CN113621962B - Sintered porous coating pipe for enhancing flowing boiling and preparation method thereof - Google Patents
Sintered porous coating pipe for enhancing flowing boiling and preparation method thereof Download PDFInfo
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- CN113621962B CN113621962B CN202110963457.2A CN202110963457A CN113621962B CN 113621962 B CN113621962 B CN 113621962B CN 202110963457 A CN202110963457 A CN 202110963457A CN 113621962 B CN113621962 B CN 113621962B
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C24/00—Coating starting from inorganic powder
- C23C24/08—Coating starting from inorganic powder by application of heat or pressure and heat
- C23C24/10—Coating starting from inorganic powder by application of heat or pressure and heat with intermediate formation of a liquid phase in the layer
- C23C24/103—Coating with metallic material, i.e. metals or metal alloys, optionally comprising hard particles, e.g. oxides, carbides or nitrides
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
- F28F13/00—Arrangements for modifying heat-transfer, e.g. increasing, decreasing
- F28F13/18—Arrangements for modifying heat-transfer, e.g. increasing, decreasing by applying coatings, e.g. radiation-absorbing, radiation-reflecting; by surface treatment, e.g. polishing
- F28F13/185—Heat-exchange surfaces provided with microstructures or with porous coatings
Abstract
The invention discloses a preparation method of a sintering porous coating pipe for enhancing flowing boiling, which comprises the following steps: coating slurry containing metal particles on the surface of a metal pipe, and sintering the metal pipe at high temperature to obtain the sintered porous coating pipe; the coating slurry on the inner surface of the metal pipe is coated in a mode that the first end of the metal pipe is closed, the coating slurry is poured from the second end of the metal pipe until the metal pipe is filled with the coating slurry, and after the metal pipe is placed still, the first end of the metal pipe is opened to discharge the redundant coating slurry. The preparation method provided by the invention has lower cost, is beneficial to large-scale production of the sintered porous coating pipe, and the prepared sintered porous coating pipe has the micro-nano porous metal coating with uniformly distributed metal particles, firmness and no falling, so that the flow boiling heat transfer coefficient in the pipe can be further improved by multiple times, and the sintered porous coating pipe has wide application prospects in the fields of nuclear energy, aerospace, high-power device heat dissipation and the like.
Description
Technical Field
The invention relates to the field of flow boiling enhanced heat transfer, relates to a surface coating and a surface hydrophilic and hydrophobic modification technology, and particularly relates to a preparation method of a micro-nano scale sintered porous coating on the surface of a pipeline and a sintered porous coating pipe prepared by the method.
Background
The flow boiling enhanced heat transfer is a key technology for solving the difficult problem of temperature control of a high-power device and maintaining temperature uniformity. Metal materials such as copper, aluminum, stainless steel, etc. are widely used to process various heat transfer modules and are applied to different thermal control devices. Even in the semiconductor field, a metal-semiconductor heterojunction is constructed in a magnetron sputtering mode and the like, and then is processed into a micro-channel heat sink, so that the implementation of a high-efficiency heat control scheme is facilitated. Therefore, constructing an efficient boiling heat transfer coating on a metal surface is one of the key technologies for improving the feasibility and reliability of a thermal control solution.
The enhanced boiling heat transfer is mainly divided into fluid side enhancement and surface side enhancement, and the surface side enhancement improves the roughness of the surface by introducing the structural surface characteristics. The porous coating with the micro-nano scale composite structure on the surface has random pore size and recess curvature, and provides space for stable growth of bubbles. Compared with the periodic structure surface of the traditional photoetching processing, the coating has more diversity, and has more advantages of inhibiting dry flow and improving critical heat flow density under the working condition of high heat load. The sintered porous coating structure not only can effectively increase the specific surface area, but also can reduce the superheat degree required to be met by bubble nucleation, promote the vaporization of metastable state liquid in the micro-nano scale recess into saturated steam, improve the nucleation density of vaporization cores and accelerate the growth and separation speed of bubbles on the surface.
The metal micro-nano powder sintered coating and the base body are fused and welded, the strength of the coating and the base body metal is equivalent in the annealing process, and the coating and the spraying coating obtained by the traditional cold surface processing have better mechanical properties and mechanical properties.
In the prior art, patent CN105258548B discloses a method for preparing a porous boiling surface capable of controlling a vaporization core, which comprises the steps of pressing and covering metal micro-nano particles deposited on the surface of a substrate by using a micro-column mold designed and processed into a specific structure, fixing the metal micro-nano particles into a green body, sintering the green body under the protection of inert gas, and finally preparing the porous boiling heat transfer surface with the fixed vaporization core. However, this method requires an extra oversized mold, which not only has high production cost and is not easy to realize mass production, but also may cause irreparable damage to the material during demolding and molding after sintering. In addition, the conventional porous coating preparation process is mainly used for forming a sintered porous coating on the outer surface of a substrate, and cannot be applied to the substrate with a narrow processing space, such as the inner surface of a pipe.
