Preparation method and application of phase-change nanocapsule-based latent heat type functional hot fluid

Abstract

According to the preparation method and application of the phase-change nanocapsule-based latent heat type functional hot fluid, a nuclear material with the phase-change temperature of 20-80 DEG C is packaged in polystyrene or silicon dioxide to form a phase-change nanocapsule, and the phase-change nanocapsule has the characteristics of being controllable in size, large in phase-change enthalpy, high in encapsulation efficiency and excellent in thermal stability and cycling stability. Dispersing the phase-change nanocapsules in deionized water containing the modified multi-walled carbon nanotubes; and finally, forming the uniformly mixed latent heat type functional thermal fluid under the action of an emulsifier and magnetic stirring. The phase change nanocapsule prepared by the invention has the characteristics of controllable size, larger phase change enthalpy, higher encapsulation efficiency and excellent thermal stability and cycling stability, is prepared into latent heat type functional thermal fluid with better dispersion stability, larger heat storage capacity and excellent photothermal conversion performance, and can be popularized and applied in the field of solar photothermal.

Description

Technical Field

[0001] The present application relates to the field of phase change energy storage material preparation and solar thermal energy field, and in particular to a method for preparing a phase change nanocapsule-based latent heat functional thermal fluid and its application. Background Art

[0002] The efficient use of solar energy has become a major challenge in today's world. Direct absorption solar collectors are favored by many researchers due to their excellent light-to-heat conversion efficiency and minimal heat loss. However, the performance of direct absorption solar collectors is limited by their working fluids. Some researchers have suggested adding dark and large particles with high thermal conductivity, such as graphite powder, to traditional working fluids to improve their absorption rate of sunlight. However, the use of such particles in the working fluid of direct absorption solar collectors may impair the stability of the system due to sedimentation, leading to blockage, corrosion and wear of the solar collector pipes. In recent years, nanomaterials with excellent light absorption properties have been incorporated into traditional working fluids. This not only enhances the dispersion stability of the working fluid, but also significantly improves its heat transfer capacity. Nanofluids lack good heat storage capacity due to the simple use of sensible heat technology. Therefore, latent heat functional thermal fluids that integrate heat storage and heat transfer can be prepared by introducing phase change materials into traditional working fluids, thereby expanding their application in the field of solar energy.

[0003] As a new type of environmentally friendly energy storage material, solid-liquid phase change materials are widely used in various industries because they can absorb and release a large amount of heat energy during the phase change process while keeping the temperature within a specific range. However, solid-liquid phase change materials exhibit a certain degree of fluidity during the transition from solid to liquid, which may cause the risk of leakage during use. Summary of the invention

[0004] The present application aims to solve one of the technical problems in the related art at least to some extent.

[0005] On the one hand, the present application proposes a method for preparing a phase-change nanocapsule-based latent heat functional thermal fluid and its application, to prepare phase-change nanocapsules with controllable size, large phase change enthalpy, high encapsulation rate, excellent thermal stability and cyclic stability, and to prepare them into latent heat functional thermal fluids with good dispersion stability, large heat storage capacity and excellent photothermal conversion performance, which have potential application value in the field of solar thermal energy.

[0006] According to an embodiment of the first aspect of the present application, a phase-change nanocapsule is provided, which is a core-shell structure with controllable size, including a core structure and a shell structure; wherein the mass percentage of the core structure is 55.68%-85.12% based on the phase-change nanocapsule;

[0007] and / or, the core structure is an alcohol material having a phase transition temperature of 20-80°C;

[0008] And / or, the shell structure is polystyrene or silicon dioxide.

[0009] In some implementations, the average particle size of the phase-change nanocapsules is about 27.13-167.3 nm, and the particle size is regulated by any one of an emulsifier, an initiator, and a cross-linking agent.

[0010] In some implementations, the phase change temperature of the phase change nanocapsule is 20-80°C.

[0011] According to an embodiment of the second aspect of the present application, a method for preparing a phase-change nanocapsule-based latent heat functional thermal fluid is proposed, wherein the phase-change nanocapsules described in any of the above embodiments are dispersed in deionized water containing modified multi-walled carbon nanotubes, and mixed evenly through the action of an emulsifier to form the stable functional thermal fluid.

