Waste heat recovery heat exchanger and small gas turbine

Abstract

The invention discloses a waste heat recovery heat exchanger and a small gas turbine. Comprises: a housing arranged in an annular shape; the multiple heat exchange pipes extend in the axis direction of the shell, and the multiple heat exchange pipes are tightly arranged in the shell; a first channel used for flowing of a low-temperature medium is formed in the heat exchange pipe, an opening of the first channel is formed in the end face of the shell, a second channel used for flowing of a high-temperature medium is formed outside the heat exchange pipe, and an opening of the second channel is formed in the side face of the shell. And the low-temperature medium and the high-temperature medium exchange heat through the pipe wall of the heat exchange pipe. The compact degree and the heat exchange efficiency of the heat exchanger can be improved, and the flow resistance can be reduced.

Description

Technical Field

[0001] This application relates to the field of waste heat recovery technology for gas turbines, specifically to a waste heat recovery heat exchanger and a small gas turbine. Background Technology

[0002] In the energy cycle of small gas turbines, heat exchangers are typically used to preheat the low-temperature compressed air at the compressor outlet before it is sent into the combustion chamber in order to recover waste heat from the high-temperature exhaust gas and improve overall thermal efficiency. However, in small mobile platforms or compact power systems, the installation space for heat exchangers is extremely limited, which places stringent requirements on the compactness of the heat exchanger structure, heat exchange efficiency, and flow resistance.

[0003] Common heat exchanger types include plate-fin, shell-and-tube, and tube-fin. Traditional shell-and-tube heat exchangers are bulky and difficult to use in confined spaces; while plate-fin heat exchangers are compact, they are prone to thermal stress concentration, poor fatigue resistance, and channel blockage in high-temperature environments. Furthermore, traditional manufacturing processes struggle to achieve complex and refined integrated heat exchange structures, resulting in limited flow channel optimization, high contact thermal resistance, insufficient reliability, and often making it difficult to balance efficient heat exchange with low pressure drop.

[0004] Therefore, there is an urgent need for a heat exchanger that is compact, has high heat exchange efficiency, low flow resistance, and is suitable for integrated manufacturing, in order to meet the waste heat recovery needs of small gas turbines under strict space constraints.

[0005] It should be noted that the above information is only used to understand the background technology of the present invention. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this application discloses a waste heat recovery heat exchanger and a small gas turbine, which can solve the problems of how to improve the compactness of the heat exchanger, the heat exchange efficiency, and the flow resistance.

[0007] To achieve the above objectives, this application provides the following technical solution: Waste heat recovery heat exchangers for small gas turbines, including: The casing is designed to be ring-shaped; Heat exchange tubes, a plurality of heat exchange tubes extending along the axial direction of the shell, and the plurality of heat exchange tubes being arranged in a close arrangement within the shell; wherein... A first channel for the flow of a low-temperature medium is formed inside the heat exchange tube, and the opening of the first channel is located on the end face of the shell. A second channel for the flow of a high-temperature medium is formed outside the heat exchange tube, and the opening of the second channel is located on the side of the shell. The low-temperature medium and the high-temperature medium exchange heat through the tube wall of the heat exchange tube.

[0008] In a preferred embodiment, the first channel includes a portion formed by the inner side of the heat exchange tube.

[0009] In a preferred embodiment, the inner surface of the heat exchange tube includes a first fin for increasing the contact area of ​​the low-temperature medium, and the first fin extends from the inner surface of the heat exchange tube toward the interior of the heat exchange tube.

[0010] In a preferred embodiment, the second channel includes a portion formed by the outer side of the heat exchange tube and the inner side of the shell, or / and a portion formed by the outer side of a plurality of adjacent heat exchange tubes.

[0011] In a preferred embodiment, the adjacent heat exchange tubes are separated from each other at the opening of the second channel.

[0012] In a preferred embodiment, the outer surface of the heat exchange tube includes a second fin for increasing the contact area of ​​the high-temperature medium, the second fin extending from the outer surface of the heat exchange tube in the direction of the outside of the heat exchange tube.