Disclosure of Invention
The invention aims to provide a sintered porous coating pipe for reinforcing flow boiling and a preparation method thereof, and aims to solve the problems that the traditional porous coating preparation process cannot be suitable for the inner surface of a pipe, the production cost is high, and large-scale production is not easy to realize.
The above object is achieved by the following technical scheme:
a sintering porous coating pipe for strengthening flowing boiling and a preparation method thereof comprise the following steps:
coating slurry containing metal particles on the surface of a metal pipe, and sintering the metal pipe at high temperature to obtain the sintered porous coating pipe;
the coating slurry on the inner surface of the metal pipe is coated in a mode that the first end of the metal pipe is closed, the coating slurry is poured from the second end of the metal pipe until the metal pipe is filled with the coating slurry, and after the metal pipe is placed still, the first end of the metal pipe is opened to discharge the redundant coating slurry.
According to the technical scheme, the prepared coating slurry containing metal particles is coated on the outer surface and/or the inner surface of the metal pipe, and then the metal pipe coated with the coating slurry is placed in a sintering furnace to be sintered, so that a porous coating is formed on the surface of the metal pipe. Preferably, the metal pipe is stainless steel pipe, and more preferably, the stainless steel pipe is 304 stainless steel or 316 stainless steel.
In the coating process, the outer surface of the metal pipe can be coated by adopting the existing coating modes such as spraying, dip coating and the like. For the inner surface of metal pipes, there is a lack of effective coating means in the prior art. In this technical scheme, metal tubular product includes first end and second end, and wherein first end is the discharge end, and the second end is the feed end. The first end of the metal pipe is blocked by a seal head, the prepared coating slurry is poured from the second end of the pipe, the pipe stands for a period of time after the coating slurry fills the inner space of the metal pipe, and then the seal head at the first end is opened to discharge the redundant coating slurry which is not attached to the inner wall of the metal pipe. The viscosity of the metal powder slurry can be completely regulated and controlled by adopting the proportion of the dispersant and the slurry in the invention, so that a coating blank which is uniform in the pipe can be prepared. In one or more embodiments, the thickness of the coating slurry on the inner wall of the metal pipe can be adjusted by adjusting parameters such as standing time, discharge time, viscosity of the coating slurry and the like, so that the thickness of the porous coating can be changed. In one or more embodiments, after the coating slurry is discharged, the metal pipe is placed in a constant temperature drying oven at 60 ℃ to be dried for 20-120 min, and the porosity of the porous coating can also be adjusted by adjusting heat treatment parameters.
In some embodiments, the metal tubing is pretreated prior to application of the coating slurry. The pretreatment procedure comprises the steps of sequentially adopting absolute ethyl alcohol and deionized water to carry out ultrasonic cleaning on the smooth metal surface for 15-20 min, taking out the metal pipe and then putting the metal pipe into a constant-temperature drying oven at 60 ℃ for drying for 20-40 min.
The preparation method is simple to operate, has lower cost and is beneficial to large-scale production, and the prepared sintered porous coating tube has the micro-nano porous metal coating with uniformly distributed metal particles and firmness and no falling. The surface is smooth, various air cavities formed by gaps among particles obviously enhance the density of a vaporization core, so that the heat transfer coefficient of flowing boiling in the tube can be improved by times, and the method has wide application prospect in the fields of nuclear energy, aerospace, high-power device heat dissipation and the like; meanwhile, the preparation method provides a method for processing the porous coating in such a narrow space (the diameter d is less than 6 mm) on the inner surface of the pipe, and the thickness and the porosity of the coating can be adjusted by adjusting parameters such as the concentration of coating slurry, the standing time of the metal pipe, the viscosity of the coating slurry, heat treatment and the like.
As a preferable preparation method of the coating slurry in the invention, the coating slurry comprises the following components in percentage by mass: 40-70% of metal particles, 2-6% of adhesive, 4-10% of dispersant and the balance of solvent; the preparation temperature of the coating slurry is 25-55 ℃. According to the technical scheme, the solvent, the metal particles, the dispersing agent and the adhesive are prepared according to the proportion and are put into a container for blending, the container is integrally put into a constant-temperature water bath, and the metal particle mixture is stirred by a high-speed shearing instrument at the temperature of 25-55 ℃ until the viscosity of the suspension of the metal particles is not changed, so that the coating slurry containing the metal particles is obtained. In the coating slurry preparation process, the porosity inside the coating is adjusted by adjusting the shape and the particle size distribution of the metal particles in the coating slurry, and the control on the parameters of the porous coating is further improved, so that all the parameters of the porous coating are controllable.
