Carbon black nanofluid, nanoreinforced composite phase change material, preparation method and solar latent heat storage device
By using modified carbon black nanofluid and nano-reinforced composite phase change materials in a solar latent heat storage device, the problem of poor thermal conductivity of phase change materials is solved, heat transfer efficiency and heat storage capacity are improved, and efficient energy storage and release are achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- BEIJING UNIV OF TECH
- Filing Date
- 2024-08-02
- Publication Date
- 2026-04-28
AI Technical Summary
In existing solar latent heat storage devices, the phase change materials have poor thermal conductivity, which limits heat storage and release, reduces friction and lubrication performance, increases energy loss, and reduces system efficiency.
By using carbon black nanofluid and nano-reinforced composite phase change material, carbon black nanoparticles are modified and mixed with myristic acid to form a composite phase change material with higher thermal conductivity. Combined with fin structure optimization, the heat transfer efficiency and heat storage capacity are improved.
It significantly improves the heat transfer performance and heat storage capacity of solar latent heat storage devices, reduces energy loss, alleviates friction problems, and achieves efficient energy storage and release.
Smart Images
Figure CN118978891B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the fields of fluid mechanics, heat transfer management, and thermal energy storage technology, specifically to a carbon black nanofluid, a nano-reinforced composite phase change material, a preparation method, and a solar latent heat energy storage device for solar latent heat energy storage. Background Technology
[0002] Shell-and-tube thermal storage tanks are currently the most typical latent heat energy storage devices. Due to the poor thermal conductivity of phase change materials, the heat storage and release of latent heat energy storage systems are limited. With the development of latent heat energy storage systems, their output performance will deteriorate, friction and wear and lubrication performance will decrease, and energy loss will increase. This will lead to a decrease in the volumetric efficiency and mechanical efficiency of the latent heat energy storage system, an increase in power loss, and a decrease in overall efficiency.
[0003] Existing technologies indicate that adding fins or altering the heat exchange interface structure are among the most common methods for improving the efficiency of latent heat energy systems. Du Jun, Ren Fan, and others disclosed an irregular snowflake-shaped finned phase change heat storage device, which incorporates irregular snowflake-shaped fins between the phase change heat storage material and the inner tube shell, enhancing the heat exchange process between the hot and cold fluids and the phase change material. Liu Qing, Ge Ruihuan, and others disclosed a latent heat phase change energy storage device based on additive manufacturing of a three-cycle minimum curved surface concentric circular tube. Its gradient design allows the heat from the central heat source to dissipate evenly and rapidly to the surrounding areas, providing a larger heat exchange space and improving heat exchange efficiency. Fins increase the surface area available for heat transfer and promote natural convection within the device, thus enhancing the thermal performance of the heat storage device. However, due to natural convection, the heat transfer characteristics within the liquid phase change material change. Although optimizing the fin structure is beneficial for improving heat transfer performance, the addition of fins does not solve the problem of long melting and solidification times for the phase change material, resulting in drawbacks such as multiple heat transfer links and large heat loss at high-temperature surfaces, leading to low heat collection efficiency. Therefore, it is crucial to select a base working fluid with a higher thermal conductivity as the heat transfer fluid in the latent heat energy storage system.
[0004] Li Yichao, Li Xueling, and others disclosed a method for preparing MXene nanofluids, MXene nanofluids, and a solar collector. This method utilizes the direct absorption of solar radiation by the heat transfer fluid itself to achieve solar energy utilization. This approach effectively overcomes the drawbacks of multiple heat transfer stages and large heat loss at high temperatures, thereby further improving heat collection efficiency. In the heated pipe, the thermophysical properties of the working fluid are crucial. Therefore, given that this method is beneficial for improving the heat collection efficiency of solar latent heat storage systems, carbon black nanofluids are used as cooling materials. They are a good choice for maintaining small temperature gradients, sometimes even below 10°C, which is quite feasible in the heat transfer process. The collected solar energy can be transferred to the nano-enhanced latent heat storage device with minimal energy loss. Although integrating phase change materials into latent heat storage systems is a promising strategy, the poor thermal conductivity of simple phase change materials negatively impacts the phase-time transition and the commercial feasibility of the proposed system. Summary of the Invention
[0005] To address the shortcomings of existing technologies, this invention provides a carbon black nanofluid, a nano-reinforced composite phase change material, a preparation method, and a solar latent heat energy storage device. To improve the heat transfer performance of the solar latent heat energy storage device, this invention integrates a composite phase change material with added highly conductive nanoparticles and carbon black nanofluid into the solar latent heat energy storage device. The material properties of the modified carbon black nanofluid are analyzed, and a nano-reinforced latent heat energy storage system configuration is creatively proposed, which to a certain extent completely eliminates energy loss and significantly reduces friction problems. Furthermore, this method is simple and easy to operate, effectively obtaining the required mass fraction of carbon black nanofluid, and exhibits better dispersion stability. By studying the mechanism by which the thermal conductivity of the phase change material improves the performance of the solar thermal system, a suitable energy storage phase change material can be selected.
