Pin-fin thermoelectric generator applied to SOFC tail gas waste heat recovery

Abstract

The invention discloses a pin-fin thermoelectric generator applied to SOFC tail gas waste heat recovery, and relates to the technical field of solid oxide fuel cells (SOFC). The pin-fin thermoelectric generator comprises a tail gas heat exchanger, a thermoelectric module and a cooling water heat exchanger; the cooling water heat exchanger is arranged at the end, away from the tail gas heat exchanger, of the thermoelectric module. And a plurality of pin fins are arranged in the tail gas heat exchanger and are arranged in a staggered manner. According to the arrangement, the optimal pin fin parameters are set according to the SOFC tail gas parameters, and compared with a flat plate thermoelectric generator, the net output power can be improved by more than three times; different types of thermoelectric modules are arranged in different areas through the heat exchanger, it is ensured that thermoelectric materials work in the optimal temperature interval, and the power generation performance is improved.

Description

Technical Field

[0001] This invention relates to the field of waste heat recovery technology for solid oxide fuel cells (SOFCs), and particularly to a needle-fin thermoelectric generator for waste heat recovery from SOFC exhaust gases. Background Technology

[0002] Fuel cells directly convert fuel and oxidant into electrical energy through an electrochemical reaction, unaffected by the Carnot cycle effect. Theoretically, their energy conversion efficiency can reach over 60%, and the main byproducts are water, carbon dioxide, and heat, producing almost no air pollution such as sulfur oxides and nitrogen oxides. Among all fuel cells, solid oxide fuel cells (SOFCs) have advantages such as low emissions, strong fuel adaptability, and high power generation efficiency. SOFCs operate at high temperatures, with exhaust gas temperatures reaching 600-1000℃, indicating significant potential for exhaust gas utilization.

[0003] A thermoelectric generator is a solid-state energy conversion device with no moving parts, no noise, and high reliability. It can be used to recover waste heat from SOFC exhaust gas for power generation, thereby improving the system's power generation efficiency.

[0004] CN111917336B discloses a method for recovering waste heat energy from automobile exhaust using semiconductor thermoelectric power generation technology. The heat transfer fins are arranged in a sparse to dense manner to ensure that the temperature of the hot end of the thermoelectric module does not change significantly along the way, so that the thermoelectric material works in the optimal operating range and improves the thermoelectric conversion efficiency.

[0005] CN120896475A discloses a structure for a vehicle exhaust gas thermal differential heat exchanger, which provides an adjustable-angle fin structure to enhance exhaust gas heat exchange and improve system power generation efficiency.

[0006] CN114352391A combines heat pipe technology with thermally conductive fins for the recovery of waste heat from automotive exhaust, thereby improving the system's effective output power and thermoelectric conversion efficiency.

[0007] CN119572447A discloses an internal combustion engine exhaust gas temperature difference generator with a perforated plate structure, and provides an optimal setting method for the perforated plate for the internal combustion engine exhaust parameters, which effectively improves the performance of the generator.

[0008] However, most existing technologies utilize thermoelectric generators to recover waste heat from vehicle exhaust for power generation, and enhance heat transfer in the exhaust gas through fins to improve thermoelectric conversion efficiency. But the exhaust gas from micro / miniature SOFCs differs significantly from that of vehicles; SOFC exhaust gas has a higher temperature and a lower flow rate. The heat transfer enhancement structure is directly related to the exhaust gas parameters. Traditional enhanced fins cannot maximize the thermoelectric performance of SOFC exhaust thermoelectric generators; therefore, novel enhanced structural parameters need to be determined based on the characteristics of SOFC exhaust gas. Summary of the Invention

[0009] The purpose of this invention is to overcome the deficiencies in the existing technology and to propose a needle-fin thermoelectric generator for SOFC exhaust heat recovery.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: A needle-fin thermoelectric generator for waste heat recovery from SOFC exhaust gas is characterized by comprising an exhaust gas heat exchanger, a thermoelectric module, and a cooling water heat exchanger. Multiple sets of thermoelectric modules are provided on the opposite two ends of the exhaust gas heat exchanger, and the cooling water heat exchanger is located at the end of the thermoelectric modules away from the exhaust gas heat exchanger. The exhaust gas heat exchanger is equipped with several needle-like fins arranged in a staggered pattern.

[0011] Furthermore, the thermoelectric module is connected to the outer shell of the exhaust gas heat exchanger; the plane on which the thermoelectric module is located is perpendicular to the length direction of the needle fins.

[0012] Furthermore, the needle fins have a spacing of 3-5 mm along the direction of exhaust gas flow and a spacing of 3-5 mm along the direction perpendicular to the exhaust gas flow; both ends of the needle fins are connected to the heat exchanger shell.

[0013] Furthermore, the needle wing has a diameter of 2-3 mm and a wing height of 50-60 mm.

