Fluorine plastic pipe heat exchanger

Abstract

The fluorine plastic pipe heat exchanger comprises a heat exchanger shell, heat exchange pipes and pipe plates, the pipe plates are located on the two sides in the heat exchanger shell, the heat exchange pipes are arranged on the pipe plates on the two sides, and a flue gas inlet and a flue gas outlet are formed in the position, between the pipe plates on the two sides, of the heat exchanger shell. A cooling water inlet and a cooling water outlet are formed in the positions, on the outer sides of the pipe plates on the two sides, of the heat exchanger shell respectively, the cooling water inlet and the cooling water outlet are connected to the two ends of the heat exchange pipe, the heat exchange pipe comprises an inner-layer pipe wall, an outer-layer pipe wall, a phase change working medium and a pulsating heat pipe array, and the phase change working medium is located between the inner-layer pipe wall and the outer-layer pipe wall. The pulsating heat pipe array is composed of pulsating heat pipes. One end of the pulsating heat pipe is embedded into the phase change working medium, and the other end of the pulsating heat pipe extends out of the surface of the outer-layer pipe wall; and the cooling water inlet and the cooling water outlet are communicated with the inner-layer pipe wall of the heat exchange pipe. According to the heat exchanger, the problems that a traditional heat exchanger is low in low-temperature-difference heat transfer efficiency, poor in heat supply and demand matching and insufficient in corrosion resistance are effectively solved, efficient heat exchange can be achieved under the complex working condition, and the energy utilization rate is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of heat exchangers, and in particular to a heat exchanger that can be applied to many industries requiring heat exchange and having complex working conditions, such as chemical industry, electric power, and environmental protection. Background Art

[0002] In industrial production and energy conversion, heat exchangers are key equipment for efficient heat utilization. However, the performance shortcomings of traditional heat exchangers under specific operating conditions have gradually become a bottleneck for industry development. For example, in the waste heat recovery process at the end of coal-fired power generation and steel smelting, when the temperature difference between the flue gas and the coolant is small, the heat transfer efficiency of traditional heat exchangers decreases significantly. A large amount of low-temperature heat energy cannot be effectively recovered and is discharged with the flue gas, restricting the intensive utilization of waste heat. Furthermore, in conditions where heat supply and demand fluctuate dynamically, such as in waste incineration power generation where fluctuating waste calorific value leads to large fluctuations in flue gas temperature, or in industrial production where the coolant supply is unstable, the fixed structure of traditional heat exchangers cannot quickly respond to fluctuations in heat demand. This leads to delayed heat exchange rate regulation, unstable steam parameters, energy waste, and unstable process operations, seriously affecting the continuity and stability of production. Furthermore, traditional metal heat exchangers are susceptible to corrosion, which significantly shortens equipment life and increases maintenance costs. Despite the use of coatings and alloy strengthening methods, it is still difficult to balance the contradiction between material corrosion resistance and heat transfer performance. It can be seen that the multiple deficiencies of traditional heat exchangers in low-temperature heat transfer efficiency, heat supply and demand matching, and corrosion resistance have made it urgent to break through technical bottlenecks by developing new heat exchangers to meet the needs of efficient, safe, and green industrial development. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a heat exchanger that effectively solves the problems of low heat transfer efficiency and unsatisfactory heat supply and demand matching of traditional heat exchangers in low temperature difference environments.

[0004] The present invention adopts the following technical solutions: A fluoroplastic tube heat exchanger comprises a heat exchanger shell, heat exchange tubes and tube sheets, the tube sheets being located on both sides of the heat exchanger shell, the heat exchange tubes being arranged on the tube sheets on both sides, a flue gas inlet and a flue gas outlet being provided on the heat exchanger shell between the tube sheets on both sides, a cooling water inlet and a cooling water outlet being provided on the heat exchanger shell outside the tube sheets on both sides, the cooling water inlet and the cooling water outlet being connected to both ends of the heat exchange tube, the heat exchange tube comprising an inner tube wall, an outer tube wall, a phase change medium and a pulsating heat pipe array, the phase change medium being located between the inner tube wall and the outer tube wall, the pulsating heat pipe array being composed of pulsating heat pipes; one end of the pulsating heat pipe is embedded in the phase change medium, and the other end of the pulsating heat pipe extends out of the surface of the outer tube wall; the cooling water inlet and the cooling water outlet are connected to the inner tube wall of the heat exchange tube.

