CN117015191A - Heat storage type phase change loop device, control system and control method - Google Patents
Heat storage type phase change loop device, control system and control method Download PDFInfo
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- CN117015191A CN117015191A CN202310596108.0A CN202310596108A CN117015191A CN 117015191 A CN117015191 A CN 117015191A CN 202310596108 A CN202310596108 A CN 202310596108A CN 117015191 A CN117015191 A CN 117015191A
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- 230000008859 change Effects 0.000 title claims abstract description 52
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- 239000012782 phase change material Substances 0.000 claims abstract description 32
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- 238000002844 melting Methods 0.000 claims abstract description 4
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K7/00—Constructional details common to different types of electric apparatus
- H05K7/20—Modifications to facilitate cooling, ventilating, or heating
- H05K7/2029—Modifications to facilitate cooling, ventilating, or heating using a liquid coolant with phase change in electronic enclosures
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K7/00—Constructional details common to different types of electric apparatus
- H05K7/20—Modifications to facilitate cooling, ventilating, or heating
- H05K7/2029—Modifications to facilitate cooling, ventilating, or heating using a liquid coolant with phase change in electronic enclosures
- H05K7/20318—Condensers
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K7/00—Constructional details common to different types of electric apparatus
- H05K7/20—Modifications to facilitate cooling, ventilating, or heating
- H05K7/2029—Modifications to facilitate cooling, ventilating, or heating using a liquid coolant with phase change in electronic enclosures
- H05K7/20381—Thermal management, e.g. evaporation control
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/14—Thermal energy storage
Abstract
The invention discloses a heat storage type phase change loop device, a control system and a control method. The intermittent mode of operation is alternated by transient high thermal load phases and non-thermal load phases, in which the cooler continues to operate. In the transient high heat load stage, the micro-channel heat sink generates boiling phase change to take away heat of the power consumption device, and the phase change material in the heat storage type condenser generates melting phase change; in the non-thermal load stage, fluid in the micro-channel heat sink flows in a single phase, and the phase change material in the heat storage type condenser is subjected to solidification phase change. The heat storage type condenser is coupled with the condensing surface of the double-gradient structure and the venation fin-shaped porous structure, so that the cooperative reinforcement of condensing heat transfer and solid-liquid phase change heat transfer is realized. The control method is used for restraining internal disturbance and compensating external disturbance by adopting the self-adaptive control method, so that the accurate temperature control of the phase-change loop is ensured.
Description
Technical Field
The invention relates to a phase-change loop device and an automatic control method, in particular to a heat storage type phase-change loop device and an automatic control method for actively and accurately controlling temperature, which are provided for improving heat exchange performance, boiling stability and energy storage efficiency, and are used for dealing with efficient heat dissipation of intermittent high-heat load electronic equipment.
Background
With the rapid development of electronic technology, the integration degree and power requirements of electronic devices are continuously improved, and the heat flux density of the unit volume of the electronic devices is continuously increased. The working reliability of the electronic equipment is very sensitive to temperature change, and if the electronic equipment cannot be effectively subjected to heat management, the local high temperature of the electronic equipment can be caused, so that the working performance and the equipment safety of the electronic equipment are seriously affected. In addition, besides the common heat dissipation requirement, in the environment of periodical fluctuation, the electronic equipment is often accompanied by the characteristics of high heat flux density, wen Shengkuai, large thermal stress and the like. High energy devices such as high speed aircrafts in military equipment, radars, laser weapons and the like have short time high heat load effect (i.e. instantaneously output high heat flow with heat flow density of 500W/cm) 2 The heat flux density in extreme case reaches 1kW/cm 2 The general duration is 1 minute), and has the characteristics of short temperature control time, rapid load fluctuation and high temperature control difficulty. How to improve the heat dissipation efficiency of the instant operation of electronic devices in a limited space is an urgent problem to be solved.
