Modular heat exchange device for high-temperature flue gas and high-melting-point molten salt

Abstract

The present invention relates to a modular heat exchange device for high-temperature flue gas and high-melting-point molten salt, which includes a flue gas passage and a number of modular heat exchange units. The modular heat exchange units are multiple heat exchange unit layers, and the modular heat exchange unit arrays of each heat exchange unit layer are distributed in an array; each modular heat exchange unit includes a support body and multiple rows of heat exchange pipes connected in parallel. A multi-stage outflow header is provided at the salt inlet end of the heat exchange pipe, and a multi-stage confluence header is provided at the salt outlet end of the heat exchange pipe; each heat exchange pipe is arranged in the flue gas passage in a reciprocating bending manner from top to bottom, and each of its straight pipe segments is inclined downward; an external heat transfer enhancement structure is provided on the outer wall of the heat exchange pipe, and an internal heat transfer enhancement structure is provided on the inner wall of the heat exchange pipe. This device can solve technical problems such as large molten salt flow resistance, space waste, poor regulation flexibility, heat transfer deviation, over-temperature decomposition, and low-temperature solidification, realize the engineering of the heat exchange device, and effectively meet the actual application requirements.

Description

Technical Field

[0001] The present invention relates to the technical field of fluid heat transfer, and particularly to a modular heat exchange device for high-temperature flue gas and high-melting-point molten salt. Background Art

[0002] High-temperature gases widely exist in high-energy-consuming fields such as electric power and chemical industry. Extracting and utilizing the heat of high-temperature gases is the core process in the above industrial fields.

[0003] With the continuous increase in the proportion of renewable energy, it is urgent to develop large-scale long-term energy storage technologies to mitigate the impact of the spatio-temporal instability endowment of renewable energy on grid security. Thermal energy storage technology has the characteristics of large scale and low cost. For example, molten salt thermal energy storage has developed rapidly, and the heat of high-temperature gases in fields such as electric power and chemical industry can be transferred to molten salt for heat storage. This process requires a flue gas-molten salt heat exchange device.

[0004] However, the flue gas-molten salt heat exchange devices in related technologies have the following several key problems:

[0005] First, molten salt is a high-melting-point and high-viscosity liquid. High-melting-point and high-viscosity fluids have a large flow resistance, increasing the operating cost of power equipment.

[0006] Second, considering the special function of pressure relief, the heat exchange pipes are often set at an inclination angle, and the inclined pipes cause an increase in ineffective space, resulting in a large floor area;

[0007] Third, when heat exchange occurs between flue gas and molten salt, the heat transfer on the flue gas side is poor, and the thermal resistance is much larger than that on the molten salt side. The thermal resistance often concentrates on the flue gas side, resulting in little impact of the molten salt side flow parameters on the overall heat transfer performance. It is difficult to regulate the overall heat transfer performance through molten salt parameters, increasing the difficulty of temperature control. Only the performance such as heat exchange power can be regulated by the flue gas side parameters, which is not conducive to the flexible operation of the equipment.

[0008] Fourth, during actual operation, problems such as uneven flow rate and uneven temperature widely exist in the flue gas side fluid, which in turn leads to a large thermal deviation in the heat exchange device, and may cause local overheating or overcooling, resulting in the denaturation of the molten salt fluid.

[0009] Fifth, there are risks of low-temperature solidification and high-temperature decomposition during the operation of molten salt. There is a temperature difference between the mainstream temperature of the molten salt fluid in the pipe and the film temperature of the inner wall of the heat exchange pipe. Even at a safe design temperature, the temperature of the molten salt close to the pipe wall may be too high or too low, causing the denaturation of the high-melting-point liquid.

[0010] That is to say, the traditional flue gas-molten salt heat exchange device has problems such as large flow resistance, large floor area, only gas-side regulation, uneven heating, and liquid denaturation that need to be solved. Summary of the Invention

[0011] The object of the present invention is to provide a modular heat exchange device for high-temperature flue gas and high-melting-point molten salt, which can effectively solve the above technical problems, realize the engineering of the heat exchange device, and truly meet the requirements of practical applications.

