CN111981882B

CN111981882B - Discontinuous phase separation loop heat pipe

Info

Publication number: CN111981882B
Application number: CN202010842171.4A
Authority: CN
Inventors: 谢剑; 徐进良; 纪献兵; 庄俊杰; 周庆
Original assignee: North China Electric Power University
Current assignee: North China Electric Power University
Priority date: 2020-08-20
Filing date: 2020-08-20
Publication date: 2021-10-29
Anticipated expiration: 2040-08-20
Also published as: CN111981882A

Abstract

The invention discloses a discontinuous phase separation loop heat pipe, belonging to the technical field of electronic chip heat dissipation. The loop heat pipe is mainly divided into an evaporation cavity and a condensation cavity; the upper parts of the evaporation cavity and the condensation cavity are connected through a steam channel; the lower parts of the two parts are connected through a condensate passage; installing an intermittent hydrophobic nano-film plate on the surface of the micro-groove in the evaporation cavity, and dividing a vapor cavity from the evaporation cavity; the evaporation surface adopts a graded micro-groove structure, and a unidirectional elastic membrane is arranged at the inlet of the micro-groove to prevent the working medium from flowing backwards; an intermittent hydrophilic micron membrane is arranged in a condensation cavity of the loop heat pipe to separate condensate in gas-liquid two-phase flow, so that the dryness and heat transfer performance of gas-liquid two-phase steam in the condensation cavity are improved. The outer wall of the condensation cavity of the loop heat pipe adopts the barb fins, so that the natural convection heat transfer performance of air is improved. The invention realizes the purposes of cheaply, stably and efficiently solving the heat dissipation problem of the high-power and dispersed heat source chip; the key technology for heat dissipation of the electronic chip is developed aiming at high power and dispersed heat sources of a 5G chip.

Description

Discontinuous phase separation loop heat pipe

Technical Field

The invention belongs to the technical field of electronic chip heat dissipation, and particularly relates to an interrupted phase separation loop heat pipe.

Background

With the advent of artificial intelligence, big data and cloud computing era, the demand of chip heat dissipation is increasingly tense. Especially, the heat dissipation requirement represented by a high-power and heat-source-dispersed 5G chip provides challenges and opportunities for a stable and efficient heat dissipation technology. Heat pipes are used as a low-cost, efficient heat dissipation means, and have been applied to the field of heat dissipation of electronic chips. However, heat pipe technology needs to be innovative to address the new need for high power, distributed heat sources. For example, a complex two-phase flow system is provided inside the heat pipe, and in the case of a dispersed heat source, the problem of instability of two-phase flow heat transfer exists, which may cause local over-temperature, fatigue thermal stress, and chip burnout. Secondly, the current two-phase flow heat transfer strengthening technology mainly adopts a single-phase flow heat transfer strengthening thought, and aiming at the heat dissipation of a high-power chip, a heat pipe needs to develop a heat transfer strengthening technology aiming at the characteristics of two-phase flow. In addition, the porous material has a single function in the heat pipe, is only used as a capillary wick, has insufficient attention on the functions of selective circulation and regulation of gas-liquid two-phase flow, and has further utilization and development values.

Disclosure of Invention

The invention aims to provide a discontinuous phase separation loop heat pipe, which is developed by utilizing an wettability micro-nano porous membrane to selectively circulate and regulate gas-liquid two-phase flow on the basis of a phase separation principle, and is characterized in that: the discontinuous phase separation loop heat pipe is mainly divided into an evaporation cavity and a condensation cavity; the upper parts of the evaporation cavity and the condensation cavity are connected through a steam channel; the lower parts of the two parts are connected through a condensate passage; installing an intermittent hydrophobic nano-film plate on the surface of the micro-groove in the evaporation cavity, and dividing a vapor cavity from the evaporation cavity; a unidirectional elastic membrane is arranged at an inlet of an evaporation surface of a micro groove at the lower part of the evaporation cavity, and the micro groove is a primary micro groove to prevent working medium from flowing backwards; the evaporation cavity absorbs the heat of an external dispersed heat source through the evaporation surface of the micro-groove; installing an intermittent hydrophilic micro-membrane plate on the surface of a liquid absorption core in the condensation cavity; the condensation cavity is divided into a liquid cavity by the discontinuous hydrophilic micron diaphragm plate, and a liquid suction core is arranged in the liquid cavity; barb fins are arranged on the outer wall of the condensation cavity; the section of barb fin is certain contained angle ≠ 0 with the horizontal direction.

