Operation method of shell and tube heat exchanger for organic Rankine cycle

Abstract

The invention relates to an operation method of a shell and tube heat exchanger for an organic Rankine cycle. A refrigerant is input into the cylinder through the liquid inlet connecting pipe and sequentially flows through the preheating area, the evaporation area and the overheating area. A high-temperature heat source enters from the water inlet chamber, sequentially flows through the evaporation area heat exchange pipe, the overheating area heat exchange pipe, the water return chamber and the preheating area heat exchange pipe and then is discharged from the water outlet chamber, and a reverse pure countercurrent flow heat exchange path is formed. In the preheating area, a refrigerant is preheated through a condensation heat exchange pipe of an inner-tooth outer-fin structure, and forced convection is formed by means of a baffle plate until the saturated evaporation temperature is reached; in the evaporation area, the refrigerant absorbs heat and is gasified in the evaporation heat exchange pipes on the outer surfaces of the micropores and the inner walls of the threads; and in the overheating area, refrigerant gas is subjected to overheating treatment through the heat exchange pipe with the reinforced turbulent flow structure, flows circuitously through the baffle plate and then is output to the expansion machine through the gas outlet connecting pipe. According to the method, preheating, evaporation and overheating functions are integrated in single equipment, and the heat exchange efficiency is improved and the system complexity is reduced by optimizing a heat exchange tube structure and a flow path in a partitioned manner.

Description

Technical Field

[0001] The present invention relates to the technical field of organic Rankine cycle, and particularly to an operation method for a shell-and-tube heat exchanger used in an organic Rankine cycle. Background Art

[0002] The organic Rankine cycle (ORC), as an efficient medium- and low-temperature heat energy recovery technology, is widely used in fields such as industrial waste heat power generation, geothermal power generation, and solar thermal utilization. Its core lies in driving an expander to do work through the phase change process of an organic working fluid under a low-temperature heat source, thereby realizing the conversion of heat energy into electrical energy. In this system, as one of the key devices, the performance of the heat exchanger directly affects the cycle efficiency and the overall operating cost.

[0003] Traditional shell-and-tube heat exchangers are commonly used in the ORC system for the preheating, evaporation, and superheating processes of the working fluid. However, the shell-and-tube heat exchangers in the prior art generally have the following problems: The separation of functions leads to a complex structure. Traditional solutions usually use multiple independent heat exchangers to complete the preheating, evaporation, and superheating functions respectively, resulting in a large system volume and complex pipeline connections, increasing the installation and maintenance costs. The heat transfer efficiency is limited. Conventional heat exchange tube designs (such as smooth tubes or simple finned tubes) are difficult to effectively enhance heat transfer. Especially in the evaporation stage, the lack of gasification cores of the working fluid easily leads to local overheating or a decrease in heat transfer efficiency. The heat source utilization is insufficient. The design of the high-temperature heat source flow path in the existing heat exchangers often fails to maximize countercurrent heat exchange, resulting in a reduction in waste heat recovery efficiency. Therefore, there is an urgent need for an integrated and highly efficient shell-and-tube heat exchanger that can realize the preheating, evaporation, and superheating functions of the working fluid in a single device, while optimizing the heat transfer efficiency, reducing the amount of working fluid, and simplifying the system configuration through structural innovation. The present invention is proposed based on this technical need.

[0004] In view of the above problems, the prior art urgently needs to be improved. Summary of the Invention

[0005] In order to solve the above problems, the purpose of the present invention is to provide an operation method for a shell-and-tube heat exchanger used in an organic Rankine cycle, which has the advantages of integration, high efficiency, and simplified system configuration.

[0006] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0007] An operation method for a shell-and-tube heat exchanger used in an organic Rankine cycle, characterized by comprising the following steps:

[0008] Step S1: Input the refrigerant into the inner cavity of the cylinder through the liquid inlet connecting pipe, and sequentially flow through the preheating zone, evaporation zone, and superheating zone formed by the baffle plates.

