A high-efficiency, compact superheater for solar thermal power plants that can suppress steam flow fluctuations.

Abstract

This invention provides a high-efficiency, compact superheater for concentrated solar power (CSP) plants that can suppress steam flow fluctuations. It includes a superheater core, a header, and a connector. The superheater core is a printed circuit board type and is connected to the header. The connector is located on the header. The superheater core includes several heat exchange plates for high-temperature molten salt and water vapor, arranged alternately from top to bottom. Each heat exchange plate has several parallel flow channels, and the flow channels of the water vapor heat exchange plate have several swirling structures. This invention can suppress steam flow fluctuations and has a compact size.

Description

Technical Field

[0001] This invention relates to the field of heat exchanger technology, and more specifically to a high-efficiency, compact superheater for solar thermal power plants that can suppress steam flow fluctuations. Background Technology

[0002] Concentrated solar power (CSP) is one of the core forms of new energy utilization, and it has broad development prospects in my country and globally due to its advantages such as compatibility with thermal storage systems and strong power generation stability. The core principle of mainstream CSP systems such as tower and trough systems is to concentrate solar energy through concentrating solar collectors to heat molten salt or thermal oil as the heat transfer medium. This heat is then used to generate high-temperature, high-pressure steam through a steam generation system, which drives a turbine to generate electricity. The steam generation system typically consists of a preheater, an evaporator, and a superheater. The working fluid, water, undergoes a process of preheating, boiling and evaporating into saturated steam, and further heating into superheated steam, ultimately outputting steam that meets the operating requirements to the turbine.

[0003] As a key component of the steam generation system, the superheater's performance directly determines core quality parameters such as the temperature and pressure of the steam at the turbine inlet, thus affecting the turbine's operating efficiency and safety stability. Traditional concentrated solar power (CSP) plants mostly use shell-and-tube superheaters. These superheaters have inherent defects such as large flow channel dimensions, loose structure, and low overall heat exchange efficiency, making it difficult to stably output high-quality steam and failing to fully meet the stringent steam quality requirements of CSP plants.

[0004] Furthermore, concentrated solar power (CSP) systems rely on solar energy for heat collection. However, the inherent intermittency and instability of solar energy cause frequent fluctuations in solar radiation intensity due to factors such as cloud cover. This leads to drastic fluctuations in the temperature and flow rate of the molten salt or heat transfer oil at the collector outlet. Since the primary heat source of the superheater directly receives the aforementioned heat transfer medium, these fluctuations are directly transmitted to the superheater, causing a sharp deterioration in the superheater's heat exchange conditions. This not only makes it difficult to maintain stable outlet steam temperature and pressure but also causes significant fluctuations in outlet steam flow rate.

[0005] Unstable superheater outlet steam flow directly impacts the operating conditions of the subsequent steam turbine, leading to a series of chain reactions such as a significant decrease in unit power generation efficiency, accelerated fatigue damage to core components, and increased operating noise. This severely restricts the overall power generation efficiency improvement and long-term operational safety and reliability of concentrated solar power (CSP) plants. Therefore, designing a novel system or control method that can effectively suppress superheater outlet steam flow fluctuations and adapt to fluctuating heat source conditions has become a critical technical challenge that urgently needs to be addressed in the field of CSP technology. Summary of the Invention

[0006] In view of this, the present invention provides a highly efficient and compact superheater for solar thermal power plants that can suppress steam flow fluctuations and has a compact size.

[0007] The technical solution adopted in this invention is as follows: A high-efficiency, compact superheater for a solar thermal power plant that can suppress steam flow fluctuations includes a superheater core, a header, and a connector. The superheater core is a printed circuit board type and is connected to the header. The connector is located on the header. The superheater core includes a plurality of heat exchange plates through which high-temperature molten salt flows and heat exchange plates through which water vapor flows, arranged alternately from top to bottom. The heat exchange plates through which the high-temperature molten salt flows and the heat exchange plates through which the water vapor flows are respectively provided with a plurality of parallel flow channels. The flow channels of the heat exchange plates through which the water vapor flows are provided with a plurality of swirling structures.