[0013] In a preferred embodiment, at the opening of the second channel, the second fins of adjacent heat exchange tubes are separated from each other.

[0014] In a preferred embodiment, the inner wall, outer wall, and two end faces of the shell form a closed annular cavity, and the multiple heat exchange tubes are arranged closely within the annular cavity.

[0015] In addition, this application also discloses a small gas turbine, including a waste heat recovery heat exchanger, wherein the waste heat recovery heat exchanger is the waste heat recovery heat exchanger described in any of the above technical solutions.

[0016] In a preferred embodiment, the waste heat recovery heat exchanger is used for preheating low-temperature compressed air.

[0017] This application discloses a waste heat recovery heat exchanger and a small gas turbine, which have the following advantages: This invention significantly increases the effective heat exchange area within a limited volume through a ring structure and a compact tube-fin flow channel layout. By optimizing systematic parameters including tube diameter, number of fins, height, thickness, and arrangement, an optimal balance between heat exchange efficiency and flow resistance is achieved. Simulation and experimental data show that this heat exchanger can still achieve a heat exchange efficiency of up to 70% under strictly limited space conditions, while reducing the cold air side pressure to 1.5% and the gas side pressure to 4%. This improves heat recovery while minimizing the negative impact on the gas turbine output power, resulting in an overall system efficiency improvement of approximately 6.8%.

[0018] This invention employs a counter-current heat exchange method, where the hot and cold media flow in opposite directions, significantly improving the heat transfer temperature difference and heat exchange efficiency. The first fin inside the tube and the second fin outside the tube together form a multi-stage enhanced heat transfer surface, greatly increasing the contact area between the medium and the wall. In particular, by designing the flow state as laminar and utilizing the heat transfer enhancement effect of the laminar inlet section, heat transfer performance is further improved while controlling pressure loss. The fin parameters have been optimized through numerical simulation and experiments, exhibiting good adaptability and maintaining efficient and stable operation under various working conditions.

[0019] The heat exchanger adopts a ring-shaped integral structure, achieving a conformal design with the combustion chamber. This not only saves installation space but also enhances the system's structural continuity and sealing. The heat exchange tubes have a simple structure and uniform specifications, achieving efficient space filling and flow channel organization through a close arrangement of regular hexagons. This design has excellent modularity, allowing for rapid layout adjustments and expansion according to the space dimensions of different models, significantly improving product applicability and design reusability.

[0020] The annular structure naturally conforms to the combustion chamber, facilitating the uniform introduction and exhaust of high-temperature combustion gases and reducing localized thermal stress and flow dead zones. Cold air enters and exits from both ends, while combustion gases enter and exit from the sides. The flow channels are clearly defined and rationally laid out, facilitating integration with existing gas turbine piping systems. The overall structure is compact and lightweight, making it particularly suitable for applications on mobile platforms or compact power units. This improves energy efficiency while also enhancing the overall reliability and environmental adaptability of the system.

[0021] All structures in this invention are optimized for 3D printing, enabling one-piece molding and avoiding the contact thermal resistance, leakage risks, and weld fatigue problems associated with traditional multi-step assembly processes such as brazing and splicing. Integrated manufacturing not only improves the structural strength and thermal stability of the heat exchanger but also significantly reduces the number of parts, assembly difficulty, and manufacturing costs. Furthermore, 3D printing supports the precise realization of complex internal flow channels and fin structures, providing a technological foundation for subsequent performance optimization and customized production. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0023] Figure 1 This is a schematic diagram of this application; Figure 2 This is a schematic diagram of the application in the main viewing direction; Figure 3 This is a schematic diagram of the present application in a side view direction; Figure 4 This is a sectional view of the present application in a side view direction; Figure 5This is a schematic diagram of a single heat exchange tube in the main view direction in this application; Figure 6 This is a schematic diagram of multiple heat exchange tubes in the main view direction in this application. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below.

[0025] Example 1 The heat exchanger described in this application has an annular structure, the shape of which is adapted to the external contour of a small gas turbine combustion chamber, enabling compact spatial integration. The annular shell is formed by the inner sidewall, the outer sidewall, and the two end faces, creating a closed annular cavity 1. This structural design not only maximizes the use of the limited space around the combustion chamber but also provides stable support and a sealed boundary for the arrangement of the internal heat exchange units.