[0009] Step S2: Input the high-temperature heat source into the water inlet chamber, and it flows through the evaporation zone heat exchange tubes, superheat zone heat exchange tubes, return water chamber, and preheating zone heat exchange tubes in sequence, and finally discharges from the water outlet chamber, forming a pure countercurrent heat exchange path opposite to the refrigerant flow direction;

[0010] Step S3: In the preheating zone, preheat the refrigerant through the condensation heat exchange tubes with an internal tooth and external fin structure, and use the staggered baffles to guide the refrigerant to form axial and radial forced convection until the refrigerant temperature reaches the saturated evaporation temperature;

[0011] Step S4: In the evaporation zone, evaporate the refrigerant through the evaporation zone heat exchange tubes with a microporous structure on the outer surface and a threaded structure on the inner wall. At the same time, fix the evaporation zone heat exchange tubes in the lower area through the support plate, so that a vapor-liquid separation zone is formed in the upper part;

[0012] Step S5: In the superheat zone, superheat the refrigerant gas through the high-efficiency heat exchange tubes with a strengthened turbulent flow structure, and form a tortuous flow path through the baffles, so that after the refrigerant gas reaches the preset superheat degree, it is output to the expander through the gas outlet connecting pipe.

[0013] Preferably, in step S3, the baffles in the preheating zone are staggered, forming a tortuous preheating zone channel, and the high-temperature heat source and the refrigerant achieve pure countercurrent heat exchange in the preheating zone.

[0014] Preferably, in step S4, gasification cores are evenly distributed on the surface of the microporous structure of the evaporation zone heat exchange tubes, and the pitch of the inner wall thread is 0.5 - 2.0 mm to enhance the evaporation efficiency.

[0015] Preferably, in step S5, the baffles in the superheat zone are staggered, forming a tortuous superheat zone channel, and the high-temperature heat source and the refrigerant gas achieve pure countercurrent heat exchange in the superheat zone.

[0016] Preferably, in step S2, the water inlet chamber and the water outlet chamber of the high-temperature heat source circulation path are separated by a partition to ensure the one-way flow of the heat source.

[0017] Preferably, in step S4, by adjusting the installation position of the support plate, the spatial ratio between the evaporation zone heat exchange tubes and the vapor-liquid separation zone is controlled to optimize the gas-liquid separation effect.

[0018] Preferably, in steps S3 and S5, the fin height of the internal tooth and external fin structure of the preheating zone heat exchange tubes is 0.8 - 1.5 mm, and the tooth pitch is 1.0 - 3.0 mm; the strengthened turbulent flow structure of the superheat zone heat exchange tubes includes spiral guide vanes or turbulence protrusions. Description of the Drawings

[0019] Figure 1A cross-sectional schematic diagram of a shell-and-tube heat exchanger for a novel organic Rankine cycle provided by the present application.

[0020] Figure 2 An end-face schematic diagram of a shell-and-tube heat exchanger for a novel organic Rankine cycle provided by the present application. Detailed implementation manners

[0021] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals denote the same or similar elements or elements with the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are intended to explain the present invention, but should not be construed as a limitation of the present invention.

[0022] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "clockwise", "counterclockwise", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation of the present invention.

[0023] In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more, unless otherwise clearly defined.

[0024] In the present invention, unless otherwise clearly specified and defined, the terms "mounted", "connected", "connected to", "fixed", etc. should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the internal communication of two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0025] In the present invention, unless otherwise clearly specified and defined, the first feature being "on" or "under" the second feature may include the direct contact between the first and second features, or may include the situation where the first and second features are not in direct contact but in contact through additional features therebetween. Moreover, the first feature being "above", "over" and "on top of" the second feature includes that the first feature is directly above and obliquely above the second feature, or merely indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature being "under", "beneath" and "underneath" the second feature includes that the first feature is directly under and obliquely under the second feature, or merely indicates that the horizontal height of the first feature is lower than that of the second feature.

