A new energy graphite heat pipe and a preparation method thereof

Abstract

The application relates to a new energy graphite heat pipe and a preparation method thereof. The method comprises the following steps: 1) mixing, oscillating and stirring nanographene, N-methyl-2-pyrrolidone and polyether modified polysiloxane to obtain a mixed solution A; 2) weighing 4,4'-oxybisphthalic anhydride and 4,4'-oxydianiline, adding the two into the mixed solution A, heating, stirring for 3-5 hours to obtain a mixture B; 3) weighing N-hydroxyethyl acrylamide, polytrimethylene ether glycol and methylene succinic acid, adding the three into the mixture A, stirring, drying and grinding to obtain modified nanographene; 4) mixing, oscillating and stirring the modified nanographene, water and a settlement preventing agent to obtain a modified nanographene fluid; 5) adopting copper material to make a heat pipe, filling the modified nanographene fluid into the heat pipe, intercommunicating two ends of the heat pipe and forming a closed loop circuit to obtain a graphite heat pipe; the fluid in the graphite heat pipe is not prone to settlement, and the heat conduction performance and practicability are improved.

Description

Technical Field

[0001] This application relates to the technical field of heat pipes, and more specifically, to a graphite heat pipe for new energy applications and its preparation method. Background Technology

[0002] New energy vehicles have become one of the solutions to the current problems of air pollution and petrochemical resource shortage. New energy vehicles are mainly pure electric vehicles. Since the batteries of electric vehicles generate a lot of heat during use, if the heat is not dissipated in time, it will affect the performance and cycle life of the electric vehicle's power source. In severe cases, it may even lead to thermal runaway, or even safety problems such as combustion and explosion.

[0003] To address the above issues, current methods include air cooling, liquid cooling, phase change material cooling, and heat pipe cooling. Among these, heat pipe cooling is the most widely used, and as a highly efficient heat transfer device, it is also an ideal heat dissipation device for electric vehicle power batteries. Heat pipe cooling mainly uses pulsating heat pipes, which are made by bending or coiling capillary copper tubes. The two ends are interconnected to form a closed loop, which is filled with a circulating phase change heat transfer medium. However, traditional phase change heat transfer media are mostly water, ethanol, acetone, etc., which have low thermal conductivity, thus limiting the application of heat pipes in terms of high-efficiency heat dissipation performance.

[0004] In recent years, titanium dioxide fluid and graphene fluid have also been used as phase change heat transfer media. Among them, graphene fluid has been widely used due to its good thermal conductivity.

[0005] Graphene is produced from natural graphite through any of the following methods: mechanical exfoliation, redox reaction, SiC epitaxial growth, or chemical vapor deposition. However, graphene exhibits poor dispersibility in water, and its large specific surface area often leads to agglomeration and sedimentation, all of which negatively impact its thermal conductivity. To improve dispersibility, sodium dodecyl sulfate or sodium dodecyl sulfonate are sometimes used as dispersants. However, after prolonged use or storage, sedimentation or uneven dispersion can still occur, resulting in reduced heat transfer. Summary of the Invention

[0006] To reduce the occurrence of sedimentation or uneven dispersion of graphene, this application provides a graphite heat pipe for new energy and its preparation method.

[0007] In a first aspect, this application provides a method for preparing a graphite heat pipe for new energy applications, comprising the following steps:

[0008] 1) Weigh out nano-graphene, N-methyl-2-pyrrolidone, and polyether-modified polysiloxane according to the weight parts, mix them, and shake to disperse them evenly to obtain mixture A;

[0009] 2) Weigh 4,4'-oxophthalic anhydride and 4,4'-diaminodiphenyl ether according to the weight parts, add them to the mixture A obtained in 1), mix well, seal, introduce nitrogen gas, heat to 50-65℃, stir and react for 3-5 hours to obtain mixture B;

[0010] 3) Weigh N-hydroxyethyl acrylamide, polytrimethylene ether glycol, methylene succinic acid, and ammonium persulfate according to the weight ratio, add them to mixture A, continue stirring for 1-3 hours, distill under reduced pressure, dry, and grind to obtain modified nano-graphene.