[0005] The heat exchange tube adopts a double-layer tube wall structure. The cavity formed by the inner and outer tube walls is filled with a mixture of phase change material, metal particles and compressible microspheres. The phase change medium changes phase to stabilize the temperature when the flue gas temperature fluctuates. The metal particles improve the heat transfer coefficient, and the compressible microspheres relieve the expansion stress caused by the phase change.

[0006] The inner surface of the pulsating heat pipe is provided with a composite gradient microcolumn group structure: the evaporation section adopts slender and dense microcolumns with a length-to-diameter ratio of 3.5-4 to enhance the capillary force to drive the working medium backflow; the condensation section adopts short and sparse microcolumns with a length-to-diameter ratio of 1-1.5 to reduce the flow resistance; the length of the microcolumns in the evaporation section is 2-2.5 times that of the microcolumns in the condensation section, and the density is 1.5-2 times that of the microcolumns in the condensation section. This structure realizes efficient heat transfer through the synergy of vapor pressure difference and capillary force, significantly improving the heat transfer efficiency under small temperature difference conditions.

[0007] The pulsating heat pipe utilizes a composite gradient micro-column structure to enhance capillary forces and reduce fluid flow resistance. The pulsating heat pipe increases the heat exchange area, and adjacent pulsating heat pipes are arranged in a diamond-shaped pattern to disrupt the flue gas flow, significantly improving heat exchange efficiency. This heat exchanger effectively addresses the challenges of traditional heat exchangers, such as low heat transfer efficiency at low temperature gradients, poor heat supply and demand matching, and insufficient corrosion resistance. It enables efficient heat exchange under complex operating conditions, improving energy efficiency.

[0008] The pulsating heat pipe is a closed serpentine tubular structure.

[0009] The pulsating heat pipe is a flat-plate heat pipe, consisting of four pulsating heat pipes arranged in a diamond pattern, forming an array subunit. In the radial direction of the heat exchange tube, the four array subunits are arranged in a ring, surrounding the heat exchange tube; in the axial direction of the heat exchange tube, the array subunits are arranged in sequence with equal spacing. The angle formed between adjacent pulsating heat pipes disrupts the flow of flue gas, increasing the contact area between the heat pipe, the flue gas, and the phase change medium, improving overall heat exchange efficiency, especially the heat transfer efficiency in the small temperature difference section at the rear end of the heat exchange tube.

[0010] The phase change fluid is a mixture of approximately 90% phase change material, approximately 5% metal particles, and approximately 5% compressible microspheres. The phase change material is a solid-liquid phase change material. The organic phase change fluid absorbs or releases heat through phase change when flue gas flow or cooling water fluctuates, maintaining a stable outlet flue gas temperature. The metal particles increase the heat transfer coefficient of the phase change fluid and enhance the heat exchange effect. The compressible microspheres relieve the expansion stress generated by the phase change, improving reliability.

[0011] The phase change material is paraffin, high molecular weight polyethylene glycol or nitrate; the metal particles are inactive metal powder; and the compressible microspheres are glass microspheres or rubber microspheres.

[0012] The inactive metal powder is copper powder or platinum powder.

[0013] The inner and outer wall materials of the heat exchange tubes are both made of fluoroplastics with strong corrosion resistance and good thermal conductivity, so as to ensure sufficient service life and basic thermal conductivity.

[0014] The diameter of the pulsating heat pipe is 5-8 mm, and the number of turns is greater than 3.

[0015] The heat exchanger shell is made of a composite material of aluminum-zinc-coated steel plate with good thermal insulation performance and certain strength. The outer surface of the aluminum-zinc-coated steel plate material is provided with a polyurethane thermal insulation layer, which can reduce heat loss and improve energy utilization.

[0016] The tube plate is provided with tube holes adapted to the fluoroplastic heat exchange tubes, and the fluoroplastic heat exchange tubes are arranged according to an equilateral triangle method, which increases the turbulence of the fluid in the heat exchanger and further improves the heat exchange efficiency.

