CN110763055B - Surface hydrophobic modified composite condensation enhanced heat transfer pipe and preparation method thereof - Google Patents
Surface hydrophobic modified composite condensation enhanced heat transfer pipe and preparation method thereof Download PDFInfo
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- CN110763055B CN110763055B CN201910784603.8A CN201910784603A CN110763055B CN 110763055 B CN110763055 B CN 110763055B CN 201910784603 A CN201910784603 A CN 201910784603A CN 110763055 B CN110763055 B CN 110763055B
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
- F28D15/00—Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls ; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies
- F28D15/02—Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls ; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies in which the medium condenses and evaporates, e.g. heat pipes
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- General Engineering & Computer Science (AREA)
- Rigid Pipes And Flexible Pipes (AREA)
- Laminated Bodies (AREA)
Abstract
本发明公开了一种表面疏水改性复合冷凝强化传热管及其制备方法，其特点在于该表面疏水改性冷凝传热管具有较大表面接触角，这一特点可使管外表面的凝液厚度被减薄，使管外热阻减小，从而提高制冷剂管外凝结换热系数，从而起到强化凝结换热的效果，并且这种强化效果会在整个工况的热流密度变化范围内持续作用。通过本发明制备的传热管可用于使用管壳式冷凝器的制冷、空调和暖通设备中，该表面疏水改性复合传热管可在大热流密度和小热流密度范围内对冷凝换热器的换热性能进行持久强化。在使用表面疏水改性传热管后，由于冷凝换热器换热性能的增强，因而能够缩小冷凝器的尺寸，从而降低系统的成本。
The invention discloses a surface hydrophobically modified composite condensation-enhanced heat transfer tube and a preparation method thereof. The thickness of the liquid is reduced, which reduces the external thermal resistance of the tube, thereby increasing the condensation heat transfer coefficient outside the refrigerant tube, thereby enhancing the effect of condensation heat transfer, and this enhanced effect will change the range of heat flux density in the entire working condition. persistent effect. The heat transfer tube prepared by the present invention can be used in refrigeration, air conditioning and HVAC equipment using shell-and-tube condensers, and the surface hydrophobically modified composite heat transfer tube can conduct heat transfer for condensation in the range of large heat flux density and small heat flux density The heat transfer performance of the device is permanently enhanced. After using the surface hydrophobically modified heat transfer tube, due to the enhanced heat exchange performance of the condensing heat exchanger, the size of the condenser can be reduced, thereby reducing the cost of the system.
Description
Technical Field
The invention belongs to the technical field of a surface hydrophobic modified condensation enhanced heat transfer pipe capable of enhancing condensation phase change heat transfer of an external refrigerant, and particularly relates to a surface hydrophobic modified composite condensation enhanced heat transfer pipe and a preparation method thereof.
Background
The shell-and-tube condenser is widely applied to refrigeration, air conditioning and waste heat recovery equipment. In the air conditioning unit, a liquid refrigerant circulating in the system absorbs indoor heat in an evaporator and is gasified into high-temperature low-pressure refrigerant steam, the refrigerant steam is sucked into a compressor immediately and is converted into high-temperature high-pressure refrigerant steam, the high-temperature high-pressure refrigerant steam is discharged and then enters a condenser to be cooled and condensed to become low-temperature high-pressure refrigerant liquid, and then the low-temperature high-pressure refrigerant liquid is changed into low-temperature low-pressure refrigerant liquid through a throttle valve to continuously absorb the indoor heat, and the circulation is continued. The main functions of the cycle process condenser are to reduce the refrigerant temperature and condense the liquid. If the cooling effect of the condenser does not reach the expected cooling temperature, the power of the compressor is increased, the energy efficiency of the system is reduced, more electric energy is consumed, and the running cost of the system is increased. Therefore, it is important to improve the cooling efficiency of the shell-and-tube condenser for the performance of the refrigeration system. The general method for improving the heat exchange performance of the shell-and-tube condenser is to optimize the structure of the condenser. Generally, more measures are taken, such as adopting heat transfer pipes with better heat exchange performance, optimizing the arrangement of the pipe rows, adopting liquid baffle plates and the like. With the continuous maturity of the technology, the optimization of the heat exchange performance of the condenser is gradually close to the bottleneck, the difficulty in further improving the heat exchange performance is increased, and people have to find other directions and methods to improve the heat exchange performance of the shell-and-tube condenser.
At present, after decades of development, the difficulty of further strengthening the heat transfer by only using machined three-dimensional geometric fins is very high, even 10% of the heat transfer is very difficult. It is therefore desirable to propose a new way to enhance.
