Bidirectional countercurrent micro-channel structure, micro-channel assembly, test fixture and assembly method

Abstract

The invention provides a bidirectional countercurrent micro-channel structure, a micro-channel assembly, a test fixture and an assembly method.The upper surface of the bidirectional countercurrent micro-channel structure comprises two sets of cooling channels which are arranged in parallel and alternately, each cooling channel is arranged independently, and inlets of the two sets of cooling channels are located in opposite directions; and the outlet of each group of cooling channels is communicated with a lumped outlet in the side wall of the micro-channel structure through two turns. The micro-channel structure adopts a bidirectional reverse flow type design, all micro-channels are located on the same heat dissipation datum plane, heat transfer enhancement, pressure drop reduction and boiling instability suppression can be achieved, and the micro-channel structure is high in reliability, high in stability, wide in applicability and capable of being applied to heat dissipation of micro equipment / parts.

Description

Technical Field

[0001] The invention belongs to the technical field of microscale heat dissipation, and in particular relates to a bidirectional countercurrent microchannel structure, a microchannel component, a test fixture and an assembly method. Background Art

[0002] With the development of the information age, electronic technology has been widely used in all areas of human daily life. Restricted by the conditions of the equipment itself, the device will inevitably generate a lot of waste heat when it is powered on. It is worth noting that the reliability of electronic devices is directly related to the temperature of the device. Taking GaN devices as an example, for every 20°C increase in chip temperature, the mean failure-free time of GaN devices will drop by an order of magnitude. At the level of 70-80°C, the reliability of the chip decreases by 5% for every 1°C increase. For every 10°C increase, the life of the capacitor decreases by 50%. In addition, high temperature will also reduce the insulation performance of devices such as inductors, transformers, and chokes, and even cause the equipment to burn out. In view of this, thermal management has become a key technology to ensure the working performance and reliability of electronic equipment and to develop new electronic devices.

[0003] The idea of ​​microchannel flow heat dissipation has been considered the most promising method for heat dissipation of micro-devices since it was proposed. The supercooled fluid flows directly into the microchannel and comes into direct contact with the overheated object, thereby removing heat through heat conduction and convection. Compared with conventional heat dissipation methods such as pool boiling, spray cooling, and air cooling, microchannels have the advantages of large specific surface area, high heat transfer efficiency per unit area, strong heat treatment capacity, easy processing, and miniaturization. At present, microchannel heat dissipation technology has been widely used in aerospace, new energy vehicles, wind power generation, computing centers, smart grids and other fields.

[0004] Although flow boiling heat transfer in microchannels has great potential and broad application prospects for the heat dissipation process of electronic chips, it still faces very severe challenges. On the one hand, due to the increasing integration density of transistors in microelectronic chips, the heat flux density generated is continuously increasing; at the same time, the heat distribution on the chip surface is not uniform, and the excessive heat flux density at local sites leads to the generation of hot spots, which seriously threatens the uniformity of chip surface temperature. In the single-phase flow process, the phenomenon that the temperature gradually rises along the flow channel is inevitable. In the boiling two-phase flow process, the cavitation rate and dryness cannot violate the objective physical laws and gradually increase along the flow channel, which will lead to extremely uneven temperature on the chip surface. Under extreme conditions, it may even exceed tens of degrees Celsius, which is difficult for most electronic devices to bear. On the other hand, severe flow boiling instability is difficult to control, which is also difficult to meet the stringent temperature requirements of electronic components, and the corresponding internal flow boiling regulation mechanism is still unclear. Therefore, while improving the heat dissipation capacity of the microchannel heat sink as much as possible, achieving surface temperature regulation, avoiding premature drying up of the downstream, reducing the two-phase pressure drop and suppressing boiling instability, further exploring the heat transfer mechanism of microscale flow boiling, especially its complex heat and mass transfer laws and regulation mechanisms, not only has important practical significance for solving practical engineering problems, but is also an important way to promote the in-depth development of related disciplines.

[0005] In addition, given the design and difficulty of countercurrent microchannels, the current design and research are still in the initial stage, and the understanding of its flow boiling process is very limited, mostly staying at the double-layer countercurrent microchannel, long flow path countercurrent microchannel and manifold countercurrent microchannel. On the one hand, for manifold countercurrent microchannels and double-layer countercurrent microchannels, the heat dissipation ratio of the lower layer close to the heat source and the upper layer far away from the heat source is difficult to estimate, the heat transfer difference between the layers is large, there is a large contact thermal resistance between the upper and lower layers, and there is a large overall packaging difficulty, which brings great difficulty to the application of countercurrent microchannels; on the other hand, the long flow path (loop) countercurrent microchannel has a significant reduction in its heat dissipation effect due to the increase in its flow path, forcing it to be applied only to single-phase flow conditions, and the space utilization rate on the same heat dissipation reference plane is extremely low. Referring to the above two difficulties, the application of bidirectional countercurrent microchannels is still in the demonstration stage. Summary of the invention

[0006] The present invention aims to solve one of the above technical problems and provides a bidirectional countercurrent microchannel structure, a microchannel assembly, a test fixture and an assembly method. The microchannel structure adopts a countercurrent design and constructs a bidirectional countercurrent microchannel corresponding to a traditional parallel microchannel on a single heat dissipation reference plane, which can enhance heat transfer, reduce pressure drop, and suppress boiling instability, and has high reliability, strong stability, wide applicability, and high space utilization. At the same time, the microchannel has low processing difficulty, low contact thermal resistance, low packaging difficulty, and low space occupancy, which can be directly compared with the traditional parallel microchannel, and can be applied to the heat dissipation of micro devices / components.