[0026] The core heat exchange unit of this invention consists of multiple heat exchange tubes 2 extending parallel to each other along the axis of the annular shell. These heat exchange tubes 2 are arranged in a close hexagonal pattern within the annular cavity 1, forming a honeycomb-like network of regular flow channels. This arrangement maximizes the space filling rate, ensuring structural rigidity while providing numerous uniformly distributed flow paths for the hot and cold media. Each heat exchange tube 2 constitutes an independent heat transfer unit.

[0027] In this embodiment, the cryogenic medium specifically refers to cryogenic compressed air drawn from the compressor outlet, which flows along the first channel 10. The first channel 10 is formed by the inner cavity of the heat exchange tubes 2. Both ends of all the heat exchange tubes 2 are connected to the two end faces of the shell and open, forming the inlet and outlet of the cold air. The compressed air enters each heat exchange tube 2 uniformly from one end face, absorbs heat and is preheated, then flows out from the other end face and is subsequently sent into the combustion chamber.

[0028] In this embodiment, the high-temperature medium is the high-temperature exhaust gas generated by the gas turbine, which flows along channel 20. This second channel 20 is specifically formed by the space defined by the outer wall of the heat exchange tube 2, the inner wall of the shell, and the outer wall of adjacent heat exchange tubes 2. A gas inlet 3 and a gas outlet 4 are respectively opened on the side of the annular shell. The high-temperature gas enters the annular cavity 1 from the inlet, passes through the outer wall of the heat exchange tube 2, and the heat is transferred through the tube wall to the low-temperature compressed air inside the heat exchange tube 2. The cooled gas is finally discharged from the outlet. The hot and cold media generally flow in counter-current flow, thereby maintaining a high average heat transfer temperature difference.

[0029] To improve heat transfer efficiency, fins are provided on both the inner and outer surfaces of the heat exchange tube 2. First fins 6 are uniformly distributed circumferentially inside the heat exchange tube 2, extending from the inner wall towards the center, increasing the contact area between the cold air and the tube wall. Second fins 8 extend radially outside the heat exchange tube 2, further increasing the heat exchange area on the high-temperature combustion gas side. By finely optimizing the number, height, thickness, and distribution of the fins, a significant improvement in heat transfer performance can be achieved within a limited pressure drop budget. In a preferred embodiment, six first fins 6 can be arranged inside the tube, and eighteen second fins 8 can be arranged outside. Specific geometric parameters such as inner diameter, outer diameter, fin height, and thickness need to be optimized through multi-objective collaborative calculations using fluid dynamics and heat transfer simulations to achieve the optimal balance between efficiency and pressure drop under given spatial constraints.

[0030] In the core heat transfer section 5 of the heat exchanger, the second fins 8 on the outer walls of each heat exchange tube 2 are interconnected, forming a stable, integrated network structure. This connection not only enhances the mechanical integrity of the entire heat exchanger structure but also improves the uniformity of heat distribution. However, in the end region near the gas inlet 3 and outlet, some of the outer fins of the heat exchange tubes 2 are removed, creating gas communication channels between adjacent heat exchange tubes 2. This design ensures that the gas can smoothly enter and exit the heat transfer area formed by the dense bundle of heat exchange tubes 2, avoiding excessive local flow resistance at the inlet and outlet.

[0031] In this embodiment, the entire heat exchanger structure, including the annular shell, all heat exchange tubes 2 and their fins, is designed as a non-removable integral unit. It employs metal additive manufacturing technology, specifically 3D printing for integrated molding. The preferred material is a high-temperature resistant alloy, such as a nickel-based high-temperature alloy or stainless steel. This manufacturing method eliminates the contact thermal resistance and potential leakage points inherent in traditional brazing or assembly processes, significantly improving the heat exchanger's long-term operational reliability, thermal fatigue resistance, and high-temperature sealing performance. Simultaneously, integrated molding makes it possible to achieve the aforementioned complex and precise fin and flow channel structures, which is difficult to accomplish economically and reliably using traditional processing methods.