[0011] 4) Mix the modified nano-graphene, water, and anti-settling agent, and shake to obtain the modified nano-graphene fluid.

[0012] 5) A coiled heat pipe is made of copper material, and then modified nano-graphene fluid is filled into the heat pipe. The two ends of the heat pipe are then connected to form a closed loop to obtain a graphite heat pipe.

[0013] In the above preparation step 1), N-methyl-2-pyrrolidone is a polar solvent. The polyether-modified polysiloxane has good wetting and dispersing properties, which can further promote the dispersion efficiency of nano-graphene in N-methyl-2-pyrrolidone, thereby obtaining a uniformly dispersed mixture A from the raw material system. Furthermore, using nano-graphene allows for better dispersion and improves thermal conductivity.

[0014] In step 2), 4,4'-oxydiphthalic anhydride and 4,4'-diaminodiphenyl ether are added and mixed with mixture A. Under nitrogen protection, the 4,4'-oxydiphthalic anhydride and 4,4'-diaminodiphenyl ether react to generate a polyimide composite that is fully and evenly dispersed with the nano-graphene and coats the surface of the nano-graphene.

[0015] At this point, the polyimide complex in mixture B is in a semi-polymerized state. Therefore, in step 3), under the action of ammonium persulfate, the polyimide complex in mixture B is further compounded and cross-linked with N-hydroxyethyl acrylamide, polytrimethylene ether glycol, and methylene succinic acid to obtain a large-molecule cross-linked network polymer, which promotes film formation and further improves the coating properties of the nano-graphene. Therefore, after vacuum distillation, a stable coating film is formed on the surface of the nano-graphene, thereby reducing the specific surface energy of the nano-graphene and reducing the agglomeration of the nano-graphene in water.

[0016] Because methyl succinic acid contains two carboxyl groups, the modified graphene nanofilm contains hydrophilic groups after the reaction, which further improves the dispersibility of the modified graphene nanofilm in water. Due to the good antistatic effect of polymers such as polyimide, the adsorption and agglomeration of graphene nanofilm is reduced, thereby further improving the heat dissipation effect.

[0017] In step 4), under the action of the anti-settling agent, the water and modified nano-graphene are evenly dispersed and form a modified nano-graphene fluid in a suspension, reducing the possibility of sedimentation of the modified nano-graphene and improving the thermal conductivity.

[0018] A coiled heat pipe is then made from copper, and modified nano-graphene fluid is filled inside the heat pipe to obtain a graphite heat pipe. The modified nano-graphene fluid inside the graphite heat pipe does not easily adhere to the inner wall of the copper pipe, nor does it easily settle, thus improving the heat dissipation effect and practicality of the graphite heat pipe.

[0019] In summary, this application first involves uniformly dispersing nano-graphene in N-methyl-2-pyrrolidone with the assistance of polyether-modified polysiloxane. The resulting mixture A can be used as a solvent to facilitate the polymerization of 4'-oxydiphthalic anhydride and 4,4'-diaminodiphenyl ether to obtain a polyimide composite. At this point, the nano-graphene is uniformly dispersed in the polyimide composite, forming a uniformly dispersed mixture B raw material system.

[0020] Further addition of N-hydroxyethyl acrylamide, polytrimethylene ether glycol, and methylene succinic acid allows for further compounding and cross-linking, resulting in a macromolecular cross-linked complex that readily forms a coating film on the surface of the graphene nanoparticles, reducing their specific surface energy and improving their dispersibility.

[0021] Meanwhile, the coating film contains hydrophilic groups, which further promotes the dispersibility of modified nano-graphene in water. With the cooperation of anti-settling agent, the nano-graphene in the obtained modified nano-graphene fluid is evenly dispersed and is not prone to sedimentation. Even in long-term operation, sedimentation and agglomeration are not likely to occur, thus further improving the thermal conductivity of the heat pipe and its practicality.