Furthermore, the raw material of the adhesive is 0.2-3% of methyl cellulose aqueous solution, the dispersing agent is 0.5-3.5% of hot zinc stearate ethanol solution, and the solvent is absolute ethyl alcohol. According to the technical scheme, the formula of the adhesive is a methyl cellulose aqueous solution with the mass fraction of 0.2-3%, the dispersing agent is a hot zinc stearate-ethanol solution with the mass fraction of 0.5-3.5%, and the solvent is 99.99% absolute ethyl alcohol.
In a preferred embodiment of the present invention, the metal particles include first metal particles having an irregular shape and/or second metal particles having a regular shape, and the material of the first metal particles and the material of the second metal particles are the same as the material of the metal pipe. In this technical solution, the metal particles may only include the first metal particles with irregular shapes, may only include the second metal particles with regular shapes, or may include both of the metal particles. Preferably, the metal particles comprise both the first metal particles and the second metal particles. In addition, the first metal particles and the second metal particles are made of the same material as the metal pipe, for example, when the metal pipe is made of stainless steel, the first metal particles and the second metal particles are made of stainless steel with the same grade, the first metal particles can be made of stainless steel cutting powder (particles) with irregular shapes, and the second metal particles can be made of spherical stainless steel powder (particles) with regular shapes, so that the metal particles and the metal wall surface of the metal pipe can be firmly welded together by melting, the connection stability and mechanical strength of the coating are improved, and the coating is effectively prevented from falling off.
Furthermore, the central particle size distribution of the first metal particles and the second metal particles is between 10nm and 100 mu m, and the central particle size distribution of the first metal particles is 2 to 10 times of the central particle size distribution of the second metal particles. In the present embodiment, the particle size of the metal particles follows a normal distribution of a central particle size of 10nm to 100 μm. The size of the first metal particles with irregular shapes is larger than that of the second metal particles with regular shapes, so that enough gaps can be overlapped randomly among the first metal particles, and part of the gaps are filled with the second metal particles, so that the curvature of the capillary porous channel with the micro-nano scale is large, residual air pockets are formed in the coating, the capillary porous channel is convenient to convert into a vaporization core in the boiling process, and the growth frequency of vapor bubbles and the frequency of separating from the wall surface can be obviously promoted. Moreover, the roughness of the porous coating can be greatly improved on the basis of ensuring that residual air pockets are formed in the porous coating by adopting two kinds of metal particles, the critical heat flow density of nucleate boiling can be remarkably improved by the micro-nano rough structure, and the adaptability of the boiling surface to the extreme heat flow density is enhanced. Preferably, the center particle size distribution of the first metal particles is 2 to 10 times that of the second metal particles, and more preferably, the center particle size distribution of the first metal particles is 2.25 times that of the second metal particles.
Further, the mass ratio of the first metal particles to the second metal particles is 2. The quality of the first metal particles is not high enough, otherwise, the gaps between the adjacent metal particles are too large, the curvature of the channels of the porous coating is reduced, and the number of residual air cavities is reduced; meanwhile, the quality of the first metal particles is not too low, so that the roughness of the porous coating is reduced, and the heat exchange coefficient is reduced. It is found through experiments that the heat transfer enhancement effect is significant when the mass of the first metal particles is 1 to 3 times of the mass of the second metal particles, preferably, the mass of the first metal particles is 2 to 3 times of the mass of the second metal particles, and further preferably, the mass ratio of the first metal particles to the second metal particles is 2.
In some embodiments, the second metal particles may have a cylindrical, disc, strip or spherical shape, and preferably, the second metal particles have a spherical shape.
Furthermore, the high-temperature sintering process adopts a programmed temperature rise. In particular, the amount of the solvent to be used,sintering the metal pipe at high temperature in a protective gas atmosphere, heating to a preheating temperature at a heating rate of 5-10 ℃/min and preserving heat for 20-60 min during high-temperature sintering, then heating to a sintering temperature from the preheating temperature at a heating rate of 10-25 ℃/min, preserving heat for 60-150 min and then cooling, wherein the preset temperature is 0.15T melt ～0.3T melt The sintering temperature is 0.75T melt ～0.8T melt Said T is melt Is the melting point of the metal pipe. Preferably, the protective gas atmosphere is argon, and the cooling mode is natural cooling.