[0032] During operation, low-temperature compressed air flows into each heat exchange tube 2 from one end face, while high-temperature combustion gas flows tangentially or radially into the annular cavity 1 from the side inlet. As the two fluids flow through their respective channels, heat is continuously transferred from the combustion gas to the air through the walls and fins of the heat exchange tubes 2. Through fully optimized design, this heat exchanger can achieve a heat exchange efficiency of approximately 70% within an extremely limited space, while controlling the pressure drop on the cold air side to within 1.5% and the pressure drop on the combustion gas side to within 4%, thereby improving the overall thermal efficiency of the small gas turbine by approximately 6.8%.

[0033] In summary, this invention effectively resolves the contradiction between limited space and waste heat recovery performance in small gas turbines through a compact annular layout, tube-fin counter-current heat exchange, synergistic enhancement of inner and outer fins, and optimized end flow channel design. Furthermore, relying on 3D printing integrated manufacturing technology, this invention achieves a balance between structural performance and production feasibility, possessing comprehensive advantages such as compact structure, high heat exchange efficiency, low flow resistance, high reliability, ease of integration, and controllable manufacturing costs. Those skilled in the art can make various modifications and combinations based on the above embodiments, such as adjusting the fin shape to corrugated or perforated shapes.

[0034] Example 2 The small gas turbine described in this application includes a waste heat recovery heat exchanger, wherein the waste heat recovery heat exchanger is the waste heat recovery heat exchanger described in the above embodiments. The waste heat recovery heat exchanger is used for preheating cryogenic compressed air.

[0035] The above are embodiments used to illustrate the technical solution of this application.

Claims

1. Waste heat recovery heat exchangers for small gas turbines, including: The casing is designed to be ring-shaped; Heat exchange tubes, a plurality of heat exchange tubes extending along the axial direction of the shell, and the plurality of heat exchange tubes being arranged in a close arrangement within the shell; wherein... A first channel for the flow of a low-temperature medium is formed inside the heat exchange tube, and the opening of the first channel is located on the end face of the shell. A second channel for the flow of a high-temperature medium is formed outside the heat exchange tube, and the opening of the second channel is located on the side of the shell. The low-temperature medium and the high-temperature medium exchange heat through the tube wall of the heat exchange tube.

2. The waste heat recovery heat exchanger according to claim 1, wherein, The first channel includes a portion formed by the inner side of the heat exchange tube.

3. The waste heat recovery heat exchanger according to claim 2, wherein, The inner surface of the heat exchange tube includes a first fin for increasing the contact area of ​​the low-temperature medium, the first fin extending from the inner surface of the heat exchange tube toward the interior of the heat exchange tube.

4. The waste heat recovery heat exchanger according to claim 1, wherein, The second channel includes a portion formed by the outer side of the heat exchange tube and the inner side of the shell, and / or a portion formed by the outer side of a plurality of adjacent heat exchange tubes.

5. The waste heat recovery heat exchanger according to claim 4, wherein, At the opening of the second channel, the adjacent heat exchange tubes are separated from each other.

6. The waste heat recovery heat exchanger according to claim 4, wherein, The outer surface of the heat exchange tube includes a second fin for increasing the contact area of ​​the high-temperature medium. The second fin extends from the outer side of the heat exchange tube toward the outside of the heat exchange tube.

7. The waste heat recovery heat exchanger according to claim 6, wherein, At the opening of the second channel, the second fins of adjacent heat exchange tubes are separated from each other.

8. The waste heat recovery heat exchanger according to claim 1, wherein, The inner wall, outer wall, and two end faces of the shell form a closed annular cavity, and the multiple heat exchange tubes are arranged closely within the annular cavity.

9. A small gas turbine, including a waste heat recovery heat exchanger, wherein, The waste heat recovery heat exchanger is the waste heat recovery heat exchanger as described in any one of claims 1 to 8.

10. The small gas turbine according to claim 9, wherein, The waste heat recovery heat exchanger is used to preheat low-temperature compressed air.

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