[0026] As Figure 1 and 2 shown, this embodiment relates to a shell-and-tube heat exchanger for a novel organic Rankine cycle, comprising:

[0027] A cylinder body 3, the inner cavity of which is separated into a preheating zone, an evaporation zone and a superheating zone that are sequentially communicated from a liquid inlet pipe 8 to a gas outlet pipe 9 by a baffle 5. A tube sheet 1 is fixed to both ends of the cylinder body 3. A water inlet chamber 6 and a water outlet chamber 12 are formed at one end of the cylinder body 3. A return water chamber 7 is formed at the other end of the cylinder body 3. A plurality of groups of heat exchange tubes, including: evaporation zone heat exchange tubes 13 and superheating zone heat exchange tubes 14, are respectively connected to the water inlet chamber 6 and the return water chamber 7 at both ends. Preheating zone heat exchange tubes 15 are respectively connected to the return water chamber 7 and the water outlet chamber 12 at both ends. Baffles 4 are arranged in the preheating zone, the evaporation zone and the superheating zone, and cooperate with the baffle 5 to form a refrigerant flow channel. A liquid inlet pipe 8 is arranged at the bottom of the cylinder body 3 for refrigerant input. A gas outlet pipe 9 is arranged at the top of the cylinder body 3 for refrigerant output. A high-temperature heat source circulation path is sequentially formed by connecting the water inlet chamber 6, the evaporation zone heat exchange tubes 13, the superheating zone heat exchange tubes 14, the return water chamber 7, the preheating zone heat exchange tubes 15 and the water outlet chamber 12. This technical solution realizes the functions of preheating, evaporation and superheating of the working medium in a single device by separating the inner cavity of the cylinder body 3 into a preheating zone, an evaporation zone and a superheating zone, and forming a refrigerant flow channel by the baffle 5 and the baffles 4. The arrangement of the plurality of groups of heat exchange tubes optimizes the heat transfer efficiency and reduces the consumption of the working medium. The design of the high-temperature heat source circulation path simplifies the system configuration and improves the overall operation efficiency. Compared with the prior art, this solution avoids the use of multiple independent heat exchangers through an integrated design, reduces the system volume and the complexity of pipeline connection, and at the same time optimizes the heat transfer efficiency through structural innovation and improves the waste heat recovery effect.

[0028] Furthermore, the heat exchange tubes 15 in the preheating zone adopt condensation heat exchange tubes with an inner-toothed and outer-finned structure. The outer surface of the heat exchange tubes 13 in the evaporation zone has a microporous structure and the inner wall is a threaded structure. The heat exchange tubes 14 in the superheating zone are high-efficiency heat exchange tubes with a strengthened turbulent flow structure. The condensation heat exchange tubes with an inner-toothed and outer-finned structure significantly increase the heat exchange area by setting a toothed structure on the inner wall and fins on the outer wall, thereby improving the heat transfer efficiency in the preheating zone. The condensation heat exchange tubes with an inner-toothed and outer-finned structure can be achieved by machining toothed protrusions on the inner side of the tube wall and fins on the outer side. The height and spacing of the toothed protrusions and fins can be adjusted according to specific requirements to achieve the best heat transfer effect. The application of the microporous structure on the outer surface and the threaded structure on the inner wall in the heat exchange tubes 13 in the evaporation zone can effectively enhance the distribution of the gasification nuclei of the working fluid and optimize the heat transfer effect during evaporation. The high-efficiency heat exchange tubes with a strengthened turbulent flow structure further improve the heat transfer efficiency in the superheating zone by increasing the turbulence degree of the fluid. The microporous structure on the outer surface can be achieved by laser drilling or chemical etching processes, and the threaded structure on the inner wall can be completed by threading processes. The high-efficiency heat exchange tubes with a strengthened turbulent flow structure can be achieved by setting turbulators in the tube or changing the geometric shape of the pipeline. Thus, the present application significantly improves the heat transfer efficiency of the heat exchanger by optimizing the structures of the heat exchange tubes in the preheating zone, evaporation zone, and superheating zone. The inner-toothed and outer-finned structure increases the heat exchange area in the preheating zone, the microporous structure and the threaded structure optimize the distribution of the gasification nuclei in the evaporation zone, and the strengthened turbulent flow structure enhances the turbulence degree in the superheating zone. These technical features work together to solve the technical problem of improving the heat transfer efficiency of the heat exchanger. Compared with the prior art, the present application realizes the functions of preheating, evaporation, and superheating of the working fluid in a single device, optimizes the heat transfer efficiency through structural innovation, reduces the consumption of the working fluid, and simplifies the system configuration.

