Micro-channel evaporator

Abstract

The invention provides a micro-channel evaporator, comprising: a micro-channel substrate, a bottom plate of which is provided with a plurality of parallel micro-channels; the bottom surface of the micro-channel substrate is used for being in contact with a heat source; the countercurrent suppression device is arranged above the micro-channel and seals the top surface of the micro-channel; the countercurrent suppression device comprises a plurality of groups of sub-runners, and the sub-runners are arranged in the working medium flowing direction of the micro-channel; an included angle between the flow-in direction of the initial end of the sub-channel and the working medium flow forward direction of the micro-channel is an obtuse angle; an included angle between the flowing-out direction of the tail end of the sub-channel and the working medium flowing forward direction of the micro-channel is an acute angle or zero degree; the starting ends and the tail ends of the sub-runners are positioned at the bottom ends of the sub-runners; and the starting ends and the tail ends of the same group of sub-channels are sequentially distributed along the working medium flowing forward direction of the micro-channel. According to the technical scheme, the reverse flow resistance is large, steam reverse flow of the micro-channel evaporator is restrained, a liquid-phase working medium stably flows in the forward direction, the channel density is not affected, and the heat transfer limit of the micro-channel evaporator is improved.

Description

Technical Field

[0001] The invention relates to the technical field of microchannels, and in particular to a microchannel evaporator. Background Art

[0002] The microchannel evaporator is the core component of the pump-driven two-phase flow cooling system. It has the advantages of good temperature uniformity, strong heat dissipation capacity and small size. It has broad application prospects in aerospace thermal control systems, large-scale electronic integrated circuits and other fields. It is the preferred solution to solve the heat dissipation problem of high heat flux density in highly integrated electronic equipment.

[0003] However, under high heat flux density, due to the restriction of the flow channel, the steam generated by flow boiling in the conventional evaporator with multiple parallel microchannels diffuses upstream and downstream at the same time, resulting in a backflow of steam to the channel entrance. The backflow of steam may cause the liquid phase working fluid flow to be unable to be stably supplied, causing the heat transfer of the evaporator to deteriorate, resulting in the problem of premature evaporation of the flow channel.

[0004] Some researchers have designed a microchannel evaporator based on the Tesla valve principle, which has the function of suppressing the backflow of gas-phase working fluid. However, due to the space occupied by the additional Tesla valve structure in the width direction of the microchannel, the number of microchannels that can be accommodated within the same width is small, that is, the flow channel density for the forward flow of liquid-phase working fluid is small, which is not conducive to the application of high heat flux density heat dissipation scenarios. Summary of the invention

[0005] The present invention provides a micro-channel evaporator to solve the problems of steam counter-flow or low channel density in the prior art.

[0006] In order to solve the above technical problems, the present invention is achieved through the following technical solutions:

[0007] The present invention provides a microchannel evaporator, comprising:

[0008] A microfluidic channel substrate, on the bottom plate of which a plurality of parallel microfluidic channels are arranged; the bottom surface of the microfluidic channel substrate is used to contact with a heat source;

[0009] A backflow suppression device, which is disposed above the microchannel and forms a closed structure with the top surface of the microchannel;

[0010] The backflow suppression device comprises a plurality of flow channels, wherein the plurality of flow channels are arranged at intervals along the flow direction of the working medium in the micro-channel;

[0011] The angle between the inflow direction of the start end of the branch channel and the positive direction of the working medium flow of the microchannel is an obtuse angle; the angle between the outflow direction of the end end of the branch channel and the positive direction of the working medium flow of the microchannel is an acute angle or zero degree;

[0012] The start and the end of the branch channel are located at the bottom of the branch channel; along the forward direction of the working medium flow of the microchannel, the start and the end of the branch channel of the same group are distributed in sequence.

[0013] Optionally, the backflow suppression device comprises: a backflow suppression module and a cover plate; the flow diversion channel is formed by the backflow suppression module and the cover plate;

[0014] The backflow suppression module is located between the cover plate and the microfluidic channel substrate, and the gap between the backflow suppression module and the cover plate forms the branch channel.

[0015] Optionally, the angle between the outflow direction of the end of the branch channel and the forward direction of the working medium flow in the microchannel is any value between 20° and 30°.