[0022] Preferably, in step 1), there are 50-80 parts of nano-graphene, 120-150 parts of N-methyl-2-pyrrolidone, and 1-3 parts of polyether-modified polysiloxane.

[0023] Preferably, step 2) contains 22-28 parts of 4'-oxobisphthalic anhydride and 18-26 parts of 4,4'-diaminodiphenyl ether.

[0024] Preferably, in step 3), the components are 0.5-1.5 parts of N-hydroxyethyl acrylamide, 1.5-1.9 parts of polytrimethylene ether glycol, 1-3 parts of methylene succinic acid, and 0.1-0.8 parts of ammonium persulfate.

[0025] Preferably, 4) contains 30-50 parts of modified nano-graphene, 10-50 parts of water, and 1-3 parts of dispersant.

[0026] The modified nano-graphene prepared using the above raw materials has good thermal conductivity, and the probability of sedimentation and agglomeration after long-term storage or use is low, further improving the practicality and heat transfer effect of the heat pipe.

[0027] Preferably, the modified graphene nanoparticles have a particle size of 10-100 nm.

[0028] By using particle sizes within the above range, the dispersibility of modified nano-graphene is further improved. At the same time, the resulting modified nano-graphene fluid is less prone to sedimentation or agglomeration, thereby improving the heat transfer effect and practicality of the heat pipe.

[0029] Preferably, the oscillation in steps 1) and 4) is ultrasonic oscillation with a frequency of 10-50 kHz. Using ultrasonic oscillation improves the dispersibility of nano-graphene / modified nano-graphene in the raw material system, thereby further enhancing the heat dissipation effect of the heat pipe.

[0030] Preferably, the anti-settling agent is a wax emulsion of ethylene vinyl acetate copolymer.

[0031] The wax emulsion of ethylene-vinyl acetate copolymer is a modified ethylene-vinyl acetate copolymer emulsion with good dispersibility and anti-settling effect. When mixed with modified nano-graphene and water, it can make the modified nano-graphene uniformly dispersed in water and reduce the possibility of sedimentation of modified nano-graphene, so as to form a uniformly dispersed modified nano-graphene fluid, further improving the heat transfer effect of heat pipe.

[0032] Preferably, the solid content of the wax emulsion of the ethylene vinyl acetate copolymer is 46-56%.

[0033] Wax emulsions using ethylene-vinyl acetate copolymers within the above solids content range exhibit good dispersibility and anti-settling effects. The preferred brand is BYK, model AQUATIX 8421.

[0034] Secondly, this application provides a graphite heat pipe for new energy applications, comprising a coiled heat pipe copper tube body, wherein the coiled heat pipe copper tube body is filled with modified graphene fluid, and the two ends of the coiled heat pipe copper tube body are interconnected to form a closed loop circuit. The graphite heat pipe is prepared by a method for preparing a graphite heat pipe for new energy applications.

[0035] In summary, this application has the following beneficial effects:

[0036] This application first involves uniformly dispersing nano-graphene in N-methyl-2-pyrrolidone with the assistance of polyether-modified polysiloxane. The resulting mixture A can be used as a solvent to facilitate the polymerization of 4'-oxydiphthalic anhydride and 4,4'-diaminodiphenyl ether to obtain a polyimide composite. At this point, the nano-graphene is uniformly dispersed in the polyimide composite, forming a uniformly dispersed mixture B raw material system. Further addition of N-hydroxyethylacrylamide, polytrimethylene ether glycol, and methylene succinic acid further promotes their composite and crosslinking. The resulting macromolecular crosslinked composite easily forms a coating film on the surface of the nano-graphene, reducing the specific surface energy of the nano-graphene and improving its dispersibility.

[0037] Meanwhile, the coating film contains hydrophilic groups, which further promotes the dispersibility of modified nano-graphene in water. With the cooperation of anti-settling agent, the nano-graphene in the obtained modified nano-graphene fluid is evenly dispersed and is not prone to sedimentation. Even in long-term operation, sedimentation and agglomeration are not likely to occur, thus further improving the thermal conductivity of the heat pipe and its practicality. Detailed Implementation

[0038] The present application will be further described in detail below with reference to the embodiments.

