A device for generating micro-bubbles to enhance boiling heat transfer

Abstract

The application provides a device for generating micro-bubble enhanced boiling heat transfer, comprising a micro-bubble generator and a boiling heat exchanger; the micro-bubble generator is used for generating micro-bubbles; a boiling heat transfer inner surface of the boiling heat exchanger is provided with hydrophilic surface regions and hydrophobic surface regions with wetting properties in an alternating distribution, one hydrophilic surface bubble hole is arranged in each hydrophilic surface region, and one hydrophobic surface bubble hole is arranged in each hydrophobic surface region; the micro-bubble generator is in communication with each hydrophilic surface bubble hole through a first bubble conveying channel; and the micro-bubble generator is in communication with each hydrophobic surface bubble hole through a second bubble conveying channel. The application actively introduces fine seed bubbles on a boiling surface to promote bubble nucleation on the hydrophilic surface, effectively increases nucleation points, and can weaken the problem of boiling delay.

Description

Technical Field

[0001] This invention relates to the field of boiling heat transfer, and particularly to a device for generating microbubbles to enhance boiling heat transfer. Background Technology

[0002] With the rapid development of science and technology and the high demands of industrial production, the miniaturization and integration of equipment have become an inevitable trend. This miniaturization and high integration lead to a continuous increase in energy density on equipment, posing a significant challenge to the effective heat dissipation of components. Therefore, achieving high heat flux density cooling within a limited space is crucial for ensuring stable system operation. Boiling heat transfer technology is considered one of the most promising technologies for solving the thermal management problems of high heat flux density systems. Enhancing boiling heat transfer is of great significance for further improving energy utilization and thermal protection of materials under high heat loads.

[0003] Reducing boiling hysteresis (delayed nucleation of new bubbles) and increasing the film boiling transition temperature are key to enhancing boiling heat transfer. Surface modification is one important means of addressing these two issues. Hydrophobic surfaces have the advantages of easier bubble nucleation and a lower boiling initiation point; however, at high heat flux densities, a large number of bubbles on the surface easily condense to form film boiling, leading to a decrease in heat transfer efficiency. Hydrophilic surfaces have the disadvantages of a higher boiling initiation point and lower heat transfer performance, but they have a higher film boiling transition temperature and a larger critical heat flux density. Meanwhile, boiling hysteresis is unavoidable on both types of surfaces. Therefore, further reducing or eliminating boiling hysteresis and increasing the film boiling transition temperature are crucial for improving boiling heat transfer efficiency and critical heat flux density. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a device for generating microbubbles to enhance boiling heat transfer. By actively introducing micro-seed bubbles into the boiling surface, it promotes bubble nucleation on the hydrophilic surface, effectively increasing the nucleation points and mitigating boiling hysteresis. To increase the film boiling transition temperature, this invention proposes a boiling surface with alternating hydrophilic and hydrophobic wettability. At high superheat levels, seed bubbles are introduced only or not at all on the hydrophobic surface, allowing boiling to occur primarily on the hydrophobic surface, thereby suppressing film boiling and preventing heat transfer deterioration.

[0005] The present invention achieves the above-mentioned technical objectives through the following technical means.

[0006] An apparatus for generating microbubbles to enhance boiling heat transfer includes a microbubble generator and a boiling heat exchanger. The microbubble generator is used to generate microbubbles. The inner surface of the boiling heat exchanger is provided with hydrophilic surface regions and hydrophobic surface regions with alternating wettability. Each hydrophilic surface region has one hydrophilic surface bubble pore, and each hydrophobic surface region has one hydrophobic surface bubble pore. The microbubble generator is connected to each hydrophilic surface bubble pore through a first bubble delivery channel and to each hydrophobic surface bubble pore through a second bubble delivery channel.

[0007] Furthermore, the length and width of the hydrophilic surface region are both in the range of 0.5-10 mm; the contact angle of the hydrophilic surface region is in the range of 5° to 60°; and the pore size of the hydrophilic surface bubble pores is in the range of 10 to 100 μm.

[0008] Furthermore, the length and width of the hydrophobic surface region are both in the range of 0.5-10 mm; the contact angle of the hydrophobic surface region is in the range of 135° to 170°; and the pore size of the hydrophobic surface bubble pores is in the range of 10 to 100 μm.