[0017] In the heat exchanger of this invention, when temperature fluctuates, the phase-change fluid absorbs or releases heat through its own phase change process, maintaining a stable temperature within the heat exchanger and thus ensuring stable heat transfer performance. The addition of metal particles effectively addresses the low thermal conductivity of the phase-change fluid and enhances the heat transfer efficiency of the heat exchanger. The compressible microspheres act as a buffering medium. Their inherent compressibility effectively mitigates the expansion stress caused by density differences during the solid-liquid phase change process, thereby improving the reliability and stability of the overall system operation.

[0018] Preferably, the pulsating heat pipe embedded in the outer tube wall is a closed serpentine tubular structure, with a stepped microcolumn cluster structure inside. A dense, slender first microcolumn is arranged in the evaporation section, and a sparse, short, and thick second microcolumn is arranged in the condensation section. On the one hand, the dense, slender first microcolumns in the evaporation section effectively enhance capillary force. When the working liquid in the tube is heated and vaporized into steam, the strong capillary force causes the condensed liquid to flow back to the evaporation section more quickly. On the other hand, the sparse, short, and thick second microcolumns in the condensation section reduce the resistance to liquid flow, allowing the condensed steam to flow more smoothly, reducing energy loss. The interior of the pulsating heat pipe is evacuated and filled with working fluid. During operation, the working fluid absorbs heat in the evaporation section and vaporizes into steam. The steam flows to the condensation section under the action of a pressure differential. In the condensation section, it releases heat and condenses into liquid. The liquid then flows back to the evaporation section under the combined action of capillary force and the vapor pressure differential. This cycle achieves efficient heat transfer, greatly improving the efficiency of the entire heat exchange process.

[0019] Preferably, the pulsating heat pipes are arranged non-parallel, with adjacent pulsating heat pipes arranged in a diamond pattern. This arrangement optimizes the heat transfer path and increases the contact area between the heat pipes and the heat transfer medium. This significantly improves the heat transfer efficiency in the rear end, where the temperature difference is small, significantly increasing overall heat exchange efficiency and enabling faster and more uniform heat transfer within the heat exchange tubes.

[0020] Preferably, the inner wall material and the outer wall material of the fluoroplastic heat exchange tube are both fluoroplastics with strong corrosion resistance and good thermal conductivity.

[0021] Preferably, the heat exchanger shell is made of aluminum-zinc-coated steel plate with good thermal insulation performance and a certain strength combined with a polyurethane foam layer material, which can concentrate more heat inside the heat exchanger for effective exchange, avoid excessive heat leakage into the surrounding environment during the transfer process, and reduce energy waste.

[0022] Preferably, the tube plate is provided with tube holes adapted to the fluoroplastic heat exchange tubes, and the fluoroplastic heat exchange tubes are arranged according to the equilateral triangle method, which enhances the heat transfer effect between the fluid and the heat exchange tubes, thereby improving the heat exchange performance of the entire heat exchanger.

[0023] Preferably, a baffle is provided between the two tube sheets in the heat exchanger shell.

[0024] The baffle is in an arched shape and is provided with through holes adapted to the heat exchange tubes. The baffle changes the flow direction of the fluid, increases the residence time of the fluid in the heat exchanger, and enhances the heat exchange effect.

[0025] Preferably, the baffle is in an arcuate shape, and is provided with a through hole adapted to fit the fluoroplastic heat exchange tube.

[0026] Compared with the prior art, the present invention has the following beneficial effects: Compared to traditional heat exchange regulation methods, this invention uses a phase-change fluid. When the heat exchanger is operating, facing complex operating conditions such as unstable cooling fluid supply and large fluctuating flue gas temperatures, it can timely phase change within the temperature fluctuation range by virtue of its appropriate phase change temperature and large phase change latent heat. It absorbs heat when the temperature rises and releases heat when the temperature drops, thereby maintaining a stable internal temperature of the heat exchanger, effectively reducing the impact of temperature changes on heat exchange performance, ensuring efficient heat exchange under complex operating conditions, and greatly improving the heat exchanger's ability to adapt to different operating conditions.