Disclosure of Invention
In order to solve the problems, the invention provides the surface hydrophobic modified composite condensation enhanced heat transfer pipe and the preparation method thereof, which improve the heat transfer coefficient of the heat transfer pipe, and improve the cooling efficiency of a shell-and-tube condenser when the surface hydrophobic modified composite condensation enhanced heat transfer pipe is applied to the shell-and-tube condenser.
In order to achieve the purpose, the surface hydrophobic modified composite condensation enhanced heat transfer pipe comprises a pipe wall, wherein fins are arranged outside the pipe wall, each fin comprises a fin root, the root part of each fin root is connected to the pipe wall, the tail end of each fin root outwards extends to form a first tip and a second tip, the lower parts of the first tips and the second tips are connected, and the angles of the tips of the first tips and the second tips are smaller than 30 degrees; and hydrophobic layers are covered on the tube wall and the outer surfaces of the fins.
Further, the hydrophobic layer comprises a first hydrophobic layer and a second hydrophobic layer covering the first hydrophobic layer, and the thickness of the hydrophobic layer is less than 0.1 micrometer; the thickness of the first hydrophobic layer is greater than the thickness of the second hydrophobic layer.
Furthermore, the hydrophobic layer is made of high molecular material or plasma.
Furthermore, an internal thread strengthening structure is arranged in the pipe wall.
Furthermore, the angle of the joint surface of the first tip and the second tip is more than or equal to 90 degrees.
Furthermore, the height of the rib root is 2H/3, the height of the first tip is 1H/3, the height of the second tip is 1H/9, and H is the height of the rib.
Furthermore, the rib density of the rib is 38fpi-50fpi, and the rib height is 0.5mm-0.9 mm.
A preparation method of a surface hydrophobic modified composite condensation enhanced heat transfer pipe comprises the following steps:
and 4, sealing two ends of the heat transfer pipe:
and 5, performing hydrophobic modified coating on the outer surface of the heat transfer pipe to form a hydrophobic layer on the outer surface of the heat transfer pipe.
Further, in step 1, the surface of the heat transfer pipe is washed by sequentially using isopropyl alcohol, isopropyl alcohol and clear water, and then water drops on the surface of the heat transfer pipe are blown off by using a spray gun.
Further, the specific process of step 5 is as follows: vacuumizing the vapor deposition system, and performing vapor deposition on the surface of the heat transfer pipe when the vacuum degree reaches a coating condition to coat a film on the outer surface of the heat transfer pipe to form a hydrophobic layer; and after the film coating is finished, recovering the pressure in the vapor deposition system to atmospheric pressure, and finishing the hydrophobic modification on the outer surface of the heat transfer pipe when the temperature of the heat transfer pipe is cooled to room temperature.
Compared with the prior art, the invention has at least the following beneficial technical effects:
the surface hydrophobic modified composite condensation enhanced heat transfer pipe is characterized in that the heat transfer of the heat transfer pipe is enhanced by using a three-dimensional fin which is machined, and the heat transfer pipe is subjected to secondary hydrophobic treatment by using a surface hydrophobic modification method. The main reason that the tubular type can strengthen the condensation heat exchange outside the tube is that the surface contact angle developed based on the three-dimensional structure is further increased. Compared with the three-dimensional fins without surface modification and the surfaces only adopting modification treatment, the heat transfer coefficient is greatly enhanced. Because the refrigerant is generally an organic working medium, the surface tension is very small, generally about one tenth of that of water, and the influence on the condensation heat exchange coefficient is small only by adopting the surface modification treatment technology. And the heat transfer coefficient of the surface heat transfer pipe with the hydrophobic coating plated outside by adopting the three-dimensional geometric structure can be greatly enhanced. The reason why the composite modified surface heat transfer pipe can enhance the heat transfer of the refrigerant is as follows:
the fins arranged outside the tube wall are of three-dimensional reinforced structures, and the peak surfaces formed by the first tips and the second tips can break through a liquid film formed by the refrigerant to promote the liquid film to be discharged; after the hydrophobic layer is added, when refrigerant condensate is generated outside the heat transfer pipe, the large contact angle of the surface of the composite structure formed by the three-dimensional reinforced structure and the hydrophobic layer can accelerate the discharge of a liquid film on the surface of the reinforced structure, so that the thickness of the condensate on the outer surface of the pipe is reduced, the thermal resistance outside the pipe is reduced, the condensation heat exchange coefficient outside the refrigerant pipe is improved, the effect of reinforcing condensation heat exchange is achieved, and the reinforcing effect can continuously play a role in the heat flow density change range of the whole working condition.