[0012] To achieve the above object, the modular heat exchange device for high-temperature flue gas and high-melting-point molten salt provided by the present invention includes a vertical flue gas passage and a plurality of modular heat exchange units arranged in the flue gas passage. The modular heat exchange units are divided into multiple heat exchange unit layers along the Z direction, and the modular heat exchange units of each heat exchange unit layer are arranged in an array along the X direction and the Y direction; each modular heat exchange unit includes a support body and multiple rows of parallel heat exchange pipes arranged on the support body. A flue gas passage that is used to accommodate the heat exchange pipes and is vertically through is formed inside the support body; the heat exchange pipes are used to introduce liquid molten salt, and a multi-stage outflow main pipe that is gradually branched along the molten salt flow direction is provided at the salt inlet end of the heat exchange pipes, and a multi-stage confluence main pipe that is gradually converged along the molten salt flow direction is provided at the salt outlet end of the heat exchange pipes; each heat exchange pipe is arranged in the flue gas passage in a reciprocating bending manner from top to bottom, and each straight pipe section thereof slopes downward; an external enhanced heat transfer structure is provided on the outer wall of the heat exchange pipe, and an internal enhanced heat transfer structure is provided on the inner wall of the heat exchange pipe, and the internal enhanced heat transfer structure is arranged in alignment with the external enhanced heat transfer structure; the modular heat exchange unit, the multi-stage outflow main pipe, and the multi-stage confluence main pipe form an external fluid network for heat exchange between the molten salt and the flue gas, and the heat exchange pipes of the modular heat exchange unit form an internal fluid network for heat exchange between the molten salt and the flue gas.

[0013] Optionally, each heat exchange unit layer is provided with a shared primary confluence main pipe; the primary confluence main pipe is arranged along the Z direction and is connected with a secondary confluence main pipe for supplying each heat exchange unit layer. Each secondary confluence main pipe is arranged along the X direction; the secondary confluence main pipe is connected with a plurality of tertiary confluence main pipes, and each tertiary confluence main pipe is arranged along the Y direction; the tertiary confluence main pipe is connected with a plurality of quaternary confluence main pipes, and the quaternary confluence main pipe is arranged along the X direction and is connected with the salt outlet header corresponding to the modular heat exchange unit, and the salt outlet header is connected with the heat exchange pipes of the modular heat exchange unit; the heat exchange pipes of each modular heat exchange unit are connected with a salt inlet header, the salt inlet header is connected with a quaternary outflow main pipe, the quaternary outflow main pipe is arranged along the X direction and is connected with a tertiary outflow main pipe, the tertiary outflow main pipe is arranged along the Y direction and is connected with a secondary outflow main pipe, and the secondary outflow main pipe is arranged along the X direction and is connected with the primary outflow main pipe shared by each heat exchange unit layer.

[0014] Optionally, each of the heat exchange unit layers is provided with a plurality of third-level busbars arranged along the X direction and connected to a fourth-level busbar. Each of the fourth-level busbars is connected to the salt outlet header of the corresponding modular heat exchange unit, and the salt outlet header is connected to the heat exchange pipeline of the modular heat exchange unit; the heat exchange pipelines of each of the modular heat exchange units are connected to a salt inlet header, and each of the salt inlet headers is connected to the corresponding fourth-level outlet busbar. The fourth-level outlet busbar is connected to a third-level outlet busbar arranged along the X direction; the topmost heat exchange unit layer is provided with a first-level busbar arranged along the Z direction, and the first-level busbar is connected to a plurality of second-level busbars arranged along the Y direction, and the second-level busbars are connected to the third-level busbars; the bottommost heat exchange unit layer is provided with a second-level outlet busbar connected to the third-level outlet busbar, and the second-level outlet busbar is arranged along the Y direction and connected to a first-level outlet busbar arranged along the Z direction; the corresponding third-level busbars and third-level outlet busbars of adjacent two heat exchange unit layers are connected through vertical inter-layer pipelines.

[0015] Optionally, the inner diameters of the first-level busbar, the second-level busbar, the third-level busbar, and the fourth-level busbar decrease in sequence, and the inner diameters of the fourth-level outlet busbar, the third-level outlet busbar, the second-level outlet busbar, and the first-level outlet busbar increase in sequence.

[0016] Optionally, the support body of each of the modular heat exchange units includes a front side support plate, a rear side support plate, a left side support plate, and a right side support plate. The straight pipe section of the heat exchange pipeline is located between the left side support plate and the right side support plate, and the elbow pipe section of the heat exchange pipeline is located outside the left side support plate and the right side support plate and is connected to the corresponding straight pipe section through the corresponding opening; the salt inlet end of the heat exchange pipeline passes through the opening of the right side support plate and is connected to the salt inlet header, and the salt outlet end of the heat exchange pipeline passes through the opening of the left side support plate and is connected to the salt outlet header.

[0017] Optionally, each of the modular heat exchange units is provided with a support base.

[0018] Optionally, the inner enhanced heat transfer structure includes threads, spiral channels, annular protrusions, or corrugations on the inner wall of the heat exchange pipeline, and the outer enhanced heat transfer structure includes heat exchange fins on the outer wall of the heat exchange pipeline, and the heat exchange fins are arranged in alignment with the threads, spiral channels, annular protrusions, or corrugations.

[0019] Optionally, the heat exchange fins are arranged at an angle with the heat exchange pipeline to conform to the air flow direction.

[0020] Optionally, the fins include spiral fins, corrugated fins, annular fins, square fins, or H-shaped fins.