[0012] In some implementations, the method for preparing the phase change nanocapsule with polystyrene as the shell structure includes: preparing an aqueous phase by evenly mixing an emulsifier and deionized water; preparing an oil phase by evenly mixing a core structure material with polystyrene, an initiator, a cross-linking agent and a comonomer; and subjecting the aqueous phase and the oil phase to a polymerization reaction.

[0013] In some implementations, the emulsifier includes sodium lauryl sulfate and octylphenol polyoxyethylene-10 in a mass ratio of (1:3)-(3:1);

[0014] And / or, the mass fraction of the material of the shell structure is 100 parts, and the mass fraction of the emulsifier is 6-14 parts.

[0015] In some implementations, the mass ratio of the material of the core structure to the material of the shell structure is (1:2)-(3:1);

[0016] And / or, the initiator comprises potassium persulfate or azobisisobutyronitrile;

[0017] and / or, the cross-linking agent comprises n-dodecyl mercaptan or ethylene glycol dimethacrylate;

[0018] and / or, the comonomer comprises acrylic acid, acrylamide, butyl acrylate or methyl methacrylate;

[0019] And / or, the mass fraction of the material of the shell structure is 100 parts, the mass fraction of the initiator is 1.2-2.8 parts; the mass fraction of the cross-linking agent is 1.2-2.8 parts; and the mass fraction of the comonomer is 0-1.2 parts.

[0020] In some implementations, the mass fraction of the deionized water is 100 parts, the mass fraction of the phase change nanocapsules is 5-15 parts, and the mass fraction of the modified multi-walled carbon nanotubes is 0.1 parts.

[0021] In some implementations, the water phase and the oil phase are dispersed at a high speed of 3000-8000 rpm for 5-10 min to achieve fine emulsification;

[0022] And / or, the polymerization reaction is carried out under a protective atmosphere;

[0023] And / or, the polymerization reaction conditions are: temperature of 30-100°C; stirring speed of 150-500rpm; time of 6-10h;

[0024] And / or, after the polymerization reaction is completed, filtering, washing and drying are performed to obtain the phase change nanocapsules with polystyrene as the shell structure.

[0025] In some embodiments, the method for preparing phase change nanocapsules with a silica shell structure includes uniformly mixing a core material, an emulsifier and deionized water to prepare a first mixed liquid; uniformly mixing an initiator and silica to prepare a second mixed liquid; and dropwise adding the second mixed liquid to the first mixed liquid to cause a condensation reaction.

[0026] In some implementations, when the phase-change nanocapsules are dispersed in deionized water containing modified multi-walled carbon nanotubes, the deionized water further contains ethylene glycol.

[0027] In some implementations, the emulsifier includes Tween-80 and Span-80 in a mass ratio of (1:3)-(3:1);

[0028] And / or, based on 100 parts by mass of the deionized water, the weight fraction of the emulsifier is 5.3 parts.

[0029] In some implementations, the mass fraction of the deionized water is 100 parts, the mass fraction of the shell structure material is 6 parts; the weight fraction of the initiator is 1.6-3.0 parts;

[0030] And / or, the mass ratio of the material of the core structure to the material of the shell structure is (5:9)-(20:9).

[0031] In some implementations, the second mixed solution is added dropwise to the first mixed solution and magnetically stirred at 400-800 rpm to achieve fine emulsification;

[0032] And / or, the polycondensation reaction temperature is 30-100°C and the time is 6-10h;

[0033] And / or, after the polycondensation reaction is completed, filtering, washing and drying are performed to obtain the phase change nanocapsules with silicon dioxide as the shell structure.

[0034] According to an embodiment of the third aspect of the present application, a phase-change nanocapsule-based latent heat functional thermal fluid is proposed, characterized in that it is obtained using the preparation method described in any of the above embodiments, wherein the eta potential of the functional thermal fluid is 31.8-39.87mV.

[0035] In some implementations, the photothermal conversion efficiency of the functional thermal fluid is 50%-98.09%.