Furthermore, the hydrophobic layer comprises a first hydrophobic layer and a second hydrophobic layer covering the first hydrophobic layer, and the thickness of the hydrophobic layer is less than 0.1 micrometer; the thickness of the first hydrophobic layer is larger than that of the second hydrophobic layer, and the first hydrophobic layer is used for enhancing the adhesion strength of the second hydrophobic layer, so that the second hydrophobic layer can be used for enhancing the condensation heat exchange outside the tube more continuously.
Furthermore, the angle of the joint surface of the first tip and the second tip is more than or equal to 90 degrees, and the thickness of the refrigerant condensate at the top end of the three-dimensional fin can be obviously thinned.
Furthermore, the height of the rib root is 2H/3, the height of the first tip is 1H/3, the height of the second tip is 1H/9, and H is the height of the rib.
Furthermore, the rib density of the ribs is 38fpi-50fpi, the rib height is 0.5mm-0.9mm, the parameters are optimized rib parameters, and the condensation heat exchange effect of the refrigerant is optimal under the parameters.
The heat transfer pipe can be used in refrigeration, air conditioning and heating equipment using a shell-and-tube condenser, and the surface hydrophobic modified composite heat transfer pipe can be used for permanently strengthening the heat exchange performance of a condensation heat exchanger in the ranges of large heat flux density and small heat flux density. After the surface hydrophobic modified heat transfer pipe is used, the size of the condenser can be reduced due to the enhancement of the heat exchange performance of the condensing heat exchanger, and therefore the cost of a refrigeration system is reduced.
The preparation method of the heat transfer pipe comprises two steps, namely the processing of the reinforced pipe and the double-layer and multi-layer film coating processes. The coating material is a high polymer material or plasma, the use cost is low, and because the running time of the central air-conditioning water cooling unit is long, the energy consumption is high, and compared with the increase of the coating cost, the heat exchange efficiency is improved, and the benefit return brought by the increase of the energy efficiency ratio is more. The formation of the double-layer coating can also obviously improve the corrosion resistance of the heat transfer pipe, so that the average service life of the heat transfer device is prolonged.
Drawings
FIG. 1 is a schematic representation of hydrophobic modification of the surface of a light pipe;
FIG. 2 is a two-sided three-dimensional enhanced heat transfer tube;
FIG. 3 is a schematic diagram of a three-dimensional fin outer coating;
FIG. 4a is a schematic view of the static contact angle before coating the light pipe;
FIG. 4b is a schematic view of the static contact angle after the light pipe is coated;
FIG. 4c is a schematic diagram of the static contact angle after the light pipe coating experiment;
FIG. 4d is a schematic view of the static contact angle of the three-dimensional strengthened tube before coating;
FIG. 4e is a schematic view of the three-dimensional strengthened tube after being coated with a film and showing the static contact angle;
FIG. 4f is a schematic diagram showing a static contact angle after a three-dimensional strengthened tube coating experiment;
FIG. 4g is a schematic diagram of an advancing angle-dynamic contact angle of a three-dimensional strengthened tube before film coating;
FIG. 4h is a schematic diagram of the advancing angle-dynamic contact angle of the three-dimensional reinforced tube after coating;
FIG. 4i is a schematic diagram of the advancing angle-dynamic contact angle after the three-dimensional strengthened tube coating experiment;
FIG. 4j is a schematic view of a dynamic contact angle of a three-dimensional reinforced tube before film coating;
FIG. 4k is a schematic diagram of a dynamic contact angle after a back-entering angle and a three-dimensional strengthened tube are coated;
FIG. 4l is a schematic diagram of a dynamic contact angle after a back-entering angle-three-dimensional strengthened tube coating experiment;
FIG. 5a is an electron micrograph of an uncoated three-dimensional reinforcement tube at 100X;
FIG. 5b is an electron micrograph of a 500-fold three-dimensional reinforcement tube without a coating film thereon;
FIG. 5c is a 5000 times-electron micrograph of an uncoated three-dimensional strengthened tube;
FIG. 5d is an electron microscope image of a 100-fold three-dimensional strengthened tube after being coated with a film;
FIG. 5e is a 500 times-SEM image of the three-dimensional strengthened tube after coating;
FIG. 5f is a 5000 times-electron microscope image after the three-dimensional reinforced tube is coated with a film;
FIG. 5g is an electron microscope image after a 100-fold three-dimensional strengthened tube coating experiment;
FIG. 5h is a 500 times-electron microscope image after the three-dimensional reinforced tube coating experiment;
FIG. 5i is a 5000 times-electron microscope image after the three-dimensional reinforced tube coating experiment;
FIG. 6a is a comparison of the condensation heat transfer coefficients of the refrigerant R134a before and after the light pipe coating at a saturation temperature of 40 ℃;