[0029] Furthermore, gasification nuclei are evenly distributed on the surface of the microporous structure of the evaporation zone heat exchange tube 13, and the pitch of the inner wall thread is 0.5 - 2.0 mm. The fin height of the inner tooth and outer fin structure of the preheating zone heat exchange tube 15 is 0.8 - 1.5 mm, and the tooth pitch is 1.0 - 3.0 mm. Specifically, gasification nuclei are evenly distributed on the surface of the microporous structure of the evaporation zone heat exchange tube 13, which helps to form more gasification nuclei during the gasification process of the working fluid, thereby improving the gasification efficiency and avoiding local overheating. The pitch of the inner wall thread is 0.5 - 2.0 mm, which can enhance the flow disturbance of the working fluid inside the tube and further improve the heat transfer effect. For the inner tooth and outer fin structure of the preheating zone heat exchange tube 15, the fin height is 0.8 - 1.5 mm and the tooth pitch is 1.0 - 3.0 mm. By increasing the heat transfer surface area and optimizing the fluid flow path, the heat transfer efficiency of the preheating zone is significantly improved. Thus, the technical solution of this application effectively solves the problems of insufficient gasification nuclei in the evaporation zone heat exchange tube 13 and low heat transfer efficiency of the preheating zone heat exchange tube 15 by optimizing the structural design of the evaporation zone heat exchange tube 13 and the preheating zone heat exchange tube 15, thereby improving the performance of the overall heat exchanger. Compared with the prior art, the technical solution of this application has significant advantages in terms of gasification efficiency and heat transfer efficiency, and has a simple structure and is easy to implement.

[0030] As Figure 1 shown, there are multiple baffles 4 arranged in a staggered manner in the preheating zone, forming a circuitously arranged preheating zone channel. There are multiple baffles 4 arranged in a staggered manner in the superheating zone, forming a circuitously arranged superheating zone channel. The staggered distribution design of the baffles 4 makes the flow path of the refrigerant in the preheating zone and the superheating zone more complex. Specifically, the arrangement method of the baffles 4 can be horizontal staggering, vertical staggering or diagonal staggering, thereby increasing the contact area and contact time between the refrigerant and the heat exchange tube. As a preferred embodiment, the shape of the baffle 4 can be rectangular, trapezoidal or wavy to further optimize the flow path. In addition, the spacing of the baffles 4 can be adjusted according to the flow rate of the refrigerant and the heat exchange requirements. For example, a smaller spacing can increase the turbulence effect, and a larger spacing can reduce the flow resistance. By arranging the staggered baffles 4 in the preheating zone and the superheating zone, a circuitously arranged channel is formed, increasing the flow path length of the refrigerant in the preheating zone and the superheating zone and prolonging the contact time between the refrigerant and the heat exchange tube, thereby improving the heat exchange efficiency. The staggered distribution design of the baffles 4 makes the refrigerant generate more turbulence during the flow process, further strengthening the heat transfer effect and solving the problems of single flow path of the refrigerant and low heat exchange efficiency in traditional heat exchangers. Compared with the prior art, this technical solution significantly improves the overall performance of the heat exchanger by optimizing the flow path and increasing the turbulence effect, while simplifying the structural design, reducing the manufacturing cost and maintenance difficulty.

[0031] Furthermore, the heat exchange tubes 13 in the evaporation zone are arranged in the lower region of the evaporation zone through the support plate 10, and a vapor-liquid separation zone 19 is formed above the heat exchange tubes 13 in the evaporation zone. Among them, the function of the support plate 10 is to fix the position of the heat exchange tubes 13 in the evaporation zone to ensure their stable arrangement in the evaporation zone. A vapor-liquid separation zone is formed above the heat exchange tubes 13 in the evaporation zone. This design enables the effective separation of the liquid working medium and the gaseous working medium during the evaporation process, avoiding the influence of gas-liquid mixing on the heat exchange efficiency. After the liquid refrigerant is carried up, it will condense and fall, and then continue to evaporate.