[0039] Partial raw material parameters:

[0040] The hydroxyl value of polytrimethylene ether glycol is 102.0-124.6 mgKOH / g, and the molecular weight is 900-1100 g / mol.

[0041] Example

[0042] Example 1

[0043] A graphite heat pipe for new energy uses includes a coiled copper heat pipe body, which is filled with modified graphene fluid, and the two ends of the coiled copper heat pipe body are interconnected to form a closed loop.

[0044] The graphite heat pipe for this new energy source is manufactured by the following method:

[0045] 1) Weigh 5 kg of nano-graphene, 12 kg of N-methyl-2-pyrrolidone, and 0.1 kg of polyether-modified polysiloxane, mix them, and then place them in an ultrasonic oscillation chamber for 30 min at a frequency of 28 kHz to ensure that the nano-graphene, N-methyl-2-pyrrolidone, and polyether-modified polysiloxane are fully and evenly dispersed to obtain mixture A.

[0046] 2) Transfer mixture A to a reaction vessel. Weigh 2.2 kg of 4'-oxophthalic anhydride and 1.8 kg of 4,4'-diaminodiphenyl ether and add them to mixture A obtained in 1). Stir for 20 min at 60 min to ensure that the 4'-oxophthalic anhydride and 4,4'-diaminodiphenyl ether are fully mixed with mixture A. Seal the vessel and evacuate it to a vacuum state. At this time, the vacuum gauge reads -0.1 MPa. Introduce nitrogen into the reaction vessel and raise the temperature to 60°C. Stir and react for 3 h at 60 r / min to obtain mixture B.

[0047] 3) Weigh 0.05 kg of N-hydroxyethyl acrylamide, 0.15 kg of polytrimethylene ether glycol, 0.1 kg of methylene succinic acid, and 0.01 kg of ammonium persulfate, and add them to mixture B obtained in 2). Stir at 60 r / min for 1 h, heat to 80 °C, and perform vacuum distillation for 1 h. Then, dry the mixture further by passing it through an oven at 50 °C and grind it again to obtain modified nano-graphene.

[0048] 4) Weigh 3 kg of modified nano-graphene, 1 kg of water, and 0.1 kg of ethylene-vinyl acetate copolymer wax emulsion, mix them, and then place them in an ultrasonic oscillation chamber for 30 minutes at a frequency of 28 kHz to ensure that the modified nano-graphene, water, and ethylene-vinyl acetate copolymer are completely and uniformly dispersed to obtain modified nano-graphene fluid.

[0049] 5) A coiled heat pipe is made of copper material, and then modified nano-graphene fluid is filled into the heat pipe. The two ends of the heat pipe are then connected to form a closed loop to obtain a graphite heat pipe.

[0050] The solid content of the wax emulsion of ethylene-vinyl acetate copolymer is 46%; the particle size of the modified nanographene is 10-30 nm.

[0051] Example 2

[0052] The difference between Example 2 and Example 1 is that the graphite heat pipe for new energy in Example 2 is prepared by the following method:

[0053] 1) Weigh 6.5 kg of nano-graphene, 13 kg of N-methyl-2-pyrrolidone, and 0.2 kg of polyether-modified polysiloxane, mix them, and then place them in an ultrasonic oscillation chamber for 30 min at a frequency of 28 kHz to ensure that the nano-graphene, N-methyl-2-pyrrolidone, and polyether-modified polysiloxane are fully and evenly dispersed to obtain mixture A.

[0054] 2) Transfer mixture A to a reaction vessel. Weigh 2.5 kg of 4'-oxophthalic anhydride and 2.3 kg of 4,4'-diaminodiphenyl ether and add them to mixture A obtained in 1). Stir for 20 min at 60 min to ensure that the 4'-oxophthalic anhydride and 4,4'-diaminodiphenyl ether are thoroughly mixed with mixture A. Seal the vessel and evacuate it to a vacuum state. At this time, the vacuum gauge reads -0.1 MPa. Introduce nitrogen into the reaction vessel and raise the temperature to 60°C. Stir and react for 4 h at 60 r / min to obtain mixture B.