FIG. 6b is a comparison of the condensation heat transfer coefficients of the refrigerant R134a before and after the light pipe coating at a saturation temperature of 30 ℃;
FIG. 7a is a comparison of the condensation heat transfer coefficients of refrigerant R1234ze (E) before and after the light pipe coating at a saturation temperature of 40 ℃;
FIG. 7b is a comparison of the condensation heat transfer coefficients of refrigerant R1234ze (E) before and after the light pipe coating at a saturation temperature of 30 ℃;
FIG. 8a is a comparison of the condensation heat transfer coefficients of the refrigerant R290 before and after the light pipe coating at a saturation temperature of 40 ℃;
FIG. 8b is a comparison of the condensation heat transfer coefficients of the refrigerant R290 before and after the light pipe coating at a saturation temperature of 30 ℃;
FIG. 9a is a comparison of the heat transfer coefficient of condensation from R134a before and after machining the three-dimensional fin surface coating at a saturation temperature of 40 ℃;
FIG. 9b is a comparison of the R134a condensation heat transfer coefficients before and after machining the three-dimensional fin surface coating at a saturation temperature of 30 ℃;
FIG. 10a is a comparison of the heat transfer coefficient of condensation of R1234ze (E) before and after machining of the three-dimensional fin surface coating at a saturation temperature of 40 ℃;
FIG. 10b is a comparison of the heat transfer coefficient of condensation of R1234ze (E) before and after machining of the three-dimensional fin surface coating at a saturation temperature of 30 ℃;
FIG. 11a is a comparison of the heat transfer coefficient of the R290 condensation before and after machining the three-dimensional fin surface coating at a saturation temperature of 40 ℃;
FIG. 11b is a comparison of the heat transfer coefficient of the R290 condensation before and after machining the three-dimensional fin surface coating at a saturation temperature of 30 ℃.
In the drawings: the heat transfer pipe comprises a pipe wall, 2 fins, 3 internal thread strengthening structures, 4 hydrophobic layers, 41 first hydrophobic layers, 42 second hydrophobic layers, 5 light pipes and three-dimensional strengthening pipes, wherein the pipe wall is externally provided with a heat transfer pipe with three-dimensional strengthening fins.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.
In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on those shown in the drawings, and are used only for convenience in describing the present invention and for simplicity in description, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present invention. Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless otherwise specified. In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
A surface hydrophobic modified composite condensation strengthened heat transfer pipe is characterized in that a machined three-dimensional fin is used for strengthening heat transfer of the heat transfer pipe, and a surface hydrophobic modification method is used for carrying out hydrophobic treatment on the heat transfer pipe. The surface contact angle developed based on the three-dimensional fins is further increased, and compared with the three-dimensional fins without surface modification and the surfaces only adopting modification treatment, the heat transfer coefficient is greatly enhanced.
Referring to fig. 2, the surface hydrophobic modified composite condensation enhanced heat transfer pipe comprises a pipe wall 1, an internal thread enhanced structure 3 is arranged in the pipe wall 1, three-dimensional enhanced fins 2 are arranged outside the pipe wall 1, and roots of fin roots are connected to the pipe wall 1. The rib 2 has a rib density of 38fpi to 50fpi (fins per inch), a rib height of 0.5mm to 0.9mm, the rib 2 is Y-shaped, and the rib 2 includes a rib root 21, a first tip 22, and a second tip 23. The tail end of the fin root 21 extends outwards to form a first tip 22 and a second tip 23, the lower parts of the first tip 22 and the second tip 23 are connected, the angle of the connection surface of the first tip 22 and the second tip 23 is more than or equal to 90 degrees, the tops of the first tip 22 and the second tip 23 are in an inverted V shape, and the included angle of the tops is less than 30 degrees. The height of the rib root 21 is 2H/3, the height of the first tip 22 is 1H/3, the height of the second tip 23 is 1H/9, and H is the height of the rib 2.
The outer surface of the heat transfer pipe is covered with a hydrophobic layer 4, the hydrophobic layer 4 can adopt a double-layer coating film or a single-layer or multi-layer coating film, and the total thickness of the two layers is less than 0.1 micron.
When the hydrophobic layer 4 is two layers, the hydrophobic layer 4 includes a first hydrophobic layer 41 and a second hydrophobic layer 42 covering the first hydrophobic layer 41; the material of the first hydrophobic layer 41 is a high molecular material, such as polytetrafluoroethylene and parylene, and the thickness of the first hydrophobic layer 41 is greater than 0.05 micrometers; the material of the second hydrophobic layer 42 is a polymer material or plasma, and the material of the first hydrophobic layer may be the same or different.
The coating material of the hydrophobic layer 4 can be a high molecular material or plasma, and a chemical etching method can also be adopted to form the hydrophobic layer.