[0027] The pulsating heat pipes employed in this invention utilize a unique stepped micro-column structure with varying heights, densities, and aspect ratios, combined with a unique non-parallel diamond pattern. This allows for rapid heat transfer from the high-temperature end to the low-temperature end, particularly enhancing heat transfer efficiency in the rear end of the heat exchanger where the temperature difference is minimal. Compared to traditional heat transfer pathways, this optimizes the heat transfer path, significantly improving the heat exchange efficiency of the heat exchanger and boosting energy efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The overall schematic diagram of the heat exchanger.

[0029] Figure 2AA section of the heat exchanger.

[0030] Figure 3 A partial cross-sectional view of the tube.

[0031] Figure 4 Schematic diagram of the cross section of the heat exchange tube.

[0032] Figure 5 Schematic diagram of the surface pulsating heat pipe arrangement.

[0033] Figure 6 This is a cross-sectional view of a pulsating heat pipe.

[0034] Figure 7 Schematic diagram of the micro-column group in the evaporation section of the pulsating heat pipe.

[0035] Figure 8 Schematic diagram of the microcolumn group in the condensation section of the pulsating heat pipe.

[0036] Figure 9 This is a comparison chart of the equivalent thermal conductivity of gradient micro-column pulsating heat pipes and conventional pulsating heat pipes.

[0037] Among them: 1-heat exchanger shell; 11-flue gas inlet; 12-flue gas outlet; 13-cooling water outlet; 14-cooling water inlet; 2-fluoroplastic tube heat exchanger; 21-pulsating heat pipe; 211-pulsating heat pipe shell; 212-pulsating heat pipe working medium flow circuit; 213-gradient micro-column group on the inner wall surface of the pulsating heat pipe; 22-inner wall of the heat exchange tube; 23-outer wall of the heat exchange tube; 24-phase change working medium filling cavity; 25-cooling water channel; 26-flue gas channel; 3-tube sheet; 4-baffle. DETAILED DESCRIPTION

[0038] The present invention will be described in further detail, clearly and completely below with reference to the accompanying drawings and specific embodiments.

[0039] like Figure 1 As shown, the present invention provides a heat exchanger comprising a heat exchanger housing 1, a fluoroplastic tube heat exchanger 2, a tube sheet 3, and baffles 4. The fluoroplastic tube heat exchanger 2 is mounted on the tube sheets 3 on both sides, with several baffles 4 equidistantly installed between the two tube sheets to control the flue gas flow space and direction. During operation, flue gas flows from a flue gas inlet 11 through the heat exchanger to a flue gas outlet 12, while cooling water flows from a cooling water inlet 13 to a cooling water outlet 14. The flue gas and cooling water flow in countercurrents, resulting in more uniform thermal stress on the heat exchange tubes and improved heat exchange performance. The fluoroplastic heat exchange tubes 2 can enhance corrosion resistance and thermal conductivity.

[0040] The installation of the fluoroplastic tube heat exchanger 2 in the tube sheet 3 can be done according to the equilateral triangle method, see Figure 2 .

[0041] like Figure 3As shown, the fluoroplastic tube heat exchanger 2 utilizes a double-layer circular tube structure, consisting of an outer wall 22 and an inner wall 23. A mixture of phase change material, metal particles, and compressible microspheres is injected into the chamber between the outer and inner walls 22 and 23 of the heat exchange tube. During operation, the phase change material exhibits its peak-shaving and valley-filling regulation properties, absorbing latent heat during periods of excess heat to suppress temperature peaks and releasing it during periods of insufficient heat to fill the heat gap. This dynamic heat regulation mechanism effectively regulates the rate and effectiveness of heat transfer, ensuring stable and efficient operation of the heat exchanger under various operating conditions.

[0042] The addition of metal particles into the phase change fluid can effectively compensate for the low thermal conductivity of the phase change fluid, significantly improve the heat transfer coefficient of the phase change fluid, and enhance the heat transfer effect of the heat exchanger; compressible microspheres act as a buffer medium due to their compressible properties, which can effectively eliminate the expansion stress caused by density differences during solid-liquid phase change, significantly improving the reliability and stability of the system operation.

