A heat exchanger scale prevention, noise reduction and heat transfer enhancement device and method with vortex generators

Abstract

The application belongs to the technical field of gas water heaters, and particularly relates to a heat exchanger scale prevention, noise reduction and heat transfer enhancement device and method with a vortex generator, which comprises a heat exchange pipe and a turbulence device; the turbulence device comprises turbulence fins and a plurality of turbulence baffles; the turbulence fins are arranged in the heat exchange pipe and divide the heat exchange pipe into an upper heat exchange cavity and a lower heat exchange cavity; a plurality of turbulence channels are equally and interval set on the turbulence fins along the flow direction; the turbulence baffles are alternately arranged on the turbulence fins at intervals; and there is a flow gap between the turbulence baffles and the inner wall of the heat exchange pipe. The turbulence device is arranged to make the fluid reciprocate between the upper heat exchange cavity and the lower heat exchange cavity, improve the mixing degree of fluid flow and the sufficient shear on the boundary layer, reduce the temperature difference of the fluid near the pipe wall and at the center of the pipe, improve the flow heat transfer effect, reduce the temperature of the heat exchange pipe wall, greatly inhibit and destroy the formation conditions of scale, and reduce the generation of vaporization noise.

Description

Technical Field

[0001] This invention belongs to the field of gas water heater technology, and particularly relates to a device and method for preventing scale buildup, reducing noise and enhancing heat transfer in a heat exchanger with an eddy current generator. Background Technology

[0002] Gas water heaters have many advantages, such as small size, fast hot water supply, high efficiency and energy saving, and convenience, playing an important role in people's daily lives. The heat exchanger, as its core heat exchange component, is responsible for transferring the heat generated by the combustion of gas to the cold water flowing through it, thus achieving the purpose of producing hot water.

[0003] Currently, heat exchangers still face numerous problems in actual operation. For example, calcium and magnesium ions in water easily form scale on the inner wall of the heat exchange tubes under high temperatures. Scale has a low thermal conductivity, only 2% to 5% of that of ordinary steel, severely hindering heat transfer to the water side. This leads to a significant decrease in the heat exchanger's heat transfer efficiency, and external high-temperature heat cannot be transferred in a timely manner, causing localized overheating and other problems on the heat exchange tube walls, thus shortening the heat exchanger's lifespan. Furthermore, with the continuous accumulation of scale, the flow area decreases, water flow drops, and in severe cases, even causes pipe blockage, rendering the heat exchanger unable to function properly.

[0004] Meanwhile, when the heat exchanger tube wall temperature is too high, and the temperature difference between the water flow near the tube wall and the water flow in the central area of ​​the tube axis is large, the local temperature rise is too rapid, which easily generates a large number of bubbles, forming vaporization noise, affecting the normal operation of the heat exchanger, and bringing an uncomfortable experience to the user. Therefore, inhibiting and destroying scale adhesion, improving flow heat transfer efficiency, reducing heat exchanger tube wall temperature, and reducing bubble generation are crucial for the safe, reliable, and efficient operation of the heat exchanger.

[0005] As one of the core components of a heat exchanger, the turbulence device plays an important role in flow heat transfer, scale prevention, and noise reduction. An ideal turbulence structure design can effectively improve heat transfer efficiency, reduce heat exchanger tube wall temperature, inhibit and break down scale deposits inside the heat exchanger tubes, and reduce vaporization noise.

[0006] Chinese invention patent CN118312453A discloses a heat exchange tube, heat exchanger, water heater, and anti-scaling control method. By adding a turbulence-inducing structure to the heat exchange tube, the bottom temperature of the heat exchanger body is reduced, preventing localized overheating and scaling. However, this turbulence-inducing structure is relatively complex, and the turbulence effect cannot effectively reduce the bottom temperature of the heat exchanger body. In practical applications, it may also lead to problems such as low heat exchanger efficiency and vaporization noise, affecting the efficient operation and service life of the heat exchanger.