Next, a description will be given of a surface hydrophobic modification treatment method which is applicable to a light pipe and a reinforced pipe, and a schematic view of the preparation is shown in FIG. 1.
And 2, drying the surface of the heat transfer pipe. Because the equipment for modifying the hydrophobic surface must ensure the surface drying, the heating table is used for drying the surface of the heat transfer pipe for surface hydrophobic modification, the temperature of the heating table is adjusted to 110 ℃, the heat transfer pipe is placed on the heating table, when the temperature of the heating table reaches 110 ℃, the heating table is enabled to act on the heat transfer pipe for 15 to 20 minutes, the heating can be stopped, and the heat transfer pipe is stood to enable the heat transfer pipe to radiate the ambient temperature, so that the next operation can be carried out.
And 3, sealing two ends of the heat transfer pipe. Because only the outer surface of the heat transfer pipe is subjected to hydrophobic modification, in order to avoid the influence on subsequent experimental measurement caused by the hydrophobic modification of the inner surface of the heat transfer pipe in the preparation process, the two ends of the heat transfer pipe are subjected to sealing treatment, and the sealing method used in the method is to seal the two ends of the heat transfer pipe by using rubber plugs which are slightly larger than the inner diameter of the heat transfer pipe.
And 4, performing surface hydrophobic modification coating on the heat transfer pipe. Put the heat-transfer pipe that has sealed into hydrophobic layer vapor deposition system, seal the sealed lid that the system used again, the mode of hydrophobic layer deposition is carried out in the selection this moment, in order to make the hydrophobic cladding material of heat-transfer pipe surface can more lasting effect, at first plate first hydrophobic layer to the heat-transfer pipe surface, plate the second hydrophobic layer again on the basis of first hydrophobic layer, the thickness of second hydrophobic layer is less than the thickness of first water transmission layer (the more great surface contact angle of thinner hydrophobic layer), utilize vapor deposition equipment deposit two-layer hydrophobic membrane on three-dimensional reinforced pipe promptly:
vacuumizing a vapor deposition system, performing vapor deposition on the surface of the heat transfer pipe when the vacuum degree reaches a coating condition, and coating a first hydrophobic layer on the outer surface of the heat transfer pipe, wherein the process parameters are as follows: power 105W, pressure 200mTorr, time 15 min; and then, vacuumizing the vapor deposition system, performing vapor deposition when the vacuum degree reaches a coating condition, and coating a second hydrophobic layer on the first hydrophobic layer, wherein the process parameters are as follows: the power is 90W, the pressure is 400mTorr, and the time is 20 min; and after the second hydrophobic layer is coated, recovering the pressure in the system to atmospheric pressure, and finishing hydrophobic modification on the outer surface of the heat transfer pipe when the temperature of the heat transfer pipe is cooled to room temperature.
The hydrophobic layer can also be formed by chemical etching.
The condensation heat transfer coefficient of the composite modified surface heat transfer pipe adopted by the invention can be further greatly improved, and particularly, the enhancement effect of the condensation heat transfer is introduced by using the sample pipe, and the condensation heat transfer coefficient of the sample pipe can be at least improved by more than 70% for three typical refrigerants. The machined three-dimensional heat transfer tubes listed in table 1 are taken as an example to illustrate the implementation process, the heat exchange enhancement principle and the implementation effect of the invention.
Table 1 test and comparison of geometric parameters of heat exchange tubes
The coating of the surface modified tube is based on the three-dimensional ribbed tube machined by copper, and the three-dimensional ribs are further machined on the basis of the two-dimensional low-ribbed tube by the characteristics of the ribbed tube, so that a heat exchange surface with higher condensation heat exchange coefficient is obtained. The three-dimensional finned tube can enhance heat transfer through different three-dimensional structures. On the basis of the three-dimensional reinforced heat transfer pipe, different plating layers or modification modes on the surface are adopted for processing. Compared with a mechanically processed three-dimensional ribbed tube, the heat transfer coefficient of the three-dimensional ribbed tube is greatly improved.