[0036] According to an embodiment of the fourth aspect of the present application, the application of the functional thermal fluid described in any of the above embodiments in the field of solar thermal energy is proposed.

[0037] Compared with the related art, this application has the following beneficial effects:

[0038] (1) The phase change nanocapsules described in the present application have an average particle size of 27.13-167.3 nm, which can be regulated by any one of an emulsifier, an initiator or a cross-linking agent. The melting point is between 52.41-56.96°C, the freezing point is between 54.90-55.56°C, and they have a typical spherical structure. They have a strong heat storage capacity, for example, a phase change enthalpy of more than 220 J / g, a high encapsulation rate, for example, an encapsulation rate of more than 80%, and excellent thermal stability and cyclic stability.

[0039] (2) The latent heat functional thermal fluid based on polystyrene phase change nanocapsules described in this application has excellent dispersion stability (zeta potential of 39.17 mV), heat storage capacity (specific heat capacity of 5.72 J·g -1 ·K -1 ) and photothermal conversion performance (up to 64.91%).

[0040] (3) The latent heat functional thermal fluid based on silica phase change nanocapsules described in this application has excellent dispersion stability (zeta potential of 35.63 mV), heat storage capacity (specific heat capacity of 5.11 J·g -1 ·K -1 ) and photothermal conversion performance (up to 98.09%).

[0041] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0043] Figure 1 is a DSC curve of a phase change nanocapsule provided in one embodiment of the present application;

[0044] Figure 2 It is a TG curve and a thermal cycle curve of a phase change nanocapsule provided in one embodiment of the present application;

[0045] Figure 3 is a SEM image of a phase change nanocapsule provided in one embodiment of the present application;

[0046] Figure 4 is a TEM image of a phase change nanocapsule provided in one embodiment of the present application;

[0047] Figure 5 is a dispersion stability diagram of a phase-change nanocapsule-based latent heat functional thermal fluid provided in one embodiment of the present application;

[0048] Figure 6 It is a diagram of the heat storage capacity and light-to-heat conversion performance of a phase-change nanocapsule-based latent heat functional thermal fluid provided in one embodiment of the present application;

[0049] Figure 7 is a DSC curve of a phase change nanocapsule provided in one embodiment of the present application;

[0050] Figure 8 It is a TG curve and a thermal cycle curve of a phase change nanocapsule provided in one embodiment of the present application;

[0051] Fig. 9 is a SEM image of a phase change nanocapsule provided in one embodiment of the present application;

[0052] Fig.10 is a TEM image of a phase change nanocapsule provided in one embodiment of the present application;

[0053] Fig.11 is a dispersion stability diagram of a phase-change nanocapsule-based latent heat functional thermal fluid provided in one embodiment of the present application;

[0054] Fig.12 1 is a diagram showing the heat storage capacity and light-to-heat conversion performance of a phase-change nanocapsule-based latent heat functional thermal fluid provided in one embodiment of the present application. DETAILED DESCRIPTION

[0055] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be construed as limiting the present application. On the contrary, the present application includes all changes, modifications and equivalents that fall within the spirit and connotation of the appended claims.

[0056] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0057] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0058] To achieve the above-mentioned purpose, according to the embodiment of the first aspect of the present application, a phase-change nanocapsule is proposed, which is a core-shell structure with controllable size, including a core structure and a shell structure; wherein the mass percentage of the core structure is 55.68%-85.12% based on the phase-change nanocapsule. That is, based on the total mass of the phase-change nanocapsule as 100%, the mass percentage of the core structure is 55.68%-85.12%, for example, the mass percentage of the core structure is 62.24%, 65.03%, 69.59%, 70.85%, 80.63%, etc.

[0059] The core structure is an alcohol material with a phase transition temperature of 20-80°C; for example, the alcohol material is octadecyl alcohol. In this embodiment, if the alcohol material is octadecyl alcohol, the core material has a high phase transition enthalpy and a high phase transition temperature, and has a strong heat storage performance.