[0007] Chinese invention patent CN115355748A discloses a heat exchange tube, heat exchanger, and gas water heater. By incorporating a flow-guiding structure within the heat exchange tube, it accelerates convection between the horizontally flowing high-temperature water and the hot water inside the inner tube, resulting in more uniform hot water distribution, reduced uneven heating in certain areas, and decreased generation of high-temperature bubbles, thereby reducing vaporization noise and improving heat exchange efficiency. However, the flow-guiding vane is spiral-shaped, making its manufacturing process complex. Furthermore, the complex flow channels and dead zones created by the spiral structure easily provide opportunities for scale adhesion and deposition, increasing manufacturing costs and affecting the lifespan of the heat exchanger.

[0008] Therefore, developing a simple and low-cost turbulence device to reduce the temperature of the heat exchange tube wall, inhibit and destroy scale formation, improve heat transfer efficiency, and reduce vaporization noise is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0009] To address at least one of the shortcomings of existing turbulence devices, such as complex structure, low flow heat transfer efficiency, excessively high heat exchanger tube wall temperature, scale adhesion, and vaporization noise, this invention proposes a device and method for preventing scale buildup, reducing noise, and enhancing heat transfer in a heat exchanger with a vortex generator. This device can significantly improve the mixing degree of fluid flow and the sufficient shearing of the boundary layer, reduce the temperature difference between the fluid near the pipe wall and the center of the pipe, improve the flow heat transfer effect, reduce the heat exchanger tube wall temperature, significantly suppress and disrupt the conditions for scale formation, and reduce the generation of vaporization noise.

[0010] To achieve the objectives of this invention, a heat exchanger anti-scaling, noise reduction, and heat transfer enhancement device with an eddy current generator is provided, comprising a heat exchange tube and a flow-turbulence device; the flow-turbulence device is centrally located inside the heat exchange tube, with corresponding sides parallel; the flow-turbulence device includes a flow-turbulence plate and N flow-turbulence baffles, where N is a positive integer not less than 10; the flow-turbulence plate is fixedly connected to the inner wall of the heat exchange tube, dividing the interior of the heat exchange tube into an upper heat exchange cavity and a lower heat exchange cavity; the flow-turbulence plate has multiple flow-turbulence holes evenly spaced along the incoming flow direction; the flow-turbulence baffles are evenly spaced and alternately arranged on the flow-turbulence plate, with an angle θ between the flow-turbulence baffles and the flow-turbulence plate, and θ is an acute angle; a flow gap exists between the top of the flow-turbulence baffle and the semi-circular inner wall surface of the heat exchange tube.

[0011] Preferably, the heat exchange tube is a flat heat exchange tube, and its cross-section consists of two symmetrical semicircular arcs and two straight lines.

[0012] Preferably, the turbulence channel is rectangular, with a width of 4~6mm and a length of 4~10mm.

[0013] Preferably, the baffles are arranged in pairs, wherein the value of N is 10, 12, 14, 16, 18 or 20.

[0014] Preferably, the angle θ between the baffle and the baffle plate is in the range of 55°. 80°.

[0015] Preferably, the top two sides of the baffle are rounded with a radius of 1mm to 3mm.

[0016] Preferably, the vertical distance H between the top center of the turbulence baffle and the center of the semi-circular inner wall of the heat exchange tube is in the range of 1mm to 6mm.

[0017] Preferably, the materials of the heat exchange tubes and the turbulence device are not limited to stainless steel, copper, and aluminum.