The surface of the micro groove adopts a hierarchical structure, the inlet of the primary micro groove is communicated with the condensate passage, and the outlet of the primary micro groove is communicated with the steam passage to play a role in conveying the working medium; the first-stage micro grooves are branched at the heating part of the dispersed heat source to form second-stage micro grooves with smaller through-flow size, so that the heat exchange area is increased.

The discontinuous hydrophobic nano-film plate is formed by inserting hydrophobic nano-films into a dovetail groove of the alloy plate at intervals; the mounting position of the hydrophobic nano-film corresponds to the position of the secondary micro-groove, and part of steam generated by heating the liquid working medium by the secondary micro-groove is separated into a steam cavity to flow; the residual steam and the liquid working medium form two-phase flow and flow in the first-stage micro groove.

The steam flowing in the steam cavity is mixed with the two-phase flow at the outlet of the first-stage micro groove and enters the condensation cavity through the steam channel.

The discontinuous hydrophilic micron membrane plate is formed by welding hydrophilic micron membranes on a metal plate at intervals; part of condensate formed by condensing the steam in the condensation cavity is separated by the hydrophilic micron membrane and is guided to a condensate channel by the liquid absorption core; the residual condensate and the steam form gas-liquid two-phase flow, and the gas-liquid two-phase flow is continuously condensed into condensate in the condensing cavity; the condensate flows out from the outlet of the condensation cavity, the discharged condensate is converged with the condensate guided by the liquid suction core, and the condensate returns to the evaporation cavity through the condensate passage to provide liquid working medium and form a closed loop.

The outer wall of the condensation cavity adopts the barb fins, and heat generated by condensation of steam in the condensation cavity is efficiently taken away through natural convection of air.

The hydrophobic nano-membrane is a Polytetrafluoroethylene (PTFE) nano-membrane, and the hydrophilic micro-membrane is a metal wire mesh membrane, which are low-cost commercial phase separation membranes.

The invention has the beneficial effects that: the discontinuous phase separation loop heat pipe can solve the heat dissipation problem of a high-power and dispersed heat source chip with low cost, stability and high efficiency, and has the following characteristics: (1) the second-stage micro-grooves in the evaporation cavity increase the heat exchange area at the dispersed heat source. Partial steam is separated by the discontinuous hydrophobic nano-film, so that the gas-liquid two-phase flow resistance in the secondary micro-groove is reduced, and local high temperature and chip burnout caused by steam bubble congestion are prevented. (2) The discontinuous hydrophilic micron membrane in the condensation cavity separates condensate in the gas-liquid two-phase flow, thereby improving the dryness and heat transfer performance of the gas-liquid two-phase flow steam in the condensation cavity. (3) The one-way elastic membrane at the inlet of the primary micro-groove prevents the working medium from flowing reversely, thereby inhibiting the instability of two-phase flow and fatigue thermal stress caused by the inconsistent power of dispersed heat sources; (4) the fin with barbs on the outer wall of the condensation cavity can improve the natural convection heat transfer performance of air.

Drawings

Fig. 1 is a schematic diagram of the overall structure of an intermittent phase-separated loop heat pipe.

Fig. 2a, fig. 2b, fig. 2c, fig. 2d, fig. 2e and fig. 2f are schematic diagrams illustrating different cross-sectional structures of an intermittent phase-separated loop heat pipe.

Fig. 3a and fig. 3b are respectively a schematic cross-sectional structure diagram and a schematic phase separation operating principle diagram of an intermittent phase separation loop heat pipe.

Reference numbers in the figures: the device comprises an evaporation chamber 1, a condensation chamber 2, a steam channel 3, a condensate channel 4, a micro-groove evaporation surface 5, a dispersed heat source 6, a discontinuous hydrophobic nano-membrane plate 7, a steam chamber 8, a unidirectional elastic membrane 9, a discontinuous hydrophilic micro-membrane plate 10, a liquid chamber 11, a liquid absorption core 12, a barbed fin 13, a primary groove 14, a secondary groove 15, a hydrophobic nano-membrane 16, an alloy plate 17, a dovetail groove 18, a hydrophilic micro-membrane 19, a metal plate 20, a liquid working medium 21, a vapor bubble 22 and a condensate 23.

Detailed Description

The invention provides an interrupted phase separation loop heat pipe; the present invention will be described in further detail with reference to the accompanying drawings.