Further, the surface of the sintered porous coating pipe is subjected to anodic corrosion, the anodic corrosion solution adopts dilute sulfuric acid or dilute hydrochloric acid, the cathode adopts graphite, and the applied direct-current voltage range is 16-48V. The anode corrosion can be used for nano-scale roughening of the surface of the porous coating, so that the roughness of the surface of the porous coating is further improved. Preferably, the solution is dilute sulfuric acid solution, the concentration of the dilute sulfuric acid solution can be prepared to be 0.5-5.5 mol/L according to the size requirement of a target hole, the corrosion time in a direct current electric field is 1-6 min, and finally the porous coating pipe with the micro-nano composite rough structure is obtained.
The invention also provides a sintering porous coating pipe for enhancing flow boiling, which is prepared by any preparation method, the thickness of the porous coating arranged on the surface of the sintering porous coating pipe is 0.05-5 mm, and the porous coating contains irregular-shaped first metal particles and spherical second metal particles;
at a mass flow rate of 450kg/m 2 Under the working condition of s, the heat exchange coefficient of the sintered porous coating pipe is 19000-24000W/(m) 2 K)。
In the porous coating surface of the prepared sintered porous coating pipe, metal particles are bridged in the porous coating surface, the metal particle surfaces are welded with each other, gaps exist among the metal particles, and the metal particles are welded with the metal pipe metal wall surface in a melting way. Through the test of a flowing boiling experiment in the pipe, the mass flow rate is 350kg/m 2 s and 450kg/m 2 Under s working condition, cooling working medium is in the pipeline with porous coatingThe boiling heat transfer coefficient of (a) is enhanced by at least 2.5 times over that of a smooth channel.
The porous coating of the sintered porous coating pipe prepared by the invention has a micro-nano scale capillary porous channel with large curvature, residual air pockets are formed in the coating, the residual air pockets are convenient to convert into a vaporization core in the boiling process, and the growth frequency of vapor bubbles and the frequency of separating from the wall surface can be obviously promoted; meanwhile, the hydrophilic and hydrophobic properties of the smooth surface are improved by the porous coating, and the nucleation boiling starting point (ONB) is obviously reduced in the boiling process compared with the smooth untreated surface, namely the superheat degree required by the surface liquid boiling is obviously reduced; in addition, the micro-nano coarse structure on the surface of the porous coating reconstructs the distribution of the wall vaporization core, and the temperature distribution is more uniform and the temperature stability is better compared with the untreated surface in the boiling heat transfer process.
Compared with the prior art, the invention has the following advantages and beneficial effects:
1. the preparation method provided by the invention has lower cost and is beneficial to large-scale production of the sintered porous coating pipe, and the prepared sintered porous coating pipe has the micro-nano porous metal coating with uniformly distributed metal particles and firm and non-shedding property, so that the flow boiling heat transfer coefficient in the pipe can be further improved by multiple times, and the sintered porous coating pipe has wide application prospects in the fields of nuclear energy, aerospace, high-power device heat dissipation and the like;
2. the invention provides a method for processing a porous coating in such a narrow space of the inner surface of a pipe, the thickness of the coating can be adjusted by adjusting parameters such as the concentration of coating slurry, the standing time of a metal pipe, the viscosity of the coating slurry, heat treatment and the like, the porosity inside the coating can be adjusted by adjusting the shape and the particle size distribution of metal particles in the coating slurry, and all parameters of the porous coating can be controlled;
3. the material of the metal particles in the porous coating is the same as that of the pipe, so that the metal particles and the metal wall surface of the metal pipe can be firmly fused and welded together, the connection stability of the coating is improved, and the coating is effectively prevented from falling off;
4. the porous coating adopts the first metal particles with irregular shapes and the second metal particles with regular shapes, and the first metal particles and the second metal particles meet a certain size ratio and mass ratio, so that enough gaps can be randomly lapped between the first metal particles, and part of the gaps are filled with the second metal particles, so that the curvature of a capillary porous channel with a micro-nano scale is large, residual air pockets are formed in the coating, the coating is convenient to convert into a vaporization core in the boiling process, and the growth frequency of vapor bubbles and the frequency of separating from the wall surface can be remarkably promoted; meanwhile, the roughness of the porous coating can be greatly improved by adopting two kinds of metal particles, the micro-nano rough structure can obviously improve the critical heat flux density of nucleate boiling, and the adaptability of the boiling surface to the extreme heat flux density is enhanced;
5. according to the invention, the surface of the porous coating is subjected to nanoscale roughening through an anodic corrosion process, so that the roughness of the surface of the porous coating is further improved, the hydrophilic and hydrophobic properties of the surface are improved, and the acceleration of bubble nucleation and separation processes in a boiling process is facilitated;
6. the porous coating of the sintered porous coating pipe prepared by the invention has a micro-nano-scale capillary porous channel with large curvature, residual air pockets are formed in the coating, the residual air pockets are convenient to convert into a vaporization core in the boiling process, and the growth frequency of vapor bubbles and the frequency of separating from the wall surface can be obviously promoted; meanwhile, the hydrophilic and hydrophobic properties of the smooth surface are improved by the porous coating, and the nucleation boiling starting point (ONB) is obviously reduced in the boiling process compared with the smooth untreated surface, namely the superheat degree required by the surface liquid boiling is obviously reduced; in addition, the micro-nano coarse structure on the surface of the porous coating reconstructs the distribution of wall vaporization cores, and the temperature distribution is more uniform and the temperature stability is better than that of an untreated surface in the boiling heat transfer process.