[0007] The technical solution adopted by the present invention to solve the above technical problems is as follows:

[0008] The present invention provides a bidirectional countercurrent microchannel structure, wherein the upper surface of the microchannel structure includes two groups of parallel, alternately arranged cooling channels, each cooling channel is independently arranged, the inlets of the two groups of cooling channels are located in opposite directions, and the outlet of each group of cooling channels is connected to a lumped outlet on the side wall of the microchannel structure through two turns. In the present invention, all microchannels are located on the same heat dissipation reference plane (i.e., the upper surface of the microchannel structure), there is no multi-layer microchannel configuration, and there is no microchannel reverse loop, which enhances the heat dissipation effect, reduces the pressure drop, suppresses boiling instability, and has high reliability, strong stability, wide applicability, and high space utilization.

[0009] Furthermore, the outlet of each group of cooling channels is connected to a lumped outlet on the side wall of the microchannel structure through two 90-degree turns, and the outlet of each group of cooling channels is connected to a vertical channel perpendicular to the cooling channels and downward, and a horizontal channel connected to the lumped outlet and perpendicular to the cooling channels;

[0010] The two lumped outlets corresponding to the two groups of cooling channels are located on the same side wall of the microchannel structure, and the cross section of the cooling channel is a square cross section.

[0011] Furthermore, the side wall of the microchannel structure also includes a plurality of thermocouple placement holes, in which thermocouples are installed for real-time monitoring of the temperature of the microchannel structure and controlling the flow rate of the cooling medium in the cooling channel according to the heat flux density;

[0012] The thermocouple placement hole is located on a side of the microchannel structure that is away from the lumped outlet;

[0013] An air slit is arranged between two adjacent thermocouple placement holes along the cooling channel direction.

[0014] Furthermore, the bottom of the microchannel structure includes a plurality of heating rod placement holes, and the heating rod placement holes are equipped with heating rods, which are used as heat sources in the microchannel structure test process.

[0015] The present invention also provides a microchannel component, comprising a bidirectional countercurrent microchannel structure and a flow layer, wherein the microchannel structure is embedded in the flow layer, and the flow layer comprises two inlets connected to the cooling channel inlet and two outlets connected to the lumped outlet;

[0016] The upper surface of the flow layer is provided with a first inlet header, a second inlet header, a first outlet header, and a second outlet header. The first inlet header and the second inlet header are respectively located between the inlets of the two groups of cooling channels of the microchannel structure and the inlet of the flow layer, and simultaneously replenish cooling medium for the two groups of cooling channels. The first outlet header and the second outlet header are respectively located between the two lumped outlets of the microchannel structure and the outlet of the flow layer.

[0017] Further, the widths of the first inlet header, the second inlet header, the first outlet header, and the second outlet header are not less than the width of the microchannel structure perpendicular to the cooling channel direction;

[0018] The upper surface of the fluidized bed further comprises a first shallow groove and a second shallow groove, wherein the first shallow groove is located between the first inlet header and a group of cooling channel inlets, and the second shallow groove is located between the second inlet header and another group of cooling channel inlets;

[0019] The depth of the first shallow groove and the second shallow groove is less than the depth of the first inlet header and the second inlet header, and is greater than or equal to the depth of the cooling channel.

[0020] The present invention also provides a test fixture of a bidirectional countercurrent microchannel structure, comprising a base, an electrical insulation layer, a heat insulation layer, a flow layer, a visualization layer, and a cover plate which are fixedly connected in sequence from bottom to top, wherein the upper surface of the electrical insulation layer comprises a first groove, the centers of the heat insulation layer and the flow layer comprise through holes, and the lower surface of the visualization layer comprises a second groove;

[0021] The microchannel structure is placed in the first groove and passes through the through holes of the heat insulation layer and the flow layer. The second groove is sealed and connected to the upper surface of the microchannel structure. The cover plate includes a through window matching the position of the second groove.

[0022] The flow layer includes two inlets communicating with the cooling channel inlets, and two outlets communicating with the lumped outlet.

[0023] Furthermore, a first inlet header, a second inlet header, a first outlet header, and a second outlet header are provided on the upper surface of the flow layer. The first inlet header and the second inlet header are respectively located between the inlets of the two groups of cooling channels of the microchannel structure and the inlet of the flow layer, and cooling medium is replenished for the two groups of cooling channels at the same time. The first outlet header and the second outlet header are respectively located between the two lumped outlets of the microchannel structure and the outlet of the flow layer.

[0024] The widths of the first inlet header, the second inlet header, the first outlet header, and the second outlet header are not less than the width of the microchannel structure perpendicular to the cooling channel direction.

[0025] Furthermore, the upper surface of the fluidized bed further comprises a first shallow groove and a second shallow groove, wherein the first shallow groove is located between the first inlet header and a group of cooling channel inlets, and the second shallow groove is located between the second inlet header and another group of cooling channel inlets;

[0026] The depth of the first shallow groove and the second shallow groove is less than the depth of the first inlet header and the second inlet header, and is greater than or equal to the depth of the cooling channel.

[0027] Furthermore, the thermocouple placement hole on the side of the flow layer corresponding to the microchannel structure also includes a thermocouple through hole for installing a thermocouple;

[0028] The first inlet header, the second inlet header, the first outlet header and the second outlet header of the fluidized bed are provided with thermocouple holes and pressure measuring holes, and thermocouples and pressure gauges are installed to measure the temperature and pressure of the inlet and outlet cooling medium;

[0029] The base and the electrical insulation layer are both provided with heating rod through holes for installing the heating rod.