[0016] Optionally, the microfluidic channel has a bend on a plane perpendicular to the bottom surface of the microfluidic channel substrate and parallel to the flow direction of the working medium;

[0017] On a plane perpendicular to the bottom surface of the microfluidic substrate, along the positive direction of the working fluid flow of the microfluidic channel, between the end of the previous branch channel and the beginning of the next branch channel, the microfluidic channel is inclined downward so that the angle between the outflow direction of the end of the branch channel and the positive direction of the working fluid flow of the microfluidic channel is smaller than the angle between the two when the microfluidic channel is parallel to the bottom surface of the microfluidic substrate.

[0018] Optionally, the transition between the start and end of the branch channel includes an arc transition.

[0019] Optionally, on a plane perpendicular to the bottom surface of the microfluidic channel substrate and parallel to the flow direction of the working medium, the cross-section of the flow branch channel is shaped like a water droplet;

[0020] The tip of the water drop shape faces the outlet of the micro-channel.

[0021] Optionally, the straight line length between the starting end of the branch channel and the arc transition is less than or equal to 10 times the hydraulic diameter of the microchannel.

[0022] Optionally, each group of the flow diversion channels includes a plurality of flow diversion branches, and each flow diversion branch corresponds to one of the micro-channels.

[0023] Optionally, adjacent diversion branches of each group of diversion channels are separated by a retaining wall.

[0024] Optionally, the cross-section of the microchannel is rectangular, triangular or arc-shaped.

[0025] The microchannel evaporator provided by the present invention has a backflow suppression device arranged above the microchannel, which has a branch channel for suppressing steam backflow. For forward flow, when the working medium flows through the beginning of the branch channel, since the angle is an obtuse angle, only a small amount of fluid will enter the branch channel. At the end of the branch channel, since the angle is an acute angle or zero degrees, the flow directions are basically consistent, and the fluids can converge at the end. Therefore, the flow resistance of the forward flow is small; for reverse flow, when the working medium passes through the end of the branch channel, since the angle is an acute angle or zero degrees, more fluid flows into the branch channel. At the beginning of the branch channel, the fluids in the branch channel and the microchannel meet, resulting in a large energy loss. After passing through multiple backflow suppression devices, the energy losses are superimposed. Therefore, the flow resistance of the reverse flow is large. The liquid-phase working fluid flows forward in the microchannel, absorbs heat from the heat source, and evaporates into a gas-phase working fluid. Due to the restrictive effect of the microchannel, the gas-phase working fluid expands toward the inlet and outlet of the microchannel at the same time, that is, it flows toward the outlet and countercurrently toward the inlet at the same time. As analyzed above, the microchannel evaporator of the present invention has a large reverse flow resistance, which suppresses the steam countercurrent of the microchannel evaporator, allowing the liquid-phase working fluid to flow forward stably, thereby improving the heat dissipation limit of the evaporator.

[0026] The microchannel evaporator provided by the present invention has a branch channel located on a plane perpendicular to the bottom surface (i.e., the heating surface) of the microchannel substrate, does not occupy the space where multiple microchannels are arranged in parallel, and the channel density for the forward flow of the liquid phase working medium is equivalent to that of conventional parallel microchannels. Compared with the general microchannel with an added Tesla valve structure, the channel density is larger, and can be used in heat dissipation scenarios with higher heat flux density, and has a wide range of applications.

[0027] In an optional scheme of the present invention, on a plane perpendicular to the bottom surface of the microfluidic substrate, along the positive direction of the working fluid flow of the microfluidic channel, the microfluidic channel is inclined downward between the end of the previous branch channel and the beginning of the next branch channel, so that the angle between the outflow direction of the end of the branch channel and the positive direction of the working fluid flow of the microfluidic channel can be smaller than the angle between the two when the microfluidic channel is parallel to the bottom surface of the microfluidic substrate, and the optimal angle can be zero degrees. At this time, the end of the branch channel is in the same straight line as the microfluidic channel, and the countercurrent gas-phase working fluid can more easily enter the branch channel from the end, resulting in greater energy loss at the beginning, further improving the backflow suppression effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] 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. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0029] Figure 1It is a schematic diagram of the whole direction of a microchannel evaporator according to an embodiment of the present invention;

[0030] Figure 2 It is an overall schematic diagram of a microchannel evaporator in another direction according to an embodiment of the present invention;

[0031] Figure 3 A cross-sectional view along the AA direction of a microchannel evaporator according to an embodiment of the present invention;

[0032] Figure 4 A side view of a microchannel and a branch channel of a preferred embodiment of the present invention;

[0033] Figure 5 A side view of a microchannel and a branch channel of another preferred embodiment of the present invention;