[0006] The primary objective of this invention is to provide a carbon black nanofluid for use in solar latent heat energy storage devices. This carbon black nanofluid serves as the basic working fluid for the solar latent heat energy storage device. The raw materials required for preparing the carbon black nanofluid, by weight percentage, include: 4.5–8.0% carbon black nanoparticles, 5.0–9.0% thionyl chloride, 3.0–5.0% dibutyltin dilaurate, 9.0–15.0% toluene, 5.5–10.0% triethylamine, 4.0–8.0% surfactant, and 45.0–50.0% deionized water.
[0007] As a further improvement of the present invention, the carbon black nanoparticles have a particle size of 50-100 nm, preferably 75 nm, and are purchased from Tianjin Eborui Chemical Co., Ltd., China, and are subsequently modified; the specific modification method is as follows: steps 1 to 4.
[0008] As a further improvement of the present invention, the carbon black nanoparticles are formed by three steps of oxidation, acylation and activation grafting to form modified carbon black nanoparticles with an average particle size of 70.58 nm.
[0009] As a further improvement of the present invention, the thionyl chloride, dibutyltin dilaurate and toluene are all of analytical grade.
[0010] As a further improvement of the present invention, the triethylamine has a mass percentage of 99 wt%.
[0011] As a further improvement of the present invention, the surfactant is tetradecylhydroxypropyl sulfobetaine, which is selected based on its chemical affinity for the base fluid and its high-temperature thermal behavior.
[0012] As a further improvement of the present invention, the tetradecylhydroxypropyl sulfobetaine has a mass percentage of 60 wt%.
[0013] A second objective of this invention is to provide a method for preparing carbon black nanofluids, comprising:
[0014] Step 1: Disperse carbon black nanoparticles in nitric acid solution for oxidation, so that carboxyl groups are generated on the surface of carbon black nanoparticles through oxidation reaction;
[0015] Step 2: Add the product from Step 1, thionyl chloride, and triethylamine to toluene for reaction, so that the carboxyl groups on the surface of the carbon black nanoparticles are converted into more active acyl chloride groups through acylation.
[0016] Step 3: The product from step 2 and the surfactant are added to toluene in sequence, and dibutyltin dilaurate is added as a catalyst to allow the acyl chloride groups and hydroxyl groups to react on the surface of the surfactant. The surfactant is adsorbed onto the surface of the carbon black nanoparticles to obtain refined carbon black nanoparticles.
[0017] Step 4: Wash the product obtained in step 3 with water 4 times, then dry it in a rotary evaporator, and finally, obtain the modified carbon black nanoparticles by grinding.
[0018] Step 5: Add the product from step 4 to deionized water and stir to mix evenly to obtain carbon black nanofluid.
[0019] As a further improvement of the present invention, step 1 specifically includes:
[0020] 5–15 g of carbon black nanoparticles were dispersed in 50–150 g of HNO3 with a concentration of 30–50 wt%. The mixture was uniformly dispersed at room temperature and oxidized at 60–100 °C for 4–6 h. The final solution was filtered and washed with deionized water to obtain oxidized carbon black nanoparticles, in which carboxyl groups were generated on the surface of the carbon black nanoparticles through oxidation.
[0021] As a further improvement of the present invention, step 2 specifically includes:
[0022] Add 5–15 g of the product from step 1, 2–3 g of thionyl chloride, and 0.1–0.4 g of triethylamine to 50–150 g of toluene; disperse the mixture in an ice bath for 10–30 min, and continue the reaction at 60–80 °C for 3–5 h to obtain the final product; the above process converts the carboxyl groups on the surface of oxidized carbon black nanoparticles into more reactive acyl chloride groups through acylation.