As shown in FIG. 1 (d in the figure)i，doRespectively, inner diameter and outer diameter of the tube), passing through the outer surface of the conventional light pipe without surface hydrophobic modificationAfter the surface is subjected to hydrophobic modification, the outer surface of the surface is coated with a relatively thick first hydrophobic layer 41 and a relatively thin second hydrophobic layer 42, and the reason for firstly coating the first hydrophobic layer 41 is mainly to enhance the adhesion strength of the second hydrophobic layer 42, so that the second hydrophobic layer 42 can enhance the condensation heat exchange outside the pipe more continuously. The coating mode can also be adopted if the single or multiple layers of coatings have higher adhesive strength and can promote the thinning of a liquid film. The coating material is a high molecular material or plasma, and the coating mode is effective for three-dimensional reinforced pipes, but the effect of reinforcing the condensation heat exchange of the refrigerant by the coating of the light pipe is not obvious. The invention also uses a light pipe to compare the influence of the coating with a smooth surface on the condensation heat exchange of different refrigerants. The process of carrying out surface hydrophobic modification on the smooth pipe is similar to that of a reinforced pipe, the main difference is that a three-dimensional fin reinforced structure machined by a machine is arranged outside the reinforced pipe, and the smooth pipe is directly plated on the smooth surface without any fins.
The direct effect on the heat transfer tube after the hydrophobic layer is plated is the change in the surface contact angle. The influence of the front and back plating layers on the surface contact angle and the condensation heat exchange is illustrated by taking a smooth heat transfer pipe and a three-dimensional machining reinforced heat transfer pipe as examples. The parameters for both tubes are shown in table 1. The reinforced pipe is a double-side reinforced pipe, internal threads are reinforced in the pipe, the reinforced structure outside the pipe is fins 2, and the reinforced pipe can be processed into different three-dimensional fin geometric structures due to the fact that a copper pipe is made of soft materials, and the density of fins outside the pipe of the reinforced pipe is high as can be seen from the figure. Fig. 4a to 4l are the comparison of the contact angles of water before and after the modified coating on the surface of the three-dimensional reinforced fin. For a smooth surface, the contact angle of water on the surface of the heat transfer pipe after film coating is further increased. For the smooth heat transfer tubes tested in the test, the contact angle increased from 88 ° to 121 °. In order to test whether the organic working medium of the refrigerant corrodes the coating in the experiment, after a one-month condensation heat transfer experiment of the refrigerant at the saturation temperature of 40 ℃, static and dynamic contact angle tests are carried out, and as can be seen from the figure, the contact angle is not reduced, even is increased to a certain extent. Therefore, the refrigeration working medium has no influence on the surface heat exchange effect after the light pipe is modified. For the surface of the three-dimensional reinforced ribbed tube, the surface of the rib top is taken as a reference surface, before the modified coating is not carried out, when liquid drops are dripped on the reinforced heat transfer surface, a part of liquid enters the interior of the rib space, the liquid wraps a part of the rib top section, and the measured contact angle is 122 degrees. When the liquid drop is small, the liquid drop is suspended on the top of the reinforced fins, no liquid enters the fins, the contact angle is 152 degrees, the contact angle of the super-hydrophobic surface is achieved, after a condensation heat transfer experiment of the refrigerant at 40 ℃ saturation temperature for one month is carried out, the contact angle is almost unchanged, and the static contact angle of an actual test result is 154 degrees. The dynamic contact angle includes advancing and receding contact angles, and is similar to the static contact angle, which are close to the advancing and receding contact angles before the unmodified plating film. After surface modification, the contact angles all increased to 150 ° or more. Therefore, in the condensation heat exchange process, condensate flows on the heat transfer surface, and the contact angle of the condensate is still larger. Along with the proceeding of condensation heat transfer, the modification effect can not be changed, and the heat exchange effect of the heat exchanger is still good. After the experiment of condensation heat transfer of the refrigerant at the saturation temperature of 40 ℃ for one month, the change of the dynamic and static contact angles is still not large. The contact angle changes of the two exemplary heat exchange tubes before and after the plating film modification and before and after the experiment are shown in table 2.
TABLE 2
The appearance of the strengthened surface is changed microscopically after the plating. FIGS. 5a to 5i are graphs showing the change of the heat transfer surface under a microscope before and after the surface of the three-dimensional strengthened tube is coated with a film and after a condensation heat transfer experiment is performed. As can be seen from the figure, the surface of the reinforced pipe after coating is smoother due to the rough units generated by mechanical processing, and the mechanical chamfer is changed from sharp to smooth. The surface structure is more uniform as seen in the photograph magnified 5000 times. After the one-month condensation heat transfer test is carried out, the structure and the smoothness of the coating surface of the three-dimensional reinforced pipe do not change greatly, which is the reason why the contact angle of the surface does not change greatly after the condensation heat transfer is carried out.