Drawings
The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention. In the drawings:
FIG. 1 is a block diagram of a process for making a sintered porous coated tube according to an embodiment of the present invention;
FIG. 2 is a scanning electron microscope image of the field emission of the inner coating of a sintered tube with a porous coating of 45 μm stainless steel cutting particles, at 200 times magnification, according to an embodiment of the present invention;
FIG. 3 shows the comparison of the flow boiling heat transfer coefficient of sintered tubes (ST 45U) with 45 μm stainless steel cutting particles and Bare tubes (Bare) with unsintered porous coatings for porous coatings in a specific embodiment of the present invention;
FIG. 4 is a schematic cross-sectional electron microscope photograph of the inner surface of a sintered tube with 20 μm spherical stainless steel particles and 45 μm stainless steel cutting particles for a porous coating at 100 times magnification in an embodiment of the present invention;
FIG. 5 is a 500-fold magnified electron micrograph of the inner surface of a sintered tube with a porous coating using 20 μm spherical stainless steel particles and 45 μm stainless steel cutting particles, wherein the mass ratio of the 20 μm spherical stainless steel particles to the 45 μm stainless steel cutting particles is 1;
FIG. 6 shows the results of comparing the flow boiling heat transfer coefficient of sintered tubes (ST 45U 20R) having a porous coating using 20 μm spherical stainless steel particles and 45 μm stainless steel cutting particles with that of sintered tubes (ST 45U) having a porous coating using only 45 μm stainless steel cutting particles in a specific example of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to examples and the accompanying drawings, and the exemplary embodiments and descriptions thereof are only used for explaining the present invention and are not used as limiting the present invention.
All of the starting materials of the present invention, without particular limitation as to their source, are commercially available or can be prepared according to conventional methods well known to those skilled in the art.
All the raw materials of the invention are not particularly limited in their purity, and the invention preferably employs purity requirements that are conventional in the analytical purification or porous coating preparation arts.
All the raw materials, the marks and the acronyms thereof belong to the conventional marks and the acronyms in the field, each mark and acronym is clear and definite in the field of related application, and the raw materials can be purchased from the market or prepared by the conventional method by the technical staff in the field according to the marks, the acronyms and the corresponding application.
Example 1:
the sintered porous coating tube for enhancing flow boiling and the preparation method thereof as shown in figure 1 comprise the following steps:
pretreating a metal pipe;
coating the surface of the metal pipe with coating slurry containing metal particles;
sintering the metal pipe at a high temperature to obtain the sintered porous coating pipe;
the coating slurry on the inner surface of the metal pipe is coated in a mode that the first end of the metal pipe is closed, the coating slurry is poured from the second end of the metal pipe until the metal pipe is filled with the coating slurry, and after the metal pipe is placed still, the first end of the metal pipe is opened to discharge the redundant coating slurry.
In some embodiments, the surface of the sintered porous coating tube is subjected to anodic corrosion, the anodic corrosion solution adopts dilute sulfuric acid or dilute hydrochloric acid, the cathode adopts graphite, and the applied direct current voltage is 16-48V. Preferably, the applied dc voltage is 24V.
In some embodiments, the high temperature sintering process employs a programmed temperature increase. Specifically, the metal pipe is sintered at high temperature in a protective gas atmosphere, during high-temperature sintering, the temperature is increased to a preheating temperature at the heating rate of 5-10 ℃/min and is kept for 20-60 min, then the temperature is increased from the preheating temperature to a sintering temperature at the heating rate of 10-25 ℃/min and is kept for 60-150 min, and then the temperature is reduced, wherein the preset temperature is 0.15T melt ～0.3T melt The sintering temperature is 0.75T melt ～0.8T melt Said T is melt Is the melting point of the metal tube. Preferably, the protective gas atmosphere is argon, and the cooling mode is natural cooling. In one or more embodiments, during high-temperature sintering, the temperature is increased to the preheating temperature at the temperature increase rate of 6 ℃/min and is kept for 40min, then the temperature is increased from the preheating temperature to the sintering temperature at the temperature increase rate of 20 ℃/min, is kept for 150min and is reduced, and the preset temperature is 0.2T melt The sintering temperature is 0.8T melt 。
In some embodiments, the coating slurry comprises the following components in percentage by mass: 40-70% of metal particles, 2-6% of adhesive, 4-10% of dispersant and the balance of solvent; the preparation temperature of the coating slurry is in a constant temperature environment of 25-55 ℃. In one or more embodiments, the coating slurry comprises the following components in percentage by mass: 50% of metal particles, 5% of adhesive, 8% of dispersant and the balance of solvent; the preparation temperature of the coating slurry is 50 ℃ constant temperature environment. In one or more embodiments, the binder material is a 0.2-3% methylcellulose aqueous solution, the dispersant is a 0.5-3.5% hot zinc stearate ethanol solution, and the solvent is absolute ethanol.