[0023] As a further improvement of the present invention, step 3 specifically includes:
[0024] 5–15 g of the product from step 2 and 4–6 g of surfactant were sequentially added to 50–150 g of toluene. The mixture was dispersed at room temperature for 10–30 min. Then, 0.1–0.3 g of dibutyltin dilaurate was added as a catalyst, and the solution was heated to 50–80 °C for 3–6 h to allow the acyl chloride groups and hydroxyl groups to react on the surface of the surfactant, and the surfactant was adsorbed onto the surface of the carbon black nanoparticles. The product after the reaction was washed and dried to obtain the final refined carbon black nanoparticles.
[0025] The third objective of this invention is to provide a nano-reinforced composite phase change material for a solar latent heat energy storage device. The nano-reinforced composite phase change material, as an energy storage material for a solar latent heat energy storage device, comprises, by weight percentage, 20.0-35.0% modified carbon black nanoparticles and 65.0-80.0% myristic acid.
[0026] As a further improvement of the present invention, the modified carbon black nanoparticles have a particle size of 65.35 nm to 75.81 nm.
[0027] The fourth objective of this invention is to provide a method for preparing a nano-reinforced composite phase change material, comprising:
[0028] The carbon black nanoparticles were modified by adding them into myristic acid and melting them completely. They were then dispersed evenly by magnetic stirring and ultrasonic vibration and cooled to room temperature to obtain a nano-reinforced composite phase change material. The modification method of the carbon black nanoparticles is as described in steps 1 to 4 above.
[0029] As a further improvement of the present invention, the preparation method of the nano-reinforced composite phase change material specifically includes:
[0030] Carbon black nanoparticles were added to myristic acid and completely melted at 70°C for 5–15 minutes. After melting, the mixture was magnetically stirred for 20–40 minutes and then ultrasonically vibrated for 40–80 minutes to disperse it uniformly. After uniform dispersion, the mixture was cooled to room temperature to obtain a nano-reinforced phase change material.
[0031] The fifth objective of this invention is to provide a solar latent heat energy storage device, comprising: a basic working fluid and an energy storage material;
[0032] The basic working fluid is carbon black nanofluid prepared by the above-mentioned method for preparing carbon black nanofluid.
[0033] The energy storage material is a nano-reinforced composite phase change material prepared using the above-mentioned method for preparing nano-reinforced composite phase change materials.
[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0035] This invention integrates nano-reinforced composite phase change material and carbon black nanofluid into a solar latent heat storage device. Carbon black nanofluid has better heat absorption and heat transfer capabilities, while nano-reinforced composite phase change material has better heat storage capabilities. By utilizing the advanced performance and heat storage performance of nano-reinforced latent heat storage technology under high temperature gradients and high efficiency, this invention develops an advanced and original nano-reinforced latent heat storage technology. Attached Figure Description
[0036] Figure 1 This is a diagram illustrating the placement effect of the carbon black nanofluid of the present invention.
[0037] Figure 2 The images show the TEM thermally induced morphological changes of multi-walled carbon nanotubes before and after modification according to the present invention; where (a) 1 μm carbon nanotube before modification, (b) 200 nm carbon nanotube before modification, (c) 500 nm carbon nanotube before modification, (d) 1 μm carbon nanotube after modification, (e) 200 nm carbon nanotube after modification, and (f) 500 nm carbon nanotube after modification.
[0038] Figure 3 The images show the SEM morphology of the multi-walled carbon nanotubes before and after modification according to this invention; (a) 2μm carbon nanotube before modification, (b) 5μm carbon nanotube before modification, (c) 50μm carbon nanotube before modification, (d) 2μm carbon nanotube after modification, (e) 5μm carbon nanotube after modification, and (f) 50μm carbon nanotube after modification. Detailed Implementation
[0039] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0040] The present invention will now be described in further detail with reference to the accompanying drawings:
[0041] This invention provides a method for preparing carbon black nanofluid for solar latent heat storage devices, comprising:
[0042] Step 1: Disperse 10g of carbon black nanoparticles in 100g of 40wt% HNO3; the mixture is uniformly dispersed at room temperature and oxidized at 80℃ for 5h; filter the final solution and wash it three times with deionized water to obtain oxidized carbon black nanoparticles, so that carboxyl groups are generated on the surface of carbon black nanoparticles through oxidation reaction.
[0043] Step 2: Add 10g of the product from Step 1 (oxidized carbon black nanoparticles), 2.5g of thionyl chloride and 0.2g of triethylamine to 100g of toluene; disperse the mixture in an ice bath for 20min and continue the reaction at 70℃ for 4h to obtain the final product.