[0030] Furthermore, a limiting structure is provided on the microchannel structure so that the upper surface of the microchannel structure and the upper surface of the flow layer are located in the same plane;

[0031] The microchannel structure and the flow layer are sealed with sealant.

[0032] Furthermore, the base, the electrical insulation layer, the heat insulation layer, the flow layer, the visualization layer, and the cover plate are all provided with a plurality of through holes for bolt connection;

[0033] The base and cover are made of stainless steel, the electrical insulation layer is made of bakelite, the flow layer and heat insulation layer are made of glass fiber, and the visualization layer is made of highly transparent polycarbonate (PC) material with a light transmittance of more than 90%;

[0034] The microchannel structure is made of red copper and is installed on the structure to be cooled as a heat sink.

[0035] The present invention also provides a method for assembling a test fixture of a bidirectional countercurrent microchannel structure, comprising the following steps:

[0036] Align the insulation layer with the base, assemble the heating rod, and lay the cables;

[0037] Embed the heating rod into the bottom of the microchannel structure, and fix the microchannel structure in the first groove of the insulating layer;

[0038] The heat insulation layer and the flow layer are sequentially installed outside the microchannel structure;

[0039] Install the visualization layer and cover plate in sequence and align them;

[0040] The test fixture is fixed with bolts.

[0041] The beneficial effects of the present invention compared with the prior art are as follows:

[0042] (1) The present invention designs a bidirectional countercurrent microchannel structure, which can significantly improve the heat transfer characteristics on the same heat dissipation reference surface and effectively suppress boiling instability. At the same time, the bidirectional countercurrent microchannel proposed by the present invention has the advantages of simple processing and manufacturing, high stability, good reliability, etc., which makes it more in line with the needs of practical applications.

[0043] (2) The critical heat flux density of the flow boiling process in the microchannel increases with the increase of mass flow rate and inlet subcooling. Compared with the traditional co-current parallel microchannel, the bidirectional countercurrent microchannel can achieve a significant reduction in wall temperature under the same heat flux density. The outlet dryness of the co-current parallel microchannel when reaching the critical heat flux density decreases with the increase of mass flow rate, and the actual fluid boiling efficiency also decreases accordingly. The maximum outlet dryness of the bidirectional countercurrent microchannel basically does not change with the mass flow rate. Under different inlet subcooling degrees and mass flow rates, the critical heat flux density of the countercurrent microchannel can be greatly improved.

[0044] (3) In view of the advantages of the adjacent wall cooling mechanism, the bidirectional countercurrent microchannel can achieve good wall surface temperature uniformity at low heat flux density. The increase of temperature, cavitation rate and dryness along the flow direction makes it impossible for the downstream parallel microchannel to ensure excellent wall surface temperature uniformity in the single-phase flow stage and near the critical heat flux density. Since there is a temperature difference between the two ends and the center of the microchannel, and the temperature difference increases with the increase of heat flux density, the overall temperature uniformity of the bidirectional countercurrent microchannel decreases with the increase of heat flux density.

[0045] (4) The pressure drop on both sides of the bidirectional countercurrent microchannel can be controlled by the distribution of mass flow rate. When the mass flow rate in the countercurrent microchannel is unevenly distributed, the pressure drop deviation on both sides is large in the single-phase flow stage and the convective boiling stage under high heat flux density, while the pressure drop deviation on both sides is relatively small in the nucleate boiling stage, and the maximum pressure drop deviation is proportional to the flow deviation.

[0046] (5) The wall temperature distribution and local high / low temperature points of the bidirectional countercurrent microchannel can also be effectively controlled by changing the mass flow rate on both sides. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The included drawings are used to provide a further understanding of the embodiments of the present invention, which constitute a part of the specification, are used to illustrate the embodiments of the present invention, and together with the text description, explain the principles of the present invention. Obviously, the drawings in the following description are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0048] Figure 1 A schematic diagram of a bidirectional countercurrent microchannel structure provided in a specific embodiment of the present invention, (a) is a front view, (b) is a right view, (c) is a main view, and (d) is a bottom view of the right view;

[0049] Figure 2 Schematic diagrams of a bidirectional countercurrent microchannel structure and a conventional downstream parallel microchannel structure provided in a specific embodiment of the present invention, (a1) is a schematic diagram of the structural parameters of a conventional downstream parallel microchannel, (a2) is a schematic diagram of the structural parameters of a conventional downstream parallel microchannel, (a3) ​​is an enlarged view of the cooling channel of the conventional downstream parallel microchannel structure, (b1) is a schematic diagram of the structural parameters of a bidirectional countercurrent microchannel, (b2) is a schematic diagram of the structural parameters of a bidirectional countercurrent microchannel, and (b3) is an enlarged view of the cooling channel of the bidirectional countercurrent microchannel structure;

[0050] Figure 3 The side view scanning diagram of the microchannel heat sink provided by the specific embodiment of the present invention, (a) is a traditional downstream parallel microchannel structure, (b) is a bidirectional countercurrent microchannel structure;

[0051] Figure 4 A top view scanning diagram of a microchannel heat sink provided in a specific embodiment of the present invention, (a) is a conventional downstream parallel microchannel structure, (b) is a bidirectional countercurrent microchannel structure;

[0052] Figure 5 A schematic diagram of the test fixture structure provided in a specific embodiment of the present invention.