In some embodiments, the metal particles include first metal particles with irregular shapes and/or second metal particles with regular shapes, and the material of the first metal particles and the material of the second metal particles are the same as the material of the metal pipe. In one or more embodiments, the first metal particles and the second metal particles have a central particle size distribution of 10nm to 50 μm, and the central particle size distribution of the first metal particles is 2 to 5 times that of the second metal particles. Preferably, the first metal particles have a central particle size distribution that is 2.25 times the central particle size distribution of the second metal particles. In one or more embodiments, the mass ratio of the first metal particles to the second metal particles is from 2. Preferably, the mass of the first metal particles is 2 times the mass of the second metal particles.
In some embodiments, the second metal particles are cylindrical, disc-shaped, bar-shaped, or spherical in shape, and preferably, the second metal particles are spherical in shape.
Example 2:
on the basis of the embodiment 1, the embodiment provides a method for preparing a stainless steel particle sintered porous coating ST45U on the inner surface of a stainless steel pipe with the inner diameter of 4mm, and the specific preparation method comprises the following steps:
the method comprises the following steps: and (4) pretreating the surface of the stainless steel pipe. Placing a stainless steel pipe with the length of 1m in absolute ethyl alcohol, ultrasonically cleaning for 15min, taking out, placing in an ultrasonic cleaning pool of deionized water, cleaning for 20min, and finally placing in a custom drying oven for drying for 30min;
step two: preparing the coating slurry of the stainless steel particle uniform dispersion system. 5g of methyl cellulose aqueous solution with the mass fraction of 1.5%, 180ml of absolute ethyl alcohol and 20ml of zinc stearate-ethyl alcohol solution with the mass fraction of 1% are placed in a 300ml beaker. Mixing 150g of stainless steel cutting particles with the central particle size distribution of 45 mu m with the solution, placing a beaker in a constant-temperature water bath kettle at 45 ℃, and stirring for 10min by a high-speed shearing instrument until the metal particles are uniformly dispersed in the slurry;
step three: pouring the coating slurry into a vertically placed stainless steel pipe, blocking a lower end outlet by using an end enclosure when metal particle slurry flows out from the bottom end, standing the stainless steel pipe filled with the coating slurry for 3min, opening the end enclosure at the bottom end, and discharging redundant coating slurry;
step four: placing the stainless steel tube into a custom drying oven, and drying at 60 deg.C for 30min;
step five: and horizontally placing the stainless steel pipe with the coating in a vacuum sintering furnace, vacuumizing, filling argon as protective atmosphere, heating to 300 ℃ at the speed of 10 ℃/min, preserving the heat for 30min, then quickly heating to 1000 ℃ at the speed of 20 ℃/min, preserving the heat for 1.5h, and naturally cooling to room temperature after the temperature is up.
The scanning electron microscope shooting image of the internal surface structure of the prepared stainless steel powder sintered coating tube ST45U is shown in FIG. 2. The fusion bridging among the powder particles can be clearly seen under the visual angle of 200 times of magnification, the formed air holes are more uniform, the sizes are diversified, and the surface area is obviously increased compared with that of a smooth wall surface.
And (4) testing the flowing boiling experiment in the coating pipe. As shown in FIG. 3, at a mass flow rate of 350kg/m 2 s and 450kg/m 2 The flow boiling heat transfer coefficient of the sintered porous coating tube ST45U under the working condition of s is tested and compared with that of a light tube. Experimental data show that the boiling heat transfer coefficient of the cooling working medium in the ST45U channel is enhanced by 2.5-4.2 times than that of the smooth channel, the wall surface superheat degree is lower than that of the smooth surface in the nucleate boiling process, and the bubble separation frequency is higher than that of the smooth surfaceAnd higher.
Example 3:
this example is a method for preparing a layer of stainless steel powder sintered porous coating tube ST45U20R on the inner surface of a stainless steel tube with an inner diameter of 4mm by adding spherical stainless steel particles with smaller particle size on the basis of example 1, and the specific preparation method comprises the following steps:
the method comprises the following steps: and (4) pretreating the surface of the stainless steel pipe. Placing a stainless steel tube with the length of 1m in absolute ethyl alcohol, carrying out ultrasonic cleaning for 15min, taking out, placing in an ultrasonic cleaning pool of deionized water, cleaning for 20min, and finally placing in a custom drying oven for drying for 30min.