[0008] Furthermore, the flow channel of the heat exchange plate through which the water vapor flows also includes a direct flow channel connected to the swirling structure. The swirling structure is composed of several airfoil regions arranged in a staggered manner, each airfoil region including two staggered airfoil fins and flow channel regions.

[0009] Furthermore, the width of the direct current channel is L1, ranging from 1 to 4 mm; the radius of the airfoil arc is R1, and the central angle at the tail is... , The value range is 30°~90°; the side containing the arc portion of the airfoil is the inlet direction; the outer arc of the airfoil region and the arc of the airfoil have the same center, and the radius of the arc is R2 and the central angle is... , The value range is 90°~150°, the distance between the two arcs is L2, and the value range of L2 is 1~4mm; the distance between two adjacent airfoil fins on the same flow channel is L3, and the value range is 5~20mm; the inlet and outlet length of the flow channel is L4, and the value range is 5~10mm; the distance between two adjacent flow channels on the same heat exchange plate is L5, and the value range is 10~30mm; the number of cycles of the airfoil region along the flow direction is N, where N is a positive integer.

[0010] Furthermore, the airfoil regions of adjacent flow channels are arranged alternately or side by side.

[0011] Furthermore, the flow channels of the heat exchange plate through which the water vapor flows are manufactured by photochemical etching; several heat exchange plates through which high-temperature molten salt flows and heat exchange plates through which water vapor flows are welded together by diffusion welding.

[0012] Furthermore, the flow channel of the heat exchange plate through which the high-temperature molten salt flows is a finned flow channel.

[0013] Beneficial effects: 1. The superheater core of this invention is a printed circuit board type, combining the advantages of high-efficiency heat exchange and compact size, while also possessing excellent temperature and pressure resistance and heat exchange efficiency. Several swirling structures are incorporated within the steam flow channels of the heat exchange plate. These structures maintain the high heat transfer performance of the printed circuit board type heat exchange structure while simultaneously increasing flow resistance by 20-30 times when the working fluid flows backward, effectively preventing backflow. When the fluid flows through the swirling structures, thanks to the distribution of their airfoil regions, the fluid undergoes expansion and mixing processes within each cycle unit, significantly enhancing the turbulent pulsation effect and generating longitudinal vortices. This strengthens the heat and mass transfer process between the mainstream region and the heat exchange surface, greatly increasing the convective heat transfer coefficient and ultimately achieving enhanced heat transfer. This design not only significantly improves heat transfer efficiency but also significantly reduces equipment operating energy consumption and costs, achieving energy conservation and cost reduction. Simultaneously, the compact core size effectively reduces material usage, further lowering manufacturing costs, thus balancing energy efficiency and cost control.

[0014] 2. The swirling structure of this invention has unidirectional flow characteristics, which can effectively suppress the generation of backflow. When the fluid flows in the forward direction, the fluid is in the direction of pressure gradient, and the fluid can flow from the inlet to the outlet along the flow direction, and the flow pressure drop generated in this process is small; when the fluid flows in the reverse direction, the fluid is in the direction of pressure gradient, and the fluid will be divided into two secondary flows with the same flow rate. The secondary flows will lose most of their energy after passing through the large curvature bending structure and the 180° rotation of the flow direction, so that the fluid does not have enough kinetic energy to continue flowing.

[0015] 3. This invention forms a swirling structure inside the heat exchange plate through a photochemical etching process, which can improve the self-cleaning ability of the flow channel and effectively inhibit the deposition of dirt on the wall surface. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0017] Figure 2 This is a cross-sectional view (straight pipe section) showing the stacked heat exchange plates through which high-temperature molten salt flows and through which water vapor flows.

[0018] Figure 3 This is a schematic diagram of multiple swirling structures of the present invention on the same heat exchange plate.

[0019] Figure 4 This is a schematic diagram of multiple swirling structures with bent portions on the same heat exchange plate according to the present invention.

[0020] Figure 5 This is a top view and shape determination diagram of a single spiral structure of the present invention.

[0021] Figure 6This is a top view of the multiple swirling structures of the present invention on the same heat exchange plate.