[0021] Optionally, the cross-sectional shape of the heat exchange pipes of the modular heat exchange unit is circular, elliptical, square, rectangular or polygonal.

[0022] Optionally, during operation, the flow rate of the molten salt in the heat exchange pipes is less than or equal to 2 m / s.

[0023] Compared with the traditional flue gas - molten salt heat exchange device, the modular heat exchange device provided by the present invention has at least the following advantages:

[0024] 1) Since the heat exchange pipelines arranged in the flue gas channel as a whole are divided into several modular heat exchange units, and the modular heat exchange units are distributed in a three-dimensional manner, the molten salt can complete the full path from the inlet to the outlet through only a relatively small number of heat exchange pipes, greatly reducing the frictional pressure drop loss of the molten salt in the heat exchange pipes.

[0025] 2) Since there are inclinations in the heat exchange pipes of each modular heat exchange unit, and the total length of the heat exchange pipes is decomposed in each dimension, the space waste caused by the inclination can be reduced geometrically.

[0026] 3) Due to the matching of the internal and external thermal resistances of the heat exchange pipes through the enhanced heat transfer structure, the thermal resistances on the flue gas side and the molten salt side can be at the same or similar levels. During variable load operation, the heat exchange power can be regulated by adjusting either the flue gas flow rate or the molten salt flow rate, enhancing the flexibility of the regulation of the heat exchange device.

[0027] 4) During actual operation, if the problem of uneven flow rates on the flue gas or molten salt side occurs, the multi-stage main pipe structure can achieve the function of gradually mixing the heat transfer fluid, equalizing the temperature field between each stage, and automatically correcting the heat transfer deviation caused by uneven flow rates.

[0028] 5) Through the inclination structure, when the molten salt exits the system, it can achieve self-emptying without power, ensuring that when the operating state is switched, the molten salt is prevented from low-temperature solidification or over-temperature decomposition. On the other hand, the internal enhanced heat transfer structure set reduces the thermal resistance on the molten salt side, making the film temperature of the heat exchange pipes closer to the mainstream temperature of the molten salt in the pipes, preventing excessive deviation between the local film temperature and the mainstream temperature from causing over-temperature decomposition or low-temperature solidification. Description of the Drawings

[0029] Figure 1 It is a schematic structural diagram of the modular heat exchange device for high-temperature flue gas and high-melting-point molten salt provided by the first embodiment of the present invention;

[0030] Figure 2 It is Figure 1 a schematic structural diagram of the modular heat exchange unit shown in;

[0031] Figure 3 It is a schematic diagram of the flow path comparison between non-modular heat exchange pipes and modular heat exchange pipes in the same space;

[0032] Figure 4 It is a cross-sectional view of a heat exchange pipeline;

[0033] Figure 5 It is a schematic structural diagram of a modular heat exchange device for high-temperature flue gas and high-melting-point molten salt provided by the second embodiment of the present invention.

[0034] In the figure:

[0035] 10. Flue gas channel 20. Modular heat exchange unit 21. Support body 211. Rear support plate 212. Left support plate 213. Right support plate 22. Heat exchange pipeline 221. External heat transfer enhancement structure 222. Internal heat transfer enhancement structure 223. Straight pipe section 224. Elbow pipe section 23. Salt outlet header 24. Salt inlet header 25. Support base 31. First-stage confluence main pipe 32. Second-stage confluence main pipe 33. Third-stage confluence main pipe 34. Fourth-stage confluence main pipe 41. First-stage outflow main pipe 42. Second-stage outflow main pipe 43. Third-stage outflow main pipe 44. Fourth-stage outflow main pipe 50. Interlayer pipeline Detailed implementation manners

[0036] In order to enable those skilled in the art to better understand the solution of the present invention, the present invention will be further described in detail below with reference to the drawings and specific implementation manners.

[0037] In this article, terms such as "upper, lower, inner, outer" are established based on the positional relationship shown in the drawings. Depending on the different drawings, the corresponding positional relationship may also change accordingly. Therefore, it cannot be understood as an absolute limitation of the protection scope; moreover, relational terms such as "first" and "second" are only used to distinguish one component with the same name from another, and do not necessarily require or imply any such actual relationship or order between these components.

[0038] Please refer to Figure 1 , Figure 1 It is a schematic structural diagram of a modular heat exchange device for high-temperature flue gas and high-melting-point molten salt provided by the first embodiment of the present invention.

[0039] As shown in the figure, in a specific embodiment, the modular heat exchange device for high-temperature flue gas and high-melting-point molten salt provided by the present invention mainly consists of a flue gas channel 10 and modular heat exchange units 20. The flue gas channel 10 is vertically arranged, and a plurality of modular heat exchange units 20 are arranged inside the flue gas channel 10. The modular heat exchange units 20 are divided into multiple heat exchange unit layers along the Z direction, and the modular heat exchange units 20 of each heat exchange unit layer are arranged in an array along the X direction and the Y direction.