Step two: preparing the coating slurry of the stainless steel particle uniform dispersion system. 5g of methyl cellulose aqueous solution with the mass fraction of 1.5%, 180ml of absolute ethyl alcohol and 20ml of zinc stearate-ethyl alcohol solution with the mass fraction of 1% are placed in a 300ml beaker. Then 100g of stainless steel cutting particles with the central particle size distribution of 45 mu m and 50g of spherical stainless steel particles with the central particle size distribution of 20 mu m are mixed with the solution, a beaker is placed in a constant-temperature water bath kettle at 45 ℃, and a high-speed shearing instrument is used for stirring for 10min until the metal particles are uniformly dispersed in the slurry;
step three: pouring the coating slurry into a vertically placed stainless steel pipe, blocking a lower end outlet by using an end enclosure when metal particle slurry flows out from the bottom end, standing the stainless steel pipe filled with the coating slurry for 3min, opening the end enclosure at the bottom end, and discharging redundant coating slurry;
step four: placing the stainless steel tube into a custom drying oven, and drying at 60 deg.C for 30min;
step five: and horizontally placing the stainless steel pipe with the coating in a vacuum sintering furnace, vacuumizing, filling argon as protective atmosphere, heating to 300 ℃ at the speed of 10 ℃/min, preserving the heat for 30min, then quickly heating to 1000 ℃ at the speed of 20 ℃/min, preserving the heat for 1.5h, and naturally cooling to room temperature after the temperature is up.
FIG. 4 is a schematic view of a sintered coated tube ST45U20R line-cut section coating structure taken by an electron microscope at a magnification of 100 times, spherical powder particles can be clearly seen to be distributed around the cutting powder and in the pore passage, the coating and the wall surface of the tube are fused and welded, and the bonding strength is equivalent to that of the base metal. FIG. 5 is a photographic image of a sintered coating at 500 times magnification ST45U20R, showing that spherical powder particles are distributed relatively uniformly in the channel gaps, the spherical shape of the particles remains intact, and the mixed powder formulation enhances the micropore distribution density and surface roughness of the surface coating.
FIG. 6 is a comparison of the results of the flow boiling heat transfer experiments in the sintered porous coated tubes ST45U20R and ST45U, from which it can be seen that the mass flow rate is 350kg/m 2 s and 450kg/m 2 Under the working condition of s, the boiling heat transfer coefficient of the cooling working medium in the ST45U20R channel is further improved, and the mass flow rate is 450kg/m 2 Under the working condition of s, the heat exchange coefficient of the sintered porous coating pipe is 19000-24000W/(m) 2 K) (ii) a At a mass flow rate of 350kg/m 2 Under the working condition of s, the heat exchange coefficient of the sintered porous coating pipe is 17000-22000W/(m) 2 K)。
Therefore, the invention takes stainless steel powder particles with different sizes and shapes as raw materials, reconstructs the metal surface by a high-temperature sintering process, and endows the metal surface with different roughness, porosity and hydrophilic-hydrophobic interface characteristics. The surface is simply further processed into a super-lubricating surface to be applied to the anti-icing and anti-icing field. The coating obtained by the preparation method has the advantages of high surface bonding strength, good stability, low large-scale preparation cost, wide application range and very high application value.
As used herein, "first," "second," etc. (e.g., first metal particles, second metal particles, etc.) merely distinguish the respective components for clarity of description and are not intended to limit any order or to emphasize importance or the like. Further, the term "connected" used herein may be either directly connected or indirectly connected via other components without being particularly described.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are merely exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (7)
1. A preparation method of a sintered porous coating tube for enhancing flow boiling is characterized by comprising the following steps:
coating slurry containing metal particles on the surface of a metal pipe, and sintering the metal pipe at a high temperature to obtain a sintered porous coating pipe;
the coating method of the coating slurry on the inner surface of the metal pipe comprises the following steps of sealing a first end of the metal pipe, pouring the coating slurry from a second end of the metal pipe until the metal pipe is filled with the coating slurry, standing, and opening the first end of the metal pipe to discharge redundant coating slurry;
the coating slurry comprises the following components in percentage by mass: 40 to 70 percent of metal particles, 2 to 6 percent of adhesive, 4 to 10 percent of dispersant and the balance of solvent; the preparation temperature of the coating slurry is 25 to 55 ℃, the metal particles comprise irregular first metal particles and regular second metal particles, the materials of the first metal particles and the second metal particles are the same as that of the metal pipe, the central particle size distribution of the first metal particles and the central particle size distribution of the second metal particles are 10nm to 100 micrometers, and the central particle size distribution of the first metal particles is 2 to 10 times that of the central particle size distribution of the second metal particles.