[0055] 3) Weigh 0.1 kg of N-hydroxyethyl acrylamide, 0.17 kg of polytrimethylene ether glycol, 0.2 kg of methylene succinic acid, and 0.05 kg of ammonium persulfate, and add them to mixture B obtained in 2). Stir at 60 r / min for 2 h, heat to 80 °C, and perform vacuum distillation for 1 h. Then, dry the mixture further by passing it through an oven at 50 °C and grind it again to obtain modified nano-graphene.

[0056] 4) Weigh 3 kg of modified nano-graphene, 1 kg of water, and 0.1 kg of ethylene vinyl acetate copolymer wax emulsion, mix them, and then place them in an ultrasonic oscillation chamber for 30 min at a frequency of 28 kHz to ensure that the modified nano-graphene, water, and ethylene vinyl acetate copolymer are completely and evenly dispersed to obtain modified nano-graphene fluid.

[0057] 5) A coiled heat pipe is made of copper material, and then modified nano-graphene fluid is filled into the heat pipe. The two ends of the heat pipe are then connected to form a closed loop to obtain a graphite heat pipe.

[0058] Example 3

[0059] The difference between Example 3 and Example 1 is that the graphite heat pipe for new energy in Example 3 is prepared by the following method:

[0060] 1) Weigh 8 kg of nano-graphene, 15 kg of N-methyl-2-pyrrolidone, and 0.3 kg of polyether-modified polysiloxane, mix them, and then place them in an ultrasonic oscillation chamber for 20 min at a frequency of 28 kHz to ensure that the nano-graphene, N-methyl-2-pyrrolidone, and polyether-modified polysiloxane are fully and evenly dispersed to obtain mixture A.

[0061] 2) Transfer mixture A to a reaction vessel. Weigh 2.8 kg of 4'-oxophthalic anhydride and 2.6 kg of 4,4'-diaminodiphenyl ether and add them to mixture A obtained in 1). Stir for 20 minutes at 60 min to ensure that the 4'-oxophthalic anhydride and 4,4'-diaminodiphenyl ether are fully mixed with mixture A. Seal the vessel and evacuate it to a vacuum state. At this time, the vacuum gauge reads -0.1 MPa. Introduce nitrogen into the reaction vessel and raise the temperature to 60°C. Stir and react for 3 hours at 60 r / min to obtain mixture B.

[0062] 3) Weigh 0.15 kg of N-hydroxyethyl acrylamide, 0.19 kg of polytrimethylene ether glycol, 0.3 kg of methylene succinic acid, and 0.08 kg of ammonium persulfate, and add them to mixture B obtained in 2). Stir at 60 r / min for 1 h, heat to 80 °C, and perform vacuum distillation for 1 h. Then, dry the mixture further by passing it through an oven at 50 °C and grind it again to obtain modified nano-graphene.

[0063] 4) Weigh 3 kg of modified nano-graphene, 1 kg of water, and 0.1 kg of ethylene-vinyl acetate copolymer wax emulsion, mix them, and then place them in an ultrasonic oscillation chamber for 30 minutes at a frequency of 28 kHz to ensure that the modified nano-graphene, water, and ethylene-vinyl acetate copolymer are completely and uniformly dispersed to obtain modified nano-graphene fluid.

[0064] 5) A coiled heat pipe is made of copper material, and then modified nano-graphene fluid is filled into the heat pipe. The two ends of the heat pipe are then connected to form a closed loop to obtain a graphite heat pipe.

[0065] Example 4

[0066] The difference between Example 4 and Example 1 is that: in step 4), 4 kg of modified nano-graphene, 3 kg of water, and 0.2 kg of wax emulsion of ethylene-vinyl acetate copolymer were used.

[0067] Example 5

[0068] The difference between Example 5 and Example 1 is that: 5 kg of modified nano-graphene, 5 kg of water, and 0.3 kg of ethylene-vinyl acetate copolymer wax emulsion were used in step 4).

