Intensified boiling heat exchange device for particle fluid

Abstract

The invention provides an enhanced boiling heat exchange device for particle fluid, which comprises a cooling channel, particles and a cooling medium, the cooling channel is provided with a cold surface and a hot surface, the particles and the cooling medium can flow in the cooling channel, the particles comprise a particle shell and an inner core, the inner core is positioned in the particle shell, and the inner core is positioned in the particle shell. A cavity communicated with an external cooling medium exists between the particle shell and the inner core, and steam bubbles are generated or collapsed in the cavity through temperature change between the cold surface and the hot surface, so that the particle density is changed, and the particles are made to oscillate between the cold surface and the hot surface. According to the invention, steam bubbles or steam bubble collapse are generated in the cavity by utilizing temperature change, the generated steam bubbles can reduce the particle density and increase the particle buoyancy at the same time, and the steam bubble collapse can increase the particle density, so that the particles are promoted to oscillate between a cold surface and a hot surface.

Description

Technical Field

[0001] The invention relates to the field of boiling heat exchange, in particular to an enhanced boiling heat exchange device for a particle fluid. Background Art

[0002] With the in-depth implementation of the "dual carbon" goals, various energy and power devices are evolving towards high power density, compact structure and lightweight. This trend has brought about the contradiction and challenge of a sharp increase in equipment heat generation and a significant reduction in heat dissipation space. In view of the excellent heat transfer efficiency of flow boiling technology, it has been widely used in the field of cooling and heat dissipation. In addition, the granular fluid formed by adding solid particles to the cooling medium further significantly improves the heat exchange capacity due to the high thermal conductivity and convection enhancement of the particles. Therefore, the enhanced cooling strategy that combines granular fluid with flow boiling in cooling channels has attracted increasing attention from the industry.

[0003] However, since the density of particles is often higher than that of fluids, they tend to deposit on hot surfaces, which not only significantly weakens the effect of convective disturbances, but may also have adverse effects on the structure of the hot surface, thereby causing instability in the boiling process. In order to solve this problem, many scholars have tried to actively control the movement of particles by applying alternating magnetic fields or electric fields, thereby creating an oscillating disturbance effect and enhancing heat transfer performance. However, a significant disadvantage of this method is that the introduction of an external field is inevitably accompanied by the consumption of additional energy. Therefore, exploring new ways to achieve autonomous regulation of particles without the need for additional energy input has become an innovative direction in the current research on enhanced heat transfer technology.

[0004] Invention patent CN202410685578.9 provides a thermal expansion and contraction particle, the core idea of ​​which is to wrap a thermal expansion and contraction material inside the particle, thereby achieving the regulation of particle density. However, during the experiment, the degree of thermal expansion of the material volume is limited, and the expansion degree is determined by the temperature. When the temperature is low, the expansion degree is low. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides an enhanced boiling heat exchange device for granular fluids. A cavity connected to an external cooling medium exists between the outer shell and the inner core of the particles. Temperature changes are used to generate bubbles or collapse the bubbles in the cavity. The generation of bubbles can reduce the particle density while increasing the particle buoyancy, and the collapse of bubbles can increase the particle density, thereby causing the particles to oscillate between the cold surface and the hot surface.

[0006] The present invention achieves the above technical objectives through the following technical means.

[0007] A device for enhancing boiling heat exchange of particle fluid comprises a cooling channel, particles and a cooling medium, wherein the cooling channel has a cold surface and a hot surface, wherein the particles and the cooling medium can flow in the cooling channel, wherein the particles comprise a particle shell and a core, wherein the core is located in the particle shell, and there is a cavity between the particle shell and the core which is connected to an external cooling medium, wherein bubbles are generated or collapsed in the cavity by temperature changes between the cold surface and the hot surface, thereby changing the particle density, and making the particles oscillate between the cold surface and the hot surface.

[0008] Furthermore, when the particles are close to a hot surface, boiling occurs in the cavity and bubbles are generated, which provide buoyancy to move the particles toward a cold surface; when the particles are away from the hot surface, the bubbles in the cavity condense and collapse, causing the particles to move toward the hot surface.

[0009] Furthermore, the inner core is composed of a phase change material wrapped by an elastic material, and the phase change material undergoes a phase change through temperature changes.

[0010] Furthermore, when the phase change material is close to a cold surface, the temperature of the phase change material is lower than the melting point of the phase change material, and the phase change material is in a solid phase; when the temperature of the phase change material exceeds the melting point of the phase change material, the phase change material is transformed from a solid phase to a liquid phase, which is used to discharge part of the cooling medium in the cavity.

[0011] Furthermore, the equivalent diameter of the particle is 0.2-2 mm, the volume ratio of the cavity to the particle is 20-60%, and the volume ratio of the core to the particle is 45-70%.