[0009] Furthermore, it also includes a controller, a first control valve, a second control valve, and a temperature sensor; the temperature sensor is used to measure the temperature of the inner surface of the boiling heat exchanger; the first control valve is installed on the first bubble delivery channel, and the second control valve is installed on the second bubble delivery channel; the controller controls the first control valve and / or the second control valve according to the temperature of the inner surface of the boiling heat exchanger measured by the temperature sensor, so as to allow microbubbles to enter the inner surface of the boiling heat exchanger through the first bubble delivery channel and / or the second bubble delivery channel.

[0010] Furthermore, the controller uses the boiling heat exchange inner surface temperature T measured by the temperature sensor. W The superheat ΔT is determined, and the controller controls the opening and closing of the first control valve and / or the second control valve based on the superheat ΔT; superheat ΔT = T W -T M T M This is the saturation temperature of the liquid medium inside the boiling heat exchanger.

[0011] Furthermore, when the superheat ΔT < 30% * ΔT0, the controller controls the first control valve and the second control valve to allow microbubbles to enter the boiling heat exchange inner surface through the first bubble delivery channel and the second bubble delivery channel, respectively.

[0012] When 30%*ΔT0<ΔT<80%*ΔT0, the controller controls the second control valve to allow microbubbles to enter the inner surface of the boiling heat exchanger through the second bubble delivery channel.

[0013] When the superheat ΔT > 80% * ΔT0, the controller controls both the first control valve and the second control valve to close.

[0014] Where: ΔT0=T S -T M T S This refers to the film boiling transition temperature of the liquid medium inside the boiling heat exchanger at the inner surface of the boiling heat exchanger.

[0015] The beneficial effects of this invention are as follows:

[0016] 1. The device for generating microbubbles to enhance boiling heat transfer according to the present invention can promote the nucleation of bubbles on the hydrophilic surface and reduce the boiling initiation point by actively introducing micro-seed bubbles into the boiling surface, and can also reduce the boiling hysteresis problem of the entire surface.

[0017] 2. The device for generating microbubbles to enhance boiling heat transfer according to the present invention can make the bubbles evenly distributed by using a boiling surface with a uniform distribution of wettability between the wettability and the wettability. The bubble pores on each wettability and wettability surface block introduce bubbles, which can effectively increase the nucleation points.

[0018] 3. The device for generating microbubbles to enhance boiling heat transfer according to the present invention, by using a surface with alternating hydrophilic and hydrophobic phases and actively introducing insoluble bubbles, can facilitate the detachment of bubbles from the boiling surface during the boiling process, thereby promoting boiling heat transfer.

[0019] 4. The device for generating microbubbles to enhance boiling heat transfer according to the present invention controls the bubble delivery mode according to the superheat. When the superheat is high, seed bubbles are introduced only on the hydrophobic surface or not introduced at all. This can make boiling occur on the hydrophobic surface as much as possible, increase the film boiling transition temperature, thereby inhibiting the occurrence of film boiling and preventing heat transfer deterioration. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings described below are some embodiments of the present invention. For those skilled in the art, it is obvious that other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the device for generating microbubbles to enhance boiling heat transfer according to the present invention.

[0022] Figure 2 This is a schematic diagram illustrating the enhanced surface wettability distribution of boiling heat transfer according to the present invention.

[0023] Figure 3 This is a schematic diagram of the microbubble delivery logic of the present invention;

[0024] Figure 4 This is a graph showing the variation of the initial boiling wall heat flux density with wall superheat in an embodiment of the present invention.

[0025] Figure 5 This is a graph showing the variation of wall heat flux density near film boiling with wall superheat in an embodiment of the present invention.

[0026] In the picture:

[0027] 1-Microbubble generator; 2-Boiling heat exchange inner surface; 3-Controller; 4-Temperature sensor; 5-First control valve; 6-Second control valve; 7-Wires connecting the controller and the bubble generator; 8-First bubble delivery channel; 9-Second bubble delivery channel; 10-Hydrophilic surface area; 11-Hydrophobic surface area; 12-Hydrophobic surface bubble pores; 13-Hydrophilic surface bubble pores. Detailed Implementation