The phase change material has high latent heat of fusion, and the phase change heat storage system can store heat in transient load by utilizing the phase change material, so that the temperature uniformity of the electronic equipment is maintained. However, the conventional phase-change material has low heat conductivity coefficient, and severely limits the application of the phase-change heat storage system in the heat dissipation field. To solve this problem, it is necessary to strengthen the thermal conductivity of the phase change material and optimize the structure of the heat storage device. In addition, micro-channel boiling is widely applied to heat dissipation of electronic equipment with high heat flux density due to the advantages of high heat transfer coefficient, high temperature uniformity, low requirement of working medium and the like. However, for microchannel boiling, boiling instability due to explosive growth of bubbles can lead to deterioration of microchannel heat transfer performance and even burnout of the heat sink. In order to ensure efficient, stable and safe operation of the micro-channels, it is necessary to effectively suppress boiling instability of the micro-channels. Meanwhile, the steam from the micro-channel heat sink needs to be subjected to timely condensation heat exchange, the condensation heat transfer performance of the wall surface is influenced by surface characteristics, the common condensation surface has the defects of low liquid drop nucleation rate and falling delay, and the condensation surface needs to be modified and optimally designed to strengthen the condensation heat transfer performance. The heat-storage type phase-change loop device has the functions of efficient cooling of micro-channel boiling, solid-liquid phase-change heat storage buffer instantaneous thermal shock and the like, but in order to ensure the efficient dynamic cooling requirement of intermittent high-heat load electronic equipment, a set of automatic control method for actively regulating and controlling the heat-storage type phase-change loop is also urgently needed.
Disclosure of Invention
The invention aims to solve the technical problems of the prior art, and provides a heat storage type phase change loop device for coping with heat dissipation of intermittent high-heat load electronic equipment, wherein the heat storage type phase change loop device comprises a micro-expansion micro-channel for inhibiting two-phase flow instability; a heat storage type condenser coupled with a condensing surface with a double-gradient structure and a venation fin-shaped porous structure realizes the cooperative reinforcement of condensing heat transfer and solid-liquid phase-change heat transfer. In addition, a control system and a control method of the phase-change loop are provided, internal disturbance is restrained by the self-adaptive control method, external disturbance is compensated, and efficient and accurate heat dissipation of the phase-change loop system is guaranteed.
In order to solve the technical problems existing in the design of the heat storage type phase change loop device, the invention adopts the following technical scheme:
the invention provides a heat storage type phase change loop device, which comprises a mechanical pump, a preheater, a micro-channel heat sink, a heat storage type condenser, a cooler, a liquid storage tank and a power consumption device, wherein the mechanical pump is connected with the preheater; the fluid in the liquid storage tank circulates in the preheater, the micro-channel heat sink, the heat storage type condenser and the cooler sequentially through the mechanical pump; the power consumption device is arranged below the expansion section of the micro-channel heat sink, and the low-temperature fluid absorbs the heat released by the power consumption device at the expansion section to generate boiling heat exchange;
the heat storage type condenser comprises an end cover, a cavity, porous foam metal and a venation fin-shaped through; the end covers are fixed on the upper side and the lower side of the cavity, and the porous foam metal and the venation fin-shaped channel are positioned in the cavity; the venation fin-shaped channel consists of a primary channel, a secondary channel, venation fin-shaped ribs and a tertiary channel; the venation fin-shaped hot fluid channels are symmetrically distributed by the central axis, and different channels meet the optimal transportation principle on the pipe diameter; hot fluid is injected from a first-stage channel, enters a second-stage channel after being split, and enters a third-stage channel after being split; the venation fin-shaped ribs are arranged on the tertiary channel and are symmetrically distributed by taking the tertiary channel as an axis; the phase change material is dispersed into the porous foam metal, and the porous foam metal and the phase change material are contacted with the tertiary channel;
in the transient high heat load stage, the low-temperature fluid in the cooler absorbs heat of the power consumption device through boiling convection heat exchange in the micro-channel heat sink, the generated gas-liquid two-phase flow transfers the heat to the heat storage type condenser through convection heat exchange, and the phase change material in the heat storage type condenser absorbs the heat through melting phase change; the medium-high temperature single-phase fluid after releasing heat flows through the cooler for further cooling, the liquid storage tank maintains the pressure balance of the system, the preheater regulates and controls the temperature of the fluid entering the micro-channel heat sink, and the fluid flows back to the micro-channel heat sink under the action of the mechanical pump to complete the circulation of the transient high thermal load stage;
in the non-thermal load stage, the low-temperature fluid in the cooler flows through the micro-channel heat sink to absorb a small amount of heat released by the power consumption device, and flows through the heat storage type condenser to absorb the heat released by solidification of the phase change material. And the fluid after absorbing heat flows through the cooler for cooling, and the fluid flows back to the micro-channel heat sink under the action of the mechanical pump to complete the circulation in the non-heat load stage.