[0014] Furthermore, the height of the thermoelectric arm of the thermoelectric module is greater than or equal to 3mm.

[0015] Furthermore, the exhaust gas heat exchanger, thermoelectric module, and cooling water heat exchanger are clamped together by a clamp, and the two ends of the thermoelectric module are provided with a thermally conductive silicone grease layer or a graphite sheet layer.

[0016] Furthermore, the thermoelectric modules are SiGe-based thermoelectric modules and BiTe-based thermoelectric modules. SiGe-based thermoelectric modules are arranged in the front section and BiTe-based thermoelectric modules are arranged in the rear section in the exhaust gas flow direction of the heat exchanger, wherein the proportion of SiGe-based thermoelectric modules is greater than or equal to 50%.

[0017] Furthermore, the exhaust gas heat exchanger is a rectangular flow channel, a cylindrical or polygonal exhaust gas flow channel; the cross-section of the needle fins is a streamlined structure.

[0018] Beneficial effects

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: By setting the optimal needle fin parameters based on SOFC exhaust gas parameters, the net output power can be increased by more than 3 times compared with flat-plate thermoelectric generators.

[0020] By arranging different types of thermoelectric modules in different zones of the heat exchanger, the thermoelectric materials can be ensured to operate within their optimal temperature range, thereby improving power generation performance. Attached Figure Description

[0021] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0022] Figure 1 A cross-sectional structural schematic diagram of the needle-fin thermoelectric generator provided by the present invention; Figure 2 The effect of fin layout on ETEG output performance under different flow channel heights; Figure 3 The effect of different needle fin diameters on the net output performance of ETEG; Figure 4 The effect of different thermoelectric arm heights on the net output performance of ETEG; In the diagram: 1. Exhaust gas heat exchanger; 2. Thermoelectric module; 3. Cooling water heat exchanger; 4. Needle fins. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0024] In the description of this invention, it should be understood that the terms "upper," "lower," "front," "rear," "left," "right," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Example 1: A needle-fin thermoelectric generator for SOFC exhaust heat recovery includes an exhaust heat exchanger, a thermoelectric module, and a cooling water heat exchanger. Multiple thermoelectric modules are arranged on opposite ends of the exhaust gas heat exchanger, and the cooling water heat exchanger is located at the end of the thermoelectric modules away from the exhaust gas heat exchanger. The exhaust gas heat exchanger contains several needle-like fins arranged in a staggered pattern.

[0025] In other preferred embodiments, the thermoelectric module is connected to the outer shell of the exhaust gas heat exchanger; the plane of the thermoelectric module is perpendicular to the length direction of the needle fins.

[0026] The exhaust gas heat exchanger is internally arranged with needle-fins, which are staggered and connected to the surface of the flow channel.

[0027] In other preferred embodiments, the needle fin spacing is 3-5 mm along the exhaust gas flow direction and 3-5 mm along the exhaust gas flow perpendicular direction; both ends of the needle fins are connected to the heat exchanger shell.

[0028] Specifically, the needle-wing diameter is 2-3mm, and the wing height is 50-60mm.

[0029] In other preferred embodiments, the height of the thermoelectric arm of the thermoelectric module is greater than or equal to 3 mm.

[0030] In other preferred embodiments, the exhaust gas heat exchanger, the thermoelectric module, and the cooling water heat exchanger are clamped together by a clamp, and the two ends of the thermoelectric module are provided with a thermally conductive silicone grease layer or a graphite sheet layer.

[0031] In other preferred embodiments, the thermoelectric modules are SiGe-based thermoelectric modules and BiTe-based thermoelectric modules. Multiple sets of thermoelectric modules are arranged first in the direction of heat exchanger exhaust gas flow, followed by BiTe-based thermoelectric modules, wherein the proportion of SiGe-based thermoelectric modules is not less than 50%.

[0032] The exhaust gas heat exchanger has a rectangular flow channel, a cylindrical or polygonal exhaust gas flow channel; the needle fins have a streamlined cross-section.

[0033] Example 2: The following is in conjunction with the appendix Figure 1-4 The present invention will be further described in detail with reference to specific embodiments. It should be noted that the technical solution of the present invention will be described in detail below with only one optimized technical solution, but the protection scope of the present invention is not limited thereto.

[0034] This example uses a 5kW SOFC, with an exhaust gas temperature of 1073K and a mass flow rate of 4.3g / s. Figure 1 A needle-fin tail gas temperature differential generator designed for this tail gas parameter includes a tail gas heat exchanger 1, a thermoelectric module 2, and a cooling water heat exchanger 3.

[0035] Ten thermoelectric modules 2 are installed in two groups between the exhaust gas heat exchanger 1 and the cooling water heat exchanger 3, with each group of thermoelectric modules 2 arranged in a single row along the exhaust gas flow direction.

