A high-temperature heat exchanger with a three-layer tube sheet and its application method

Abstract

This invention discloses a high-temperature heat exchanger with a three-layer tube sheet, comprising a heat exchange cavity formed by a shell for heat exchange between a cold medium and a hot medium. A tube sheet structure is disposed inside the heat exchange cavity, dividing the shell into an upper medium cavity and a lower medium cavity. The tube sheet structure includes multiple layers of tube sheets, with a sealed chamber formed between adjacent layers. An internal pressure is preset within each sealed chamber. A pressure sensor is installed in each sealed chamber, and a differential pressure sensor monitors the integrity of the tube sheet between adjacent sealed chambers. This patent's three-layer tube sheet structure allows for long-term monitoring of internal leaks in the upper, middle, or lower tube sheet. Even if a leak occurs due to damage to a single tube sheet, the cold and hot media can only communicate with the upper and lower small cavities respectively, preventing direct contact and mixing between the two media. This patent's three-layer tube sheet structure and differential pressure sensors constitute a real-time leak detection system.

Description

Technical Field

[0001] This invention relates to the field of heat pipe heat exchanger technology, specifically to a high-temperature heat exchanger with a three-layer tube sheet and its usage method. Background Technology

[0002] A heat pipe high-temperature gas-to-gas heat exchanger is a heat transfer device with high thermal conductivity. Its heat exchange element—the heat pipe—transfers heat through the evaporation and condensation of the working fluid within a fully enclosed vacuum shell. It boasts a series of advantages, including extremely high thermal conductivity, good isothermal properties, adjustable heat transfer area on both the hot and cold sides, long-distance heat transfer capability, and temperature control. This heat exchanger is typically used for heat exchange between two gases at different temperatures, thereby completing heating, heat dissipation, and cooling processes. It is widely used in energy-saving applications in industries such as metallurgy, chemical engineering, oil refining, boilers, ceramics, transportation, textiles, machinery, and electronics.

[0003] Existing heat pipe heat exchangers, such as Figure 1 As shown, heat pipe high-temperature gas-to-gas heat exchangers are typically integral, and the structure of this type of heat exchanger is as follows: Figure 1 As shown, it consists of a shell, an intermediate tube sheet, and several vertical heat pipe elements. The tube sheet divides the shell into upper and lower cavities. The heat pipes pass through and connect to the tube sheet, with one end of the heat pipe located in the lower cavity and the other end in the upper cavity. The cold medium enters from the left side of the upper cavity and exits from the right side. The hot medium enters from the right side of the lower cavity and exits from the left side. The transfer of heat between the cold and hot media is accomplished through the heat pipes.

[0004] For example, patent document 1 (application number: CN03227241.3) discloses a heat pipe heat exchanger. This heat exchanger operates at high temperatures, typically above 350℃, and can reach over 1000℃. The only tube sheet between the two heat exchange media is susceptible to thermal oxidation and corrosion during long-term use. Simultaneously, the gaseous medium may contain corrosive components, leading to chemical corrosion of the tube sheet. Furthermore, the expansion and contraction of the material during alternating heating and cooling processes can cause internal stress damage to the tube sheet. Thermal oxidation corrosion, chemical corrosion, and internal stress damage to the tube sheet can lead to leakage, direct contact, and mixing of the cold and hot sides, posing safety hazards such as media contamination and even explosions. Because the leakage location is inside the heat exchanger, the initial leakage is relatively small and cannot be detected immediately or visually, thus lacking effective prevention and monitoring measures.