A micro-expansion micro-channel for inhibiting the instability of two-phase flow is composed of a micro-channel heat sinkThe oral cavity, the outlet cavity, a plurality of sections of parallel micro-channels and a cover plate. The inlet cavity is composed of a channel with the direction from bottom to top and the angle of 90 degrees, so that the stability of flow is ensured. The micro-channel consists of a necking section and an expanding section, and the width ratio of the necking section to the expanding section meets the requirement of w 1 /w 2 ＝p,0<p<0.5; the length ratio satisfies L 1 /L 2 ＝q,0<q<1, the said micro-channel reduces the compressible space of the inlet section of the channel and increases the pressure gradient of the inlet section, prevents the reverse flow of steam, and inhibits the instability of the boiling of the micro-channel. The cover plate is positioned at the upper end of the micro-channel, and the two-phase flow state of the working fluid in the micro-channel is visually observed in real time. The whole micro-channel device is compact in structure, and the throttling effect and the compressibility space of the necking end maintain the flow stability of the micro-channel heat sink and strengthen the boiling heat transfer capacity.
A heat storage type condenser coupled with a double-gradient structure condensation surface and a venation fin-shaped porous structure is composed of a multistage fluid channel, porous foam metal, a phase change material, a square cavity, a heat preservation shell and an end cover. The multi-stage fluid channel comprises a primary channel, a secondary channel, a tertiary channel and venation fin-shaped heat exchange fins, and the middle section heat exchange pipeline is positioned in the square cavity and is in contact with the porous foam metal. The fluid channel is characterized in that the fluid channels are symmetrically distributed in the vertical direction, and adjacent different channels meet the optimal transport principle in the width and length directions. The three-stage channel comprises 10 venation fin-shaped ribs which are symmetrically distributed, and the bifurcation angle of the venation fin-shaped ribs is theta and satisfies 0 degrees < theta <90 degrees; the porous foam metal is positioned in the square cavity, and the upper end and the lower end of the porous foam metal are respectively contacted with the end covers. The porous foam metal is of an open-cell structure, and is made of a metal material with good expansibility and high thermal conductivity; the phase change material is distributed in the foam metal; the whole energy storage device has a regular and compact structure, the structure of the fluid channel accords with the optimal transportation principle, and the porous metal foam with large heat transfer surface area and the phase change material with high latent heat can effectively improve the heat exchange efficiency.
The invention also provides a control system for the heat storage type phase change loop, which comprises an adaptive controller and an extended state observer;
the extended state observer is:
wherein beta is 1 ，β 2 ，β 3 Is an observer parameter; z 1 ，z 2 ，z 3 Respectively the two groups of the three groups are y,an estimated value of f, y is the average temperature of the surface of the micro-channel heat sink, f is the total disturbance,/->A first derivative of y;
the self-adaptive controller is as follows:
u 0 ＝k p (r-z 1 )-k d z 2
wherein u is 0 Is the rotation speed of the mechanical pump; k (k) p ，k d Is a controller parameter; r is the average temperature set value of the surface of the micro-channel heat sink. And setting an average temperature set value r of the surface of the micro-channel heat sink according to the working temperature range of an actual device.
Compared with the prior art, the invention has the remarkable advantages that:
(1) According to the optimal transportation principle, the heat storage type condenser with the venation fin-shaped porous structure is constructed, the flow resistance is reduced by the venation fin-shaped heat transfer fluid channel, the fluid transportation is optimized, the heat exchange area is increased, and therefore the energy storage and heat exchange efficiency is enhanced. The venation fin-shaped channel wall is provided with a double-gradient enhanced heat transfer surface, and the separation of steam condensate is accelerated through the synergistic effect of the wetting gradient and the periodic gradual change groove, so that the effects of high-efficiency heat exchange and energy conservation are achieved. The heat exchange area of the phase change material is increased by the venation fin-shaped porous structure formed by the fin-shaped fins and the foam metal, the low heat conduction area of the heat storage type heat exchanger is reduced, and the defects of low heat conduction coefficient of the phase change material, high flow resistance of the conventional heat storage type condenser, difficult fluid transportation and low heat exchange efficiency are overcome.
(2) The condensation surface with the double-gradient structure utilizes the wettability gradient to accelerate the liquid drop nucleation rate, the gradient groove structure which is periodically arranged enhances the Laplace acting force, and accelerates the separation surface frequency of condensed liquid, thereby effectively solving the defects of low liquid drop nucleation rate and falling hysteresis of the conventional condensation surface and remarkably enhancing the condensation heat transfer performance of the surface.
(3) The micro-channel heat sink with the micro-channel expansion and contraction reduces the compressible space of the inlet section to increase the pressure gradient of the inlet section and the steam reverse flow resistance, so that the steam reverse flow in the boiling process is restrained, the stability of flow boiling is maintained, meanwhile, the boiling heat transfer of the micro-channel is enhanced through the throttling and depressurization effect, and the boiling heat transfer efficiency is enhanced.