FIG. 1 is a schematic diagram of an overall structure of an intermittent phase-separated loop heat pipe according to the present invention. The discontinuous phase separation loop heat pipe is mainly divided into an evaporation cavity 1 and a condensation cavity 2, and the upper parts of the evaporation cavity 1 and the condensation cavity 2 are connected through a steam channel 3; the lower parts of the evaporation cavity 1 and the condensation cavity 2 are connected through a condensate passage 4. The evaporation cavity 1 absorbs heat of an external dispersed heat source 6 through the micro-groove evaporation surface 5, the surface of the micro-groove evaporation surface 5 is provided with an intermittent hydrophobic nano-film plate 7, and a vapor cavity 8 is divided from the evaporation cavity 1. The inlet of the evaporation surface 5 of the micro-groove at the lower part of the evaporation cavity 1 is provided with a one-way elastic membrane 9 to prevent the working medium from flowing backwards.

The condensation chamber 2 is divided into a liquid chamber 11 by an intermittent hydrophilic micro-membrane plate 10, and a wick 12 is arranged in the liquid chamber 11. The outer wall of the condensation cavity 2 is provided with a barb fin 13, and the barb fin 13 is mainly characterized in that the section plane and the horizontal direction form a certain included angle which is not equal to 0 degrees.

Fig. 2a, fig. 2b, fig. 2c, fig. 2d, fig. 2e and fig. 2f are schematic views of different cross-sectional structures of the discontinuous phase separation loop heat pipe of the present invention, showing details of important components. Fig. 2a is a section a-a in fig. 1 showing details of the micro-groove evaporation surface 5: the micro-groove evaporation surface 5 is of a hierarchical groove structure and comprises a first-stage groove 14 and a second-stage groove 15. The inlet of the primary micro-groove 14 is communicated with the condensate passage 4, and the outlet is communicated with the steam passage 3 to play a role in conveying the working medium. The primary micro-grooves 14 are branched at the heating part of the dispersed heat source 6 to form secondary micro-grooves 15 with smaller through-flow size, so that the heat exchange area is increased.

Fig. 2B reflects section B-B in fig. 1, showing details of the discontinuous hydrophobic nanomembrane plate 7: the hydrophobic nano-film 16 is inserted into the dovetail groove 18 of the alloy plate 17 at intervals to form an interrupted hydrophobic nano-film plate 7 (as reflected in fig. 2F, which is a schematic view of the cross-sectional structure of F-F in fig. 1, showing the position of the dovetail groove 18 on the alloy plate 17), and the installation position of the hydrophobic nano-film 16 corresponds to the position of the secondary micro-groove 15.

Fig. 2C reflects section C-C of fig. 1, showing details of the discontinuous hydrophilic microfilm plate 10: the hydrophilic micron membranes 19 are welded on the metal plate 20 at intervals to form the discontinuous hydrophobic nano-membrane plate 10, and the installation positions of the hydrophilic micron membranes 19 are determined according to the condensation condition of the condensation cavity 2.

Figure 2D reflects the cross-section D-D in figure 1, showing details of the barbed fins 13: preferably, the barbed fins 13 are distributed in two rows of a splayed shape, and the included angle between the barbed fins and the vertical direction is 60 degrees.

FIG. 2E is a schematic cross-sectional view of an interrupted phase separation loop heat pipe E-E, illustrating the operation principle of phase separation; fig. 3a and 3B are schematic structural diagrams of the part a and the part B of fig. 2e, respectively.

The invention is a discontinuous phase separation loop heat pipe which is vacuumized in advance and filled with liquid working medium 21; the liquid working medium 21 climbs under the capillary force of the primary micro-groove 14, is distributed into the secondary micro-groove 15, and is heated by the dispersed heat source 6 to generate steam bubbles 22.

After the steam bubble 22 is contacted with the hydrophobic nano-film 16, part of steam in the steam bubble 22 enters the steam cavity 8 to flow; but the liquid working medium 21 cannot enter the vapor chamber 8 through the hydrophobic nanomembrane 16. Therefore, the liquid working medium 21 and the vapor bubble 22 from which part of the vapor is separated form a two-phase flow to continue flowing in the secondary micro-groove 15 and the primary micro-groove 14 (as shown in fig. 2e), and finally the two-phase flow is mixed with the vapor separated from the vapor cavity 8 and enters the condensation cavity 2 through the vapor channel 3.