[0018] A method for preventing scale buildup, reducing noise, and enhancing heat transfer in a heat exchanger with an eddy current generator, comprising the following steps:

[0019] S1. The inlet end of the heat exchange tube is connected to the water inlet connector, and the outlet end is connected to the water outlet connector. The outer wall of the heat exchange tube receives the heat transferred by the high-temperature flue gas and the fins. The baffles and turbulence plates divide the inside of the heat exchange tube into multiple upper heat exchange chambers and lower heat exchange chambers. S2. Cold water enters the heat exchange tube through the incoming flow direction and moves back and forth between the upper and lower heat exchange chambers, inducing the formation of a large longitudinal vortex, which significantly enhances the secondary flow intensity and improves the mixing effect and flow heat transfer efficiency of the fluid. S3. By inducing longitudinal vortices and the gap between the top of the turbulence baffle and the inner wall of the heat exchange tube, the semi-circular arc wall of the heat exchange tube is fully sheared, reducing the wall temperature of the heat exchange tube, significantly inhibiting and destroying the conditions for scale formation, reducing the temperature difference between the fluid near the pipe wall and the center of the pipe, and reducing the generation of vaporization noise.

[0020] Compared with existing technologies, the present invention provides a device and method for preventing scale buildup, reducing noise, and enhancing heat transfer in a heat exchanger with an eddy current generator, which has at least the following beneficial effects: 1. Simple structure and cost advantage. By setting up baffles, deflectors and channels, complex structures such as irregular curved surfaces and holes are avoided, and mass production can be carried out using stamping dies, effectively reducing processing and manufacturing costs.

[0021] 2. Mixing effect and enhanced heat transfer. The turbulence device installed within the heat exchanger causes the fluid to reciprocate between the upper and lower heat exchange chambers, significantly increasing the degree of fluid turbulence and mixing, enhancing the intensity of secondary flow and the size of vortices, and improving the flow heat transfer effect.

[0022] 3. Scaling Inhibition and Noise Reduction: The longitudinal vortex induced by this turbulence device and the gap between the top of the turbulence baffle and the inner wall of the heat exchange tube enhance the scouring effect of the fluid on the heat exchange tube wall, reduce the heat exchange tube wall temperature, increase the wall shear stress, effectively inhibit and destroy the formation and adhesion of scale, and at the same time improve the uniformity of water temperature distribution inside the tube, reduce bubble generation, and thus reduce vaporization noise. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of a heat exchanger device with an eddy current generator provided in an embodiment of the present invention; Figure 2 This is a two-dimensional cross-sectional temperature diagram of Embodiment 1 of the present invention, where (a)~(e) and (f)~(j) are different cross-sections of the conventional turbulence device and the turbulence device provided in the embodiment of the present invention along the mainstream direction, respectively. Figure 3 This is a comparison diagram of wall shear stress in Embodiment 1 of the present invention; Figure 4 This is a comparison chart of the average wall temperature in Embodiment 1 of the present invention; Figure 5 This is a comparison chart of the heat exchange performance of Embodiment 1 of the present invention; Figure 6 This is a three-dimensional streamline diagram of Embodiment 2 of the present invention; The figure shows: 1-heat exchange tube, 2-turbulence device, 21-turbulence plate, 22-turbulence baffle, 23-turbulence channel. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] In the description of this invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0026] Example 1 A heat exchanger anti-fouling, noise reduction, and heat transfer enhancement device with an eddy current generator, such as... Figure 1As shown, the device includes a heat exchange tube 1 and a flow-disrupting device 2. The flow-disrupting device 2 is coaxially disposed inside the heat exchange tube 1, and the corresponding sides are parallel and aligned. The flow-disrupting device 2 includes a flow-disrupting plate 21 and N flow-disrupting baffles 22, where N is a positive integer not less than 10. The flow-disrupting plate 21 is fixedly connected to the inner wall of the heat exchange tube 1, dividing the interior of the heat exchange tube 1 into an upper heat exchange cavity and a lower heat exchange cavity. Multiple flow-disrupting channels 23 are equally spaced on the flow-disrupting plate 21 along the incoming flow direction. The flow-disrupting baffles 22 are equally spaced and alternately disposed on the flow-disrupting plate 21, with an angle θ between the flow-disrupting baffles 22 and the flow-disrupting plate 21, and θ is an acute angle. There are flow gaps between the top of the flow-disrupting baffle 22 in the upper heat exchange cavity and the upper semi-circular inner wall surface of the heat exchange tube 1, and between the bottom of the flow-disrupting baffle 22 in the lower heat exchange cavity and the lower semi-circular inner wall surface of the heat exchange tube 1.