[0060] The shell structure is polystyrene or silicon dioxide. In this embodiment, when the shell structure is polystyrene, it is highly economical and has quite good mechanical properties against the external environment, while when the shell structure is silicon dioxide, it has the advantages of high encapsulation efficiency, good thermal conductivity, good leakproof performance, good thermal stability, etc. Both polystyrene and silicon dioxide are very suitable as shell materials for phase change nanocapsules.

[0061] In some implementations, the average particle size of the phase-change nanocapsules is about 27.13-167.3 nm, and the particle size is regulated by any one of an emulsifier, an initiator, and a cross-linking agent.

[0062] For example, the average particle size of the phase change nanocapsules is about 27.13-167.3 nm. In some embodiments, the particle size of the phase change nanocapsules is regulated by any one of the emulsifiers, initiators and cross-linking agents in the preparation process of the phase change nanocapsules. For example, controlling the emulsifier can regulate the average particle size of a phase change nanocapsule to be in the range of 62.24-80.63 nm.

[0063] In some implementations, the phase change temperature of the phase change nanocapsules is 20-80°C.

[0064] In some implementations, the phase change temperature of the phase change nanocapsule is 52.41-56.96° C., for example, in some implementations, the phase change temperature of the phase change nanocapsule is 52.91, 53.61, 54.23, 55.38° C., etc.

[0065] According to an embodiment of the second aspect of the present application, a method for preparing a phase-change nanocapsule-based latent heat functional thermal fluid is proposed, wherein the phase-change nanocapsules in any of the above embodiments are dispersed in deionized water containing modified multi-walled carbon nanotubes, and mixed evenly to form a stable functional thermal fluid through the action of an emulsifier.

[0066] In some implementations, the method for preparing phase change nanocapsules with polystyrene as the shell structure includes: preparing an aqueous phase by evenly mixing an emulsifier and deionized water; preparing an oil phase by evenly mixing a core structure material with polystyrene, an initiator, a cross-linking agent and a comonomer; and subjecting the aqueous phase and the oil phase to a polymerization reaction.

[0067] In some implementations, the emulsifier includes sodium lauryl sulfate and octylphenol polyoxyethylene-10 in a mass ratio of (1:3)-(3:1);

[0068] And / or, the mass fraction of the material of the shell structure is 100 parts, and the mass fraction of the emulsifier is 6-14 parts.

[0069] In this embodiment, the mass fraction of the shell structure material is 100 parts as the reference, and the mass fraction of the emulsifier is 6-14 parts. For example, the mass fraction of the emulsifier is 8 parts, 10 parts, 12 parts, etc. The emulsifier in this application includes sodium lauryl sulfate and octylphenol polyoxyethylene-10, and the mass ratio of the two can be 1:2, 1:1, 2:1, etc.

[0070] In some embodiments, in the preparation method of phase change nanocapsules with polystyrene as the shell structure, the mass ratio of the material of the core structure to the material of the shell structure is (1:2)-(3:1); the initiator includes potassium persulfate or azobisisobutyronitrile; the cross-linking agent includes n-dodecyl mercaptan or ethylene glycol dimethacrylate; the comonomer includes acrylic acid, acrylamide, butyl acrylate or methyl methacrylate; the mass fraction of the material of the shell structure is 100 parts, the mass fraction of the initiator is 1.2-2.8 parts; the mass fraction of the cross-linking agent is 1.2-2.8 parts; the mass fraction of the comonomer is 0-1.2 parts.

[0071] In some implementations, the mass ratio of the core structure material to the shell structure material is 1:2, 1:1, 2:1, etc.; based on 100 parts by mass of the shell structure material, the mass fraction of the initiator can be 1.6 parts, 2.0 parts or 2.4 parts, etc.; the mass fraction of the comonomer can be 4 parts, 6 parts, 8 parts, etc.

[0072] In some implementations, the mass fraction of deionized water is 100 parts, the mass fraction of phase change nanocapsules is 5-15 parts, and the mass fraction of modified multi-walled carbon nanotubes is 0.1 parts.

[0073] Among them, in the preparation method of phase change nanocapsules with polystyrene as shell structure, the mass fraction of phase change nanocapsules can be 5 parts, 10 parts or 15 parts, etc., based on the mass fraction of deionized water being 100 parts; and the mass fraction of modified multi-walled carbon nanotubes is 0.1 parts.