2. The method as claimed in claim 1, wherein the binder is 0.2-3% methylcellulose solution in water, the dispersant is 0.5-3.5% hot zinc stearate in ethanol, and the solvent is absolute ethanol.
3. The method for preparing the flow boiling enhanced sintered porous coating tube according to claim 1, wherein the mass ratio of the first metal particles to the second metal particles is 2 to 1.
4. The method for preparing the flow boiling enhanced sintered porous coated tube according to any one of claims 1 to 3, wherein the second metal particles are spherical in shape.
5. The method for preparing the flow boiling enhanced sintered porous coating tube according to any one of claims 1 to 3, characterized in that the metal tube is sintered at high temperature in a protective gas atmosphere, and during high-temperature sintering, the temperature is raised to a preheating temperature at a temperature raising rate of 5 to 10 ℃/min and is kept for 20 to 60min, and then the temperature is raised from the preheating temperature to the sintering temperature at a temperature raising rate of 10 to 25 ℃/min and is kept for 60 to 150min and is then lowered, wherein the preheating temperature is 0.15T melt ~ 0.3T melt The sintering temperature is 0.75T melt ~ 0.8T melt Said T is melt Is the melting point of the metal tube.
6. The method for preparing the flow boiling enhanced sintered porous coated pipe according to any one of claims 1 to 3, wherein the surface of the sintered porous coated pipe is subjected to anodic corrosion, the anodic corrosion solution adopts dilute sulfuric acid or dilute hydrochloric acid, the cathode adopts graphite, and the applied direct current voltage range is 16 to 48V.
7. A sintered porous coating pipe with enhanced flowing boiling is characterized in that the sintered porous coating pipe is prepared by the preparation method of any one of claims 1 to 6, the thickness of a porous coating arranged on the surface of the sintered porous coating pipe is 0.05 to 5mm, and irregular-shaped first metal particles and spherical second metal particles are contained in the porous coating;
at a mass flow rate of 450kg/m 2 Under the working condition of s, the heat exchange coefficient of the sintered porous coating pipe is 19000 to 24000W/(m) 2 K)。
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Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3821018A (en) * | 1969-10-10 | 1974-06-28 | Union Carbide Corp | Porous metallic layer formation |
| FR2229783A1 (en) * | 1973-05-14 | 1974-12-13 | Union Carbide Corp | Coating metal substrates - with a porous metal layer |
| JPS60190573A (en) * | 1984-03-12 | 1985-09-28 | Hitachi Cable Ltd | Treatment of inside surface of metallic pipe material |
| JPH0193479A (en) * | 1987-10-05 | 1989-04-12 | Kubota Ltd | Coating method for permeating sealant |
| USH971H (en) * | 1988-10-24 | 1991-10-01 | The United States Of America As Represented By The Secretary Of The Air Force | Regidized porous material and method |
| CN102689014A (en) * | 2012-06-15 | 2012-09-26 | 西北有色金属研究院 | Preparation method of metal fiber porous surface heat exchange tube |
| CN111207619A (en) * | 2020-01-15 | 2020-05-29 | 郑州轻工业大学 | Efficient boiling reinforced heat exchange tube and manufacturing method thereof |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10047880B2 (en) * | 2015-10-15 | 2018-08-14 | Praxair Technology, Inc. | Porous coatings |
-
2021
- 2021-08-20 CN CN202110963457.2A patent/CN113621962B/en active Active
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3821018A (en) * | 1969-10-10 | 1974-06-28 | Union Carbide Corp | Porous metallic layer formation |
| FR2229783A1 (en) * | 1973-05-14 | 1974-12-13 | Union Carbide Corp | Coating metal substrates - with a porous metal layer |
| JPS60190573A (en) * | 1984-03-12 | 1985-09-28 | Hitachi Cable Ltd | Treatment of inside surface of metallic pipe material |
| JPH0193479A (en) * | 1987-10-05 | 1989-04-12 | Kubota Ltd | Coating method for permeating sealant |
| USH971H (en) * | 1988-10-24 | 1991-10-01 | The United States Of America As Represented By The Secretary Of The Air Force | Regidized porous material and method |
| CN102689014A (en) * | 2012-06-15 | 2012-09-26 | 西北有色金属研究院 | Preparation method of metal fiber porous surface heat exchange tube |
| CN111207619A (en) * | 2020-01-15 | 2020-05-29 | 郑州轻工业大学 | Efficient boiling reinforced heat exchange tube and manufacturing method thereof |
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