A comparison of the heat transfer coefficients of the refrigerant condensation before and after coating the two exemplary heat transfer tubes is shown in fig. 6 a-11 b. In order to research whether the surface of the coating still works on different refrigerants, three refrigerants of R134a (hydrofluoro hydrocarbon), R1234ze (E) (hydrofluoro olefin, novel environment-friendly refrigerant) and R290 (hydrofluoro hydrocarbon) are selected to research the influence of the coating on the condensation heat transfer coefficient of the coating. The experimental results before and after the surface hydrophobic modification are shown in fig. 6 a-11 b, wherein fig. 6 a-8 b show the influence of the surface hydrophobic modification on the heat transfer coefficient of the condensation outside the R134a, R1234ze (E) and R290 light tubes at different saturation temperatures. FIGS. 9 a-11 b are graphs showing the effect of machined three-dimensional fin surface hydrophobic modification on the heat transfer coefficient of condensation outside the R134a, R1234ze (E) and R290 tubes at different saturation temperatures. The saturation temperatures for the condensation heat transfer test were 40 ℃ and 30 ℃.
As can be seen from FIGS. 6a to 8b, the hydrophobic modification of the outer surface of the light pipe can increase the condensation coefficient of R134a, R1234ze (E) and R290 at different saturation temperatures. Because the thermophysical parameters of R134a and R1234ze (E) are similar at different saturation temperatures, the condensation heat transfer coefficients of the R134a and the R1234ze (E) are also similar from FIG. 6a, FIG. 6b, FIG. 7a and FIG. 7b, the strengthening effect is not very obvious when the heat flow density is higher, but the strengthening effect of the surface hydrophobic modification is strengthened continuously along with the reduction of the heat flow density, the strengthening effect is maximized when the heat flow density is minimum, and the surface hydrophobic modification can make the condensation heat transfer coefficients of the R134a and the R1234ze (E) outside the light pipe maximally increase by 16.5% and 12.3%, respectively. The strengthening effect of the surface hydrophobic modification on the external condensation heat exchange coefficient of the R290 light tube is more remarkable than that of R134a and R1234ze (E), the difference between the thermal physical parameters of R290 and R134a and R1234ze (E) is larger, especially the difference between the density and the viscosity is larger, the strengthening effect of the surface hydrophobic modification on the external condensation heat exchange coefficient of the R290 light tube is stronger due to the difference, and the maximum strengthening effect can reach 19.7%.
Also, as can be seen from FIGS. 9a to 11b, the hydrophobic modification of the surface for R13 at different saturation temperatures4a, R1234ze (E) and R290, the enhancement of the condensation coefficient outside the tube is much more pronounced than for light pipes. As mentioned above, the thermophysical parameters of R134a and R1234ze (E) are similar, and the influence of the surface hydrophobic modification on the heat transfer coefficient of the condensation outside the reinforced tubes of R134a and R1234ze (E) is also similar. When the heat flux density is higher, the enhanced heat exchange effect tends to be constant value along with the reduction of the heat flux density because the condensate outside the pipe is thicker. When the heat flux density is less than 60 kW.m–2In the process, the strengthening effect is obviously and continuously enhanced along with the continuous reduction of the density of the heat flow, and the strengthening effect of the surface hydrophobic modification on the external condensation heat exchange coefficient of the R134a and R1234ze (E) three-dimensional strengthening pipes can reach 112.4 percent and 186.3 percent respectively to the maximum. Also for R290, the enhancement effect of the surface hydrophobic modification on the condensation heat transfer coefficient outside the three-dimensional enhanced tube of R290 is more remarkable than that of R134a and R1234ze (E). When the heat flux density is as high as 150 kW.m–2In the process, the surface hydrophobic modification can still enhance about 70% of the condensation heat exchange system outside the R290 pipe.
As can be seen from the condensation heat transfer experiments of the two heat transfer pipes illustrated above, the surface hydrophobic modified composite pipe can enhance the condensation heat transfer coefficients of R134a, R1234ze (E) and R290 outside the light pipe and the three-dimensional enhanced pipe, and the enhancement effect of the surface hydrophobic modified composite pipe is more remarkable on the enhanced pipe. If the heat transfer pipe equipment of the type is used for manufacturing the air conditioner condenser, the heat exchange area can be reduced by more than one third, and the heat transfer pipe equipment has good application prospect and economic value.
The heat transfer pipe prepared by the invention can be used in refrigeration, air conditioning and heating ventilation equipment using a shell-and-tube condenser, and the surface hydrophobic modified heat transfer pipe can be used for permanently strengthening the heat exchange performance of a condensation heat exchanger in the ranges of large heat flux density and small heat flux density. After the surface hydrophobic modified heat transfer pipe is used, the heat exchange performance of the heat exchanger can be enhanced, so that the size of the condenser can be reduced, and the hardware cost of the system can be reduced.
The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.