[0069] Comparative Example

[0070] Comparative Example 1

[0071] The difference between Comparative Example 1 and Example 1 is that step 3 is omitted, as follows:

[0072] 1) Weigh 5 kg of nano-graphene, 12 kg of N-methyl-2-pyrrolidone, and 0.1 kg of polyether-modified polysiloxane, mix them, and then place them in an ultrasonic oscillation chamber for 30 min at a frequency of 28 kHz to ensure that the nano-graphene, N-methyl-2-pyrrolidone, and polyether-modified polysiloxane are fully and evenly dispersed to obtain mixture A.

[0073] 2) Transfer mixture A to a reaction vessel. Weigh 2.2 kg of 4'-oxophthalic anhydride and 1.8 kg of 4,4'-diaminodiphenyl ether and add them to mixture A obtained in 1). Stir for 20 min at 60 min to ensure that the 4'-oxophthalic anhydride and 4,4'-diaminodiphenyl ether are thoroughly mixed with mixture A. Seal the vessel and evacuate it to a vacuum state. The vacuum gauge should read -0.1 MPa. Introduce nitrogen into the reaction vessel and raise the temperature to 60°C. Stir and react for 3 h at 60 r / min. Heat to 80°C and perform vacuum distillation for 1 h. Then, dry the mixture in a 50°C oven. Finally, grind the mixture again to obtain modified nanographene.

[0074] 3) Weigh 3 kg of modified nano-graphene, 1 kg of water, and 0.1 kg of ethylene-vinyl acetate copolymer wax emulsion, mix them, and then place them in an ultrasonic oscillation chamber for 30 min at a frequency of 28 kHz to ensure that the modified nano-graphene, water, and ethylene-vinyl acetate copolymer are completely and uniformly dispersed to obtain modified nano-graphene fluid.

[0075] 4) A coiled heat pipe is made of copper material, and then modified nano-graphene fluid is filled into the heat pipe. The two ends of the heat pipe are then connected to form a closed loop to obtain a graphite heat pipe.

[0076] Comparative Example 2

[0077] The difference between Comparative Example 2 and Example 1 is that methylene succinic acid was replaced with an equal amount of N-hydroxyethyl acrylamide.

[0078] Comparative Example 3

[0079] The difference between Comparative Example 3 and Example 1 is that step 2 is omitted, as detailed below:

[0080] 1) Weigh 5 kg of nano-graphene, 12 kg of N-methyl-2-pyrrolidone, and 0.1 kg of polyether-modified polysiloxane, mix them, and then place them in an ultrasonic oscillation chamber for 30 min at a frequency of 28 kHz to ensure that the nano-graphene, N-methyl-2-pyrrolidone, and polyether-modified polysiloxane are fully and evenly dispersed to obtain mixture A.

[0081] 2) Weigh 0.05 kg of N-hydroxyethyl acrylamide, 0.15 kg of polytrimethylene ether glycol, 0.1 kg of methylene succinic acid, and 0.01 kg of ammonium persulfate, and add them to mixture A obtained in 1). Stir at 60 r / min for 1 h, heat to 80 °C, and perform vacuum distillation for 1 h. Then, dry the mixture further by passing it through an oven at 50 °C and grind it again to obtain modified nano-graphene.

[0082] 3) Weigh 3 kg of modified nano-graphene, 1 kg of water, and 0.1 kg of ethylene-vinyl acetate copolymer wax emulsion, mix them, and then place them in an ultrasonic oscillation chamber for 30 min at a frequency of 28 kHz to ensure that the modified nano-graphene, water, and ethylene-vinyl acetate copolymer are completely and uniformly dispersed to obtain modified nano-graphene fluid.

[0083] 4) A coiled heat pipe is made of copper material, and then modified nano-graphene fluid is filled into the heat pipe. The two ends of the heat pipe are then connected to form a closed loop to obtain a graphite heat pipe.