[0005] Patent document 2 (application number: CN200910184195.9) discloses a combined shell-and-tube heat pipe heat exchanger. The upper and lower tube sheets are directly connected or separately installed at both ends of a connecting cylinder. A vapor-liquid separation and exchange space is formed between the upper and lower tube sheets, connecting the upper and lower heat pipes. This exchange space is equipped with an exhaust and filling pipe. This patent document addresses the problem that "heat pipe heat exchangers typically have a horizontally placed sealing partition in the middle of the shell, creating two spaces. Multiple heat exchange tubes are connected to the partition, and the shell shape is mostly square, which limits the pressure of the medium, generally to near-normal pressure, greatly restricting the use of heat pipe heat exchangers." It addresses this by using two thickened tube sheets, forming a vapor-liquid exchange space between them for the heat pipes. Its drawback is that, through the sealed connection of the upper and lower tube sheets, it only allows the originally independent heat pipes to form a shell-and-tube heat pipe heat exchanger interconnected through the gaps in the tube sheets; although it provides some compensation for the strength of the tube sheets, it cannot detect internal leakage.

[0006] Another patent document 3 (application number: CN202220059896.0) describes a safe gravity heat pipe heat exchanger, which is similar in structure to patent document 2. It also has an upper tube sheet and a lower tube sheet, and an adiabatic section is formed between the two (which has the same function as the exchange space). A pressure gauge is installed in the adiabatic section to monitor the pressure. Although the pressure gauge is used for monitoring, it cannot monitor the leakage of the tube sheet.

[0007] In view of the above, it is necessary to propose a high-temperature heat exchanger with a three-layer tube sheet and its application method to solve the above problems. Summary of the Invention

[0008] The purpose of this invention is to solve the above-mentioned technical problems by providing a high-temperature heat exchanger with a three-layer tube sheet and its usage method.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: a high-temperature heat exchanger with a three-layer tube sheet, comprising a heat exchange cavity formed by a shell for heat exchange between a cold medium and a hot medium, wherein a tube sheet structure is provided inside the shell;

[0010] The tube sheet structure is set inside the heat exchange cavity to divide the shell into an upper medium cavity and a lower medium cavity. The tube sheet structure includes multiple tube sheets, and a sealed chamber is formed between two adjacent tube sheets. An internal pressure is preset in the sealed chamber. Each sealed chamber is equipped with a pressure sensor, and the integrity of the tube sheet is monitored between two adjacent sealed chambers through a differential pressure sensor.

[0011] Furthermore, the tube sheet structure includes three tube sheets: an upper tube sheet, a middle tube sheet, and a lower tube sheet. An upper cavity is formed between the upper tube sheet and the middle tube sheet, and a lower cavity is formed between the middle tube sheet and the lower tube sheet. Several heat pipes are arranged vertically through the tube sheet structure.

[0012] Furthermore, a differential pressure sensor is connected between the upper cavity and the lower cavity; an upper differential pressure sensor is connected between the upper cavity and the upper medium cavity; and a lower differential pressure sensor is connected between the lower cavity and the lower medium cavity.

[0013] Furthermore, it also includes a control and alarm device, wherein the differential pressure transmission signals generated by the upper differential pressure sensor, the middle differential pressure sensor, and the lower differential pressure sensor are transmitted to the control and alarm device.

[0014] Furthermore, an upper valve is connected to one side of the upper cavity, and a lower valve is connected to one side of the lower cavity.

[0015] Furthermore, the sealed chamber is filled with an inert gas to create internal pressure; the inert gas is nitrogen or argon.

[0016] Furthermore, the interior of the sealed chamber is evacuated to a negative pressure state.

[0017] Furthermore, the spacing between two adjacent tube sheets is 10-50mm.

[0018] A method for using a three-layer tube sheet high-temperature heat exchanger includes the following steps:

[0019] (a) The internal pressure of the two chambers is preset by filling the upper chamber with gas to create positive pressure or extracting gas to create negative pressure by using the upper valve and the lower valve respectively to fill the upper chamber and the lower chamber.

[0020] (b) The pressure in the sealed chamber is selected according to the pressure of the working medium on the adjacent sides. When the working pressure of the cold and hot medium does not exceed 50 kPa, the preset pressure of the upper chamber is controlled to be 10 kPa to 50 kPa higher than the working pressure of the cold medium; the preset pressure of the lower chamber is controlled to be 10 kPa to 50 kPa higher than the working pressure of the hot medium.