[0028] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0029] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "axial," "radial," "vertical," "horizontal," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing the 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, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0030] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0031] like Figure 1 and Figure 2 As shown, the device for generating microbubbles to enhance boiling heat transfer according to the present invention includes a microbubble generator 1 and a boiling heat exchanger; the microbubble generator 1 is used to generate microbubbles, where microbubbles refer to micro-nano-sized bubbles; the boiling heat exchanger's inner surface 2 is provided with hydrophilic surface regions 10 and hydrophobic surface regions 11, with wettability exhibiting an alternating distribution of hydrophilic and hydrophobic properties, such as... Figure 2 As shown, several hydrophilic surface regions 10 and hydrophobic surface regions 11 are staggered in the inner surface 2 of the boiling heat exchanger. Each hydrophilic surface region 10 is provided with a hydrophilic surface bubble pore 13, and each hydrophobic surface region 11 is provided with a hydrophobic surface bubble pore 12. The microbubble generator 1 is connected to each hydrophilic surface bubble pore 13 through a first bubble delivery channel 8; the microbubble generator 1 is connected to each hydrophobic surface bubble pore 12 through a second bubble delivery channel 9.

[0032] The length and width of the hydrophilic surface region 10 are both 0.5-10 mm; the contact angle of the hydrophilic surface region 10 is 5° to 60°; and the pore size of the hydrophilic surface bubble pores 13 is 10 to 100 μm. The length and width of the hydrophobic surface region 11 are both 0.5-10 mm; the contact angle of the hydrophobic surface region 11 is 135° to 170°; and the pore size of the hydrophobic surface bubble pores 12 is 10 to 100 μm.

[0033] For ease of control, the system also includes a controller 3, a first control valve 5, a second control valve 6, and a temperature sensor 4. The temperature sensor 4 is used to measure the temperature of the inner surface 2 of the boiling heat exchanger. The first control valve 5 is installed on the first bubble delivery channel 8, and the second control valve 6 is installed on the second bubble delivery channel 9. The controller 3 controls the first control valve 5 and / or the second control valve 6 according to the temperature of the inner surface 2 of the boiling heat exchanger measured by the temperature sensor 4, so as to allow microbubbles to enter the inner surface 2 of the boiling heat exchanger through the first bubble delivery channel 8 and / or the second bubble delivery channel 9.

[0034] like Figure 3 As shown, the controller 3 uses the temperature T of the boiling heat exchange inner surface 2 measured by the temperature sensor 4. WThe superheat ΔT is determined, and the controller 3 controls the opening and closing of the first control valve 5 and / or the second control valve 6 based on the superheat ΔT; superheat ΔT = T W -T M T M The saturation temperature of the liquid medium inside the boiling heat exchanger is T. This saturation temperature can be determined based on the physical properties of the liquid medium. M This is the set value in controller 3. In this embodiment, three temperature sensors 4 are installed on the inner surface 2 of the boiling heat exchanger. The average value measured by the three temperature sensors 4 is the temperature T of the inner surface 2 of the boiling heat exchanger. W .

[0035] When the superheat ΔT < 30% * ΔT0, the controller 3 controls the first control valve 5 and the second control valve 6 to allow microbubbles to enter the boiling heat exchange inner surface 2 through the first conveying bubble channel 8 and the second conveying bubble channel 9 respectively.

[0036] When 30%*ΔT0<ΔT<80%*ΔT0, the controller 3 controls the second control valve 6 to allow microbubbles to enter the boiling heat exchange inner surface 2 through the second conveying bubble channel 9.

[0037] When the superheat ΔT > 80% * ΔT0, the controller 3 controls both the first control valve 5 and the second control valve 6 to close.

[0038] Where: ΔT0=T S -T M T S This refers to the film boiling transition temperature of the liquid medium inside the boiling heat exchanger at the inner surface 2. Once the inner surface 2 and the liquid medium are determined, T can be measured experimentally. S .

[0039] This invention actively introduces micro-seed bubbles into the boiling surface to promote bubble nucleation on the hydrophilic surface, effectively increasing the nucleation points and mitigating boiling hysteresis. To increase the film boiling transition temperature, this invention proposes a boiling surface with alternating hydrophilic and hydrophobic wettability. At high superheats, seed bubbles are introduced only or not at all on the hydrophobic surface, allowing boiling to occur primarily on the hydrophobic surface, thereby inhibiting film boiling and preventing heat transfer deterioration.

[0040] In this embodiment, the length and width of the hydrophilic surface 10 are 5 mm, and the contact angle is 40°; the length and width of the hydrophobic surface 11 are 5 mm, and the contact angle is 150°; the pore diameter of the hydrophilic surface bubble pore 13 and the hydrophobic surface bubble pore 12 are both 40 μm.