[0027] Specifically, the turbulence channel 23 is rectangular, with a width of 6mm and a length of 7mm, which facilitates actual manufacturing and processing and can effectively ensure that more fluid passes through, enhancing the fluid mixing between the upper heat exchange cavity and the lower heat exchange cavity.

[0028] Specifically, the baffles 22 are arranged in pairs, and the number N of the baffles 22 can be 10, 12, 14, 16, 18, or 20. Within this range, the intensity of the longitudinal vortex generated by the baffle device 2 and the scouring effect on the inner wall of the heat exchange tube 1 can be guaranteed, thereby significantly improving the flow heat transfer efficiency, reducing the inner wall temperature, and enhancing the wall shear stress with a suitable pressure drop. In this embodiment of the invention, 14 baffles are preferred.

[0029] Specifically, the angle θ between the baffle 22 and the baffle plate 21 ranges from 55° to 80°. Increasing the angle θ can induce larger-scale longitudinal vortices, thereby improving flow heat transfer efficiency, reducing inner wall temperature, and enhancing wall shear stress. In this embodiment, 60° is preferred.

[0030] Specifically, the top and bottom of the baffle 22 in the upper heat exchange cavity and the lower heat exchange cavity are both rounded with a radius of 1mm to 3mm. This effectively ensures the uniform flushing effect of the fluid on the semi-circular arc wall of the heat exchange flat tube, thereby inhibiting and destroying the formation of scale. In this embodiment, 3mm is preferred.

[0031] In this embodiment, the heat exchange tube 1 is a flat heat exchange tube, and its cross-section consists of two symmetrical semicircular arcs and two straight lines.

[0032] Specifically, the vertical distance H between the top center of the turbulence baffle 22 and the center of the semi-circular inner wall of the heat exchange tube 1 ranges from 1mm to 6mm, and is preferably 1mm in this embodiment.

[0033] Specifically, the materials of the heat exchange tube 1 and the turbulence-disrupting device 2 are not limited to stainless steel, copper, and aluminum. SUS316L stainless steel is preferred for both the heat exchange tube 1 and the turbulence-disrupting device 2.

[0034] This embodiment uses ANSYS FLUENT software to numerically calculate the turbulence device inside the heat exchanger described in this invention and a conventional heat exchanger, exploring the improvement effect of the embodiment of this invention under an inlet flow rate of 6~10 L / min. The calculation boundary conditions are: inlet temperature of 298 K, mass flow rate inlet and pressure outlet, isothermal condition of 373.15 K for the outer wall of heat exchange tube 1, and no-slip wall conditions for all walls. The governing equations are discretized using the finite volume method, and steady-state and SST k-ω turbulence models are used for simulation calculations. The SIMPLE algorithm is used to solve the pressure-velocity coupled problem, and a second-order upwind scheme is used for all solutions, with a convergence criterion set to 10. -8 Simultaneously, the average pressure at the inlet section and the average temperature at the outlet section are monitored. When the monitored values ​​tend to a constant value, the numerical calculation results are considered to have converged.

[0035] The heat exchange tube 1 and the turbulence device 2 are made of SUS316L. The thermophysical properties of liquid water are fitted, as shown in Table 1.

[0036] Table 1 Material properties of liquid water and SUS316L

[0037] See Figure 2 The diagrams show the cross-sectional temperature cloud diagrams of the flow disturbance device provided in this embodiment and a conventional flow disturbance device, where (a)~(e) and (f)~(j) represent different cross-sections of the conventional flow disturbance device and the flow disturbance device provided in this embodiment along the main flow direction, respectively. The fluid temperature in the core region of the conventional flow disturbance device varies between 303K and 304.5K, while the fluid temperature in the core region of the flow disturbance device provided in this embodiment varies between 306K and 307.5K. Clearly, the flow disturbance device provided in this embodiment significantly increases the overall temperature of the fluid in the pipe, and the temperature in the core region of the flow field is more uniform. The area of ​​the high-temperature boundary layer is significantly reduced, effectively improving the heat transfer effect of the fluid, reducing the temperature difference between the flat pipe wall region and the fluid in the center of the pipe, thereby reducing bubble formation and suppressing vaporization noise.