[0040] Each modular heat exchange unit 20 is provided with a support body 21 and multiple rows of parallel heat exchange pipes 22. The heat exchange pipes 22 are installed relying on the support body 21. A flue gas passage that penetrates up and down is formed inside the support body 21 for accommodating the heat exchange pipes 22; the heat exchange pipes 22 are used for introducing liquid molten salt, and a multi-stage outflow header that is gradually branched along the molten salt flow direction is provided at the salt inlet end of the heat exchange pipes 22, and a multi-stage confluence header that is gradually converged along the molten salt flow direction is provided at the salt outlet end of the heat exchange pipes 22.

[0041] The modular heat exchange unit 20, the multi-stage diversion header, and the multi-stage confluence header form an external fluid network for heat exchange between molten salt and flue gas. The heat exchange pipes 22 of the modular heat exchange unit 20 form an internal fluid network for heat exchange between molten salt and flue gas. There is no local low position in the entire fluid network, which can significantly reduce the flow resistance of the molten salt and ensure that the molten salt can be depressurized and discharged.

[0042] In this embodiment, the external fluid network adopts a completely parallel form. Taking a modular heat exchange device with three heat exchange unit layers, and each layer is provided with nine modular heat exchange units 20 as an example, the specific connection form of the complete parallel connection will be further introduced.

[0043] The three heat exchange unit layers share a first-stage confluence header 31. The first-stage confluence header 31 is arranged along the Z direction and is connected with three second-stage confluence headers 32 for feeding into each heat exchange unit layer. The three second-stage confluence headers 32 are arranged along the X direction; each second-stage confluence header 32 is connected with three third-stage confluence headers 33. The third-stage confluence headers 33 are arranged along the Y direction; each third-stage confluence header 33 is connected with a fourth-stage confluence header 34. The fourth-stage confluence header 34 is arranged along the X direction and is connected with the salt inlet header 23 of the corresponding modular heat exchange unit 20. The salt inlet header 23 is connected with the four rows of heat exchange pipes 22 of the modular heat exchange unit 20; similarly, the heat exchange pipes 22 of each modular heat exchange unit 20 are connected with a salt inlet header 24. The salt inlet header 24 is connected with a fourth-stage outflow header 44. The fourth-stage outflow header 44 is arranged along the X direction and is connected with a third-stage outflow header 43. The third-stage outflow header 43 is arranged along the Y direction and is connected with a second-stage outflow header 42. The second-stage outflow header 42 is arranged along the X direction and is connected with the first-stage outflow header 41 shared by each heat exchange unit layer.

[0044] The inner diameters of the above-mentioned first-stage confluence header 31, second-stage confluence header 32, third-stage confluence header 33, and fourth-stage confluence header 34 decrease in sequence. On the contrary, the inner diameters of the fourth-stage outflow header 44, third-stage outflow header 43, second-stage outflow header 42, and first-stage outflow header 41 increase in sequence.

[0045] During operation, the molten salt on the salt side of the heat exchanger enters from the bottom and exits from the top, that is, it flows in from the lower end and out from the upper end, which is conducive to filling the pipeline with liquid when adding salt; of course, in other embodiments, the molten salt can also flow in from the upper end and out from the lower end, and the flow direction of the high-temperature flue gas is in the vertical direction, which can be overall concurrent heat exchange or overall countercurrent heat exchange.

[0046] For example, the low-temperature molten salt enters from the first-stage outlet main pipe 41 at the lower end of the heat exchange device, and then is gradually shunted into the internal heat exchange pipeline 22 through the second, third, and fourth-stage outlet main pipes. After absorbing the heat of the high-temperature flue gas, it is gradually converged into the first-stage convergence main pipe 31 through the fourth, third, and second-stage convergence main pipes and flows out from the outlet. The flue gas flows downwards through the heat exchanger device, releases heat to the heat exchanger, and then flows out from the flue gas outlet.

[0047] Please also refer to Figure 2 、 Figure 3 , Figure 2 for Figure 1 the structural schematic diagram of the modular heat exchange unit shown in Figure 3 and is a schematic diagram of the flow path comparison between the non-modular heat exchange pipeline and the heat exchange pipeline after modularization in the same space.

[0048] As shown in the figure, the heat exchange pipelines 22 of each modular heat exchange unit 20 are arranged in the flue gas passage formed by the support body 21 in a reciprocating bending manner from top to bottom, and each straight pipe section 223 thereof is inclined downward at the same angle. For example, the angle of its downward inclination can be 10°, 20°, 25°, 30°, etc.