[0043] like Figure 4 and Figure 5 As shown, the pulsating heat pipes 21 installed on the outer wall of the heat exchange tube are flat-plate heat pipes. Four pulsating heat pipes arranged in a diamond pattern form an array subunit, which surrounds the four array subunits in the radial direction of the heat exchange tube; the array subunits are evenly spaced in the axial direction of the heat exchange tube. By disturbing the flow of high-temperature flue gas, the pulsating heat pipes disrupt the relatively stable laminar boundary layer, enhancing convective heat transfer between the flue gas and the pulsating heat pipe surface, thereby significantly improving heat transfer efficiency and providing strong support for the efficient operation of the entire heat exchanger.

[0044] from Figure 6 It can be seen that the micro heat pipe 21 has a stepped micro column structure 213. In the evaporation section, dense and slender micro columns ( Figure 7 ). When the working liquid in the micro heat pipe 21 is heated and vaporized into steam, these dense and slender micro columns can effectively enhance the capillary force. Under the combined action of the vapor pressure difference and the capillary force, the steam releases heat in the condensation section and condenses into liquid again, and can flow back to the evaporation section more quickly, ensuring an efficient cycle of heat transfer. In the condensation section, sparse and short micro columns ( Figure 8 ), this design can reduce the resistance to liquid flow, allowing steam to condense into liquid and flow more smoothly, reducing energy loss and further improving heat transfer efficiency.

[0045] In the actual waste heat recovery process of the thermal power generation industry, the use of pulsating heat pipes brings significant advantages. Taking the heat transfer in the small temperature difference part at the rear end as an example, the heat transfer efficiency of the traditional heat exchanger in this part is relatively low, resulting in a large amount of waste heat that cannot be fully utilized. However, the micro heat pipes in the present invention, with their special stepped micro-column group structure and unique arrangement, can quickly and efficiently transfer heat in the small temperature difference part at the rear end. In the later stage of high-temperature flue gas heat transfer, although the temperature difference gradually decreases, the working fluid in the pulsating heat pipe 21 can still circulate through phase change, continuously transferring heat to the inner tube wall 22, allowing the cooling water to absorb more heat, thereby improving the efficiency of the entire waste heat recovery system.

[0046] like Figure 9 As shown in the figure, the pulsating heat pipe is filled with acetone and has a filling ratio of 50%. When the heating power is greater than 100, the heat transfer coefficient of the gradient micro-pillar cluster pulsating heat pipe is significantly higher than that of a conventional pulsating heat pipe. In particular, when the heating power reaches above 400 W, the equivalent thermal conductivity of the gradient micro-pillar cluster pulsating heat pipe can be increased by 70% to 80% compared to a conventional heat pipe.

[0047] The working process of the fluoroplastic heat exchanger provided by the present invention is as follows: Taking the use of the heat exchanger for waste heat recovery in the thermal power generation industry as an example, high-temperature flue gas enters from the flue gas inlet 11 of the heat exchanger shell 1 and flows along the flue gas channel 26.

[0048] The high-temperature flue gas first contacts the outer wall 23 of the fluoroplastic heat exchange tube. Heat is then transferred through the outer wall 23 to the pulsating heat pipe 21 and the phase-change fluid in the phase-change fluid filling chamber 24. The working fluid in the pulsating heat pipe 21 absorbs heat in the evaporation section, vaporizing into steam. This steam, under the influence of a pressure differential, rapidly flows to the condensation section, where it releases heat and recondenses into liquid. Capillary forces cause the liquid to flow back to the evaporation section, and this cycle repeats, efficiently transferring heat to the inner wall 22.

[0049] The phase-change fluid regulates flue gas temperature fluctuations. When the flue gas temperature rises, it absorbs heat and undergoes a phase change (from solid to liquid), absorbing excess heat and preventing the heat exchange tubes from overheating. When the flue gas temperature drops, the phase-change fluid releases heat (from liquid back to solid), maintaining a stable temperature in the heat exchange tubes and ensuring continuous heat exchange.