[0053] The above drawings include the following reference numerals:

[0054] 1-Thermocouple placement hole; 2-Insulating air slit; 3-Cooling channel; 4-Heat dissipation reference surface; 5-Limiting structure; 6-Heating rod placement hole; 7-Traditional downstream parallel microchannel inlet position; 8-Traditional downstream parallel microchannel outlet position; 9, 9'-Bidirectional countercurrent microchannel inlet position; 10, 10'-Bidirectional countercurrent microchannel outlet position; 11-Stainless steel cover; 12-Polycarbonate visualization cover; 13-Glass fiber fluid flow layer; 14-Glass fiber thermal insulation layer; 15-Bakelite electrical insulation layer; 16-Stainless steel base; 17, 17'-Test fixture fluid flow layer inlet manifold; 18, 18'-Test fixture fluid flow layer outlet manifold; 19, 19'-Test fixture fluid flow layer inlet position; 20, 20'-Test fixture fluid flow layer outlet position; 21-Through hole. DETAILED DESCRIPTION

[0055] Specific embodiments of the present invention are described in detail below. In the following description, for the purpose of explanation and not limitation, specific details are set forth to help fully understand the present invention. However, it will be apparent to those skilled in the art that the present invention may also be practiced in other embodiments that depart from these specific details.

[0056] It should be noted that in order to avoid obscuring the present invention due to unnecessary details, only the device structure and / or processing steps closely related to the scheme of the present invention are shown in the drawings, while other details that are not closely related to the present invention are omitted.

[0057] The present invention belongs to the field of microscale heat transfer enhancement analysis and evaluation and related experimental technology. It is mainly used for the protection and heat dissipation of electronic components such as smart phones, tablet computers, radars, satellites, carriers, 5G base stations, computing centers, new energy vehicles, etc., which are composed of semiconductor devices, microelectronic chips, integrated circuits, optoelectronic devices and other components. It specifically designs the development and construction of a microchannel structure.

[0058] Example 1

[0059] like Figure 1 , 2 As shown, a bidirectional countercurrent microchannel structure is provided, the upper surface of the microchannel structure includes two groups of cooling channels 3, each group of cooling channels includes a plurality of independent cooling channels, and each cooling channel of the first group of cooling channels is parallel to each cooling channel of the second group of cooling channels and arranged alternately. The inlets of the two groups of cooling channels are located in opposite directions, and the outlet of each group of cooling channels is connected to a lumped outlet on the side wall of the microchannel structure through two 90-degree turns.

[0060] With the above configuration, the two groups of cooling channels in the microchannel structure are parallel and alternately distributed, which are used for the circulation of cooling medium to achieve cooling. There is no mass exchange in the fluid flow process in the two groups of cooling channels, only heat exchange. The bidirectional countercurrent microchannel structure constructed by the present invention processes both ends of the traditional microchannel into fluid inlets, and does not serve as a fluid outlet. The cooling channels in two directions are staggered, so as to better realize the mutual heat transfer between parallel channels. In addition, compared with the traditional microchannel, the tail of the bidirectional countercurrent microchannel structure is sealed, and for the bidirectional countercurrent microchannel structure, the fluid cannot flow out of the channel directly in the horizontal direction. In order to realize the flow channel arrangement, after the cooling medium flows into the microchannel, it turns two 90-degree angles continuously and then flows out of the microchannel structure through the lumped outlet. In the present invention, all countercurrent microchannels are located on the same heat dissipation plane, and there is no microchannel loop on the heat dissipation surface, and there is no multi-layer microchannel configuration. The countercurrent microchannel heat sink of the present invention can be regarded as a bidirectional countercurrent microchannel as a whole, and for a single microchannel in the whole, its structure does not involve the concept of countercurrent.

[0061] Furthermore, the cross section of the cooling channel 3 of the bidirectional countercurrent microchannel structure is a square cross section, which can realize the free regulation of the depth-to-width ratio, and the cross-sectional shape can be consistent with the traditional parallel microchannel, such as Figure 2 , 3 shown.

[0062] Furthermore, each cooling channel has a vertical small hole at the tail position away from the other end as the fluid outlet of the cooling channel in that direction, and a fluid lumped outlet is opened below the outlet, and the lumped outlet connects the independent outlets of each cooling channel of each group to each other below, thereby leading the fluid in the microchannel out. The fluids in the two directions of the bidirectional countercurrent microchannel flow independently. Each lumped outlet only collects and discharges the fluid flowing in this direction, and does not affect the fluid flowing in the other direction.

[0063] Furthermore, the surface of the microchannel structure including multiple cooling channels is the heat dissipation reference plane 4, and the total number of cooling channels on the heat dissipation reference can be completely consistent with the traditional downstream parallel microchannels, but under this premise, the number of cooling channels in each direction can only reach half of the traditional downstream parallel microchannels.

[0064] Furthermore, two rows of thermocouple placement holes 1 need to be constructed on the side wall of the microchannel structure for installing temperature measuring thermocouples. With this configuration method, the heat flux density can be corrected by the one-dimensional heat conduction law while measuring the temperature, so as to regulate parameters such as the flow rate of the cooling medium. Preferably, an insulating air slit 2 needs to be constructed between any adjacent thermocouple placement holes to reduce the influence of lateral heat conduction on the heat transfer results at each position.

[0065] Furthermore, a certain number of heating rod placement holes 6 are provided at the bottom of the microchannel structure for assembling heating rods as heat sources during the microchannel structure test process.

[0066] Furthermore, since the bidirectional countercurrent microchannel structure includes two groups of cooling channels, a gas-liquid two-phase cooling medium or a single-phase cooling medium can be used as required.

[0067] Furthermore, the microchannel structure provided by the present invention can be used as a heat sink and arranged on the structure to be cooled. The heat dissipation reference surface of the microchannel structure including two groups of cooling channels can be directly sealed and fixedly connected with the structure to be cooled to achieve maximum heat dissipation efficiency. Preferably, considering the stability, safety and applicability of the microchannel system, copper is selected as the preparation substrate of the microchannel heat sink.