[0021] (c) Make the pre-set pressures between the upper and lower chambers different to form a pressure difference, and control the absolute pressure difference within the range of 10 kPa to 50 kPa;

[0022] (d) When the working pressure of the cold or hot medium exceeds 50 kPa, the preset pressure of the adjacent upper and lower cavities should be negative, and the internal pressure of the upper and lower cavities should be set to -10 kPa to -50 kPa.

[0023] (e) The pre-set pressure between the upper and lower chambers should also maintain a certain pressure difference, with an absolute pressure difference of 10 kPa to 50 kPa.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] 1. The three-layer tube sheet structure described in this patent can be used for long-term monitoring of whether the upper tube sheet, middle tube sheet or lower tube sheet has internal leakage. Even if the upper tube sheet, middle tube sheet or lower tube sheet is damaged and leakage occurs, the cold medium and the hot medium can only communicate with the upper small cavity and the lower small cavity respectively, and the two media will not directly contact and mix.

[0026] 2. The three-layer tube sheet structure and differential pressure sensor and other components described in this patent constitute a real-time leakage detection system, which transforms leakage faults caused by internal damage that cannot be directly detected into pressure signals that can be directly monitored, and can identify the location of the damage and issue an alarm warning.

[0027] 3. This patent avoids direct contact and mixing of hot and cold media caused by damage to the tube sheet inside the heat exchanger, and provides an effective damage monitoring method. This significantly improves the safety and reliability of heat pipe-type high-temperature gas-to-gas heat exchangers. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of a heat pipe heat exchanger in the prior art.

[0029] Figure 2 This is an isometric view of a high-temperature heat exchanger with a three-layer tube sheet and its usage method according to this application;

[0030] In the diagram: 1. Shell; 2. Tube sheet structure; 3. Upper medium chamber; 4. Lower medium chamber; 5. Sealed chamber; 6. Upper tube sheet; 7. Middle tube sheet; 8. Lower tube sheet; 9. Upper cavity; 10. Lower cavity; 11. Heat pipe; 12. Middle differential pressure sensor; 13. Upper differential pressure sensor; 14. Lower differential pressure sensor; 15. Control and alarm device; 16. Upper valve; 17. Lower valve. Detailed Implementation

[0031] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0032] A high-temperature heat exchanger with a three-layer tube sheet, such as Figure 1 As shown, the structure of the present invention is in Figure 1 Based on the structure shown, improvements are made, specifically including a heat exchange cavity formed by the shell 1 for heat exchange between the cold and hot media, and a tube sheet structure 2 is provided inside the shell 1.

[0033] Example 1:

[0034] like Figure 2As shown, the tube sheet structure 2 is installed inside the heat exchange cavity, dividing the shell 1 into an upper medium cavity 3 and a lower medium cavity 4. The tube sheet structure 2 includes multiple tube sheets, and a sealed chamber 5 is formed between two adjacent tube sheets. An internal pressure is preset inside the sealed chamber 5. In actual use, the internal pressure can be set to form an internal positive pressure or negative pressure by filling inert gas or drawing a vacuum. Each sealed chamber 5 is equipped with a pressure sensor (not shown in the figure), and the integrity of the tube sheet is monitored between two adjacent sealed chambers 5 by a differential pressure sensor.

[0035] Furthermore, the tube sheet structure 2 includes a three-layer tube sheet. In this embodiment, the three-layer tube sheet structure 2 improves the leakage resistance. In actual use, it can also be set as a two-layer tube sheet according to user needs and cost control, with the same basic principle. Figure 2 As shown, the three-layer tube sheet consists of an upper tube sheet 6, a middle tube sheet 7, and a lower tube sheet 8. An upper cavity 9 is formed between the upper tube sheet 6 and the middle tube sheet 7, and a lower cavity 10 is formed between the middle tube sheet 7 and the lower tube sheet 8. Several heat pipes 11 are vertically inserted through the tube sheet structure 2. An upper valve 16 is connected to one side of the upper cavity 9, and a lower valve 17 is connected to one side of the lower cavity 10. During use, the upper valve 16 and the lower valve 17 are used to pressurize or evacuate the two cavities to create negative pressure.