[0074] In some implementations, the water phase and the oil phase are dispersed at a high speed of 3000-8000 rpm for 5-10 min to achieve fine emulsification;

[0075] and / or, the polymerization reaction is carried out under a protective atmosphere;

[0076] And / or, the polymerization reaction conditions are: temperature of 30-100°C; stirring speed of 150-500rpm; time of 6-10h;

[0077] And / or, after the polymerization reaction is completed, filtering, washing and drying are performed to obtain phase change nanocapsules with polystyrene as the shell structure.

[0078] Among them, in the preparation method of phase change nanocapsules with polystyrene as the shell structure, the fine emulsification of the water phase and the oil phase includes high-speed dispersion. In some implementations, the speed of high-speed dispersion can be 4000rpm, 5000rpm, 6000rpm or 7000rpm, etc.; the high-speed dispersion time can be 6min, 7min, 8min or 9min, etc. The polymerization reaction is carried out under a protective atmosphere, wherein the polymerization temperature is 65-100°C, for example, the polymerization temperature is 70°C, 75°C, 80°C or 85°C, etc.; at the same time, the polymerization time can be 6.5h, 7h, 7.5h, 8h, 8.5h, etc.; the stirring speed of the polymerization reaction can be 200rm, 250rm, 300rm or 350rm, etc. After the polymerization reaction is completed in this application, it is filtered, washed and dried to obtain a phase change nanocapsule with polystyrene as the shell structure.

[0079] Among them, the method for preparing functional thermal fluid with phase change nanocapsules with polystyrene as shell structure is as follows: emulsifier and deionized water are mixed evenly as water phase; core structure and shell structure materials, initiator, crosslinking agent and comonomer are mixed evenly as oil phase; the oil phase and water phase are mixed, stirred at a speed of 3000-8000rpm for 5-10min to complete fine emulsification, polymerized at 30-100℃ and 150-500rpm for 6-10h under a protective atmosphere, and then filtered, washed and dried to obtain a phase change nanocapsule with polystyrene as shell structure and controllable size; a phase change nanocapsule with polystyrene as shell structure and controllable size is dispersed in deionized water containing modified multi-walled carbon nanotubes, and mixed evenly to form a stable latent heat type functional thermal fluid through the action of emulsifier.

[0080] In some embodiments, the method for preparing phase change nanocapsules with a silica shell structure includes uniformly mixing a core material, an emulsifier and deionized water to prepare a first mixed liquid; uniformly mixing an initiator and silica to prepare a second mixed liquid; and dropwise adding the second mixed liquid to the first mixed liquid to cause a condensation reaction.

[0081] In the process of preparing phase change nanocapsules with silica as the shell structure, the emulsifier includes Tween-80 and Span-80, wherein the mass ratio of Tween-80 to Span-80 is (1:3)-(3:1); for example, the mass ratio of Tween-80 to Span-80 is 1:2, 1:1, 2:1, etc. In this embodiment, the weight fraction of the emulsifier is 5.3 parts based on 100 parts by mass of deionized water.

[0082] In some implementations, the mass fraction of deionized water is 100 parts, the mass fraction of the shell structure material is 6 parts; the weight fraction of the initiator is 1.6-3.0 parts, and the mass ratio of the core structure material to the shell structure material is (5:9)-(20:9).

[0083] Among them, in this embodiment, based on the mass fraction of deionized water as 100 parts, the mass fraction of the shell structure material is 6 parts; the weight fraction of the initiator can be exemplified as 1.6 parts, 2.3 parts or 3.0 parts, etc.; the mass ratio of the core structure material and the shell structure material can be 5:9, 10:9 or 20:9, etc.

[0084] In some implementations, the second mixed solution is added dropwise to the first mixed solution and magnetically stirred at 400-800 rpm to achieve fine emulsification; the temperature of the polycondensation reaction is 30-100°C and the time is 6-10h; after the polycondensation reaction is completed, filtration, washing and drying are performed to obtain phase change nanocapsules with a silica shell structure.