[0038] See Figure 3 The wall shear stress τ of the flow disturbance device provided in the embodiments of the present invention and the conventional flow disturbance device under the condition of an inlet flow rate of 8L / min w The changes in flow. Compared to traditional flow control devices, the flow control device τ provided by this invention... wOverall, there is a significant improvement. The turbulence device provided in this embodiment of the invention, by having turbulence baffles 22 alternately arranged at equal intervals on the turbulence plates 21, can induce the generation of larger-scale longitudinal vortices. Furthermore, the arrangement of the turbulence channels 23 can effectively enhance the velocity of the local fluid, thereby significantly enhancing the wall shear stress, which is more conducive to flushing away scale adhering to the wall and improving the long-term service life of the heat exchanger.

[0039] See Figure 4 The heat exchange tube wall temperature T of the turbulence device provided in the embodiments of the present invention and the conventional turbulence device ave Comparison chart. T of traditional turbulence device ave The heat exchange tube wall temperature T of the turbulence device provided in this embodiment of the invention varies within the range of 359.236K-363.748K. ave It varies in the range of 349.773K-355.932K.

[0040] The rate of scale formation is positively correlated with temperature. Lowering the temperature of the heat transfer surface can increase the solubility of CaCO3 and reduce the tendency for supersaturated crystallization on the heat transfer surface. The novel turbulence device provided in this embodiment of the invention can significantly reduce the temperature of the inner wall surface, thereby suppressing the conditions for scale formation.

[0041] To evaluate the heat transfer performance of the turbulence-inducing devices provided in the conventional and present invention embodiments, the Nusselt number Nu is determined by the following formula:

[0042] in, This represents the average convective heat transfer coefficient, expressed in W / (m²·K). Represents the equivalent diameter, in meters (m). The average thermal conductivity of the fluid is represented by W / (m·K).

[0043] See Figure 5 This is a comparison chart of the Nusselt number (Nu) between the flow-changing device provided in this embodiment and a conventional flow-changing device. A higher Nusselt number (Nu) indicates better heat transfer performance. As can be seen from the chart, within the inlet flow rate range of 6~10 L / min, the flow-changing device provided in this embodiment can significantly improve heat transfer performance, with a maximum improvement of 124.8% compared to the conventional flow-changing device.

[0044] Example 2 In this embodiment, all conditions are the same as in Embodiment 1, except that the vertical distance H between the center of the top of the baffle 22 and the center of the semi-circular inner wall of the heat exchange tube differs from that in Embodiment 1. In this embodiment, H is 3 mm. Figure 6As shown, the fluid moves in a spiral motion, crisscrossing upwards and downwards, along the main flow direction. This spiral motion covers the entire space between the heat exchange tube 1 and the turbulence-inducing device 2. The heat exchange tube 1 is flat, and using a flat heat exchange tube can increase the heat exchange area within a limited space, improve structural compactness, and enhance the flow heat exchange efficiency within the heat exchange tube 1. Furthermore, there is a certain size of backflow region between adjacent turbulence-inducing baffles 22 located in the upper or lower heat exchange cavity, which can significantly enhance the fluid mixing degree and improve the stability of the fluid flow.