[0049] The number of rows of the heat exchange pipelines 22 and the number of reciprocating bends can be designed according to actual needs. In the present embodiment, each modular heat exchange unit 20 is respectively provided with four rows of heat exchange pipelines 22, and each row of heat exchange pipelines 22 reciprocates and bends sixteen times, thus forming four rows of serpentine heat exchange pipelines. The cross-sectional shape of the heat exchange pipelines 22 can be circular, elliptical, square, rectangular or polygonal.

[0050] Each support body 21 of the modular heat exchange units 20 has a front side support plate (not shown in the figure to avoid blocking the heat exchange pipeline), a rear side support plate 211, a left side support plate 212 and a right side support plate 213. The straight pipe section 223 of the heat exchange pipeline 22 is located between the left side support plate 212 and the right side support plate 213, and the elbow pipe section 224 of the heat exchange pipeline 22 is located outside the left side support plate 212 and the right side support plate 213 and is connected to the corresponding straight pipe section 223 through the corresponding opening; the salt inlet end of the heat exchange pipeline 22 passes through the opening of the left side support plate 212 or the right side support plate 213 and is connected to the salt inlet header 23, and the salt outlet end of the heat exchange pipeline 22 passes through the opening of the right side support plate 213 or the left side support plate 212 and is connected to the salt outlet header 24.

[0051] In addition, support bases 25 are respectively provided at the bottoms of the modular heat exchange units 20, so as to provide stable support after installation, and thus be reliably positioned.

[0052] The materials of the heat exchange pipes 22, each stage of header tanks, and the main pipe are compatible with the molten salt to avoid internal corrosion of the pipes.

[0053] In traditional flue gas-molten salt heat exchange devices, heat exchange pipes are directly arranged across the entire width of the flue gas channel. The open part formed by the inclined arrangement of the heat exchange pipes will occupy a relatively large space, resulting in waste of space. The flue gas and the molten salt cannot exchange heat in this space. If the heat exchange is insufficient, there is a risk of solidification of the molten salt.

[0054] The present invention modularizes the heat exchange pipes into several heat exchange units. In the same space, its flow path can be increased several times. On the one hand, it can ensure sufficient heat exchange between the flue gas and the molten salt, avoiding the risk of solidification of the molten salt. On the other hand, on the premise that the total flow rate of the molten salt remains unchanged, the flow rate and flow velocity of the heat exchange pipes 22 in each heat exchange unit will also decrease. Figure 3 Taking the layout structure shown as an example, the flow path of the molten salt is divided from one path into two paths, that is, it is divided into two heat exchange units. The flow path of each heat exchange unit is the same as the original flow path. Therefore, the total flow path is twice the original, the flow rate of the heat exchange pipes in each heat exchange unit will be halved, and the flow velocity will also be halved. According to the relevant formulas of fluid mechanics, the flow resistance of the molten salt is only one-fourth of the original, and the flow resistance is significantly reduced.

[0055] Please continue to refer to Figure 4 , Figure 4 which is a cross-sectional view of the heat exchange pipe.

[0056] As shown in the figure, an external heat transfer enhancement structure 221 is provided on the outer wall of the heat exchange pipe 22, and an internal heat transfer enhancement structure 222 is provided on the inner wall of the heat exchange pipe 22, and the internal heat transfer enhancement structure 222 is arranged in alignment with the external heat transfer enhancement structure 221.

[0057] Specifically, the internal heat transfer enhancement structure 222 can be threads, spiral channels, annular protrusions or corrugations on the inner wall of the heat exchange pipe 22, and the external heat transfer enhancement structure 221 can be heat exchange fins on the outer wall of the heat exchange pipe 22, and the heat exchange fins are arranged in alignment with the threads, spiral channels, annular protrusions or corrugations.

[0058] For example, if the internal heat transfer enhancement structure 222 is an annular protrusion located on the inner wall of the heat exchange pipe 22, then the external heat transfer enhancement structure 221 is an annular heat exchange fin located on the outer wall of the heat exchange pipe 22, and the annular heat exchange fins and the annular protrusions are arranged in one-to-one correspondence; if the internal heat transfer enhancement structure 222 is a thread located on the inner wall of the heat exchange pipe 22, then the external heat transfer enhancement structure 221 is a spiral heat exchange fin located on the outer wall of the heat exchange pipe 22, and the spiral heat exchange fins and the threads are arranged in one-to-one correspondence.

[0059] By matching parameters such as the height, angle, and density of the annular protrusions, threads, annular fins, and spiral fins, the internal and external thermal resistances can be at the same level, such as both being 1, or both being 1.5, etc.

[0060] Gas is a poor conductor of heat, while liquid or solid is a good conductor of heat. For the heat exchange between flue gas and molten salt, the temperature of the flue gas is relatively high. If the heat transfer efficiency is improved through the gas side, only the gas side flow rate can be increased. However, by designing heat exchange fins for the heat exchange pipe 22, it helps to balance the external thermal resistance and the internal thermal resistance coefficient, reduce the thermal resistance coefficient on the flue gas side, and thus achieve the purpose of regulating the heat transfer efficiency on both the flue gas side and the molten salt side.