[0084] Comparative Example 4

[0085] The difference between Comparative Example 4 and Example 1 is that the graphite heat pipe for this new energy source is prepared by the following method:

[0086] 1) Weigh 3 kg of nano-graphene, 1 kg of water, and 0.1 kg of sodium dodecyl sulfate, mix them, and then place them in an ultrasonic oscillation chamber for 30 minutes at a frequency of 28 kHz to ensure that the modified nano-graphene, water, and sodium dodecyl sulfate are completely and evenly dispersed to obtain a modified nano-graphene fluid.

[0087] 2) A coiled heat pipe is made of copper material, and then nano-graphene fluid is filled into the heat pipe. The two ends of the heat pipe are then connected to form a closed loop to obtain a graphite heat pipe.

[0088] Comparative Example 5

[0089] The difference between Comparative Example 5 and Example 1 is that, based on Comparative Example 3, sodium dodecyl sulfate was replaced with an equal amount of silane coupling agent.

[0090] Comparative Example 6

[0091] The difference between Comparative Example 6 and Example 1 is that the wax emulsion of ethylene vinyl acetate copolymer was replaced with an equal amount of water.

[0092] Comparative Example 7

[0093] The difference between Comparative Example 7 and Example 1 is that the modified nano-graphene fluid was replaced with an equal amount of water to obtain a water-heating pipe.

[0094] Performance testing

[0095] The graphite heat pipes obtained in Examples 1-5 and Comparative Examples 1-6 were subjected to the following performance tests, and the specific data are shown in Table 1.

[0096] Detection methods / test methods

[0097] (1) Settlement phenomenon

[0098] Take 2 kg of the modified nano-graphene fluid or nano-graphene fluid from Examples 1-5 and Comparative Examples 1-6 and place it in a beaker, seal it, and let it stand in an environment with a humidity of 60°C and a temperature of 30°C. Observe every 3 days whether there is stratification, precipitation, or other phenomena. If the above phenomena occur, record the standing time. When no sedimentation occurs after 90 days (d), it is recorded as >90d.

[0099] (2) Heat transfer effect

[0100] After the heat pipes obtained in Examples 1-5 and Comparative Examples 1-6 were placed for 7 days, the following performance tests were performed:

[0101] Referring to GB / T 14812-2008 Test Method for Heat Transfer Performance of Heat Pipes, the heat transfer flow rate of the graphite heat pipes obtained in Examples 1-5 and Comparative Examples 1-6 was tested and denoted as Q1, while the heat transfer flow rate of the water heat pipe obtained in Comparative Example 7 was denoted as Q2. The relative change rate of heat transfer = [(Q1-Q2) / Q2]*100%.

[0102] Table 1. Experimental data of Examples 1-5 and Comparative Examples 1-6

[0103]

[0104]

[0105] Combining Example 1 and Comparative Examples 1 and 3 with Table 1, it can be seen that Comparative Examples 1 and 3 exhibited sedimentation after approximately 50 days, while Example 1 showed no sedimentation within 90 days. Furthermore, the relative heat transfer change rate of Comparative Examples 1 and 3 was lower than that of Example 1, indicating that the graphite heat pipe using Example 1 has better dispersion, anti-settling, and heat dissipation effects. This further demonstrates that the modified nano-graphene fluid obtained through this application possesses good anti-settling properties and thermal conductivity.

[0106] Combining Example 1 and Comparative Example 2 with Table 1, it can be seen that no sedimentation phenomenon was observed in Comparative Example 2 within 42 days, while no sedimentation phenomenon was observed in Example 1 within 90 days. Furthermore, the relative change rate of heat transfer in Example 1 was higher than that in Comparative Example 1. This indicates that the combination of methylene succinic acid and N-hydroxyethyl acrylamide, when used in the raw material system, enables the modified nano-graphene to play a better dispersing role in water and reduces its sedimentation.

[0107] Combining Example 1 and Comparative Example 4, it can be seen that Comparative Example 4 showed obvious sedimentation at 25 days, while Example 1 did not show sedimentation within 90 days. Furthermore, the relative rate of change in heat transfer in Example 1 was higher than that in Comparative Example 4. This indicates that using the modified nano-graphene of this application in conjunction with the anti-settling agent of this application achieves better anti-settling and dispersion effects, thereby improving the heat transfer of the heat pipe.