[0036] The sealed chamber 5 is filled with an inert gas to create internal pressure. In actual use, the filling gas is generally an inert gas such as nitrogen or argon. The selected gas cannot react with the cold or hot medium and cannot cause pollution to the cold or hot medium.

[0037] A differential pressure sensor 12 is connected between the upper cavity 9 and the lower cavity 10; an upper differential pressure sensor 13 is connected between the upper cavity 9 and the upper medium cavity 3; and a lower differential pressure sensor 14 is connected between the lower cavity 10 and the lower medium cavity 4.

[0038] During normal operation, the cold medium enters from the left side and exits from the right side of the upper medium chamber 3, while the hot medium enters from the right side and exits from the left side of the lower medium chamber 4. Heat transfer between the cold and hot media is completed through heat pipe 11. The upper differential pressure sensor obtains the pressure difference signal between the cold medium and the upper chamber 9 in real time. The lower differential pressure sensor obtains the pressure difference signal between the hot medium and the lower chamber 10 in real time. The middle differential pressure sensor obtains the pressure difference signal between the upper chamber 9 and the lower chamber 10 in real time.

[0039] Example 2:

[0040] It also includes a control and alarm device 15, to which the differential pressure transmission signals generated by the upper differential pressure sensor 13, the middle differential pressure sensor 12, and the lower differential pressure sensor 14 are transmitted. For example... Figure 2As shown, when a tube sheet is damaged and a leakage fault occurs, due to the pressure difference between the upper medium chamber 3, the upper small chamber, the lower small chamber, and the lower medium chamber 4, the medium in the high-pressure side chamber will permeate through the tube sheet into the adjacent low-pressure side chamber, resulting in a significant decrease in the differential pressure between the two adjacent chambers. By analyzing the signal changes of the three differential pressure sensors through the control and alarm device 15, the tube sheet damage fault can be identified, the location of the damage can be determined, and a leakage alarm warning can be issued.

[0041] When the pressure difference signal from the upper differential pressure sensor changes significantly, it indicates a leak in the upper tube sheet 6. When the pressure difference signal from the middle differential pressure sensor changes significantly, it indicates a leak in the middle tube sheet 7. When the pressure difference signal from the lower differential pressure sensor changes significantly, it indicates a leak in the lower tube sheet 8. The control and alarm device 15 can be set with three differential pressure sensor pressure alarm values, which are 10% to 50% lower than the positive pressure side pressure.

[0042] Example 3:

[0043] In actual setup, the spacing between two adjacent tube sheets should ideally be 10-50mm. If the tube sheet spacing is too large, the pressure changes caused by leakage of cold and hot media in the upper and lower chambers will be too small for the sensors to detect. If the tube sheet spacing is too small, the pressure changes caused by thermal expansion and contraction of gas in the upper and lower chambers will be too large, making it difficult to identify the pressure change signals caused by leakage.

[0044] A method for using a three-layer tube sheet high-temperature heat exchanger includes the following steps:

[0045] (a) The pressure inside the two chambers is preset by filling gas to form a positive pressure or extracting gas to form a negative pressure by using the upper valve 16 and the lower valve 17 to fill the upper chamber 9 and the lower chamber 10 respectively;

[0046] (b) The pressure in the sealed chamber 5 is selected according to the pressure of the working medium on the adjacent sides. When the working pressure of the cold and hot medium does not exceed 50 kPa, the preset pressure of the upper chamber 9 is controlled to be 10 kPa to 50 kPa higher than the working pressure of the cold medium; the preset pressure of the lower chamber 10 is controlled to be 10 kPa to 50 kPa higher than the working pressure of the hot medium.