[0068] The microchannel structure designed in the present invention can enhance heat transfer, reduce pressure drop, and suppress boiling instability, and has high reliability, strong stability, and wide applicability. It can be applied to microchannels for heat dissipation of micro devices / components to make up for the shortcomings of traditional parallel microchannel heat dissipation capacity, and provide a simple and feasible heat dissipation method for electronic equipment working under long-term high temperature.

[0069] It should be noted that the physical nature of the dryness in the microchannel gradually increasing along the flow direction is unavoidable. The current surface structure modification and flow channel layout cannot respond to this physical nature. The cooling medium still flows in and out of the microchannel in the traditional single-direction flow mode. The position far away from the fluid inlet will still trigger the critical heat flux density in advance, and the temperature distribution of the microchannel wall is not uniform. The bidirectional countercurrent microchannel designed by the present invention can deal with most of the problems generated in the current microchannel flow boiling process. It has the effects of delaying large-scale premature drying up downstream, suppressing wall temperature oscillation, and reducing the two-phase pressure drop. In terms of design and processing, the expandable processing range of the bidirectional countercurrent microchannel size is large, the processing method is very simple, and it also has many advantages such as good sealing. Since there is no stacking effect similar to multi-layer microchannels, the actual working stability of the entire component is very high, which also enables it to cope with complex airborne variable working conditions.

[0070] Example 2

[0071] In order to facilitate the assembly and use of a bidirectional countercurrent microchannel structure on a structure to be cooled, a microchannel assembly is provided, and an adaptive flow layer structure is designed, and the bidirectional countercurrent microchannel structure is used in different scenarios.

[0072] The microchannel component includes a bidirectional countercurrent microchannel structure and a flow layer, the microchannel structure is embedded in the flow layer, and the flow layer includes two inlets connected to the cooling channel inlet of the microchannel structure and two outlets connected to the lumped outlet;

[0073] The upper surface of the flow layer is provided with a first inlet header, a second inlet header, a first outlet header, and a second outlet header. The first inlet header and the second inlet header are respectively located between the inlets of the two groups of cooling channels of the microchannel structure and the inlet of the flow layer, and simultaneously replenish cooling medium for the two groups of cooling channels. The first outlet header and the second outlet header are respectively located between the two lumped outlets of the microchannel structure and the outlet of the flow layer.

[0074] By adopting the above configuration, the upper surface of the microchannel component is sealed and connected to the structure to be cooled to achieve cooling and heat dissipation. At the same time, the inlet and outlet headers are designed to control the steady flow of the cooling medium, and the width is not less than the width of the microchannel structure.

[0075] Furthermore, in order to minimize the upstream compressible volume, the fluid needs to pass through a shallow groove with a very small height before flowing into the microchannel after passing through the inlet header. The shallow groove is located between an inlet header and a group of cooling channel entrances. The depth of the shallow groove is less than the depth of the inlet header and greater than or equal to the depth of the cooling channel, and the width of the shallow groove is consistent with the width of the microchannel structure.

[0076] Example 3

[0077] like Figure 5 As shown, a test fixture for a microchannel structure of gas-liquid two-phase flow is provided, which includes a base, an electrical insulation layer, a thermal insulation layer, a flow layer, a visualization layer, and a protective support cover from bottom to top. The microchannel structure and the test fixture are combined to form a test structure, which can be directly connected to the flow boiling experiment system of the microchannel to carry out relevant test verification work.

[0078] In this embodiment, materials are selected according to the functions of each layer of the test fixture, which are, from bottom to top, a stainless steel base 16, a bakelite electrical insulation layer 15, a glass fiber thermal insulation layer 14, a glass fiber fluid flow layer 13, a polycarbonate visualization cover 12 and a stainless steel cover 11.

[0079] The stainless steel base and cover support the entire test fixture to prevent stress deformation when working at high temperatures. The bakelite electrical insulation layer has grooves of matching size to accommodate the microchannel structure, and the glass fiber insulation layer has a hollow through-hole structure to completely cover the microchannel structure.

[0080] The inlet manifolds (17, 17') of the fluid flow layer are located on both sides of the inlets of the two groups of cooling channels of the microchannel structure, thereby realizing two-way fluid replenishment. The inlet position of the fluid flow layer needs to be connected with the corresponding inlet manifolds; the outlet manifolds (18, 18') of the fluid flow layer need to be located on the opposite side of the thermocouple placement hole, and the fluid outlet should be completely aligned with the lumped outlet of the microchannel structure and should ensure that it is connected with the outlet manifold. The fluid flow path in a single direction is: flow layer inlet-inlet manifold-microchannel single-side channel-microchannel outlet-outlet manifold-flow layer outlet, and the two directions each form a closed loop without mass exchange.

[0081] The part of the inner side of the polycarbonate visualization cover plate that contacts the microchannel structure is constructed with a corresponding groove to prevent the sealing gasket from leaking. Correspondingly, the stainless steel cover plate should be constructed with a corresponding through window above the polycarbonate visualization cover plate to achieve real-time observation and recording of the flow process of the cooling medium in the microchannel structure.

[0082] Furthermore, the fluid flow layer matching the microchannel structure should be designed specifically. In order to match the flow channel design of the bidirectional countercurrent microchannel structure, the inlet manifolds of the fluid flow layer need to be located at both ends of the flow layer, and the outlet manifolds corresponding to each side are located near the inlet of the flow layer on the other side. The inlet manifold and outlet manifolds allow the cooling medium to flow steadily, and their width is not less than the width of the microchannel structure.