[0012] Furthermore, the inner surface of the particle shell is hydrophobic to promote bubble nucleation.

[0013] Furthermore, the contact angle of the inner surface of the particle shell is 110-170°.

[0014] Furthermore, the particle shell is shaped in one or more of spherical, ellipsoidal, and polyhedral shapes; the particle shell is made of one or more of a combination of thermally conductive metal elements, metal oxides, non-metal elements, and non-metal oxides.

[0015] The beneficial effects of the present invention are:

[0016] 1. The enhanced boiling heat exchange device for particle fluid described in the present invention has a cavity between the outer shell and the inner core of the particle that is connected to the external cooling medium. It uses temperature changes to generate bubbles or collapse bubbles in the cavity. The generation of bubbles can reduce the particle density while increasing the particle buoyancy, while the collapse of bubbles can increase the particle density, thereby promoting the oscillating movement of the particles between the cold surface and the hot surface.

[0017] 2. The enhanced boiling heat exchange device for the particle fluid described in the present invention has a core composed of a phase change material wrapped by an elastic material, so that the particles can spontaneously form an oscillating motion between the cold and hot surfaces of the cooling channel, and the phase change material will undergo a phase change between the cold and hot surfaces, making full use of the phase change ability of the phase change material to absorb latent heat. The overall density of the particles after the phase change is further reduced, thereby promoting the oscillating motion of the particles. The oscillating motion of the particles can not only improve the heat transfer efficiency between the particles and the hot surface and the cooling medium, but also collide with the bubbles on the hot surface, thereby promoting the detachment of the bubbles.

[0018] 3. In the enhanced boiling heat exchange device for particle fluid described in the present invention, the phase change degree of the phase change material wrapped by the elastic material is less affected by temperature. As long as the temperature exceeds its melting point, the phase change material can change from solid phase to liquid phase, and vice versa when the temperature is lower than that. Compared with the prior art, the expansion size of the expansion material is more affected by temperature, and when the temperature fluctuates greatly, the expansion degree is uncontrollable. The phase change material can not only absorb the latent heat of phase change and thus enhance heat transfer, but also expand its volume to reduce the overall density of the particles, thereby promoting the fluidization movement of the particles.

[0019] 4. In the enhanced boiling heat exchange device for particle fluid described in the present invention, the inner surface of the particle shell exhibits hydrophobic properties, which can promote bubble nucleation. The boiling bubbles in the particle cavity will further reduce the overall density of the particles and promote the fluidization movement of the particles. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. The drawings described below are some embodiments of the present invention. For ordinary technicians in this field, it is obvious that other drawings can be obtained based on these drawings without paying any creative work.

[0021] Figure 1 This is a schematic diagram of the enhanced boiling heat exchange device for the particle fluid described in the present invention.

[0022] Figure 2 This is a schematic diagram of the particle structure described in the present invention.

[0023] Figure 3 This is a schematic diagram of the behavior changes within the particle oscillation motion process described in the present invention.

[0024] Figure 4 This is a visualized experimental diagram of the oscillating motion behavior of particles between a hot surface and a cold surface according to the present invention.

[0025] Figure 5 The boiling heat transfer performance comparison results of the embodiment of the present invention and the prior art are shown.

[0026] In the figure:

[0027] 1-cooling channel; 2-hot surface; 3-cold surface; 4-cooling medium; 5-particles; 6-particle shell; 7-elastic material; 8-phase change material; 9-connecting hole; 10-bubble. DETAILED DESCRIPTION

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

[0029] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "axial", "radial", "vertical", "horizontal", "inner", "outer" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0030] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0031] like Figure 1As shown, the present invention comprises a cooling channel 1, particles 5 and a cooling medium 4, wherein the cooling channel 1 has a cold surface 3 and a hot surface 2, wherein the particles 5 and the cooling medium 4 can flow in the cooling channel 1, wherein the particles 5 comprise a particle shell 6 and a core, wherein the core is located in the particle shell 6, and there is a cavity between the particle shell 6 and the core that is connected to the external cooling medium 4, and through the temperature change between the cold surface 3 and the hot surface 2, bubbles are generated in the cavity or the bubbles collapse, thereby changing the density of the particles 5, so as to make the particles 5 oscillate between the cold surface 3 and the hot surface 2. By utilizing the temperature change, bubbles are generated in the cavity or the bubbles collapse, and the generation of bubbles can reduce the density of the particles 5 while increasing the buoyancy of the particles, and the collapse of bubbles can increase the density of the particles 5, thereby promoting the oscillation of the particles 5 between the cold surface and the hot surface. When the particle 5 is close to the hot surface 2, boiling occurs in the cavity and bubbles are generated. These bubbles are located between the inner core and the particle shell 6. First, they can support the inner core. More importantly, the bubbles generated in the cavity provide buoyancy for upward movement, so that the particle 5 moves toward the cold surface 3; when the particle 5 is away from the hot surface 2, the bubbles in the cavity are reduced in size until they collapse due to condensation. After the buoyancy for upward movement is lost, the particle 5 moves toward the hot surface 2.