(4) The self-control method of the phase-change loop can effectively cope with internal disturbance and external disturbance suffered by the phase-change loop, including heating load of a micro-channel heat sink, condensation efficiency of a cooler, temperature and pressure change of working medium in a liquid storage tank and the like. By the self-adaptive control method, the rotating speed of the mechanical pump and the power of the preheater are automatically adjusted in real time to realize the accurate temperature control of the phase-change loop, so that the defects of multiple disturbance, single adjusting means and large error in a conventional loop are overcome.
Drawings
FIG. 1 is a schematic diagram of a thermal storage type phase change circuit device and an automatic control method;
FIG. 2 is a schematic view of a heat storage type condenser;
FIG. 3 is a schematic diagram of the structure of a choroidal fin channel;
FIG. 4 is a two-dimensional cross-sectional schematic of a heat storage type condenser;
FIG. 5 is a schematic view of a vacuum wetting apparatus;
FIG. 6 is a schematic illustration of a periodically graded trench surface;
FIG. 7 is a schematic illustration of the wettability gradient of a wet gradient periodically graded slot dividing wall plate;
FIG. 8 is a schematic illustration of the self-driving characteristics of a wet gradient periodically graded slot dividing wall plate droplet;
FIG. 9 is a schematic diagram of a micro-channel heat sink structure with a micro-scaled micro-channel structure;
FIG. 10 is a schematic two-dimensional cross-sectional view of a micro-fluidic channel;
in the figure, 1 is a primary channel, 2 is porous foam metal, 3 is a secondary channel, 4 is a venation fin-shaped rib, 5 is a tertiary channel, 6 is an end cover, 7 is an injection hole, 8 is a square cavity, 9 is an inlet cavity, 10 is a necking section, 11 is an expanding section, 12 is an outlet cavity, 13 is a top cover, 14 is a cooler, 15 is a mechanical pump, 16 is a liquid storage tank, 17 is a preheater, 18 is a power consumption device, 19 is an adaptive controller, a condensation surface 21, a gradual change groove 22, a micro displacement platform 23, a low deformation fine line 24, a vacuum dryer 25, a latex tube 26, a vacuum pump 27, a vacuum cover 28, a double gradient structure condensation surface 29 and a beaker 30
Detailed Description
The following detailed description is presented in conjunction with the accompanying drawings to enable one skilled in the art to more readily understand the advantages and features of the present invention:
fig. 1 is a schematic diagram of a heat storage type phase change loop device according to the present invention. As shown, includes a heat storage condenser, a microchannel heat sink, a cooler 14, a mechanical pump 15, a liquid storage tank 16, and a preheater 17; the fluid in the reservoir 16 is circulated through the preheater 17, the microchannel heat sink, the heat storage condenser, and the cooler 14 in this order by the mechanical pump 15. The power dissipation device 18 is disposed below the microchannel heat sink expansion section. The cryogenic fluid absorbs heat released by the power consuming device 18 at the expansion section for boiling heat exchange.
Fig. 2 to 4 are schematic structural views of a heat storage type condenser. As shown, the porous foam metal 2 comprises an end cover 6, a cavity 8, a porous foam metal 2 and a venation fin-shaped channel, wherein the end cover 6 is fixed on the upper side and the lower side of the cavity 8. The porous metal foam 2 and the venation fin channel are located within the cavity 8.
Fig. 3 is a schematic diagram of the structure of the choroidal fin channel. The three-stage flow-path type air conditioner comprises a primary channel 1, a secondary channel 3, a venation fin-shaped rib 4 and a tertiary channel 5. The venation fin-shaped heat fluid channels are symmetrically distributed by the central axis, and different channels meet the optimal transportation principle on the pipe diameter. The hot fluid is injected from the primary channel 1, and enters the secondary channel 3 after being split, and enters the tertiary channel 5 after being split. The tertiary channels 5 are provided with venation fin-shaped ribs 4, and the venation fin-shaped ribs 4 are symmetrically distributed by taking the tertiary channels 5 as axes.
An injection hole 7 is provided in the end cap 6. The phase change material is injected into the cavity 8 from the injection hole 7 left in the end cover 6, the phase change material is dispersed into the porous metal foam 2, and the porous metal foam 2 and the phase change material are in contact with the tertiary channel 5. The two-phase fluid flows in from the primary channel 1, and heat exchanges with the phase change material through the tertiary channel 5 of the heat storage type condenser and the porous foam metal 2 on the outer wall. In the high heat load stage, when fluid enters the tertiary channel 5, heat is transferred into the porous foam metal 2 and the phase change material through the venation fin-shaped ribs 4, and the phase change material melts after absorbing the heat, so that the heat is stored. During non-thermal loading phases, the phase change material undergoes a solidification phase change to transfer heat to the fluid through the venation fin 4 and the porous metal foam 2. The high specific surface area of the porous foam metal 2 and the venation fin-shaped ribs of the optimized transmission path strengthen the energy storage and heat exchange efficiency.