[0034] Figure 6 An exploded view of a microchannel evaporator according to a preferred embodiment of the present invention;

[0035] Figure 7 A perspective view of a microchannel evaporator according to a preferred embodiment of the present invention;

[0036] Figure 8 A cross-sectional view along the AA direction of a microchannel evaporator of a preferred embodiment of the present invention;

[0037] Fig. 9 An exploded view of a microchannel evaporator according to another preferred embodiment of the present invention;

[0038] Fig.10 A perspective view of a microchannel evaporator according to another preferred embodiment of the present invention;

[0039] Fig.11 A side view of a microchannel and a flow branch channel of another preferred embodiment of the present invention;

[0040] Fig.12 An exploded view of a microchannel evaporator according to another preferred embodiment of the present invention;

[0041] Fig.13 A perspective view of a microchannel evaporator according to another preferred embodiment of the present invention;

[0042] Fig.14 A schematic diagram of a backflow suppression device and a retaining wall of a microchannel evaporator according to another preferred embodiment of the present invention;

[0043] Fig.15a is a cross-sectional view of a microfluidic channel according to an embodiment of the present invention;

[0044] Fig.15b is a cross-sectional view of a microfluidic channel according to another embodiment of the present invention;

[0045] Fig.15c is a cross-sectional view of a microfluidic channel according to another embodiment of the present invention;

[0046] Description of reference numerals:

[0047] 1-microfluidic substrate;

[0048] 11- microfluidic channel;

[0049] 2-Backflow suppression device;

[0050] 201-diversion channel;

[0051] 21-backflow inhibition module;

[0052] 22-cover plate;

[0053] 3- Heat source,

[0054] 4- Retaining wall,

[0055] 5-Card slot. DETAILED DESCRIPTION

[0056] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0057] In the description of the specification of the present invention, it is necessary to understand that the orientation or position relationship indicated by the terms "upper part", "lower part", "upper end", "lower end", "lower surface", "upper surface", etc. is based on the orientation or position relationship shown in the drawings, and is 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 a limitation on the present invention.

[0058] In the description of the present specification, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features.

[0059] In the description of the present invention, "plurality" means a plurality, such as two, three, four, etc., unless otherwise clearly and specifically defined.

[0060] In the description of the present invention, unless otherwise clearly specified and limited, the term "connection" and other terms 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, an electrical connection, or mutual communication; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0061] The technical solution of the present invention is described in detail with specific embodiments below. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.

[0062] In one embodiment, a microchannel evaporator is provided, please refer to Figure 1 , Figure 2 , Figure 3 , which comprises: a microfluidic substrate 1 and a backflow suppression device 2. A plurality of parallel microfluidic channels 11 are arranged on the bottom plate of the microfluidic substrate; the bottom surface of the microfluidic substrate is used to contact with a heat source 3. The backflow suppression device 2 is arranged above the microfluidic channel 11 and closes the top surface of the microfluidic channel 11.

[0063] The backflow suppression device 2 includes a multi-component flow channel 201, please refer to Figure 3 , the multi-component flow channels 201 are arranged at intervals along the working medium flow direction of the micro-channel. Please refer to Figure 4 , the angle α between the inflow direction of the start A of the split channel and the positive direction of the working fluid flow of the microchannel (solid arrow in the figure) is an obtuse angle; the angle β between the outflow direction of the end B of the split channel and the positive direction of the working fluid flow of the microchannel is an acute angle or zero. The start A of the split channel and the end B of the split channel are located at the bottom of the split channel; and along the positive direction of the working fluid flow of the microchannel, the start A and the end B of the same component flow channel are distributed in sequence.

[0064] The countercurrent suppression principle of the microchannel evaporator in the above embodiment is: Figure 4For forward flow (indicated by the solid arrow in the figure), when the working fluid flows through the beginning A of the shunt channel, since the angle α is an obtuse angle, only a small amount of fluid will enter the shunt channel. At the end B of the shunt channel, since the angle β is an acute angle or zero degrees, the flow directions of the shunt channel and the microchannel are basically the same, and the fluid can converge at the end B. Therefore, the flow resistance of the forward flow is small. For reverse flow (indicated by the dotted arrow in the figure), when the working fluid passes through the end B of the shunt channel, since the angle is an acute angle or zero degrees, more fluid flows into the shunt channel. At the beginning A of the shunt channel, the fluids of the shunt channel and the microchannel meet, resulting in a large energy loss. After passing through multiple backflow suppression devices, the above process is repeated, and multiple large energy losses are superimposed. Therefore, the flow resistance of the reverse flow is large. The liquid-phase working fluid flows forward in the microchannel, absorbs heat from the heat source, and evaporates into a gas-phase working fluid. Due to the restrictive effect of the microchannel, the gas-phase working fluid expands toward the inlet and outlet of the microchannel at the same time, that is, it flows toward the outlet and countercurrently toward the inlet at the same time. As analyzed above, the microchannel evaporator in the embodiment of the present invention has a large reverse flow resistance, which suppresses the steam countercurrent of the microchannel evaporator, allowing the liquid-phase working fluid to flow forward stably, thereby improving the heat dissipation limit of the evaporator.