[0047] (c) Make the preset pressure between the upper cavity 9 and the lower cavity 10 different to form a pressure difference, and control the absolute pressure difference within the range of 10 kPa to 50 kPa.

[0048] (d) When the working pressure of the cold or hot medium exceeds 50 kPa, the preset pressure of the adjacent upper cavity 9 and lower cavity 10 should be negative, and the internal pressure of the upper cavity 9 and lower cavity 10 should be set to -10 kPa to -50 kPa.

[0049] (e) The preset pressure between the upper cavity 9 and the lower cavity 10 should also maintain a certain pressure difference, so that the absolute pressure difference is 10 kPa to 50 kPa.

[0050] Before using the heat pipe 11 type high-temperature gas-to-gas heat exchanger described in this patent, the upper valve 16 and the lower valve 17 are used to fill the upper small cavity and the lower small cavity respectively to form a positive pressure by filling gas or to extract gas to form a negative pressure, so that the internal pressure of the two small cavities is preset.

[0051] The filling gas is generally an inert gas such as nitrogen or argon. The selected gas must not react with the cold or hot medium and must not contaminate the cold or hot medium.

[0052] In actual control, the preset pressure value is selected based on the working pressure of the cold and hot media. When the working pressure of the cold and hot media does not exceed +50 kPa, the preset pressure of the upper cavity 9 should generally be 10 kPa to 50 kPa higher than the working pressure of the cold media; the preset pressure of the lower cavity 10 should be 10 kPa to 50 kPa higher than the working pressure of the hot media, and a certain pressure difference should be maintained between the preset pressures of the upper cavity 9 and the lower cavity 10, generally with an absolute pressure difference of 10 kPa to 50 kPa.

[0053] When the working pressure of the cold or hot medium exceeds +50 kPa, the preset pressure of the adjacent upper and lower cavities 10 should be negative, generally -10 kPa to -50 kPa. The preset pressure between the upper cavity 9 and the lower cavity 10 should also maintain a certain pressure difference, generally 10 kPa to 50 kPa in absolute pressure.

[0054] For example, a heat pipe type 11 high-temperature gas-to-gas heat exchanger used in a certain industrial field is used to heat air with high-temperature flue gas generated by combustion and recover waste heat from the high-temperature flue gas. The cold medium is air, with an operating temperature of 20℃~350℃ and an operating pressure of +1000Pa; the hot medium is flue gas, with an operating temperature of 850℃~400℃ and an operating pressure of -2000Pa.

[0055] The heat exchanger structure and attachment Figure 2 The structures shown are identical, with the distance between the three tube sheets being 20mm.

[0056] Since the cold side is under positive pressure, the upper small cavity is evacuated to a preset pressure of -20 kPa. Since the hot side is under negative pressure, the lower small cavity is filled with inert gas to a preset pressure of +20 kPa. At this time, the absolute pressure differences between adjacent upper medium cavity 3, upper cavity 9, lower cavity 10, and lower medium cavity 4 are 21 kPa, 40 kPa, and 22 kPa, respectively.

[0057] Nitrogen is chosen as the inert gas for filling. Since nitrogen is a major component of combustion flue gas, filling with nitrogen will not react with the flue gas and will not pollute its components.

[0058] The control and alarm device 15 is set to trigger a leakage alarm when the differential pressure signal of the upper differential pressure sensor is lower than 19 kPa, the differential pressure signal of the middle differential pressure sensor is lower than 38 kPa, and the differential pressure signal of the lower differential pressure sensor is lower than 19 kPa.

[0059] At this time, when the pressure signals of the three differential pressure sensors are lower than the set value, the control and alarm device 15 will be triggered to alarm. By checking the differential pressure sensor that triggered the alarm, the damaged tube sheet can be identified.