[0032] like Figure 2 As shown, the particle 5 includes a particle shell 6 and a core, and the core is located in the particle shell 6, and can be supported in the particle shell 6 by 1-2 support columns, or it can be unsupported, so as not to affect the function of the particle 5. However, it is found through experiments that the core is not supported in the particle shell 6, and the particle 5 has a better oscillation effect between the cold surface 3 and the hot surface 2. There is a cavity between the particle shell 6 and the core, and a plurality of connecting holes 9 are provided on the particle shell 6, so that the cavity can be connected with the cooling channel 1. When boiling and generating bubbles, the bubbles can squeeze the cooling medium 4 in the cavity out of the cavity, and when the bubbles are reduced or even collapsed due to condensation, the cooling medium 4 can enter the cavity.

[0033] The inner core is composed of a phase change material 8 wrapped by an elastic material 7. The phase change material 8 undergoes a phase change through temperature changes, and the phase change can cause a change in density. The phase change material 8 will undergo a phase change between hot and cold surfaces, making full use of the phase change ability of the phase change material 8 to absorb latent heat. The overall density of the particles after the phase change is further reduced, which promotes the oscillating movement of the particles; and the oscillating movement of the particles can not only improve the heat transfer efficiency between the particles and the hot surface and the cooling medium, but also collide with the bubbles on the hot surface, thereby promoting the detachment of the bubbles. When the phase change material 8 is close to the cold surface 3, the temperature of the phase change material 8 is lower than the melting point of the phase change material, and the phase change material 8 is in a solid phase; when the temperature of the phase change material 8 exceeds the melting point of the phase change material, the phase change material 8 is transformed from a solid phase to a liquid phase, which is used to discharge the cooling medium 4 in the cavity.

[0034] like Figure 3 As shown, the particles 5 of the present invention can realize up and down oscillation motion by utilizing the temperature difference change between the cold surface 3 and the hot surface 2, and can flow in the cooling channel 1 following the flow of the cooling medium 4. Under the action of these two aspects, the motion trajectory of the particles 5 is similar to the curve of the sine function or the cosine function. The principle is: when close to the cold surface 3, the ambient temperature drops, so that the bubbles are reduced due to condensation, and the reduction of the bubbles causes the cooling medium 4 to enter the cavity. In addition, the temperature of the phase change material 8 is lower than the melting point of the phase change material, and the phase change material 8 is in a solid phase, so the particles 5 lack the buoyancy of the bubbles, and the density of the particles 5 after the solid phase is greater than the density of the cooling medium 4, so the particles 5 will sink; when close to the hot surface 2, the ambient temperature rises, the cavity boils and generates bubbles, and the bubbles can squeeze the cooling medium 4 out of the cavity, and the bubbles increase the buoyancy of the particles 5 inside the cavity; and the temperature of the phase change material 8 is higher than the melting point of the phase change material, and the phase change material 8 is in a liquid phase, and the density of the particles 5 after the liquid phase is less than the density of the cooling medium 4, so the particles 5 will rise.

[0035] The particle shell 6 is in one or more shapes of sphere, ellipsoid, and polyhedron; the material of the particle shell 6 is one or more combinations of thermally conductive metal elements, metal oxides, non-metal elements, and non-metal oxides. The equivalent diameter of the particle 5 is 0.2-2 mm, the volume ratio of the cavity to the particle 5 is 20-60%, and the volume ratio of the core to the particle 5 is 45-70%. The inner surface of the particle shell 6 is hydrophobic, which is used to promote bubble nucleation. The contact angle of the inner surface of the particle shell 6 is 110-170°.

[0036] Example

[0037] like Figure 1 As shown, the enhanced boiling heat exchange device for particle fluid described in the present invention includes a cooling channel 1, a cooling medium 4 and particles 5, wherein the cooling channel 1 has a hot surface 2 and a cold surface 3, the cooling channel 1 is a rectangular straight channel with a cross-sectional size of 10×10 mm; the cooling medium 4 is deionized water; the contact angle of the inner surface of the cooling channel 1 is 131°.

[0038] The particle 5 of the present invention comprises, from inside to outside, a phase change material 8, an elastic material 7 wrapping the phase change material, a cavity communicating with the outside, and a particle shell 6. The particle shell 6 is made of aluminum, has a diameter of 1 mm, and a contact angle of the inner surface of the particle shell 6 is 136°; a connecting hole 9 with a diameter of 0.05 mm is provided on the shell, and its volume accounts for 43% of the particle volume in the solid phase.