After condensation, the condensate 23 in the two-phase flow is separated by the hydrophilic micron membrane 19 which is installed discontinuously and is guided into the liquid chamber 11 by the liquid absorption core 12, but the steam of the steam bubble 22 in the two-phase flow cannot enter the liquid chamber 11 through the hydrophilic micron membrane 19 but continuously flows in the condensation chamber 2 together with the residual condensate 23 until being completely condensed into liquid, and is converged with the condensate 23 in the liquid chamber 11 and reenters the evaporation chamber 1 through the condensate passage 4 to become the liquid working medium 21, so that a closed-loop circulation loop is formed.

The two-stage micro-grooves 15 in the evaporation cavity 1 increase the heat exchange area at the position of the dispersed heat source 6, but the size of the through flow is reduced. The discontinuously mounted hydrophobic nano-film 16 separates partial steam, reduces the flow resistance of gas and liquid in the secondary micro-groove 15, and prevents the steam bubble 22 from being blocked in the secondary micro-groove 15 to cause local high temperature and chip burnout. The unidirectional elastic membrane 9 at the inlet of the micro-groove evaporation surface 5 at the lower part of the evaporation cavity 1 prevents the working medium from flowing reversely, and inhibits the instability of two-phase flow and fatigue thermal stress caused by different power of dispersed heat sources. In addition, the hydrophilic micron membrane 19 intermittently arranged in the condensation cavity 2 separates condensate 23 in gas-liquid two-phase flow, and improves the dryness and heat transfer performance of the gas-liquid two-phase flow steam in the condensation cavity 2. The fin with barbs on the outer wall of the condensation cavity 2 also improves the natural convection heat transfer performance of air to a certain degree. Therefore, the invention is a key technology for solving the problem of heat dissipation of a high-power and dispersed heat source chip with low cost, stability and high efficiency.

Example 1:

taking 5G base station AAU radio frequency chip heat dissipation as an example, the heat sources are uniformly dispersed on the evaporation surface of the loop heat pipe, 4 heat sources are distributed in each row, and 12 heat sources are distributed in 3 rows. The rated power of each dispersed heat source is 35W, the heating area is 30mm x 30mm, and the distance between heat sources is 80 mm. Correspondingly, the overall appearance of the loop heat pipe is a cuboid, the length is 100mm, the width is 300mm, the height is 200mm, and the material of the shell is 6063 aluminum alloy. The loop heat pipe is pre-vacuumized and filled with acetone as a circulating working medium, and the liquid filling ratio is 8%.

The wall thickness of the evaporation cavity is 2mm, the seam width is 2.5mm, and a steam cavity with the width of 1mm is divided by the interval type hydrophobic nanometer diaphragm plate. The hydrophobic nano-membrane is a polytetrafluoroethylene PTFE membrane with the average pore diameter of 100nm, rectangular strips with the length of 30mm and the width of 295mm are cut, and the strips are installed on a 6063 aluminum alloy plate with the thickness of 0.5mm in a dovetail slot mode to form an interval type hydrophobic nano-membrane plate. The installation interval of the hydrophobic nano-film is consistent with the interval of the dispersed heating source and is 80 mm.

The evaporation surface of the evaporation cavity is provided with a hierarchical micro-groove structure through an extrusion forming process, the width of a first-level groove is 0.2mm, the depth of the first-level groove is 0.8mm, and the distance between the first-level groove and the first-level groove is 5 mm. 1 first-stage groove is divided into 3 second-stage grooves, and then the grooves are converged into the first-stage grooves again, and the included angle between every two adjacent second-stage grooves is 5 degrees. The width of the secondary groove is 0.1mm, and the depth is 0.8 mm. The one-way elastic membrane at the inlet of the primary groove is made of silicon rubber and is prepared in a stamping mode, the stamping position corresponds to the inlet of the primary groove one by one, and each piece is 0.2mm by 0.8mm in size and is stuffed into the inlet of the primary groove to form tight fit.

The wall thickness of the condensation cavity is 1mm, the width of the slit is 2.5mm, and a liquid cavity with the width of 1mm is divided by the interval hydrophilic micron diaphragm plate to store the liquid absorbing core. The wick is made of 400-mesh porous copper foam and is 0.8mm thick. The interval type hydrophilic micron membrane plate is formed by welding a titanium mesh with 200 meshes with a 6063 aluminum alloy plate. The titanium net is cut into rectangular strips with the width of 30mm and 295mm, and the installation distance is 80 mm.