The heat storage type condenser has a double-gradient structure condensing surface 29 on the wall of the venation fin-shaped channel, and is composed of gradual grooves 22 on the condensing surface 21. The graded grooves 22 have grooves which are periodically arranged, the grooves remain unchanged in depth and continuously vary in width periodically, and the top view shows an isosceles trapezoid structure which is connected end to end. The intersection angle of the two waists of the trapezoid after extension is called a gradual change angle alpha, the gradual change angle is 4 degrees < alpha <15 degrees, preferably 4 degrees < alpha <9 degrees, and the larger the gradual change angle is, the stronger the driving force is within a preferred range. The periodic gradual change structure can continuously transport and discharge liquid on the condensation surface, and reduce the accumulation of the liquid on the surface to form thermal resistance, thereby ensuring the efficient heat transfer in the condensation process. A dual gradient structure condensing surface 29 is located in the channel walls of the primary channel 1, the secondary channel 2 and the tertiary channel 5 for dividing the two-phase fluid. The vapor side surface of the gradient periodically graded slot dividing wall plate has wettability gradient characteristics along the vapor entry direction in addition to the periodically arranged graded slot structural features described above, see fig. 7. The wettability gradient is a continuous change in characteristics from hydrophilic to hydrophobic; the wettability gradient is obtained by vapor deposition, and the implementation is realized by a vacuum wetting device. Referring to fig. 5, the vacuum wetting device schematically comprises a micro displacement platform 23, a low-deformation thin wire 24, a vacuum dryer 25, a latex tube 26 and a vacuum pump 27. The micro displacement platform 23 is connected with a low deformation thin wire 24. The low-deformation thread 24 passes through a preformed hole of a vacuum dryer 25. The periodically graded slot wall 29 is at the end of the low deformation filament 33 and is located within the vacuum dryer 25. The vacuum dryer 25 is connected to a vacuum pump 27 via a latex tube 26. The wettability gradient is built up by varying exposure times in a low pressure hydrophobic environment.
The preparation of the wettability gradient surface is carried out by using a vacuum wetting device, and the specific preparation process flow comprises the following steps:
the first step, the machining work of the dividing wall plate of the periodic gradient groove is realized by machining, and the gradient angle of the gradient groove is 8 degrees. The surface schematic of the processed surface is shown in fig. 6.
Secondly, obtaining wettability gradient through a vacuum wetting device, wherein the method comprises the following specific operations: a beaker 30 containing water and about 50 μl of perfluorooctyl trichlorosilane were placed in the vacuum dryer 25. The dual gradient structured condensing surface 29 is partially submerged in water. The vacuum pump 27 was turned on to reduce the pressure in the vacuum dryer 25 to within 6 kpa. At this time, perfluorooctyl trichlorosilane
The alkane volatilizes and the vacuum dryer 25 is filled with perfluorooctyl trichlorosilane vapor 28. The micro displacement platform 23 is opened and the double gradient structure condensing surface 29 is dragged by the low deformation thin line 24 so as to slowly leave from the water surface of the beaker 30. The difference in the amount of perfluorooctyl trichlorosilane vapor 28 hydrolytically deposited on the dual gradient structured condensing surface 29 results in a wettability gradient due to the difference in the time it is exposed to perfluorooctyl trichlorosilane vapor 28. The results are shown in FIG. 7, wherein 29-1 is a hydrophilic region of the condensation surface with a dual gradient structure, 29-2 is a hydrophobic region of the condensation surface with a dual gradient structure, and the wettability of the two surfaces is obviously different, so that the aggregation states of condensate on the surfaces are different.
FIG. 8 is a schematic illustration of the self-driving characteristics of a wet gradient periodically graded slot dividing wall plate droplet. By placing a drop of liquid on the condensation surface 29 of the above-described wet gradient double gradient structure, it is observed that the drop of liquid can move spontaneously to the other side in a direction consistent with the direction of the vapor in the wall plate between the condensers. The above process is recorded by a high-speed camera, timing is started when the liquid drop contacts the surface of the condensation surface 29 of the dual-gradient structure with a wetting gradient, the liquid drop is driven to spontaneously move due to surface tension formed by the difference of the wetting gradients, the liquid drop moves rightwards for a certain distance through 160ms, the liquid drop moves continuously at 220ms, the contact angle of the liquid drop is reduced at the last moment, the liquid drop moves to be close to the right end of the plate surface at 270ms, and at the moment, the contact angle is further reduced and moves for a longer distance in a shorter time. The final drop reached the far right at 320 ms.