[0045] Example 3 A method for preventing scale buildup, reducing noise, and enhancing heat transfer in a heat exchanger includes the following steps: S1. The inlet end of the heat exchange tube 1 is connected to the water inlet connector, and the outlet end is connected to the water outlet connector. The outer wall of the heat exchange tube 1 receives the heat transferred by the high temperature flue gas and the fins. The baffle plate 21 and the baffle plate 22 divide the interior of the heat exchange tube 1 into multiple upper heat exchange chambers and lower heat exchange chambers. S2. Cold water enters heat exchange tube 1 through the incoming flow direction and moves back and forth between the upper heat exchange cavity and the lower heat exchange cavity, inducing the formation of a large longitudinal vortex, which significantly enhances the secondary flow intensity and improves the mixing effect and flow heat transfer efficiency of the fluid. S3. By inducing longitudinal vortex and the gap between the top of the turbulence baffle 22 and the inner wall of the heat exchange tube 1, the semi-circular arc wall of the heat exchange tube is fully sheared, reducing the wall temperature of the heat exchange tube, significantly inhibiting and destroying the conditions for scale formation, reducing the temperature difference between the fluid near the pipe wall and the center of the pipe, and reducing the generation of vaporization noise.

[0046] In a gas water heater, the device provided in Example 1 can be used to transfer heat using the method provided in Example 3.

[0047] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A heat exchanger anti-scaling, noise reduction, and heat transfer enhancement device with an eddy current generator, characterized in that, It includes heat exchange tubes (1) and a turbulence device (2); The turbulence device (2) includes a turbulence plate (21) and multiple turbulence baffles (22). The turbulence plate (21) is coaxially arranged inside the heat exchange tube (1) and divides the interior of the heat exchange tube (1) into an upper heat exchange cavity and a lower heat exchange cavity. Multiple turbulence channels (23) are equally spaced on the turbulence plate (21) along the incoming flow direction. Multiple turbulence baffles (22) are equally spaced and alternately arranged on the turbulence plate (21), and an angle is formed between the turbulence baffle (22) and the turbulence plate (21). There is a flow gap between the end of the turbulence baffle (22) and the inner wall of the heat exchange tube (1).

2. The heat exchanger anti-scaling, noise reduction, and heat transfer enhancement device with eddy current generator according to claim 1, characterized in that, The heat exchange tube (1) is a flat heat exchange tube.

3. The heat exchanger anti-scaling, noise reduction, and heat transfer enhancement device with eddy current generator according to claim 1, characterized in that, There are N baffles (22), and N is a positive integer not less than 10.

4. The heat exchanger anti-scaling, noise reduction, and heat transfer enhancement device with eddy current generator according to claim 1, characterized in that, The angle between the baffle (22) and the baffle (21) is an acute angle.

5. The heat exchanger anti-scaling, noise reduction, and heat transfer enhancement device with eddy current generator according to claim 1, characterized in that, The angle between the baffle (22) and the baffle plate (21) ranges from 55° to 80°.

6. The heat exchanger anti-scaling, noise reduction, and heat transfer enhancement device with eddy current generator according to claim 1, characterized in that, The aforementioned turbulence channel (23) is rectangular, with a width of 4~6mm and a length of 4~10mm.

7. The heat exchanger anti-scaling, noise reduction, and heat transfer enhancement device with eddy current generator according to claim 1, characterized in that, The ends of the baffle (22) are rounded.

8. A heat exchanger anti-scaling, noise reduction, and heat transfer enhancement device with an eddy current generator according to any one of claims 1-7, characterized in that, The vertical distance between the top center of the turbulence baffle (22) and the center of the inner wall of the heat exchange tube (1) is H, and the value of H ranges from 1mm to 6mm.

9. A method for preventing scale buildup, reducing noise, and enhancing heat transfer in a heat exchanger using the apparatus described in any one of claims 1-8, characterized in that, Includes the following steps: S1, The outer wall of the heat exchange tube (1) receives the heat transferred by the high-temperature flue gas and the fins; S2. Cold water enters the heat exchange tube (1) through the incoming flow direction and moves back and forth between the upper heat exchange cavity and the lower heat exchange cavity, inducing the formation of a longitudinal vortex. S3. By inducing longitudinal vortex and the gap between the top of the baffle (22) and the inner wall of the heat exchange tube (1), the wall of the heat exchange tube (1) is fully sheared to reduce the wall temperature of the heat exchange tube (1).

10. The application of the apparatus as described in any one of claims 1-8 and the method as described in claim 9 in a gas water heater.

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