[0065] In one embodiment, the starting end A of the flow branch channel and the ending end B of the flow branch channel are in contact with the top surface of the micro-channel.

[0066] In order to reduce the flow resistance of the fluid in the branch channel, the transition between the start and end of the branch channel can be set as an arc transition.

[0067] In practice, on a plane perpendicular to the bottom surface of the microfluidic substrate and parallel to the flow direction of the working medium, the cross section of the branch channel is similar to a water droplet; the tip of the water droplet is directed toward the outlet of the microfluidic channel, such as Figure 4 , Figure 5 As shown. Figure 4 As shown, the flow channel may also include a straight line segment L1 plus an arc transition segment. Figure 5 As shown, the flow branch channel may also include a straight line segment L1 plus an arc transition segment plus a straight line segment L3.

[0068] In one embodiment, for the convenience of operation, the backflow suppression device 2 can be set as a split structure. Specifically, it includes: a backflow suppression module 21 and a cover plate 22; the split flow channel is formed by the backflow suppression module 21 and the cover plate 22, please refer to 6, Figure 7 , Figure 8 The backflow suppression module 21 is located between the cover plate 22 and the microfluidic channel substrate 1 , and the gap between the backflow suppression module 21 and the cover plate 22 forms a flow branch channel 201 .

[0069] In different embodiments, the backflow suppression device 2 may also be an integrated structure, that is, the backflow suppression module and the cover plate are an integrated structure.

[0070] In one embodiment, the angle between the outflow direction of the end of the branch channel and the forward direction of the working medium flow in the microchannel is any value between 20° and 30°.

[0071] In one embodiment, the microchannel is curved on a plane perpendicular to the bottom surface of the microchannel substrate, and the curvature of the microchannel is consistent with the distribution of the branch channel. Fig. 9 , Fig.10 , Fig.11 . On a plane perpendicular to the bottom surface of the microfluidic substrate, along the positive direction of the working fluid flow of the microfluidic channel, the microfluidic channel is tilted downward between the end of the previous branch channel and the beginning of the next branch channel, so that the angle between the outflow direction at the end of the branch channel and the positive direction of the working fluid flow of the microfluidic channel is smaller than the angle between the two when the microfluidic channel is parallel to the bottom surface of the microfluidic substrate. If the downward tilt angle is appropriate, the angle between the outflow direction at the end of the branch channel and the positive direction of the working fluid flow of the microfluidic channel can be reduced to zero, that is, the outflow direction at the end of the microfluidic channel is consistent with the positive direction of the working fluid flow of the microfluidic channel, such as Fig.11 shown.

[0072] It can be implemented that along the working medium flow direction of the microchannel, the multi-component flow channels are evenly distributed, so that the bends of the above-mentioned microchannels are regular bends, such as Fig. 9 , Fig.10 shown.

[0073] In the above embodiment, the multi-component flow channels are arranged at even intervals. In different embodiments, the multi-component flow channels may also be arranged at uneven intervals.

[0074] In one embodiment, each group of flow channels includes a plurality of flow branches, each flow branch corresponds to a micro-channel, please refer to Fig.12 .

[0075] In practice, adjacent flow branches of each group of flow channels are separated by a retaining wall 4, see Fig.13 , Fig.14 The position of the retaining wall corresponds to the wall surface between adjacent microchannels, so that the branch channels corresponding to each microchannel are independent of each other.

[0076] The retaining wall 4 may be connected to the backflow suppression module below or be an integrated structure; it may also be connected to the cover plate above or be an integrated structure.

[0077] Of course, in different embodiments, each group of flow channels can also be a whole, and the whole corresponds to each micro-channel, so there is no need to separate them with a retaining wall. Please refer to Figure 6 .