Fig. 9 is a schematic diagram of a micro-channel heat sink structure with a micro-scaled micro-channel structure. As shown in the figure, the device specifically comprises an inlet cavity 9, a necking section 10, an expanding section 11, an outlet cavity 12 and a cover plate 13. Working fluid is injected from the inlet cavity 9 and enters the micro-channel from bottom to top. The heat source is positioned at the flaring end 11, and the working fluid is throttled and depressurized by the necking section 10 and then is positioned in a gas-liquid two-phase region and then enters the expansion section 11, so that the boiling instability is reduced and the boiling heat transfer in the micro-channel is enhanced. The cover plate 13 is located at the upper end of the micro-channel structure, and the flow condition of the working fluid in the micro-channel can be observed in real time and visually through the cover plate 13.
Fig. 10 is a schematic two-dimensional cross-sectional view of a micro-channel, where the inlet chamber 9 and the outlet chamber 12 are located on the central axis, and fluid working medium flows from the inlet chamber into the necking section 10 and the expanding section 11 after flow equalization, and finally merges into the outlet chamber 12. The width ratio of the necking section to the expanding section is 1:3.5, the length ratio is 1:7.5, and the compressibility space of the inlet section is reduced by the design of the contraction and expansion structure of the micro flow channel, so that the countercurrent of steam in the boiling two-phase process is prevented, and the boiling heat transfer efficiency of the micro flow channel is enhanced through the throttling and depressurization effect.
In the phase-change loop, the system circulation flow and the inlet temperature are regulated and controlled by regulating the rotating speed of a mechanical pump and the power of a preheater, so that the average temperature of the evaporating surface is controlled to be a given set value.
The control system consists of an adaptive controller 19 and a distended state observer 20. The extended state observer 20 is equation (12) and the observer is the core part of the autonomous method. The output of the adaptive controller 19 is equation (14). When the flow boiling nonlinearity, the heating load applied to the evaporator, the condensing efficiency of the condenser, the temperature pressure of working medium in the liquid storage tank and the like are disturbed, larger disturbance is generated on the temperature of the evaporating surface, and particularly the temperature of the evaporating surface rapidly fluctuates due to the change of the heating load, so that the evaporating surface deviates from a given set value. The self-control method is characterized in that the disturbance suffered by a controlled system is observed by constructing the extended state observer, the disturbance is defined as the total disturbance of the system and is embedded into the extended state observer as an extended state quantity, and the total disturbance of the part is compensated in real time in the inner ring of the self-adaptive controller, so that the influence of the total disturbance on the control of the evaporating surface temperature is eliminated, and the high-precision control is realized. The extended state observer 20 observes the disturbance of the controlled system, so that the disturbance is defined as the system 'total disturbance', the system 'total disturbance' is embedded into the observer as an extended state quantity, the 'total disturbance' of the part is compensated in real time through the inner ring of the self-adaptive controller 19, the influence of the 'total disturbance' on the surface temperature control of the micro-channel heat sink is eliminated, the rotating speed of the mechanical pump 15 and the power of the preheater 17 are controlled to regulate and control the circulating flow and the inlet temperature to regulate the phase change heat exchange intensity, and the high-precision control of the temperature is realized.