[0050] Heat is transferred through the inner tube wall 22 to the cooling water in the cooling water channel 25. Cooling water enters the heat exchanger through the cooling water inlet 14. The cooling water flows through the cooling water channel 25, making full contact with the fluoroplastic heat exchange tubes, absorbing heat, and then flows out of the cooling water outlet 13. The presence of the baffles 4 increases the residence time of the high-temperature flue gas within the heat exchanger, enhancing the efficiency of heat exchange and allowing the cooling water to more effectively absorb heat from the flue gas.

[0051] The above provides a detailed introduction to the fluoroplastic tube heat exchanger proposed in the present invention. This article provides a detailed description of specific examples, which does not represent a complete list of implementations of the present invention. It should be noted that those skilled in the art would be able to make improvements and modifications to the present invention without departing from the principles of the present invention and would fall within the scope of protection of the claims.

Claims

1. A fluoroplastic tube heat exchanger, comprising a heat exchanger shell, heat exchange tubes, and tube sheets, wherein the tube sheets are located on both sides of the heat exchanger shell, the heat exchange tubes are arranged on the tube sheets on both sides, a flue gas inlet and a flue gas outlet are provided on the heat exchanger shell between the tube sheets on both sides, and a cooling water inlet and a cooling water outlet are respectively provided on the heat exchanger shell outside the tube sheets on both sides, the cooling water inlet and the cooling water outlet are connected to both ends of the heat exchange tubes, characterized in that: The heat exchange tube is a fluoroplastic tube, which includes an inner tube wall, an outer tube wall, a phase change medium and a pulsating heat pipe array. The phase change medium is located between the inner tube wall and the outer tube wall. The pulsating heat pipe array is composed of pulsating heat pipes. One end of the pulsating heat pipe is embedded in the phase change medium, and the other end of the pulsating heat pipe extends out of the surface of the outer tube wall. The cooling water inlet and the cooling water outlet are connected to the inner tube wall of the heat exchange tube.

2. A fluoroplastic tube heat exchanger according to claim 1, characterized in that: The inner surface of the pulsating heat pipe is provided with a composite gradient microcolumn group structure, which includes a first microcolumn located in the evaporation section and a second microcolumn located in the condensation section. The first microcolumn and the second microcolumn are both cylindrical, the length of the first microcolumn is 2-2.5 times that of the second microcolumn, the density of the first microcolumn is 1.5-2 times that of the second microcolumn, the aspect ratio of the first microcolumn is 3.5-4, and the aspect ratio of the second microcolumn is 1-1.

5.

3. A fluoroplastic tube heat exchanger according to claim 2, characterized in that: The pulsating heat pipe is a flat plate heat pipe. Four pulsating heat pipes arranged in a diamond shape constitute an array subunit. The four array subunits surround the heat exchange tube in the radial direction. The array subunits are arranged at equal intervals in the axial direction of the heat exchange tube.

4. A fluoroplastic tube heat exchanger according to any one of claims 1 to 4, characterized in that: The number of turns of the pulsating heat pipe is greater than 3.

5. A fluoroplastic tube heat exchanger according to any one of claims 1 to 3, characterized in that: The phase change working fluid is a mixture of 90%-98% phase change material, 2%-7% metal particles and 2%-7% compressible microspheres; the phase change material is a solid-liquid phase change material.

6. A fluoroplastic tube heat exchanger according to claim 5, characterized in that: The phase change working fluid is a mixture of 95% phase change material, 5% metal particles and 5% compressible microspheres.

7. The fluoroplastic tube heat exchanger according to claim 5, characterized in that: The phase change material is paraffin, high molecular weight polyethylene glycol or nitrate; the metal particles are inactive metal powder; and the compressible microspheres are glass microspheres or rubber microspheres.

8. The fluoroplastic tube heat exchanger according to claim 7, characterized in that: The inactive metal powder is copper powder or platinum powder.

9. The fluoroplastic tube heat exchanger according to claim 1, characterized in that: A baffle is arranged between the two tube sheets in the heat exchanger shell.

10. The fluoroplastic tube heat exchanger according to claim 9, characterized in that: The baffle is in an arched shape and is provided with through holes adapted to the heat exchange tubes. The baffle changes the flow direction of the fluid, increases the residence time of the fluid in the heat exchanger, and enhances the heat exchange effect.

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