[0085] The method of adding the second mixed solution dropwise to the first mixed solution for fine emulsification is that the second mixed solution is added dropwise to the first mixed solution and magnetically stirred at 400-800 rpm, for example, the magnetic stirring speed is 450 rpm, 500 rpm, 550 rpm, 600 rpm, 650 rpm, 700 rpm or 750 rpm, etc. In some embodiments, the temperature of the polycondensation reaction is 65-100° C., for example, the temperature of the polycondensation reaction is 70° C., 75° C., 80° C. or 85° C., etc.; the time of the polycondensation reaction is 6.5 h, 7 h, 7.5 h, 8 h or 8.5 h, etc.

[0086] Among them, the method for preparing functional thermal fluid with phase change nanocapsules with silica as shell structure is as follows: core structure material, emulsifier and deionized water are mixed evenly to obtain a first mixed solution; initiator and shell structure material monomer are mixed evenly to obtain a second mixed solution; the second mixed solution is added dropwise to the first mixed solution, and magnetic stirring is performed at a speed of 400-800rpm, polycondensation reaction is carried out for 6-10h, and then filtering, washing and drying are performed to obtain a phase change nanocapsule with silica as shell structure and controllable size; the phase change nanocapsule with silica as shell structure and controllable size is dispersed in deionized water containing modified multi-walled carbon nanotubes and ethylene glycol, and mixed evenly through the action of emulsifier to obtain a stable latent heat type functional thermal fluid.

[0087] According to the third aspect of the present application, a phase-change nanocapsule-based latent heat functional thermal fluid is provided, characterized in that the functional thermal fluid is obtained by using the preparation method in any of the above embodiments, wherein the eta potential of the functional thermal fluid is 31.8-39.87 mV and the specific heat capacity is 4.63-6.35 J·g -1 ·K-1 , and its light-to-heat conversion rate is 50%-98.09%.

[0088] In this embodiment, phase change nanocapsules are dispersed in deionized water containing modified multi-walled carbon nanotubes to prepare a uniformly dispersed latent heat functional thermal fluid. The functional thermal fluid has excellent dispersion stability, for example, its zeta potential is 35.63mV, 36.3mV, 38.93mV, 39.17mV, etc.; for example, the functional thermal fluid has excellent heat storage capacity, and its specific heat capacity is 5.09J·g -1 ·K -1 , 5.11 J·g -1 ·K -1 , 5.64 J·g -1 ·K -1 , 5.72 J·g -1 ·K -1 For example, the functional thermal fluid has excellent light-to-heat conversion performance, and its light-to-heat conversion rate is 53.35%, 64.91%, 73.46%, 90.43%, etc. Therefore, the functional thermal fluid in this application has excellent dispersion stability, heat storage capacity and light-to-heat conversion performance.

[0089] According to an embodiment of the fourth aspect of the present application, the application of the functional thermal fluid in any of the above embodiments in the field of solar thermal energy is proposed.

[0090] In order to facilitate the understanding of the present application, the present application is illustrated with examples as follows. Those skilled in the art should understand that the examples are only to help understand the present application and should not be regarded as specific limitations of the present application.

[0091] In this application, the raw material information of each embodiment is as follows:

[0092] Chemical agents include octadecyl alcohol (AR, C 18 H 38 O), sodium dodecyl sulfate (SDS, AR), octylphenol polyoxyethylene ether-10 (OP-10, hydrophilic, 87±10), 2,2-azobisisobutyronitrile (AIBN, C 8 H 12 N 4 ,98%), ethylene glycol dimethacrylate (EGDMA, C 10 H 14 O 4 , 98%), tetraethyl silicate (TEOS, 98%), Span-80 (sp-80, CP), Tween-80 (tw-80, AR), and triethoxysilane (97%, TES) were all purchased from Shanghai MacLean Biochemical Technology Co., Ltd.