Claims (4)
1. The surface hydrophobic modified composite condensation enhanced heat transfer pipe is characterized by comprising a pipe wall (1), wherein fins (2) are arranged outside the pipe wall (1), each fin (2) comprises a fin root (21), the root of each fin root (21) is connected to the pipe wall (1), a first tip (22) and a second tip (23) extend outwards from the tail end of each fin root (21), the lower parts of the first tip (22) and the second tip (23) are connected, and the angles of the tips of the first tip (22) and the second tip (23) are smaller than 30 degrees; the outer surfaces of the tube wall (1) and the fins (2) are covered with hydrophobic layers (4);
the hydrophobic layer (4) comprises a first hydrophobic layer (41) and a second hydrophobic layer (42) covering the first hydrophobic layer (41), and the thickness of the hydrophobic layer (4) is less than 0.1 micron; the thickness of the first hydrophobic layer (41) is greater than the thickness of the second hydrophobic layer (42);
the hydrophobic layer (4) is made of high polymer materials or plasma;
the rib density of the rib (2) is 38fpi-50fpi, and the rib height is 0.5mm-0.9 mm;
an internal thread strengthening structure (3) is arranged in the pipe wall (1);
the angle of the joint surface of the first tip (22) and the second tip (23) is more than or equal to 90 degrees.
2. The surface-hydrophobically modified composite condensation-enhanced heat transfer pipe according to claim 1, wherein the height of the fin root (21) is 2H/3, the height of the first tip (22) is 1H/3, the height of the second tip (23) is 1H/9, and H is the height of the fin (2).
3. The method for preparing the surface hydrophobic modified composite condensation enhanced heat transfer pipe according to claim 1, is characterized by comprising the following steps:
step 1, processing fins (2) outside a pipe wall (1);
step 2, removing lubricating oil remained on the surface of the heat transfer pipe in the process of processing the fins (2) on the heat transfer pipe;
step 3, drying the surface of the heat transfer pipe;
and 4, sealing two ends of the heat transfer pipe:
step 5, performing hydrophobic modified coating on the outer surface of the heat transfer pipe to form a hydrophobic layer (4) on the outer surface of the heat transfer pipe;
the specific process of the step 5 is as follows: vacuumizing the vapor deposition system, and performing vapor deposition on the surface of the heat transfer pipe when the vacuum degree reaches a coating condition to coat a film on the outer surface of the heat transfer pipe to form a hydrophobic layer (4); and after the film coating is finished, recovering the pressure in the vapor deposition system to atmospheric pressure, and finishing the hydrophobic modification on the outer surface of the heat transfer pipe when the temperature of the heat transfer pipe is cooled to room temperature.
4. The method for manufacturing the surface-hydrophobic modified composite condensation-enhanced heat transfer pipe according to claim 3, wherein in the step 1, the surface of the heat transfer pipe is washed by sequentially using isopropyl alcohol, isopropyl alcohol and clean water, and then water drops on the surface of the heat transfer pipe are blown off by using a spray gun.
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| CN1109161A (en) * | 1994-03-21 | 1995-09-27 | 施福源 | Preparation material and method of dropwise condensation pipe |
| CN104296582A (en) * | 2014-09-24 | 2015-01-21 | 天津天宗化工设备有限公司 | Self-cleaning type helical finned tube |
| CN106643262A (en) * | 2016-12-20 | 2017-05-10 | 江苏萃隆精密铜管股份有限公司 | Efficient heat transfer pipe with evaporating function and condensing function |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2012007872A (en) * | 2010-05-24 | 2012-01-12 | Kobe Steel Ltd | Multi-layered heat transfer tube, method for producing the multi-layered heat transfer tube, and molding tool used for the method |
| CN103157965A (en) * | 2011-12-12 | 2013-06-19 | 浙江宏天铜业有限公司 | Production technology of high-tooth fin copper heat tube |
| JP2019527812A (en) * | 2016-08-05 | 2019-10-03 | オブシェストフォ ス オグラニチェンノイ オトゥヴェステュヴェンノステュ “レインノルツ ラブ”Ｏｂｓｈｅｓｔｖｏ Ｓ Ｏｇｒａｎｉｃｈｅｎｎｏｉ Ｏｔｖｅｔｓｔｖｅｎｎｏｓｔ’Ｕ Ｒｅｉｎｎｏｌｔｓ Ｌａｂ | Shell and tube condenser and shell and tube condenser heat exchange tubes (multiple versions) |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1109161A (en) * | 1994-03-21 | 1995-09-27 | 施福源 | Preparation material and method of dropwise condensation pipe |
| CN104296582A (en) * | 2014-09-24 | 2015-01-21 | 天津天宗化工设备有限公司 | Self-cleaning type helical finned tube |
| CN106643262A (en) * | 2016-12-20 | 2017-05-10 | 江苏萃隆精密铜管股份有限公司 | Efficient heat transfer pipe with evaporating function and condensing function |
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