[0061] However, the applicant found in the research that if only heat exchange fins are provided, when the heat of the flue gas is conducted through the heat exchange fins, local high temperatures are extremely likely to occur at the roots of the heat exchange fins, resulting in the decomposition of the molten salt. In response to this, the present invention designs the internal heat transfer enhancement structure 222 and arranges the internal heat transfer enhancement structure 222 in correspondence with the external heat transfer enhancement structure 221. On the one hand, it strengthens the internal thermal resistance, and on the other hand, it can decompose the internal high temperature in different directions, suppress temperature non-uniformity, and safely transfer the heat of the flue gas to the molten salt, effectively avoiding the phenomenon of molten salt decomposition.

[0062] In addition, the heat exchange fins are arranged at an angle with the heat exchange pipe 22 to conform to the air flow direction, that is to say, the heat exchange fins are parallel to the direction of the flue gas. In this way, the flue gas resistance can be reduced, flue gas turbulence can be avoided, and the energy efficiency of the heating surface affected by ash accumulation can also be avoided.

[0063] The heat exchange fins can be not only spiral fins and annular fins, but also corrugated fins, square fins or H-shaped fins. The fin material and the pipe material have welding compatibility, and the two are welded together to minimize the contact thermal resistance to the greatest extent.

[0064] The pipe diameter of the heat exchange pipe 22 is determined by the flow rate and total flow of the molten salt inside the pipe. The flow rate of the molten salt inside the pipe does not exceed 2 m / s. The heat exchange fins and the outer diameter of the pipe are determined by calculating the heat transfer resistance. The principle is to ensure that the internal thermal resistance of the pipe and the external thermal resistance are at the same or similar level.

[0065] Please continue to refer to Figure 5 , Figure 5Schematic diagram of the modular heat exchange device for high-temperature flue gas and high-melting-point molten salt provided by the first embodiment of the present invention.

[0066] As shown in the figure, compared with the first embodiment, the difference in this embodiment is that the external fluid network adopts a partially parallel form. Still taking the modular heat exchange device with three heat exchange unit layers, and each layer has nine heat exchange units as an example, the specific connection form of the partial parallel connection will be further introduced below.

[0067] Each heat exchange unit layer is respectively provided with three third-level confluence headers 33. The third-level confluence headers 33 are arranged along the X direction and are connected with fourth-level confluence headers 34. Each fourth-level confluence header 34 is connected to the salt outlet header 23 of the corresponding modular heat exchange unit 20. The salt outlet header 23 is connected to the heat exchange pipeline 22 of the modular heat exchange unit 20; the heat exchange pipeline 22 of each modular heat exchange unit 20 is connected to a salt inlet header 24. Each salt inlet header 24 is connected to the corresponding fourth-level outlet main pipe 44. The fourth-level outlet main pipe 44 is connected to the third-level outlet main pipe 43. The third-level outlet main pipe 43 is arranged along the X direction; the heat exchange unit layer at the topmost layer is provided with a first-level confluence header 31 arranged along the Z direction. The first-level confluence header 31 is connected with a second-level confluence header 32. The second-level confluence header 32 is arranged along the Y direction and is connected to the third-level confluence header 33; the heat exchange unit layer at the bottommost layer is provided with a second-level outlet main pipe 42 connected to the third-level outlet main pipe 43. The second-level outlet main pipe 42 is arranged along the Y direction and is connected to the first-level outlet main pipe 41. The first-level outlet main pipe 41 is arranged along the Z direction; the corresponding third-level confluence headers 33 and third-level outlet main pipes 43 of adjacent two heat exchange unit layers are connected by two vertical inter-layer pipelines 50.

[0068] In this embodiment, the parts that are the same as those in the first embodiment are given the same reference numerals, and the same text descriptions are omitted.

[0069] The above embodiments are only the preferred solutions of the present invention, and are not specifically limited thereto. On this basis, targeted adjustments can be made according to actual needs to obtain different implementation manners. For example, each level of main pipe also has an angle of inclination downward, and so on. Since there are many possible implementation manners, they will not be enumerated one by one here.

[0070] The present invention has the following beneficial effects:

[0071] 1) The heat exchange power can be flexibly adjusted within a wide range: The modular structure can meet the flexible selection of the equipment power range. In the case of a large range of changes in the working fluid flow rate, by setting the number of module stages and dimensions, the reasonable flow rates of the working fluids on both sides are ensured, and different flow rate ranges can be adapted to obtain the characteristic of flexible adjustment of the heat exchange power within a wide range.

[0072] 2) Greatly improved heat exchange efficiency: By means of principles of enhanced heat transfer such as passive flow disturbance and expanded heating surface, and simultaneously enhancing the heat transfer processes of the working fluids on both sides, the overall heat exchange performance of the heat exchanger is greatly improved.