[0060] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A high-temperature heat exchanger with a three-layer tube sheet, comprising a heat exchange cavity formed by a shell (1) for heat exchange between a cold medium and a hot medium, characterized in that, The shell (1) is provided with a tube sheet structure (2); The tube sheet structure (2) is set inside the heat exchange cavity to divide the shell (1) into an upper medium cavity (3) and a lower medium cavity (4). The tube sheet structure (2) includes multiple tube sheets, and a closed chamber (5) is formed between two adjacent tube sheets. An internal pressure is preset inside the closed chamber (5). Each closed chamber (5) is equipped with a pressure sensor, and the integrity of the tube sheet is monitored between two adjacent closed chambers (5) through the pressure sensor. The tube sheet structure (2) includes three tube sheets, namely an upper tube sheet (6), a middle tube sheet (7), and a lower tube sheet (8). An upper cavity (9) is formed between the upper tube sheet (6) and the middle tube sheet (7), and a lower cavity (10) is formed between the middle tube sheet (7) and the lower tube sheet (8). Several heat pipes (11) are provided vertically through the tube sheet structure (2). A differential pressure sensor (12) is connected between the upper cavity (9) and the lower cavity (10); an upper differential pressure sensor (13) is connected between the upper cavity (9) and the upper medium cavity (3); and a lower differential pressure sensor (14) is connected between the lower cavity (10) and the lower medium cavity (4).

2. A high-temperature heat exchanger with a three-layer tube sheet according to claim 1, characterized in that, It also includes a control and alarm device (15), wherein the differential pressure transmission signals generated by the upper differential pressure sensor (13), the middle differential pressure sensor (12), and the lower differential pressure sensor (14) are transmitted to the control and alarm device (15).

3. A high-temperature heat exchanger with a three-layer tube sheet according to claim 1, characterized in that, An upper valve (16) is connected to one side of the upper cavity (9), and a lower valve (17) is connected to one side of the lower cavity (10).

4. A high-temperature heat exchanger with a three-layer tube sheet according to claim 3, characterized in that, The sealed chamber (5) is filled with an inert gas to form internal pressure. The inert gas is nitrogen or argon.

5. A high-temperature heat exchanger with a three-layer tube sheet according to claim 3, characterized in that, The sealed chamber (5) is evacuated to a negative pressure state.

6. A high-temperature heat exchanger with a three-layer tube sheet according to claim 1, characterized in that, The spacing between two adjacent tube sheets is 10-50mm.

7. A method of using a three-layer tube sheet high-temperature heat exchanger, comprising the three-layer tube sheet high-temperature heat exchanger as described in claim 1, characterized in that, Includes the following steps: (a) The pressure inside the two cavities is preset by filling gas to form a positive pressure or extracting gas to form a negative pressure by opening the upper valve (16) and the lower valve (17) to the upper cavity (9) and the lower cavity (10) respectively; (b) The pressure in the sealed chamber (5) is selected according to the pressure of the working medium on the adjacent sides. When the working pressure of the cold and hot medium does not exceed 50 kPa, the preset pressure of the upper chamber (9) is controlled to be 10 kPa to 50 kPa higher than the working pressure of the cold medium; the preset pressure of the lower chamber (10) is controlled to be 10 kPa to 50 kPa higher than the working pressure of the hot medium. (c) Make the preset pressure between the upper cavity (9) and the lower cavity (10) different to form a pressure difference, and control the absolute pressure difference within the range of 10kPa~50kPa; (d) When the working pressure of the cold or hot medium exceeds 50 kPa, the preset pressure of the adjacent upper cavity (9) and lower cavity (10) should be negative, and the internal pressure of the upper cavity (9) and lower cavity (10) should be set to -10 kPa to -50 kPa. (e) The pre-set pressure between the upper cavity (9) and the lower cavity (10) should also maintain a certain pressure difference, so that the absolute pressure difference is 10kPa~50kPa.

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