The control method specifically comprises the following steps:
k p ，k d ，b 0 for the controller parameters, u is the control quantity (mechanical pump rotation speed), and y is the controlled variable (micro-channel heat sink surface average temperature). When flow boiling nonlinearity and uncertainty, heating load received by the micro-channel heat sink, condenser condensation efficiency, working medium temperature pressure in the liquid storage tank and the like are disturbed, larger disturbance is generated on the surface temperature of the micro-channel heat sink, and particularly, the surface temperature of the micro-channel heat sink is rapidly fluctuated by the change of the heating load, so that the surface temperature deviates from a given set value. The self-adaptive controller is designed to construct an extended state observer to observe disturbance of a controlled system, define the disturbance as system 'total disturbance' and embed the disturbance as an extended state quantity into the extended state observer, and compensate the 'total disturbance' in real time in an inner loop of the self-adaptive controller "And the influence of total disturbance on the surface temperature control of the micro-channel heat sink is eliminated, and the high-precision control of the micro-channel heat sink is realized. Consider first that the microchannel surface temperature control process in a phase change loop can be approximated as a nominal second order object:
wherein: b is an object parameter, g represents the combination of an object higher-order part, disturbance and dynamic uncertainty, t represents time, and v is uncertainty such as noise, disturbance and the like. y represents the controlled variable and is used to control,represents the first derivative of y>Representing the second derivative of y>Representing the third derivative of y. Further definition f=g+ (b-b) 0 ) u is the total disturbance of the expansion state of the phase-change loop, and the formula (1) can be simplified as:
wherein the control amount is as follows:
the two formulas are combined to obtain:
wherein the "total perturbation" f is estimated by the extended state observer:
wherein beta is 1 ，β 2 ，β 3 Z, being observer parameter 1 ，z 2 ，z 3 Respectively the two groups of the three groups are y,an estimate of f. Consider z by accurately setting observer parameters 3 The total disturbance f can be accurately estimated, and the formula (4) can be simplified as follows:
equation (6) may be approximated as a modified integral tandem object,
u 0 ＝k p (r-z 1 )-k d z 2 (7)
wherein r represents the controlled variable set point.
The phase-change loop self-adaptive controller with the design can accurately control the surface temperature of the micro-channel heat sink, and can effectively cope with various uncertainties and disturbance of the phase-change loop.
According to the heat storage type phase change loop device, according to the intermittent working mode of the power consumption device, the phase change loop device is alternately performed in an instantaneous high heat load phase and a non-heat load phase;
(I) In the transient high heat load stage, the mechanical pump 15 pumps low-temperature fluid into the preheater 17 for preheating, the preheated fluid enters the inlet cavity 9 of the microchannel heat sink, the fluid flows through the necking section 10 and the expanding section 11, and the fluid enters the heat storage type condenser after flowing through the outlet cavity 12. Wherein the power consuming device 18 is disposed below the expanded section of the microchannel heat sink. The cryogenic fluid absorbs heat released by the power consuming device 18 at the expansion section 11 for boiling heat exchange. Two-phase fluid enters from the primary channel 1 of the heat storage type condenser, passes through the secondary channel 3 and finally flows out from the tertiary channel 5. Wherein the channel walls and the contacted porous metal foam 2 are heat exchanged with the phase change material injected from the injection hole 7 while passing through the tertiary channel 5, the phase change material absorbs heat of the two-phase fluid by melting the phase change process. The medium-high temperature single-phase fluid after releasing heat flows through the cooler 14 for further cooling, and the cooled fluid flows through the liquid storage tank 16 and completes the circulation of the instantaneous high heat load stage under the action of the mechanical pump 15.
(II) during the non-thermal load phase, the cooler 14 low-temperature fluid flows through the inlet cavity 9 of the micro-channel heat sink, the fluid flows through the necking section 10 and the expanding section 11, and the fluid enters the heat storage type condenser after flowing through the outlet cavity 12. The cryogenic fluid absorbs a small amount of heat released by the power consuming device 18 in the standby state at the expansion section 11. Fluid enters from the primary channel 1 of the heat storage type condenser and flows out from the tertiary channel 5 through the secondary channel 3. Wherein the channel walls and the contacted porous metal foam 2 are heat exchanged with the phase change material entering from the injection holes 7 while passing through the tertiary channel 3, and the fluid absorbs heat released from the phase change material by condensing the phase change process. The fluid after absorbing heat is cooled by the cooler 14, and the fluid flows back to the micro-channel heat sink under the action of the mechanical pump 15 to complete the circulation in the non-heat load stage.