[0073] 3) Enhanced flexibility of operating conditions: Through thermal resistance matching, the thermal resistances of the two-side fluids are adjusted to the same or approximate levels. Then both the total heat transfer thermal resistance and the two-side thermal resistances are sensitive. During operation, it can be regulated either through the parameters of the high-temperature side fluid or the low-temperature side fluid.

[0074] 4) Reduced risks of solidification and decomposition: For the high-melting-point molten salt inside the pipeline, the internal enhanced structure reduces the internal thermal resistance, making the temperature difference between the near-wall film temperature and the mainstream temperature of the fluid inside the pipe decrease. Under the condition of determining the heat balance design temperature parameters of the heat exchanger, the risks of high-temperature decomposition and low-temperature solidification caused by the inconsistency between the film temperature and the mainstream temperature are reduced.

[0075] 5) In the heat transfer modes of flowing gas - flowing liquid and flowing liquid - flowing gas in common industrial fields, the fluid network constructed by the heat exchange equipment has no local low points, so it has the function of pressure loss relief and emptying for high-melting-point liquids;

[0076] 6) In the heat transfer modes of flowing gas - flowing liquid and flowing liquid - flowing gas in common industrial fields, the fluid network constructed by the heat exchange equipment has a significant systematic drag reduction function. For example, in the fully parallel connection mode, the inlet fluid only flows through one heat exchange pipe of one heat exchange module, realizing the systematic flow drag reduction function.

[0077] 7) The traditional flue gas - molten salt heat exchange device does not have a modular structure. When the high-temperature gas flow rate or temperature is spatially and temporally uneven, it will lead to uneven heat transfer, and the heat deviation accumulates from the inlet to the outlet. Specifically, a certain heat exchange pipe will deviate from the design point, resulting in high-temperature decomposition or low-temperature solidification of the molten salt. The multi-stage header and main pipe structure of the fluid network constructed by the present invention can provide mixing nodes between the heat exchange pipes at all levels. Each node can be used as a mixer to self-correct the temperature field of the local high-melting-point fluid, reducing local over-temperature decomposition or low-temperature solidification caused by uneven heating.

[0078] The modular heat exchange device for high-temperature flue gas and high-melting-point molten salt provided by the present invention has been introduced in detail above. Specific examples are used in this article to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the core idea of the present invention. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements and modifications can still be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A modular heat exchange device for high-temperature flue gas and high-melting-point molten salt, characterized in that: It comprises a vertical flue gas channel and a plurality of modular heat exchange units arranged in the flue gas channel, wherein the modular heat exchange units are divided into a plurality of heat exchange unit layers along the Z direction, the Z direction being the flow direction of the high-temperature flue gas, and the modular heat exchange units of each heat exchange unit layer are arrayed along the X direction and the Y direction; each modular heat exchange unit comprises a support body and a plurality of rows of parallel heat exchange pipes arranged on the support body, wherein the interior of the support body forms a flue gas passage for accommodating the heat exchange pipes and passing through from top to bottom; the heat exchange pipes are used to pass liquid molten salt, and a multi-stage outlet main pipe is provided at the salt inlet end thereof for stepwise diversion along the flow direction of the molten salt, and the The salt outlet end of the heat exchange pipe is provided with a multi-stage converging mother pipe that converges step by step along the flow direction of the molten salt; each of the heat exchange pipes is arranged in the flue gas passage in a reciprocating manner from top to bottom, and each straight pipe section thereof is inclined downward; the outer wall of the heat exchange pipe is provided with an external enhanced heat transfer structure, and the inner wall of the heat exchange pipe is provided with an internal enhanced heat transfer structure, and the internal enhanced heat transfer structure is arranged in alignment with the external enhanced heat transfer structure; the multi-stage outlet mother pipe and the multi-stage converging mother pipe of the modular heat exchange unit constitute an external fluid network for heat exchange between molten salt and flue gas, and the heat exchange pipes of the modular heat exchange unit constitute an internal fluid network for heat exchange between molten salt and flue gas.

2. The modular heat exchange device for high-temperature flue gas and high-melting-point molten salt according to claim 1 is characterized in that: Each of the heat exchange unit layers is provided with a common primary collecting mother tube; the primary collecting mother tube is arranged along the Z direction and is connected to a secondary collecting mother tube supplied to each of the heat exchange unit layers, and each of the secondary collecting mother tubes is arranged along the X direction; the secondary collecting mother tube is connected to a plurality of tertiary collecting mother tubes, and each of the tertiary collecting mother tubes is arranged along the Y direction; the tertiary collecting mother tube is connected to a plurality of quaternary collecting mother tubes, and the quaternary collecting mother tubes are arranged along the X direction and connected to the corresponding salt outlet header of the modular heat exchange unit, and the salt outlet header is connected to the heat exchange pipe of the modular heat exchange unit; the heat exchange pipe of each modular heat exchange unit is connected to the salt inlet header, and the salt inlet header is connected to the quaternary outlet mother tube, the quaternary outlet mother tube is arranged along the X direction and connected to the tertiary outlet mother tube, the tertiary outlet mother tube is arranged along the Y direction and connected to the secondary outlet mother tube, and the secondary outlet mother tube is arranged along the X direction and connected to the primary outlet mother tube common to each of the heat exchange unit layers.