[0032] Through the fixation of the support plate 10 and the formation of the vapor-liquid separation zone, the problem of poor vapor-liquid separation effect caused by the unreasonable arrangement of the heat exchange tubes 13 in the evaporation zone is solved, and the overall performance of the heat exchanger is improved. Specifically, the support plate 10 can be implemented in various forms. For example, the support plate 10 can be a flat plate structure or a structure with grooves or protrusions to better fix the heat exchange tubes 13 in the evaporation zone. In addition, the support plate 10 can be fixed to the cylinder body 3 by welding or bolt connection to ensure its stability. The arrangement method of the heat exchange tubes 13 in the evaporation zone can also be adjusted according to actual needs. For example, multi-row arrangement or staggered arrangement can be adopted to optimize the heat exchange effect. The design of the vapor-liquid separation zone can be achieved by adjusting the distance between the heat exchange tubes 13 in the evaporation zone and the top of the cylinder body 3 to ensure that the gaseous working medium can rise and separate smoothly. In this regard, the working principle of this technical solution is that through the fixing effect of the support plate 10, the arrangement of the heat exchange tubes 13 in the evaporation zone is more reasonable, avoiding the problem of poor vapor-liquid separation effect caused by improper arrangement. At the same time, the vapor-liquid separation zone formed above the heat exchange tubes 13 in the evaporation zone enables the effective separation of the liquid working medium and the gaseous working medium during the evaporation process, avoiding the influence of gas-liquid mixing on the heat exchange efficiency. Compared with the prior art, this technical solution significantly improves the overall performance of the heat exchanger through structural optimization and solves the technical problems in practical applications.

[0033] Furthermore, a liquid inlet pipe 16 is connected to the water inlet chamber 6, and a liquid outlet pipe 17 is connected to the water outlet chamber 12. The water inlet chamber 6 and the water outlet chamber 12 are separated by a partition plate 18. Among them, the liquid inlet pipe 16 is used to input liquid into the water inlet chamber 6, and the liquid outlet pipe 17 is used to output liquid from the water outlet chamber 12. The design of the partition plate 18 completely separates the water inlet chamber 6 and the water outlet chamber 12 in space, ensuring that the liquids do not interfere with each other during the flow process. The material of the partition plate 18 can be metal, plastic or other corrosion-resistant materials, and the specific selection depends on the properties of the liquid and the use environment. In addition, the thickness and shape of the partition plate 18 can be adjusted according to actual needs to optimize the control effect of liquid flow. The connection methods of the liquid inlet pipe 16 and the liquid outlet pipe 17 can be threaded connection, flange connection or welding, etc., to ensure the sealing and stability of the connection. The installation method of the partition plate 18 can be fixed or detachable. The fixed partition plate 18 is fixed inside the cylinder body 3 by welding or bolts, and the detachable partition plate 18 is quickly installed and disassembled through a sealing ring or a snap structure. As a preferred implementation mode, the partition plate 18 can be designed as a structure with a flow guiding groove to further optimize the liquid flow path and reduce the flow resistance. In this regard, this technical solution realizes the effective control of liquid flow by connecting the water inlet chamber 6 and the water outlet chamber 12 to the liquid inlet pipe 16 and the liquid outlet pipe 17 respectively, and separating the two by the partition plate 18. The design of the partition plate 18 not only ensures that the liquids do not interfere with each other during the flow process, but also simplifies the management of liquid flow, improving the operation efficiency and stability of the system. Compared with the prior art, this solution avoids the crossing and interference of the liquid flow paths through structural innovation, thus significantly improving the control accuracy of liquid flow and the overall performance of the system.

[0034] In addition, the mounting base plate 11 is connected to the lower end of the tube sheet 1. Among them, the mounting base plate 11 can be connected to the lower end of the tube sheet 1 by welding, bolt connection or other fixing methods. As a preferred implementation mode, the mounting base plate 11 can be provided with shock pads to further reduce the risk of loosening or damage caused by vibration or external forces. In addition, the material of the mounting base plate 11 can be selected as high-strength steel or other materials with good mechanical properties to ensure that it can provide stable support for the tube sheet 1. Through this connection method, the mounting base plate 11 can provide stable support for the tube sheet 1, thereby enhancing the structural stability of the entire heat exchanger. Specifically, the connection between the mounting base plate 11 and the tube sheet 1 is more firm, reducing the risk of loosening or damage caused by vibration or external forces, and ensuring the long-term stable operation of the heat exchanger. Compared with the prior art, this design not only simplifies the structure, but also improves the reliability and service life of the heat exchanger, solving the technical problem of the unstable connection between the mounting base plate 11 and the tube sheet 1.