[0044] Step 3: Add 10g of the product from Step 2 and 5g of surfactant to 100g of toluene. Disperse the mixture at room temperature for 20min. Then add 0.2g of dibutyltin dilaurate as a catalyst and heat the solution to 65℃ for 4h to allow the acyl chloride groups and hydroxyl groups to react on the surface of the surfactant, and the surfactant is adsorbed onto the surface of the carbon black nanoparticles. Wash and dry the product after the reaction to obtain the final refined carbon black nanoparticles.
[0045] Step 4: Add the product from step 3 to deionized water and stir to mix evenly at room temperature to obtain carbon black nanofluid.
[0046] The placement state of carbon black nanofluids as follows Figure 1 As shown, based on Figure 1 It can be seen that the carbon black nanofluid prepared by the present invention has good stability.
[0047] This invention provides a method for preparing a nano-reinforced composite phase change material for a solar latent heat storage device, comprising:
[0048] Carbon black nanoparticles were modified by adding them into myristic acid and melting them completely at 70°C for 10 minutes. After melting, the nanoparticles were magnetically stirred for 30 minutes and then ultrasonically vibrated for 60 minutes to disperse them evenly. After uniform dispersion, the nanoparticles were cooled to room temperature to obtain nano-reinforced phase change materials.
[0049] Both the carbon black nanofluid and the nano-reinforced composite phase change material of this invention utilize modified multi-walled carbon nanotubes; wherein, as... Figure 2 As shown, untreated multi-walled carbon nanotubes are long and easy to aggregate. The surface of multi-walled carbon nanotubes is relatively smooth, and a small amount of impurities and amorphous carbon can be observed on the surface. Figure 2 Images (d), (e), and (f) show the morphological effects of multi-walled carbon nanotubes (MWCNTs) after oxidation in a mixed acid solution at TEM resolutions of 1 μm, 200 nm, and 500 nm, respectively. The length of individual MHCNTs is shorter than before oxidation, and the outer surface of the oxidized MHCNTs is no longer smooth, with an increased surface area. Furthermore, numerous oxidation openings appear on the MHCNTs, which facilitates heat storage and transfer.
[0050] like Figure 3 The SEM morphology of the multi-walled carbon nanotube adsorbent is shown in Figure 3(e), with resolutions of 2 μm, 5 μm, and 50 μm. The presence of silica particles is shown in Figure 3(e), indicating that the surface modification reaction of the multi-walled carbon nanotube adsorbent has been fully completed. Figure 3 (d) shows that the modified multi-walled carbon nanotube adsorbent comprises spherical solid clusters and exhibits a porous network structure. When silica-loaded multi-walled carbon nanotubes are wrapped and exposed to the silica, hundreds of nanoscale pores are observed.
[0051] The following supplementary explanations are provided regarding the implementation process:
[0052] During the melting phase, the temperature of the carbon black nanofluid remains stable in the vicinity as a constant heat source, solely because the concentrated solar field upstream allows the carbon black nanofluid's temperature to remain within a suitable range. The temperature can be regulated by the power of the electric heater, and the nano-reinforced composite phase change material in the nano-reinforced latent heat storage unit should continuously store thermal energy.
[0053] During the solidification stage, the water is used to function as low-pressure steam under heat load. Temperature is recorded and monitored throughout the solidification process. The indoor experiment was conducted at an ambient temperature of 25°C. A simulation model corresponding to the system was then established and simplified as necessary. It is assumed that the constant temperature of the carbon black nanofluid does not decrease as it flows through the heat storage tank. Uniformly arranged fins run along the length of the water tank of the nano-reinforced latent heat storage unit. The shell is symmetrical on both sides due to the periodicity of the heat transfer space along the pipe axis.
[0054] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A method for preparing carbon black nanofluid for a solar latent heat energy storage device, wherein the carbon black nanofluid serves as the basic working fluid of the solar latent heat energy storage device, characterized in that... The raw materials required for preparing carbon black nanofluids, by weight percentage, include: 4.5-8.0% carbon black nanoparticles, 5.0-9.0% thionyl chloride, 3.0-5.0% dibutyltin dilaurate, 9.0-15.0% toluene, 5.5-10.0% triethylamine, 4.0-8.0% surfactant, and 45.0-50.0% deionized water; Methods for preparing carbon black nanofluids include: Step 1: Disperse carbon black nanoparticles in nitric acid solution for oxidation, so that carboxyl groups are generated on the surface of carbon black nanoparticles through oxidation reaction; Step 2: Add the product from Step 1, thionyl chloride, and triethylamine to toluene for reaction, so that the carboxyl groups on the surface of the carbon black nanoparticles are converted into more active acyl chloride groups through acylation. Step 3: The product from step 2 and the surfactant are added to toluene in sequence, and dibutyltin dilaurate is added as a catalyst to allow the acyl chloride groups and hydroxyl groups to react on the surface of the surfactant. The surfactant is adsorbed onto the surface of the carbon black nanoparticles to obtain refined carbon black nanoparticles. Step 4: Wash the product obtained in step 3 with water 4 times, then dry it in a rotary evaporator, and finally, obtain the modified carbon black nanoparticles by grinding. Step 5: Add the product from step 4 to deionized water and stir to mix evenly to obtain carbon black nanofluid.