3. The modular heat exchange device for high-temperature flue gas and high-melting-point molten salt according to claim 1 is characterized in that: Each of the heat exchange unit layers is respectively provided with a plurality of three-stage busbars, the three-stage busbars are arranged along the X direction and connected with four-stage busbars, each of the four-stage busbars is connected with the corresponding salt outlet header of the modular heat exchange unit, the salt outlet header is connected with the heat exchange pipe of the modular heat exchange unit; the heat exchange pipe of each modular heat exchange unit is connected with the salt inlet header, each of the salt inlet header is connected with the corresponding four-stage outlet header, the four-stage outlet header is connected with the three-stage outlet header, and the three-stage outlet header is arranged along the X direction; the heat exchange pipes of the modular heat exchange units are connected with the salt inlet header, the salt inlet header is connected with the corresponding four-stage outlet header, the four-stage outlet header is connected with the three-stage outlet header, and the three-stage outlet header is arranged along the X direction; The heat exchange unit layer is provided with a primary collecting mother tube arranged along the Z direction, and the primary collecting mother tube is connected to multiple secondary collecting mother tubes, and the secondary collecting mother tubes are arranged along the Y direction and connected to the tertiary collecting mother tubes; the heat exchange unit layer located at the bottom layer is provided with a secondary outflow mother tube connected to the tertiary outflow mother tube, and the secondary outflow mother tube is arranged along the Y direction and connected to the primary outflow mother tube, and the primary outflow mother tube is arranged along the Z direction; the tertiary collecting mother tubes corresponding to the two adjacent heat exchange unit layers are connected to the tertiary outflow mother tubes through vertical interlayer pipelines.

4. The modular heat exchange device for high-temperature flue gas and high-melting-point molten salt according to claim 2 or 3, characterized in that: The inner diameters of the primary collecting mother tube, the secondary collecting mother tube, the tertiary collecting mother tube, and the quaternary collecting mother tube decrease in sequence, and the inner diameters of the quaternary outflow mother tube, the tertiary outflow mother tube, the secondary outflow mother tube, and the primary outflow mother tube increase in sequence.

5. The modular heat exchange device for high-temperature flue gas and high-melting-point molten salt according to claim 4, characterized in that: The support body of each modular heat exchange unit includes a front support plate, a rear support plate, a left support plate and a right support plate. The straight pipe section of the heat exchange pipe is located between the left support plate and the right support plate, and the elbow pipe section of the heat exchange pipe is located on the outside of the left support plate and the right support plate and is connected with the corresponding straight pipe section through corresponding openings; the salt inlet end of the heat exchange pipe is connected with the salt inlet manifold through the opening of the right support plate, and the salt outlet end of the heat exchange pipe is connected with the salt outlet manifold through the opening of the left support plate.

6. The modular heat exchange device for high-temperature flue gas and high-melting-point molten salt according to claim 1, characterized in that: Each of the modular heat exchange units is provided with a supporting base.

7. The modular heat exchange device for high-temperature flue gas and high-melting-point molten salt according to claim 1, characterized in that: The internal enhanced heat transfer structure includes threads, spiral grooves, annular protrusions or corrugations located on the inner wall of the heat exchange pipe, and the external enhanced heat transfer structure includes heat exchange fins located on the outer wall of the heat exchange pipe, and the heat exchange fins are arranged in alignment with the threads, spiral grooves, annular protrusions or corrugations.

8. The modular heat exchange device for high-temperature flue gas and high-melting-point molten salt according to claim 7, characterized in that: The heat exchange fins and the heat exchange pipes are arranged at an angle to conform to the direction of air flow.

9. The modular heat exchange device for high-temperature flue gas and high-melting-point molten salt according to claim 8, characterized in that: The fins include spiral fins, corrugated fins, annular fins, square fins or H-shaped fins.

10. The modular heat exchange device for high-temperature flue gas and high-melting-point molten salt according to claim 1, characterized in that: The cross-sectional shape of the heat exchange pipe of the modular heat exchange unit is circular, elliptical, square, rectangular or polygonal.

11. The modular heat exchange device for high-temperature flue gas and high-melting-point molten salt according to claim 1, characterized in that: During operation, the flow rate of the molten salt in the heat exchange pipe is less than or equal to 2 m / s.

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