[0108] Combining Example 1 and Comparative Example 5, it can be seen that Comparative Example 5 showed obvious sedimentation at 28 days, while Example 1 did not show sedimentation within 90 days. In addition, the relative change rate of heat transfer in Example 1 was higher than that in Comparative Example 5, indicating that the nano-graphene modified by the scheme of this application has a better dispersion effect and anti-settling effect, thereby improving the heat transfer and practicality of the heat pipe.

[0109] Combining Example 1 and Comparative Example 6, it can be seen that Comparative Example 5 showed obvious sedimentation at 54 days, while Example 1 did not show sedimentation within 90 days. In addition, the relative change rate of heat transfer in Example 1 was also higher than that in Comparative Example 6. This indicates that the wax emulsion of ethylene vinyl acetate copolymer interacts with the modified nano-graphene, thereby obtaining a modified nano-graphene fluid with better dispersion and anti-settling properties, thus improving the heat transfer and practicality of the heat pipe.

[0110] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for preparing a graphite heat pipe for new energy applications, characterized in that, Includes the following steps: 1) Weigh out nano-graphene, N-methyl-2-pyrrolidone, and polyether-modified polysiloxane according to the weight parts, mix them, and shake to disperse them evenly to obtain mixture A; 2) Weigh 4,4'-oxophthalic anhydride and 4,4'-diaminodiphenyl ether according to the weight parts, add them to the mixture A obtained in 1), mix well, seal, introduce nitrogen gas, heat to 50-65℃, stir and react for 3-5 hours to obtain mixture B; 3) Weigh N-hydroxyethyl acrylamide, polytrimethylene ether glycol, methylene succinic acid, and ammonium persulfate according to the weight parts, add them to mixture A, continue stirring for 1-3 hours, distill under reduced pressure, dry, and grind to obtain modified nano-graphene. 4) According to the weight parts, mix the modified nano-graphene, water and anti-settling agent, shake, and obtain the modified nano-graphene fluid. 5) A coiled heat pipe is made of copper material, and then modified nano-graphene fluid is filled into the inside of the heat pipe. The two ends of the heat pipe are then connected to form a closed loop to obtain a graphite heat pipe. In step 1), there are 50-80 parts of nano-graphene, 120-150 parts of N-methyl-2-pyrrolidone, and 1-3 parts of polyether-modified polysiloxane. In step 2), there are 22-28 parts of 4'-oxobisphthalic anhydride and 18-26 parts of 4,4'-diaminodiphenyl ether. In step 3), the components are: 0.5-1.5 parts of N-hydroxyethyl acrylamide, 1.5-1.9 parts of polytrimethylene ether glycol, 1-3 parts of methylene succinic acid, and 0.1-0.8 parts of ammonium persulfate. In step 4), 30-50 parts of modified nano-graphene, 10-50 parts of water, and 1-3 parts of dispersant are used.

2. The method for preparing a graphite heat pipe for new energy applications according to claim 1, characterized in that: The modified graphene nanoparticles have a particle size of 10-100 nm.

3. The method for preparing a graphite heat pipe for new energy applications according to claim 1, characterized in that: The oscillations in steps 1) and 4) are ultrasonic oscillations with a frequency of 10-50 kHz.

4. The method for preparing a graphite heat pipe for new energy applications according to claim 1, characterized in that: The anti-settling agent is a wax emulsion of ethylene-vinyl acetate copolymer.

5. The method for preparing a graphite heat pipe for new energy applications according to claim 4, characterized in that: The solid content of the wax emulsion of the ethylene vinyl acetate copolymer is 46-56%.

6. A graphite heat pipe for new energy applications, comprising a coiled copper heat pipe body, characterized in that: The coiled heat pipe copper tube body is filled with modified graphene fluid, and the two ends of the coiled heat pipe copper tube body are interconnected to form a closed loop. The graphite heat pipe is prepared by the preparation method of a new energy graphite heat pipe according to any one of claims 1-5.

Images