[0022] Figure 7 This is a schematic diagram of a single airfoil region of the present invention.

[0023] Among them, 1-superheater core, 2-header, 3-joint, 4-rotating structure, 5-direct flow channel. Detailed Implementation

[0024] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0025] This invention provides a high-efficiency, compact superheater for concentrated solar power plants that can suppress steam flow fluctuations, comprising a superheater core 1, a header 2, and a connector 3. The superheater core 1 is a printed circuit board type, and the superheater core 1 is connected to the header 2, as shown below. Figure 1 As shown, four headers 2 are respectively arranged around the superheater core 1, and joints 3 are respectively arranged on the headers 2. The two opposite joints 3 serve as the high-temperature molten salt inlet and high-temperature molten salt outlet or the steam inlet and steam outlet, respectively.

[0026] like Figure 2 As shown, the superheater core 1 includes several heat exchange plates for high-temperature molten salt and water vapor, arranged alternately from top to bottom. Each heat exchange plate has several parallel flow channels, and the flow channels of the water vapor heat exchange plate are equipped with several swirling structures 4. The heat exchange plates for high-temperature molten salt and water vapor are welded together using a diffusion welding method.

[0027] The heat exchange plate through which the high-temperature molten salt flows is a finned flow channel, or it can be a flow channel with several swirling structures 4.

[0028] Specifically, such as Figure 3 , Figure 7 As shown, the flow channel of the heat exchange plate through which water vapor flows includes a swirling structure 4 and a direct flow channel 5 connected to the swirling structure 4. The swirling structure 4 is composed of several airfoil regions arranged in a row, and each airfoil region includes two staggered airfoil fins and flow channel regions.

[0029] An airfoil consists of an arc portion and a constricted portion. The arc portion forms the first end of the airfoil, and the constricted portion extends from the arc portion to the second end and gradually narrows. The arc portion and the constricted portion are smoothly connected, and the outline of the constricted portion finally converges at a point to form the second end of the airfoil, so that the overall outline of the airfoil presents an approximate teardrop or leaf shape.

[0030] The entrance / exit is located on the side, and the corresponding straight pipe has a bend, such as... Figure 4 As shown.

[0031] like Figure 5 , Figure 6 As shown, the width of the five sections of the DC channel is L1, with a value ranging from 1 to 4 mm; the radius of the arc portion of the airfoil is R1, and the central angle at the tail (i.e., the included angle of the contraction portion) is... , The value range is 30°~90°; the side containing the airfoil fin arc is the inlet direction; the outer arc of the airfoil region (i.e., the internal contour of the flow channel region) and the airfoil fin arc have the same center, and the arc radius is R2 and the central angle is... , The values ​​range from 90° to 150°, with L2 representing the distance between the two arcs, ranging from 1 to 4 mm. The spacing between two adjacent airfoil fins in the same flow channel is L3, ranging from 5 to 20 mm. The inlet and outlet length of the flow channel is L4, ranging from 5 to 10 mm. The spacing between two adjacent flow channels on the same heat exchange plate is L5, ranging from 10 to 30 mm. The number of airfoil regions along the flow direction is N, where N is a positive integer. In practical applications, the vortex structure 4 can be changed by adjusting the above parameters (the number of airfoil regions in each flow channel, the fin structure of each airfoil fin, and the fin spacing, etc.) to adapt to different operating conditions. The airfoil regions of adjacent flow channels can be arranged alternately or side-by-side according to actual needs.

[0032] In this embodiment, the flow channels on the heat exchange plate through which the high-temperature molten salt flows and the heat exchange plate through which the water vapor flows are both flow channels with several swirling structures 4, which are manufactured by photochemical etching.

[0033] Correspondingly, the flow channel inlets on adjacent heat exchange plates face opposite directions, meaning that the sides of the arcuate portions of adjacent airfoil fins face left and right respectively.