[0036] The exhaust gas heat exchanger 1, thermoelectric module 2, and cooling water heat exchanger 3 are clamped together by a fixture, and thermally conductive silicone grease or graphite sheets are applied to both ends of the thermoelectric module 2 to reduce contact thermal resistance.

[0037] Thermoelectric module 2 uses a SiGe-based thermoelectric module. The exhaust gas heat exchanger 1 contains staggered pin fins 4, with a pin fin spacing D = 4mm along the exhaust gas flow direction and a pin fin spacing L = 4mm along the direction perpendicular to the exhaust gas flow. The two ends of the pin fins are connected to the heat exchanger wall. The entire heat exchanger can be manufactured as a single unit using additive manufacturing technology, or the pin fins 4 can be welded to the inner wall of the heat exchanger.

[0038] Figure 2 This study investigates the impact of pin fin diameter on the generator's net output power, demonstrating how optimizing the pin fin diameter can maximize the generator's net output power. Under current operating conditions, an optimal pin fin diameter of 2.5mm is found to achieve a maximum output power of 150W.

[0039] Figure 3 This illustrates the effect of fin height on the generator's net output power. The system achieves its maximum net output power when the fin height is 50 mm.

[0040] Figure 4 This illustrates the effect of the thermoelectric arm height in the thermoelectric module on the net output power of the generator. The maximum output power of 201W is achieved when the thermoelectric arm height is 3mm.

[0041] In this example, all thermoelectric modules used are high-temperature resistant SiGe-based thermoelectric modules. Since the temperature of the exhaust gas gradually decreases along the flow direction, the temperature of the thermoelectric modules on the heat exchanger surface also decreases accordingly. Therefore, replacing the four thermoelectric modules at the tail end of the exhaust gas heat exchanger with BiTe-based thermoelectric modules could further improve the system's net output power.

[0042] In this example, the exhaust gas heat exchanger is a rectangular flow channel. This invention is also applicable to exhaust gas flow channels of cylindrical, polygonal, etc.

[0043] This invention is not only applicable to the recovery of waste heat from micro / small SOFC exhaust gases, but can also be used for the recovery and utilization of other low-flow, high-temperature waste gases.

[0044] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A needle-fin thermoelectric generator for waste heat recovery from SOFC exhaust gas, characterized in that, This includes exhaust gas heat exchangers, thermoelectric modules, and cooling water heat exchangers; Multiple sets of thermoelectric modules are provided on the opposite two ends of the exhaust gas heat exchanger, and the cooling water heat exchanger is located at the end of the thermoelectric modules away from the exhaust gas heat exchanger. The exhaust gas heat exchanger is equipped with several needle-like fins arranged in a staggered pattern.

2. The needle-fin thermoelectric generator for SOFC exhaust heat recovery according to claim 1, characterized in that, The thermoelectric module is connected to the outer shell of the exhaust gas heat exchanger; the plane of the thermoelectric module is perpendicular to the length direction of the needle fin.

3. A needle-fin thermoelectric generator for SOFC exhaust heat recovery according to claim 1, characterized in that, The needle fins have a spacing of 3-5 mm along the direction of exhaust gas flow and a spacing of 3-5 mm along the direction perpendicular to the exhaust gas flow; both ends of the needle fins are connected to the heat exchanger shell.

4. A needle-fin thermoelectric generator for SOFC exhaust heat recovery according to claim 3, characterized in that, The needle wing has a diameter of 2-3 mm and a wing height of 50-60 mm.

5. A needle-fin thermoelectric generator for SOFC exhaust heat recovery according to claim 1, characterized in that, The height of the thermoelectric arm of the thermoelectric module is greater than or equal to 3mm.

6. A needle-fin thermoelectric generator for SOFC exhaust heat recovery according to claim 1, characterized in that, The exhaust gas heat exchanger, thermoelectric module, and cooling water heat exchanger are clamped together by a clamp, and the two ends of the thermoelectric module are provided with a thermally conductive silicone grease layer or a graphite sheet layer.

7. A needle-fin thermoelectric generator for SOFC exhaust heat recovery according to claim 1, characterized in that, The thermoelectric modules are SiGe-based thermoelectric modules and BiTe-based thermoelectric modules. SiGe-based thermoelectric modules are arranged in the front section and BiTe-based thermoelectric modules are arranged in the rear section in the direction of exhaust gas flow of the heat exchanger, wherein the proportion of SiGe-based thermoelectric modules is greater than or equal to 50%.

8. A needle-fin thermoelectric generator for SOFC exhaust heat recovery according to claim 1, characterized in that, The exhaust gas heat exchanger is a rectangular flow channel, a cylindrical or polygonal exhaust gas flow channel; the needle fins have a streamlined cross-section.

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