[0083] Furthermore, thermocouple holes and pressure measuring holes are dug at the inlet and outlet manifolds, and measuring equipment such as thermocouples and pressure gauges are installed to measure the temperature and pressure of the inlet / outlet fluid.

[0084] Furthermore, in order to minimize the upstream compressible volume, the fluid needs to pass through a shallow groove with a very small height before flowing into the microchannel after passing through the inlet header. The shallow groove is located between an inlet header and a group of cooling channel entrances. The depth of the shallow groove is less than the depth of the inlet header and greater than or equal to the depth of the cooling channel, and the width of the shallow groove is consistent with the width of the microchannel structure.

[0085] Furthermore, a high-temperature heat sealant is used to encapsulate the microchannel structure and the glass fiber fluid flow layer.

[0086] Furthermore, a limiting structure 5 should be provided between the microchannel structure and the matching flow layer to ensure that the height of the upper surface of the bidirectional countercurrent microchannel is consistent with that of the upper surface of the flow layer.

[0087] Furthermore, a certain number of through holes 21 are arranged around the test fixture, the number is 10-15, the relative positions of the through holes between each layer should be kept consistent, and the entire set of test fixtures should be tightened and fixed by fixing bolts. The central axis of each through hole is perpendicular to the upper and lower bottom surfaces. The position of each through hole should avoid the key core position of the microchannel heat sink and the inlet and outlet and corresponding header positions in the fluid flow layer to prevent the appearance of cross holes that penetrate each other in each fixture.

[0088] It should be noted that after the test temperature changes during the experiment, the actual maximum / lowest temperature cannot exceed / below the upper / lower limit of the ultimate allowable temperature of the fixture matrix material of each layer. If the maximum / lowest temperature exceeds the upper and lower limits of the ultimate allowable temperature of the material, the design parameters of the material and related configurations need to be improved.

[0089] Example 4

[0090] This embodiment describes the technical solution of the present invention in detail in conjunction with a copper-based microchannel heat sink.

[0091] In this embodiment, the material used to prepare the microchannel heat sink test assembly is T1 oxygen-free copper (copper content is not less than 99.95%, oxygen content is not higher than 0.003%). Through measurement, it can be seen that the wall roughness Ra of the cleaned copper used in the experiment does not exceed 0.8·m. The relevant specific design dimensions and parameters are as follows Figure 2 In order to reduce the contact thermal resistance of the entire flow boiling process, the present invention designs the microchannel and the heating block equipped with the heating rod as an integrated structure to prevent the uncertainty of the contact thermal resistance and the thickness of the welding layer in the channel welding mode.

[0092] like Figure 1 As shown, four thermocouple placement holes 1 with a diameter of 1 mm are arranged horizontally at the same height along the flow direction 3 mm below the top of the heat dissipation reference surface 4 to measure the temperature distribution in the horizontal flow direction of the microchannel heat sink. At the same time, four thermocouple placement holes 1 of the same size and depth are opened 3 mm directly below the four thermocouple placement holes 1 to facilitate calibration of the measured heat flux density and wall temperature through the one-dimensional thermal conductivity law. The thermal conductivity of pure copper is very high, and lateral heat conduction will cause the temperature measurement points to affect each other. Two adjacent thermocouple holes in the horizontal direction must be separated by air slits to ensure the accuracy of the measurement results.

[0093] like Figure 2As shown, the present invention carves parallel microchannels on oxygen-free copper by precision CNC micromachining. The size of the substrate where the microchannel is located is 7mm×35mm (width×length), and this area is used as the bottom surface to calculate the effective heat flux density of the entire flow boiling. In this embodiment, the width of the bidirectional countercurrent microchannel is 300μm, the height is 600μm, the length is 33mm, the hydraulic diameter is 400·m, the aspect ratio is 2, and the number of channels is 8. The channel heat dissipation area designed in this embodiment is relatively large, usually more than ten times the heat dissipation area of ​​silicon-based microchannels, and the problem addressed belongs to the problem of large-area efficient heat dissipation.

[0094] In this embodiment, a limiting structure 5 is processed at a distance of 9.5 mm from the upper surface of the microchannel heat sink, which is specifically a boss, so that it can limit the fluid flow layer and make the upper surface of the microchannel flush with the upper surface of the flow layer. At the same time, twelve heating rod placement holes 6 with a diameter of 6 mm are opened at the bottom of the microchannel heat sink to place the heating rods, and the heating rods are used to input power to the entire microchannel heat sink.

[0095] In this embodiment, the bidirectional countercurrent microchannel configuration is as follows: Figures 2 to 5 As shown in the figure. The flow direction of the fluid in the traditional parallel microchannel is single and unchanged, as shown in the figure. Figure 2 (a1-a3) As shown. The bidirectional countercurrent microchannel structure constructed by the present invention processes both ends of the conventional microchannel into fluid inlets, and does not serve as fluid outlets. The microchannels in two directions are arranged in an interlaced manner, thereby better realizing heat transfer between parallel channels.

[0096] like Figure 3 As shown in the figure, compared with the traditional microchannel, the tail of each cooling channel of the bidirectional countercurrent microchannel is sealed. For the bidirectional countercurrent microchannel, the fluid cannot flow out of the channel directly in the horizontal direction. Each cooling channel has a vertical hole with a diameter of 600μm dug 2mm away from the other end as the fluid outlet of this cooling channel, as shown in the figure. Figure 4 As shown, a fluid lumped outlet is dug 2.5 mm below the outlet. Each group of cooling channels corresponds to a lumped outlet, which connects the independent outlets of each group of cooling channels to each other below, thereby leading the fluid in the microchannel out. It should be noted that the fluids on both sides of the bidirectional countercurrent microchannel are independent of each other when flowing, that is, there is only heat exchange but no mass exchange. Each lumped outlet will only collect and discharge the fluid flowing in this direction, and will not affect the fluid flowing in the other direction.