[0039] In the embodiment, the phase change material is EVA wax, which is made of ethylene-vinyl acetate copolymer and has a melting point of 102°C. When the ambient temperature is higher than this temperature, it changes from a solid phase to a liquid phase, and when it is lower than this temperature, it changes from a liquid phase to a solid phase.

[0040] Figure 4 This is a visualization result diagram of the oscillating motion behavior of particles between the hot surface and the cold surface. It can be seen that, first, after the particles absorb heat on the hot surface, the inside and outside of the particles will boil due to overheating and generate bubbles. As the bubbles gradually grow, when the overall density of the particles is less than that of the surrounding medium, the particles will leave the hot surface due to buoyancy and the surrounding bubbles. Due to the large density difference between the particles and the bubbles, after the particles leave, the bubbles on their outer surface separate from the particles. As the particles move upward, they will transfer heat to the surrounding fluid, and the internal bubbles will gradually collapse due to condensation, eventually resulting in a particle density less than that of the surrounding fluid, and then settling to the hot surface. In this way, the particles form a vibrating motion between the hot and cold surfaces of the channel, promoting heat transfer.

[0041] Figure 5 Comparison of boiling heat transfer coefficients of cooling media provided by the present invention, without particles and with thermal expansion and contraction particles (prior art) at different heat flux densities. It can be seen that under the same heat flux density, the boiling heat transfer coefficients are from high to low for the present invention, with thermal expansion and contraction particles and without particles. In addition, the boiling starting point is lower than that without particles in both cases containing particles, which indicates that particles are conducive to bubble nucleation.

[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 narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0043] The series of detailed descriptions listed above are only specific descriptions of feasible embodiments of the present invention. They are not intended to limit the scope of protection of the present invention. All equivalent embodiments or changes that do not deviate from the technical spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A device for enhancing boiling heat exchange of a particle fluid, comprising a cooling channel (1), particles (5) and a cooling medium (4), wherein the cooling channel (1) has a cold surface (3) and a hot surface (2), and the particles (5) and the cooling medium (4) can flow in the cooling channel (1), characterized in that: The particle (5) comprises a particle shell (6) and a core, wherein the core is located inside the particle shell (6), and a cavity is present between the particle shell (6) and the core, which is connected to an external cooling medium (4). The temperature change between the cold surface (3) and the hot surface (2) causes bubbles to be generated or collapsed in the cavity, thereby changing the density of the particle (5), so as to cause the particle (5) to oscillate between the cold surface (2) and the hot surface.

2. The enhanced boiling heat exchange device for particle fluid according to claim 1, characterized in that: When the particle (5) approaches the hot surface (2), boiling occurs in the cavity and bubbles are generated, which provide buoyancy to enable the particle (5) to move toward the cold surface (3); when the particle (5) moves away from the hot surface (2), the bubbles in the cavity condense and collapse, causing the particle (5) to move toward the hot surface (2).

3. The enhanced boiling heat exchange device for particle fluid according to claim 1, characterized in that: The inner core is composed of a phase change material (8) wrapped by an elastic material (7), and the phase change material (8) undergoes a phase change through temperature changes.

4. The enhanced boiling heat exchange device for particle fluid according to claim 2, characterized in that: When the phase change material (8) is close to the cold surface (3), the temperature of the phase change material (8) is lower than the melting point of the phase change material, and the phase change material (8) is in a solid phase; when the temperature of the phase change material (8) exceeds the melting point of the phase change material, the phase change material (8) is transformed from a solid phase to a liquid phase, and is used to discharge part of the cooling medium (4) in the cavity.

5. The enhanced boiling heat exchange device for particle fluid according to claim 1, characterized in that: The equivalent diameter of the particle (5) is 0.2-2 mm, the volume ratio of the cavity to the particle (5) is 20-60%, and the volume ratio of the core to the particle (5) is 45-70%.

6. The enhanced boiling heat exchange device for particle fluid according to claim 1, characterized in that: The inner surface of the particle shell (6) is hydrophobic in nature, so as to promote bubble nucleation.

7. The enhanced boiling heat exchange device for particle fluid according to claim 6, characterized in that: The contact angle of the inner surface of the particle shell (6) is 110-170°.

8. The enhanced boiling heat exchange device for particle fluid according to claim 1, characterized in that: The particle shell (6) is in the shape of one or more of a sphere, an ellipsoid, and a polyhedron; the material of the particle shell (6) is a combination of one or more of a thermally conductive metal element, a metal oxide, a non-metal element, and a non-metal oxide.

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