[0034] The workflow is as follows: When the superheater (essentially a heat exchanger) acts as a regenerator, supercritical carbon dioxide under different operating conditions enters the heat exchange plates through which water vapor flows, thereby achieving heat transfer. As the fluid passes through the various airfoil regions of the heat exchange plates, the mass transfer process and turbulence intensity in the main fluid flow area and on the wall are enhanced, thus achieving enhanced heat transfer. Moreover, the flow direction of the fluid undergoes only minor changes and a smooth transition during the flow process, resulting in a smaller pressure loss compared to the zigzag flow channels used in traditional enhanced heat transfer processes. When the superheater acts as a cooler, supercritical carbon dioxide and cooling water flow separately in the heat exchange plates through which water vapor flows, achieving the purpose of heat exchange.

[0035] In one specific embodiment, the radius of the airfoil arc portion of each airfoil region is R1, which is 0.5 mm, and the central angle at the tail is... The angle is 60°; the outer radius of the airfoil region, R2, is 1 mm, and the central angle is... The angle between the two arcs is 120°, and the distance L2 between them is 0.5 mm. The spacing L3 between two adjacent airfoil fins in the same flow channel is 2.88 mm, meaning that the two adjacent airfoil fins are connected end to end. The inlet and outlet length of the flow channel is L4, which is 10 mm. The spacing L5 between two adjacent flow channels on the same heat exchange plate is 25 mm. The number of airfoil region cycles N along the flow direction is 6. According to the calculation results, compared with the direct flow channel, its heat exchange efficiency can be increased by 53.03%, the pressure drop can be increased by 32.50%, and the pressure drop in reverse flow is 23 times that in forward flow.

[0036] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A highly efficient and compact superheater for a solar thermal power plant that can suppress steam flow fluctuations, characterized in that, The device includes a superheater core, a header, and a connector. The superheater core is a printed circuit board type and is connected to the header. The connector is located on the header. The superheater core includes several heat exchange plates through which high-temperature molten salt flows and heat exchange plates through which water vapor flows, arranged alternately from top to bottom. Each heat exchange plate through which high-temperature molten salt flows and heat exchange plates through which water vapor flows are provided with several parallel flow channels. Several swirling structures are provided on the flow channels of the heat exchange plate through which water vapor flows.

2. The high-efficiency, compact superheater for solar thermal power plants capable of suppressing steam flow fluctuations as described in claim 1, characterized in that, The heat exchange plate through which the water vapor flows also includes a direct current channel connected to the swirling structure. The swirling structure is composed of several airfoil regions, each airfoil region including two staggered airfoil fins and a flow channel region.

3. The high-efficiency, compact superheater for solar thermal power plants capable of suppressing steam flow fluctuations as described in claim 1, characterized in that, The width of the direct current channel is L1, ranging from 1 to 4 mm; the radius of the airfoil arc is R1, and the central angle at the tail is... , The value range is 30°~90°; the side containing the arc portion of the airfoil is the inlet direction; the outer arc of the airfoil region and the arc of the airfoil have the same center, and the radius of the arc is R2 and the central angle is... , The value range is 90°~150°, the distance between the two arcs is L2, and the value range of L2 is 1~4mm; the distance between two adjacent airfoil fins on the same flow channel is L3, and the value range is 5~20mm; the inlet and outlet length of the flow channel is L4, and the value range is 5~10mm; the distance between two adjacent flow channels on the same heat exchange plate is L5, and the value range is 10~30mm; the number of cycles of the airfoil region along the flow direction is N, where N is a positive integer.

4. The high-efficiency, compact superheater for solar thermal power plants capable of suppressing steam flow fluctuations as described in claim 1, characterized in that, The airfoil regions of adjacent flow channels are arranged alternately or side by side.

5. The high-efficiency, compact superheater for a solar thermal power plant capable of suppressing steam flow fluctuations as described in any one of claims 1-4, characterized in that, The flow channels of the heat exchange plates through which water vapor flows are manufactured by photochemical etching; several heat exchange plates through which high-temperature molten salt flows and heat exchange plates through which water vapor flows are welded together by diffusion welding.

6. The high-efficiency, compact superheater for a solar thermal power plant capable of suppressing steam flow fluctuations as described in claim 5, characterized in that, The heat exchange plate through which the high-temperature molten salt flows has a finned flow channel.

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