[0035] In summary, by integrating the preheating zone, evaporation zone, and superheating zone within a single cylinder 3, this technical solution simplifies the system structure and reduces installation and maintenance costs. By arranging multiple groups of heat exchange tubes and baffle plates 4, the flow path of the refrigerant is optimized, improving the heat exchange efficiency. The design of the high-temperature heat source circulation path maximizes countercurrent heat exchange, enhancing the waste heat recovery efficiency. Compared with the prior art, this solution has significant advantages in terms of structural integration, heat exchange efficiency, and adequacy of heat source utilization, effectively solving the technical problems of complex structure, limited heat exchange efficiency, and insufficient heat source utilization caused by the functional separation of traditional shell-and-tube heat exchangers in organic Rankine cycle systems.

[0036] The assembly method of the above-mentioned shell-and-tube heat exchanger is characterized by including the following steps:

[0037] Step M1: Weld tube sheets 1 at both ends of the cylinder 3, and sequentially install baffle plates 5, baffle plates 4, and support plates 10 inside the cylinder to partition the preheating zone, evaporation zone, and superheating zone;

[0038] Step M2: Pass the evaporation zone heat exchange tubes and superheating zone heat exchange tubes through the tube sheet 1, and connect the two ends to the water inlet chamber 6 and the water return chamber 7 respectively; pass the preheating zone heat exchange tubes through the tube sheet 1, and connect the two ends to the water return chamber 7 and the water outlet chamber 12 respectively;

[0039] Step M3: Install a liquid inlet connecting pipe 8 at the bottom of the cylinder 3, install a gas outlet connecting pipe 9 at the top, and weld the water inlet chamber 6, water return chamber 7, and water outlet chamber 12 on the side wall;

[0040] Step M4: Fix the lower end of the tube sheet 1 through the installation base plate 11, and set shock-absorbing gaskets on the installation base plate 11 to complete the overall assembly.

[0041] The refrigeration process of the above-mentioned shell-and-tube heat exchanger is as follows:

[0042] Step S1: Input the refrigerant into the inner cavity of the cylinder 3 through the liquid inlet connecting pipe 8, and sequentially flow through the preheating zone, evaporation zone, and superheating zone formed by the partition of the baffle plate 5;

[0043] Step S2: Input the high-temperature heat source from the water inlet chamber 6, and sequentially flow through the evaporation zone heat exchange tubes, superheating zone heat exchange tubes, water return chamber 7, and preheating zone heat exchange tubes, and finally discharge it from the water outlet chamber 12 to form a pure countercurrent heat exchange path opposite to the refrigerant flow direction; a partition is provided between the water inlet chamber 6 and the water outlet chamber 12 of the high-temperature heat source circulation path to ensure the one-way flow of the heat source.

[0044] Step S3: The refrigerant is transported to the liquid inlet pipe 8 by the working medium pump and then enters the preheating zone of the heat exchanger. The heat exchange tubes 15 in the preheating zone adopt high-efficiency condensation heat exchange tubes with internal teeth and external fins. The refrigerant liquid flows outside the tubes, and the high-temperature heat source flows inside the tubes. Through the arrangement of the baffle plates 4, the refrigerant is forced to conduct convective heat exchange left and right or up and down in the preheating zone. Through the arrangement of the flow path, pure countercurrent heat exchange can be achieved, further improving the heat transfer efficiency. After heat exchange, when the temperature of the refrigerant liquid reaches the evaporation temperature corresponding to the saturation pressure, it enters the evaporation zone.