[0097] In order to conduct boiling stability test on microchannel heat sink, a test fixture was prepared.

[0098] The fluid flow layer of the bidirectional countercurrent microchannel test fixture constructed in this embodiment is as follows: Figure 5As shown, the two manifolds at both ends of the fluid flow layer serve as inlet manifolds for the fluids on both sides. Four thermocouple through holes are opened on one side of the fluid flow layer, and the distance between two adjacent horizontal thermocouple through holes is 8 mm. The horizontal distances from the entrance of the cooling channel are 5.5 mm, 13.5 mm, 21.5 mm and 29.5 mm respectively, and the positions coincide with the thermocouple placement holes on the microchannel heat sink. Two outlet manifolds are opened on the side of the fluid flow layer opposite to the thermocouple through holes, and two liquid outlet holes are processed at the position of the outlet manifolds so that they completely coincide with the position of the microchannel lumped outlet to ensure that the fluid flows out of the microchannel. Among them, the fluid inlet manifolds are all deep grooves with a length of 12 mm, a width of 7 mm and a depth of 6 mm to ensure that the fluid flows evenly into the microchannel. It should be noted that since the inlet and outlet positions are adjacent to each other on the countercurrent microchannel, the position of one group of cooling channel outlet manifolds is close to the inlet manifold of another group of cooling channels. At the same time, the bakelite electrical insulation layer 15 and the stainless steel base 16 need to be punched to match the heating rod placement hole at the bottom of the copper-based heat sink to facilitate the arrangement of the heating rod cable.

[0099] All test fixtures in the present invention should be punched at set positions to install bolts, and each layer of the test fixture should be tightened and fixed by the bolts, and the bolt holes on each layer should be guaranteed to be completely aligned.

[0100] The assembly sequence of the bidirectional countercurrent microchannel heat sink and the test fixture in the present invention is:

[0101] First, align the bakelite insulation layer 15 and the stainless steel base 16 according to the bolt holes, pass the heating rod through the corresponding through hole, and perform cable laying and welding;

[0102] Secondly, the heating rod is embedded in the bottom of the microchannel heat sink, and the heat sink microchannel is fixed in the groove of the bakelite insulation layer 15;

[0103] Subsequently, the glass fiber insulation layer 14 and the glass fiber fluid flow layer 13 are sequentially placed outside the microchannel heat sink;

[0104] Then, the polycarbonate visualization cover plate 12 and the stainless steel cover plate 11 are placed on the glass fiber fluid flow layer 13 in sequence and aligned with all the bolt holes;

[0105] Finally, all components are fixed and clamped with long and thin bolts to prevent leakage.

[0106] When conducting a flow boiling experiment, the parameters that need to be measured and calculated to estimate the experimental conditions include but are not limited to: inlet and outlet fluid temperatures, inlet and outlet fluid pressures, temperature along the microchannel heat sink, ambient temperature, fluid flow rate, heating voltage and current, ambient humidity, temperature change response speed, surface temperature uniformity, etc.

[0107] The bidirectional countercurrent microchannel heat sink and the test fixture described above can be used to implement a flow boiling experiment and test the rationality of the microchannel heat sink structural design.

[0108] The features described and presented above for a specific case may be generalized and applied in one or more other real cases in the same or similar manner, or used in combination with features in other cases.

[0109] It should also be noted that in the description of the present invention, the terms "upper", "lower", "inside", "outside", "front", "back" and the like that describe the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of simplifying the description of the present invention, rather than indicating that the device or component referred to must have a specific orientation, and therefore cannot be understood as a limitation on the present invention. The term "include" when used in the present invention refers to the presence of features, steps or components, but does not exclude the presence or addition of one or more other features, steps or components. Unless otherwise expressly specified and limited, the terms "arrangement" and "fixation" should be understood in a broad sense, for example, it can be an arrangement position, an arrangement area, an arrangement method, flexible fixation, rigid fixation, direct fixation, indirect fixation, etc. For practitioners in this field, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0110] The cases are only examples of practical applications of the present invention and do not limit the scope of the present invention. For those skilled in the art, various modifications and improvements can be made to the present invention. Any modification, equivalent substitution and improvement made to the spirit and principle of the present invention should be included in the protection scope of the present invention.

[0111] The parts of the present invention that are not described in detail are well known to those skilled in the art.

Claims

1. A bidirectional countercurrent microchannel structure, characterized in that: The upper surface of the microchannel structure includes two groups of parallel and alternately arranged cooling channels, each cooling channel is arranged independently, the inlets of the two groups of cooling channels are located in opposite directions, and the outlet of each group of cooling channels is connected to a lumped outlet on the side wall of the microchannel structure through two turns.

2. The microchannel structure according to claim 1, characterized in that: The outlet of each group of cooling channels is connected to a lumped outlet on the side wall of the microchannel structure through two 90-degree turns, and the outlet of each group of cooling channels is connected to a vertical channel perpendicular to the cooling channel and downward, and a horizontal channel connected to the lumped outlet and perpendicular to the cooling channel; The two lumped outlets corresponding to the two groups of cooling channels are located on the same side wall of the microchannel structure, and the cross section of the cooling channel is a square cross section.