[0078] In one embodiment, the straight line length L1 between the end B of the branch channel and the arc transition (eg Figure 4 As shown) is less than or equal to 10 times the hydraulic diameter D of the microchannel.

[0079] In one embodiment, a straight-line distance L2 between an end B and a start A of the branch channel is less than or equal to 10 times the hydraulic diameter of the microchannel.

[0080] In one embodiment, the cross section of the microchannel may be a rectangle. Fig.15a ; It can also be a triangle, please refer to Fig.15b ; It can also be an arc shape, please refer to Fig.15c .

[0081] In one embodiment, the hydraulic diameter D of the microchannel is less than 2 mm.

[0082] In one embodiment, the distance between adjacent microchannels is less than or equal to 2 mm.

[0083] In one embodiment, the backflow suppression module can be fixed in the form of a card slot 5, please refer to Figure 6 , Fig. 9 , Fig.14 .

[0084] In different embodiments, the backflow suppression module may also be fixed by welding.

[0085] In one embodiment, the microfluidic substrate can be made of metal, metal alloy, diamond and other materials, which have better thermal conductivity.

[0086] In one embodiment, the backflow suppression device can be made of materials such as metal, metal alloy, diamond, glass, and high temperature resistant plastic.

[0087] In the description of this specification, the description with reference to the terms "an implementation", "an example", "a specific implementation process", "an example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A microchannel evaporator, It is characterized in that include: A microfluidic channel substrate, on which a plurality of parallel microfluidic channels are arranged; the bottom surface of the microfluidic channel substrate is used to contact with a heat source; A backflow suppression device, which is disposed above the microchannel and seals the top surface of the microchannel; The backflow suppression device comprises a plurality of flow channels, wherein the plurality of flow channels are arranged at intervals along the flow direction of the working medium in the micro-channel; The angle between the inflow direction of the start end of the branch channel and the positive direction of the working medium flow of the microchannel is an obtuse angle; the angle between the outflow direction of the end end of the branch channel and the positive direction of the working medium flow of the microchannel is an acute angle or zero degree; The start and the end of the branch channel are located at the bottom of the branch channel; along the forward direction of the working medium flow of the microchannel, the start and the end of the branch channel of the same group are distributed in sequence.

2. The microchannel evaporator according to claim 1, It is characterized in that The backflow suppression device comprises: a backflow suppression module and a cover plate; the flow diversion channel is formed by the backflow suppression module and the cover plate; The backflow suppression module is located between the cover plate and the microfluidic channel substrate, and the gap between the backflow suppression module and the cover plate forms the branch channel.

3. The microchannel evaporator according to claim 1, It is characterized in that The angle between the outflow direction of the end of the branch channel and the forward direction of the working medium flow of the microchannel is any value between 20° and 30°.

4. The microchannel evaporator according to claim 1, It is characterized in that The microchannel has a bend on a plane perpendicular to the bottom surface of the microchannel substrate and parallel to the flow direction of the working medium; On a plane perpendicular to the bottom surface of the microfluidic substrate, along the positive direction of the working fluid flow of the microfluidic channel, between the end of the previous branch channel and the beginning of the next branch channel, the microfluidic channel is inclined downward so that the angle between the outflow direction of the end of the branch channel and the positive direction of the working fluid flow of the microfluidic channel is smaller than the angle between the two when the microfluidic channel is parallel to the bottom surface of the microfluidic substrate.

5. The microchannel evaporator according to claim 1, It is characterized in that The start and end of the branch channel include arc transitions.

6. The microchannel evaporator according to claim 5, It is characterized in that On a plane perpendicular to the bottom surface of the microfluidic channel substrate and parallel to the flow direction of the working medium, the cross section of the branch channel is similar to a water drop shape; The tip of the water drop shape faces the outlet of the micro-channel.

7. The microchannel evaporator according to claim 5, It is characterized in that The straight line length between the end of the branch channel and the arc transition is less than or equal to 10 times the hydraulic diameter of the microchannel.

8. The microchannel evaporator according to claim 1, It is characterized in that Each group of the flow diversion channels includes a plurality of flow diversion branches, and each flow diversion branch corresponds to one of the micro-flow channels.

9. The microchannel evaporator according to claim 8, It is characterized in that Adjacent flow diversion branches of each group of the flow diversion channels are separated by a retaining wall.

10. The microchannel evaporator according to any one of claims 1 to 9, It is characterized in that The cross section of the microchannel is rectangular, triangular or arc-shaped.

Images