcogenides, half-Heusler compounds, full-Heusler compounds, metal silicides, magnesium-group IV element compounds, inorganic clathrates, silicon germanium compounds, metal oxides, skutterudites, metal antimonides, tetrahedrites, copper compound materials, Zintl materials, silver compoundmaterials, silicon, silicon compounds, and any doped silicon, polymer thermoelectrics, carbon materials, doped carbon any doped equivalents thereof, or any mixture thereof.

[0067] As used herein, when an element or feature is described as being “configured,” that element or feature is structurally arranged or formed to accomplish the stated purpose. It is further noted that the drawings may illustrate and the description and claims may use several geometric or relational terms and directional or positioning terms, such as TPMS, channel, between, linear, curved, lateral, top, bottom, left, right, inner, exterior, side, and opposite. Those terms are merely for convenience to facilitate the description based on the embodiments shown in the figures, and are not intended to limit the disclosure. Thus, it should be recognized that the disclosure can be described in other ways without those geometric, relational, directional or positioning terms. In addition, the geometric or relational terms may not be exact. And, other suitable geometries and relationships can be provided without departing from the spirit and scope of the disclosure.

[0068] The foregoing description and drawings should be considered as illustrative only of the principles of the disclosure, which may be configured in a variety of shapes and sizes and is not intended to be limited by the embodiment herein described. Numerous applications of the disclosure will readily occur to those skilled in the art. Therefore, it is not desired to limit the disclosure to the specific examples disclosed or the exact construction and operation shown and described. Rather, all suitable modifications and equivalents may be resorted to, falling within the scope of the disclosure.

Claims

CLAIMS:1 . A heat transfer device, comprising: a thermoelectric material layer; an electric contact layer coating at least a portion of said thermoelectric material layer; and an electric insulating layer coating at least a portion of said electric contact layer.

2. The heat transfer device of claim 1, wherein said electric insulating layer is thermally conductive.

3. The heat transfer device of claim 1 or 2, wherein said heat transfer device comprises a heat exchanger.

4. The heat transfer device of any one of claims 1-3, wherein said thermoelectric material layer generates electricity in said electric contact layer.

5. The heat transfer device of any one of claims 1-4, wherein in said thermoelectric material layer, electrons move in response to a temperature differential in said thermoelectric material layer.

6. The heat transfer device of claim 5, wherein electrons pass into said electric contact layer to provide electricity.

7. The heat transfer device of any one of claims 1-6, further comprising an electric wire connected to said electric contact layer.

8. The heat transfer device of any one of claims 1-3, wherein said thermoelectric material layer pumps heat.

9. The heat transfer device of any one of claims 1-8, wherein said electric insulating layer electrically insulates said electric contact layer and the surrounding.

10. The heat transfer device of any one of claims 1-9, wherein said thermoelectric layer comprises one or more compounds selected from the group comprising bismuth chalcogenides, lead chalcogenides, tin chalcogenides, half-Heusler compounds, full-Heusler compounds, metal silicides, magnesium-group IV element compounds, inorganic clathrates, silicon germanium compounds, metal oxides, skutterudites, metal antimonides, tetrahedrites, copper compound materials, Zintl materials, silver compound materials, silicon, silicon compounds, and any dopedsilicon, polymerthermoelectrics, carbon materials, doped carbon any doped equivalents thereof, or any mixture thereof.

11. The heat transfer device of any one of claims 1-10, wherein said heat transfer device generates power and / or pumps heat.

12. The heat transfer device of any of claims 1-11, said thermoelectric material layer having a shape with triply periodic minimal surface or doubly periodic minimal surface, or periodic structures.

13. The heat transfer device of any one of claims 1-12, said heat transfer device having a first side in thermal communication with a first element, and a second side in thermal communication with a second element, said heat transfer device conducting heat from the first element to the second element.

14. The heat transfer device of claim 13, wherein the first element is a first heating liquid and the second element is a second cooling liquid, and heat is transferred from the first heated liquid to the second cooling liquid, and said thermoelectric material layer generates electricity in response to the heat transfer.

15. The heat transfer device of claim 13, wherein the first element and the second element comprise a liquid, gas, gel, or solid material.

16. The heat transfer device of any one of claims 13-15, further comprising a first passageway retaining the first element, a second passageway retaining the second element, and wherein said first side is in direct contact and thermal communication with said first passageway, and said second side is in direct contact and thermal communication with said second passageway.

17. The heat transfer device of any one of claims 1 -16, wherein said electric contact layer directly contacts said at least a portion of said thermoelectric material layer, and said electric insulating layer directly contacts said at least a portion of said electric contact layer.

18. The heattransfer device of any one of claims 1-17, further comprising a housing for at least partly enclosing said heat transfer device.

19. A heat transfer device, comprising: a thermoelectric material layer having a first thermoelectric material side and a second thermoelectric material side opposite the first side, wherein said first thermoelectric material sidein thermal communication with a first element, and said second thermoelectric material side in thermal communication with a second element; a first electric contact layer coating having a first contact side and a second contact side, said first contact side coating at least a portion of said first thermoelectric material side; a first electric insulating layer coating having a first insulating side and a second insulating side, said first insulating side coating at least a portion of said second contact side, and said second insulating side in contact with the first element; a second electric contact layer coating having a third contact side and a fourth contact side, said third contact side coating at least a portion of said second thermoelectric material side; and a second electric insulating layer coating having a third insulating side and a fourth insulating side, said first insulating side coating at least a portion of said fourth contact side, and said fourth insulating side in contact with the second element.

20. A method, comprising: transferring heat from a first element to a second element; generating power at a thermoelectric material in thermal communication with the first element and the second element during said heat transfer; and providing an electric insulating layer around at least a portion of the thermoelectric material, the electric insulating layer in contact with the first element and the second element.

21. A heat transfer device, comprising: a housing; a first input receiving a first medium at a first temperature; a second input receiving a second medium at a second temperature; a first output; a second output; a manifold having a first channel in communication with the first input and the first output, for transferring the first medium from the first input to the first output, and a second channel in communication with the second input and the second output, for transferring the second medium from the second input to the second output, said manifold formed of athermoelectric material that generates electricity based on a temperature difference of the first temperature and the second temperature.

22. The device of claim 21, further comprising an electrically conductive material layer formed about the thermoelectric material and receives the electricity from the thermoelectric material.

23. The device of claim 22, further comprising a sealing layer formed about the electrically conductive material layer.

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