Claims (9)
1. The heat storage type phase change loop device is characterized by comprising a mechanical pump, a preheater, a micro-channel heat sink, a heat storage type condenser, a cooler, a liquid storage tank and a power consumption device; the fluid in the liquid storage tank circulates in the preheater, the micro-channel heat sink, the heat storage type condenser and the cooler sequentially through the mechanical pump; the power consumption device is arranged below the expansion section of the micro-channel heat sink, and the low-temperature fluid absorbs the heat released by the power consumption device at the expansion section to generate boiling heat exchange;
the heat storage type condenser comprises an end cover, a cavity, porous foam metal and a venation fin-shaped channel; the end covers are fixed on the upper side and the lower side of the cavity, and the porous foam metal and the venation fin-shaped channel are positioned in the cavity; the venation fin-shaped channel consists of a primary channel, a secondary channel, venation fin-shaped ribs and a tertiary channel; the venation fin-shaped fluid channels are symmetrically distributed by the central axis, and the different channels meet the optimal transportation principle on the pipe diameter; hot fluid is injected from a first-stage channel, enters a second-stage channel after being split, and enters a third-stage channel after being split; the venation fin-shaped ribs are arranged on the tertiary channel and are symmetrically distributed by taking the tertiary channel as an axis; the phase change material is dispersed into the porous foam metal, and the porous foam metal and the phase change material are contacted with the tertiary channel;
in the transient high heat load stage, the low-temperature fluid in the cooler absorbs heat of the power consumption device through boiling convection heat exchange in the micro-channel heat sink, the generated gas-liquid two-phase flow transfers the heat to the heat storage type condenser through convection heat exchange, and the phase change material in the heat storage type condenser absorbs the heat through melting phase change; the medium-high temperature single-phase fluid after releasing heat flows through the cooler for further cooling, the liquid storage tank maintains the pressure balance of the system, the preheater regulates and controls the temperature of the fluid entering the micro-channel heat sink, and the fluid flows back to the micro-channel heat sink under the action of the mechanical pump to complete the circulation of the transient high thermal load stage;
in the non-thermal load stage, the low-temperature fluid in the cooler flows through the micro-channel heat sink to absorb a small amount of heat released by the power consumption device, and flows through the heat storage type condenser to absorb the heat released by solidification of the phase change material. And the fluid after absorbing heat flows through the cooler for cooling, and the fluid flows back to the micro-channel heat sink under the action of the mechanical pump to complete the circulation in the non-heat load stage.
2. The heat storage type phase change circuit device according to claim 1, wherein an injection hole is provided on the end cover; the phase change material is injected into the cavity from an injection hole reserved in the end cover, two-phase fluid flows in from the first-stage channel, and heat is exchanged with the phase change material through the third-stage channel of the heat storage type condenser and the porous foam metal on the outer wall.
3. The heat storage phase change loop device according to claim 1, wherein the microchannel heat sink is composed of a cover plate, an inlet chamber, an outlet chamber and a plurality of parallel micro-channels; the micro-channel comprises a necking section and an expansion section, and the width ratio of the necking section to the expansion section meets w 1 /w 2 ＝p,0<p<0.5; the length ratio satisfies L 1 /L 2 ＝q,0<q<1, wherein w 1 And L 1 W is the width and length of the necking section 2 And L 2 Is the width and length of the expansion section.
4. The heat-storage type phase-change loop device according to claim 1, wherein the heat-storage type condenser has a double-gradient structure condensation surface and a venation fin-shaped porous structure; the double-gradient structure condensation surface is provided with a wettability gradient with gradually increased contact angle along the fluid direction, the double-gradient structure condensation surface is composed of gradual change grooves on a condensation surface, the gradual change grooves are grooves with periodic arrangement, and the gradual change grooves show continuous change of periodic width increment in width.
5. The heat storage type phase change loop device according to claim 4, wherein the shape of the gradual change groove is an isosceles trapezoid connected end to end, and the gradual change angle alpha of the gradual change groove meets 4 degrees < alpha <15 degrees, wherein the gradual change angle alpha is an included angle formed by extending two waists of the isosceles trapezoid and then intersecting.
6. The heat storage type phase change circuit device according to claim 5, wherein the gradual change angle α satisfies 4 ° < α <9 °.
7. The heat storage type phase change loop device according to claim 1, wherein the optimal transportation principle that different channels of the venation fin-shaped channel meet in pipe diameter is as follows:
wherein r is 0 Represents the pipe diameter of an inlet channel, r n Representing the pipe diameter of the nth stage channel, coefficient i>1；
The parallel channels of each stage meet the length proportion relation in the length of the channels:
L n /L 0 ＝2 -n/δ
wherein L is n Represents the nth level of communicationTrack length, L 0 Representing the inlet channel length; delta is length coefficient, 1<δ<2。
8. A control system for the thermal storage type phase change loop of any one of claims 1-7, comprising an adaptive controller and an extended state observer;
the extended state observer is:
wherein beta is 1 ，β 2 ，β 3 Is an observer parameter; z 1 ，z 2 ，z 3 Respectively the two groups of the three groups are y,an estimated value of f, y is the average temperature of the surface of the micro-channel heat sink, f is the total disturbance,/->A first derivative of y;
the self-adaptive controller is as follows:
u 0 ＝k p (r-z 1 )-k d z 2
wherein u is 0 Is the rotation speed of the mechanical pump; k (k) p ，k d Is a controller parameter; r is the average temperature set value of the surface of the micro-channel heat sink.
9. A control method for a heat storage type phase change circuit according to any one of claims 1 to 7, characterized in that the control is performed by using the control system according to claim 8.
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