[0093] Example 1

[0094] This embodiment provides a method for preparing a phase-change nanocapsule-based latent heat functional thermal fluid, the method comprising the following steps:

[0095] (1) 0.6-1.4 g of emulsifier (SDS:OP-10=1:1) and 200 g of deionized water were mixed evenly to form the aqueous phase;

[0096] (2) 20 g of octadecyl alcohol, 10 g of styrene (St), 0.2 g of azobisisobutyronitrile (AIBN), 0.2 g of ethylene glycol dimethacrylate (EGDMA) and 0.4 g of methyl methacrylate (MMA) were mixed uniformly to form the oil phase;

[0097] (3) The oil phase and the water phase were mixed in a 250 ml conical flask, and the mixture was stirred at 3000 r / min for 5 min in a 75 °C water bath using a high-speed homogenizer to form a coarse emulsion, and then stirred at 8000 r / min for 10 min to form a stable fine emulsion.

[0098] (4) The miniemulsion was poured into a three-necked flask prepared in advance, and stirred at 250 r / min in a 65° C. water bath and nitrogen atmosphere for 8 h using a mechanical stirrer to obtain a white emulsion.

[0099] (5) The white emulsion obtained in step (4) was demulsified with a 10% by mass sodium chloride aqueous solution, filtered, and then washed three times with anhydrous ethanol and deionized water respectively, and finally dried in a drying oven at 45° C. to remove excess deionized water to obtain octadecyl alcohol@polystyrene phase change nanocapsules.

[0100] (4) 10-30 g of phase change nanocapsules with polystyrene as the shell structure are dispersed in 200 ml of deionized water containing 0.2 g of modified multi-walled carbon nanotubes, and mixed evenly with 0.1 g of emulsifier (SDS:OP-10=1:1) to form a stable latent heat functional thermal fluid.

[0101] The phase-change nanocapsule-based latent heat functional thermal fluid provided in this embodiment has polystyrene as a shell structure material and octadecyl alcohol as a core structure material. The average particle size of the phase-change nanocapsule can be adjusted by the amount of emulsifier used, and the range is 55.28-116.22 nm, as shown in Table 1.

[0102] Table 1 Effect of the amount of composite emulsifier on the phase change enthalpy and average particle size of phase change nanocapsules

[0103]

[0104] In this embodiment, the total mass of the phase change nanocapsules is 100%. Under the optimal experimental conditions, the mass percentage of the core material is 80.63%, the average particle size is 88.3 nm, the melting enthalpy and solidification enthalpy are 222.7 and 217.2 J / g respectively, and the melting point and solidification point are 54.78 and 55.15°C respectively.

[0105] The phase-change nanocapsule-based latent heat functional thermal fluid has excellent dispersion stability (zeta potential 31.8-39.87 mV), heat storage capacity and photothermal conversion performance (photothermal conversion rate 51.51%-64.91%).

[0106] Example 2

[0107] This embodiment provides a method for preparing a phase-change nanocapsule-based latent heat functional thermal fluid, the method comprising the following steps:

[0108] (1) 10 g of molten octadecyl alcohol, 0.8 g of emulsifier (tw-80:sp-80=1:3) and 150 ml of deionized water were mixed at 75°C;

[0109] (2) 2.5-4.5 g of triethoxysilane (TES) and 9 g of tetraethyl silicate (TEOS) monomer were mixed evenly;

[0110] (3) adding the mixed solution in step (2) dropwise to the mixed solution in step (1), stirring magnetically at a speed of 600 rpm and a water bath of 75° C., polycondensing for 7 h, filtering, washing and drying to obtain a phase change nanocapsule with a silica shell structure and controllable size;

[0111] (4) 10-30 g of phase change nanocapsules with a silica shell structure are dispersed in deionized water containing 0.2 g of modified multi-walled carbon nanotubes and 0.1 g of ethylene glycol, and mixed evenly under the action of 1 g of emulsifier (tw-80:sp-80=1:3) to form a stable latent heat functional thermal fluid.

[0112] In the functional thermal fluid of this embodiment, the phase change nanocapsules have silicon dioxide as the shell material and octadecyl alcohol as the core material. The average particle size of the phase change nanocapsules can be adjusted by the amount of the initiator, and the range is 27.13-167.3 nm, as shown in Table 2.