[0041] Figure 4This is a graph showing the variation of the initial boiling wall heat flux density with superheat at wettability values ​​of 40° and 150°, respectively, according to the present invention. Figure 5 The graph shows the variation of heat flux density near the wall surface during film boiling obtained by the present invention with superheat at wettability values ​​of 40° and 150°, respectively. It can be seen that, at the same superheat, the present invention exhibits a higher heat flux density, the lowest boiling initiation point, and the highest film boiling transition temperature. This indicates that the boiling heat transfer device proposed in this invention can promote nucleate boiling while slowing down film boiling, thereby facilitating heat transfer.

[0042] It should be understood that although this specification is described according to various embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0043] The detailed descriptions listed above are merely specific illustrations of feasible embodiments of the present invention, and are not intended to limit the scope of protection of the present invention. All equivalent embodiments or modifications made without departing from the spirit of the present invention should be included within the scope of protection of the present invention.

Claims

1. A device for generating microbubbles to enhance boiling heat transfer, characterized in that, The device includes a microbubble generator (1) and a boiling heat exchanger; the microbubble generator (1) is used to generate microbubbles; the boiling heat exchanger inner surface (2) of the boiling heat exchanger is provided with a hydrophilic surface region (10) and a hydrophobic surface region (11) with alternating wettability, each hydrophilic surface region (10) is provided with a hydrophilic surface bubble hole (13), and each hydrophobic surface region (11) is provided with a hydrophobic surface bubble hole (12); the microbubble generator (1) is connected to each hydrophilic surface bubble hole (13) through a first bubble delivery channel (8); the microbubble generator (1) is connected to each hydrophobic surface bubble hole (12) through a second bubble delivery channel (9).

2. The apparatus for generating microbubbles to enhance boiling heat transfer according to claim 1, characterized in that, The length and width of the hydrophilic surface region (10) are both 0.5-10 mm; the contact angle of the hydrophilic surface region (10) is 5° to 60°; and the pore size of the hydrophilic surface bubble pores (13) is 10 to 100 μm.

3. The apparatus for generating microbubbles to enhance boiling heat transfer according to claim 1, characterized in that, The length and width of the hydrophobic surface region (11) are both 0.5-10 mm; the contact angle of the hydrophobic surface region (11) is 135° to 170°; and the pore size of the hydrophobic surface bubble pores (12) is 10 to 100 μm.

4. The apparatus for generating microbubbles to enhance boiling heat transfer according to claim 1, characterized in that, It also includes a controller (3), a first control valve (5), a second control valve (6), and a temperature sensor (4); the temperature sensor (4) is used to measure the temperature of the inner surface (2) of the boiling heat exchanger; the first control valve (5) is installed on the first bubble delivery channel (8), and the second control valve (6) is installed on the second bubble delivery channel (9); the controller (3) controls the first control valve (5) and / or the second control valve (6) according to the temperature of the inner surface (2) of the boiling heat exchanger measured by the temperature sensor (4), so as to allow microbubbles to enter the inner surface (2) of the boiling heat exchanger through the first bubble delivery channel (8) and / or the second bubble delivery channel (9).

5. The apparatus for generating microbubbles to enhance boiling heat transfer according to claim 4, characterized in that, The controller (3) measures the temperature T of the boiling heat exchange inner surface (2) as measured by the temperature sensor (4). W The superheat ΔT is determined, and the controller (3) controls the opening and closing of the first control valve (5) and / or the second control valve (6) according to the superheat ΔT; superheat ΔT = T W -T M T M This is the saturation temperature of the liquid medium inside the boiling heat exchanger.

6. The apparatus for generating microbubbles to enhance boiling heat transfer according to claim 5, characterized in that, When the superheat ΔT < 30% * ΔT0, the controller (3) controls the first control valve (5) and the second control valve (6) so that the microbubbles enter the boiling heat exchange inner surface (2) through the first conveying bubble channel (8) and the second conveying bubble channel (9) respectively; When 30%*ΔT0<ΔT<80%*ΔT0, the controller (3) controls the second control valve (6) to allow microbubbles to enter the boiling heat exchange inner surface (2) through the second conveying bubble channel (9); When the superheat ΔT > 80% * ΔT0, the controller (3) controls both the first control valve (5) and the second control valve (6) to close. Where: ΔT0=T S -T M T S The film boiling transition temperature of the liquid medium inside the boiling heat exchanger on the inner surface (2) of the boiling heat exchanger.

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