2. The method for preparing carbon black nanofluid as described in claim 1, characterized in that, The carbon black nanoparticles have a particle size of 5~15nm.
3. The method for preparing carbon black nanofluid as described in claim 1, characterized in that, The surfactant is tetradecylhydroxypropyl sulfobetaine.
4. The method for preparing carbon black nanofluid as described in claim 1, characterized in that, Step 1 specifically includes: 5-15g of carbon black nanoparticles were dispersed in 50-150g of HNO3 with a concentration of 30-50wt%; the mixture was uniformly dispersed at room temperature and oxidized at 60-100℃ for 4-6h; the final solution was filtered and washed with deionized water to obtain oxidized carbon black nanoparticles, so that carboxyl groups were generated on the surface of carbon black nanoparticles through oxidation reaction.
5. The method for preparing carbon black nanofluid as described in claim 1, characterized in that, Step 2 specifically includes: Add 5-15g of the product from step 1, 2-3g of thionyl chloride, and 0.1-0.4g of triethylamine to 50-150g of toluene; disperse the mixture in an ice bath for 10-30min and continue the reaction at 60-80℃ for 3-5h to obtain the final product; the above process converts the carboxyl groups on the surface of oxidized carbon black nanoparticles into more reactive acyl chloride groups through acylation. Step 3 specifically includes: 5-15g of the product from step 3 and 4-6g of surfactant were added sequentially to 50-150g of toluene. The mixture was dispersed at room temperature for 10-30 minutes. Then, 0.1-0.3g of dibutyltin dilaurate was added as a catalyst, and the solution was heated to 50-80℃ for 3-6 hours to allow the acyl chloride groups and hydroxyl groups to react on the surface of the surfactant, and the surfactant was adsorbed onto the surface of the carbon black nanoparticles. The product after the reaction was washed and dried to obtain the final refined carbon black nanoparticles.
6. A method for preparing a nano-reinforced composite phase change material for a solar latent heat energy storage device, wherein the nano-reinforced composite phase change material serves as the energy storage material for the solar latent heat energy storage device, characterized in that... The raw materials required for preparing nano-reinforced composite phase change materials, by weight percentage, include: 20.0-35.0% modified carbon black nanoparticles and 65.0-80.0% myristic acid; The preparation methods of nano-reinforced composite phase change materials include: Carbon black nanoparticles are modified by adding them to myristic acid and completely melting them. The nanoparticles are then dispersed uniformly using magnetic stirring and ultrasonic vibration, and cooled to room temperature to obtain a nano-reinforced composite phase change material. The modification method for the carbon black nanoparticles includes: Step 1: Disperse carbon black nanoparticles in nitric acid solution for oxidation, so that carboxyl groups are generated on the surface of carbon black nanoparticles through oxidation reaction; Step 2: Add the product from Step 1, thionyl chloride, and triethylamine to toluene for reaction, so that the carboxyl groups on the surface of the carbon black nanoparticles are converted into more active acyl chloride groups through acylation. Step 3: The product from step 2 and the surfactant are added to toluene in sequence, and dibutyltin dilaurate is added as a catalyst to allow the acyl chloride groups and hydroxyl groups to react on the surface of the surfactant. The surfactant is adsorbed onto the surface of the carbon black nanoparticles to obtain refined carbon black nanoparticles. Step 4: Wash the product obtained in Step 3 with water four times, then dry it in a rotary evaporator, and finally, obtain the modified carbon black nanoparticles by grinding.
7. The method for preparing the nano-reinforced composite phase change material according to claim 6, characterized in that, The modified carbon black nanoparticles have a particle size of 65.35 nm to 75.81 nm.
8. A solar latent heat storage device, characterized in that, include: Basic working fluids and energy storage materials; The basic working fluid is carbon black nanofluid prepared by the method for preparing carbon black nanofluid as described in any one of claims 1 to 5. The energy storage material is prepared by the method described in claim 6 for preparing nano-reinforced composite phase change materials.