The evaporation cavity is connected with the upper part of the condensation cavity through a steam channel, and the width of the steam channel is 295mm and the height of the steam channel is 5 mm. The evaporation cavity is connected with the lower part of the condensation cavity through a condensate passage, and the width of the condensate passage is 295mm and the height of the condensate passage is 2 mm. The rolling barb fin of condensation chamber outer wall, the barb fin is two rows of splayed distributions, and the fin is thick 0.2mm, and the fin height is 75mm, and interval 2mm equals 60 with vertical direction contained angle. The included angle between the section of the barb fin and the horizontal direction is 10 degrees.

The embodiments are only preferred embodiments of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A discontinuous phase separation loop heat pipe is developed by selectively circulating and regulating gas-liquid two-phase flow by using an wettability micro-nano porous membrane based on a phase separation principle, and is characterized in that the discontinuous phase separation loop heat pipe is mainly divided into an evaporation cavity and a condensation cavity; the upper parts of the evaporation cavity and the condensation cavity are connected through a steam channel; the lower parts of the two parts are connected through a condensate passage; installing an intermittent hydrophobic nano-film plate on the surface of the micro-groove in the evaporation cavity, and dividing a vapor cavity from the evaporation cavity; a unidirectional elastic membrane is arranged at an inlet of an evaporation surface of a micro groove at the lower part of the evaporation cavity, and the micro groove is a primary micro groove to prevent working medium from flowing backwards; the evaporation cavity absorbs the heat of an external dispersed heat source through the evaporation surface of the micro-groove; installing an intermittent hydrophilic micro-membrane plate on the surface of a liquid absorption core in the condensation cavity; the condensation cavity is divided into a liquid cavity by the discontinuous hydrophilic micron diaphragm plate, and a liquid suction core is arranged in the liquid cavity; barb fins are arranged on the outer wall of the condensation cavity; the section of the barb fin forms an included angle alpha which is not equal to 0 degrees with the horizontal direction.

2. The discontinuous phase separation loop heat pipe according to claim 1, wherein the micro-groove surface adopts a hierarchical structure, and the inlet of the primary micro-groove is communicated with the condensate passage, and the outlet of the primary micro-groove is communicated with the steam passage to play a role in conveying the working medium; the first-stage micro grooves are branched at the heating part of the dispersed heat source to form second-stage micro grooves with smaller through-flow size, so that the heat exchange area is increased.

3. An interrupted phase separation loop heat pipe according to claim 1, wherein the interrupted hydrophobic nano-film plate is formed by hydrophobic nano-films which are inserted into dovetail grooves of an alloy plate at intervals; the mounting position of the hydrophobic nano-film corresponds to the position of the secondary micro-groove, and part of steam generated by heating the liquid working medium by the secondary micro-groove is separated into a steam cavity to flow; the residual steam and the liquid working medium form two-phase flow and flow in the first-stage micro groove.

4. An interrupted phase separation loop heat pipe according to claim 1 wherein the vapor flowing in the vapor chamber is mixed with the two-phase flow at the outlet of the primary micro-groove and enters the condensation chamber through the vapor channel.

5. A discontinuous phase separation loop heat pipe according to claim 1, wherein the discontinuous hydrophilic micro-membrane plate is formed by welding hydrophilic micro-membranes on a metal plate at intervals; part of condensate formed by condensing the steam in the condensation cavity is separated by the hydrophilic micron membrane and is guided to a condensate channel by the liquid absorption core; the residual condensate and the steam form gas-liquid two-phase flow, and the gas-liquid two-phase flow is continuously condensed into condensate in the condensing cavity; the condensate flows out from the outlet of the condensation cavity, the discharged condensate is converged with the condensate guided by the liquid suction core, and the condensate returns to the evaporation cavity through the condensate passage to provide liquid working medium and form a closed loop.

6. An interrupted phase separation loop heat pipe according to claim 1, wherein the outer wall of the condensation chamber is made of barbed fins, and the heat generated by the condensation of the vapor in the condensation chamber is efficiently removed by natural convection of air.

7. The discontinuous phase separation loop heat pipe according to claim 1, wherein the hydrophobic nano-membrane is Polytetrafluoroethylene (PTFE) nano-membrane, and the hydrophilic micro-membrane is metal wire mesh membrane, which are cheap commercial phase separation membranes.