3. The microchannel structure according to claim 2, characterized in that: The side wall of the microchannel structure also includes a plurality of thermocouple placement holes, in which thermocouples are installed for real-time monitoring of the temperature of the microchannel structure and controlling the flow rate of the cooling medium in the cooling channel according to the heat flux density; The thermocouple placement hole is located on a side of the microchannel structure that is away from the lumped outlet; An air slit is arranged between two adjacent thermocouple placement holes along the cooling channel direction.

4. A microchannel assembly, characterized in that: The invention comprises a bidirectional countercurrent microchannel structure and a flow layer, wherein the microchannel structure is the microchannel structure according to any one of claims 1 to 3, the microchannel structure is embedded in the flow layer, and the flow layer comprises two inlets connected to two groups of cooling channel inlets, and two outlets connected to two lumped outlets; The upper surface of the flow layer is provided with a first inlet header, a second inlet header, a first outlet header, and a second outlet header. The first inlet header and the second inlet header are respectively located between the two groups of cooling channel inlets of the microchannel structure and the flow layer inlet, and the first outlet header and the second outlet header are respectively located between the two lumped outlets of the microchannel structure and the flow layer outlet.

5. The microchannel assembly according to claim 4, characterized in that: The widths of the first inlet header, the second inlet header, the first outlet header, and the second outlet header are not less than the width of the microchannel structure perpendicular to the cooling channel direction; Preferably, the upper surface of the fluidized bed further comprises a first shallow groove and a second shallow groove, wherein the first shallow groove is located between the first inlet header and a group of cooling channel inlets, and the second shallow groove is located between the second inlet header and another group of cooling channel inlets; The depth of the first shallow groove and the second shallow groove is less than the depth of the first inlet header and the second inlet header, and is greater than or equal to the depth of the cooling channel.

6. A test fixture for a bidirectional countercurrent microchannel structure, characterized in that: It includes a base, an electrical insulation layer, a heat insulation layer, a flow layer, a visualization layer, and a cover plate which are fixedly connected in sequence from bottom to top, wherein the upper surface of the electrical insulation layer includes a first groove, the centers of the heat insulation layer and the flow layer include through holes, and the lower surface of the visualization layer includes a second groove; The microchannel structure is placed in the first groove, passing through the through hole of the thermal insulation layer and the flow layer, the second groove is sealed and connected to the upper surface of the microchannel structure, the cover plate includes a through window matching the position of the second groove, and the microchannel structure is the microchannel structure according to any one of claims 1 to 3; The flow layer includes two inlets communicated with the two groups of cooling channel inlets of the microchannel structure, and two outlets communicated with the two lumped outlets of the microchannel structure.

7. The test fixture according to claim 6, characterized in that: The upper surface of the fluidized bed is provided with a first inlet header, a second inlet header, a first outlet header, and a second outlet header, wherein the first inlet header and the second inlet header are respectively located between the two groups of cooling channel inlets of the microchannel structure and the fluidized bed inlet, and the first outlet header and the second outlet header are respectively located between the two lumped outlets of the microchannel structure and the fluidized bed outlet; The widths of the first inlet header, the second inlet header, the first outlet header, and the second outlet header are not less than the width of the microchannel structure perpendicular to the cooling channel direction; Preferably, the upper surface of the fluidized bed further comprises a first shallow groove and a second shallow groove, wherein the first shallow groove is located between the first inlet header and a group of cooling channel inlets, and the second shallow groove is located between the second inlet header and another group of cooling channel inlets; The depth of the first shallow groove and the second shallow groove is less than the depth of the first inlet header and the second inlet header, and is greater than or equal to the depth of the cooling channel.

8. The test fixture according to claim 6, characterized in that: The side wall of the microchannel structure includes a plurality of thermocouple placement holes, and the thermocouple arrangement holes on the side of the flow layer corresponding to the microchannel structure also include thermocouple through holes for installing thermocouples, and the thermocouple arrangement holes and thermocouple through holes are both in two rows; The first inlet header, the second inlet header, the first outlet header and the second outlet header of the fluidized bed are provided with thermocouple holes and pressure measuring holes, and thermocouples and pressure gauges are installed to measure the temperature and pressure of the inlet and outlet cooling medium; The bottom of the microchannel structure includes a plurality of heating rod placement holes, and the heating rod placement holes are equipped with heating rods; the base and the electrical insulation layer are both provided with heating rod through holes for installing the heating rods.

9. The test fixture according to claim 6, characterized in that: A limiting structure is provided on the microchannel structure so that the upper surface of the microchannel structure and the upper surface of the flow layer are located in the same plane; The microchannel structure and the flow layer are sealed with a sealant; The base, the electrical insulation layer, the heat insulation layer, the flow layer, the visualization layer, and the cover plate are all provided with a plurality of through holes for bolt connection; The base and cover are made of stainless steel, the electrical insulation layer is made of bakelite, the flow layer and heat insulation layer are made of glass fiber, and the visualization layer is made of polycarbonate; The microchannel structure is made of red copper and is installed on the structure to be cooled as a heat sink.

10. A method for assembling a test fixture of a bidirectional countercurrent microchannel structure, characterized in that: The test fixture is the test fixture according to any one of claims 6 to 9, and the assembly method comprises the following steps: Align the insulation layer with the base, assemble the heating rod, and lay the cables; Embed the heating rod into the bottom of the microchannel structure, and fix the microchannel structure in the first groove of the insulating layer; The heat insulation layer and the flow layer are sequentially installed outside the microchannel structure; Install the visualization layer and cover plate in sequence and align them; The test fixture is fixed with bolts.

Images