[0045] Step S4: High-efficiency evaporation heat exchange tubes 13 with internal teeth and external fins are adopted in the evaporation zone. The outer surface of the heat exchange tubes adopts a microporous structure design, which not only enhances the heat exchange area but also greatly increases a large number of gasification cores required for the evaporation heat exchange process. The internal thread structure form further increases the heat exchange area of the inner surface and the turbulent flow effect of the high-temperature heat source agent. During the evaporation and heat absorption process of the refrigerant, through the arrangement of the baffle plates 4, the refrigerant can flow axially and radially for evaporation, further improving the heat exchange efficiency. The refrigerant liquid in the evaporation zone is heated and evaporated into refrigerant saturated gas corresponding to the saturation pressure, and then enters the superheat zone through the baffle 5.

[0046] Step S5: Through the structure of the baffle plates 4 and the baffle 5 in the superheat zone, the refrigerant flows up and down or left and right in the superheat zone, exchanges heat with the high-temperature heat source in the heat exchange tubes, and its state becomes superheated refrigerant gas corresponding to the saturation pressure. Then it enters the expander through the air outlet to perform work.

[0047] In the description of this specification, the descriptions referring to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0048] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention without departing from the principles and purposes of the present invention.

Claims

1. A method for operating a shell and tube heat exchanger for an organic Rankine cycle, characterized in that: The following steps are involved: Step S1: The refrigerant is introduced into the inner cavity of the cylinder (3) through the liquid inlet pipe (8), and flows through the preheating zone, the evaporation zone and the superheating zone separated by the baffle (5) in sequence; Step S2: a high-temperature heat source is input from the water inlet chamber (6), flows through the evaporation zone heat exchange tube (13), the superheat zone heat exchange tube (14), the return water chamber (7), the preheat zone heat exchange tube (15) in sequence, and finally discharged from the water outlet chamber (12), forming a pure countercurrent heat exchange path opposite to the refrigerant flow direction; Step S3: in the preheating zone, the refrigerant is preheated by the condensing heat exchange tube (15) with an inner tooth and outer fin structure, and the staggered baffles (4) are used to guide the refrigerant to form axial and radial forced convection until the refrigerant temperature reaches the saturated evaporation temperature; Step S4: in the evaporation zone, refrigerant is evaporated through the evaporation zone heat exchange tube (13) having a microporous structure on the outer surface and a threaded structure on the inner wall, and at the same time, the evaporation zone heat exchange tube (13) is fixed to the lower area through the support plate (10) so that a vapor-liquid separation zone is formed in the upper part; Step S5: In the superheating zone, the refrigerant gas is superheated by means of a high-efficiency heat exchange tube (14) with an enhanced turbulent structure, and a circuitous flow path is formed by means of a baffle (4), so that the refrigerant gas reaches a preset superheat degree and is output to the expander through the gas outlet pipe (9).

2. The method according to claim 1, characterized in that: In step S3, the baffles (4) in the preheating zone are arranged in a staggered manner to form a circuitous preheating zone channel, and the high-temperature heat source and the refrigerant realize pure countercurrent heat exchange in the preheating zone.

3. The method according to claim 1, characterized in that: In step S4, the vaporization cores are evenly distributed on the surface of the microporous structure of the evaporation zone heat exchange tube (13), and the pitch of the inner wall thread is 0.5-2.0 mm to enhance the evaporation efficiency.

4. The method according to claim 1, characterized in that: In step S5, the baffles (4) in the superheating zone are arranged in a staggered manner to form a circuitous superheating zone channel, and the high-temperature heat source and the refrigerant gas realize pure countercurrent heat exchange in the superheating zone.

5. The method according to claim 1, characterized in that: In step S2, the water inlet chamber (6) and the water outlet chamber (12) of the high-temperature heat source circulation path are separated by a partition (18) to ensure unidirectional flow of the heat source.

6. The method according to claim 1, characterized in that: In step S4, the space ratio between the evaporation zone heat exchange tube (13) and the vapor-liquid separation zone is controlled by adjusting the installation position of the support plate (10) to optimize the vapor-liquid separation effect.

7. The method according to claim 1, characterized in that: In step S3 and step S5, the fin height of the inner-tooth outer-fin structure of the preheating zone heat exchange tube (15) is 0.8-1.5 mm, and the tooth spacing is 1.0-3.0 mm; the enhanced turbulence structure of the superheating zone heat exchange tube (14) includes spiral guide vanes or spoiler protrusions.

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