[0113] Table 2 Effect of initiator dosage on phase change enthalpy and average particle size of phase change nanocapsules

[0114]

[0115] In this embodiment, the total mass of the phase change nanocapsules is 100%. Under the optimal experimental conditions, the mass percentage of the core material is 85.12%, the average particle size is 27.13 nm, the melting enthalpy and solidification enthalpy are 235.1 J / g and 229.9 J / g respectively, and the melting point and solidification point are 55.53 and 54.77°C respectively.

[0116] A phase-change nanocapsule-based latent heat functional thermal fluid has excellent dispersion stability (zeta potential 35.63-38.93 mV), heat storage capacity and photothermal conversion performance (photothermal conversion rate 73.46%-98.09%).

[0117] Performance Testing

[0118] The phase change nanocapsule-based latent heat functional thermal fluid obtained in Example 1-2 was tested for thermal stability, cycle stability, dispersion stability, heat storage capacity and photothermal conversion performance. The test method is as follows, and the test results are summarized in Table 3 and Figure 1-12 middle.

[0119] (1) Thermal stability: The thermal stability of the sample was measured using a synchronous thermal analyzer (Germany, STA449F3, TGA). The specific requirements are as follows: About 7 mg of the sample was weighed and placed in an aluminum crucible, and the thermal stability of the sample was tested at a heating rate of 10°C / min in a nitrogen atmosphere at 30-600°C.

[0120] (2) Cyclic stability: The cyclic stability of a phase change nanocapsule was determined using a high and low temperature alternating humidity test chamber (China, WGDW-100). The specific requirements were as follows: 5-10 mg of the sample to be tested was placed in a crucible and cycled 500 times at a heating / cooling rate of 5°C / min in the temperature range of 10-90°C to test the cyclic stability of the sample.

[0121] (3) Dispersion stability: The prepared latent heat functional thermal fluid was placed in a vial and allowed to stand for 14 days, and then the zeta potential of the sample at room temperature was tested using a ZetasizerNano series instrument (ZetasizerNano S90, England). Each sample was tested three times and the average of the three tests was taken as the zeta potential value of the sample to eliminate errors.

[0122] (4) Heat storage capacity: 70g of latent heat functional thermal fluid was placed in a sealed culture dish, and then the culture dish containing the fluid was placed on a heat preservation cotton in a drying oven at 80°C, and the temperature of the fluid changing with time was recorded by an Agilent data acquisition instrument. The specific heat capacity of the latent heat functional thermal fluid was tested by a differential scanning calorimeter model DSC214 of NETZSCH, Germany.

[0123] (5) Photothermal conversion performance: The test was conducted using a self-made photothermal conversion test system, which included a heat insulation device, a solar simulator, and a data acquisition device. The solar radiation of the solar simulator was provided by a xenon lamp with an irradiation intensity of 1000 W / m -2 The data acquisition device consists of a thermocouple and a computer. Professional software can measure the internal temperature of the sample in real time. The specific requirements of the experiment are as follows: the data acquisition time interval is 5s, and the measurement accuracy of the K-type thermocouple is ±0.1℃. The photothermal conversion efficiency of 70g of latent heat type functional thermal fluid was evaluated at an ambient temperature of 25℃. The contact area between the sample and the light source is 22.85πcm 2 .

[0124] Table 3 Effect of hot and cold cycles on the phase change enthalpy of phase change nanocapsules

[0125]

[0126] The data in the analysis table show that after 200 hot-cold cycles and 500 hot-cold cycles, the encapsulation efficiency of octadecanol@polystyrene phase change nanocapsules only decreased by 6.23% and 10.57% respectively, showing excellent anti-leakage performance and cycle stability. The encapsulation efficiency of octadecanol@silica decreased by 7.06% and 17.92% respectively, indicating that octadecanol@silica phase change nanocapsules have good anti-leakage and cycle stability.

[0127] Taking Example 1 as an example, Figure 1 is the DSC curve of a phase change nanocapsule in Example 1, Figure 2 It is the TG curve and the hot and cold cycle curve. Figure 3 For SEM images, Figure 4 TEM images show that the size-controlled octadecyl alcohol@polystyrene phase change nanocapsules have an optimal melting enthalpy and solidification enthalpy of 222.7 and 217.2 J / g, respectively, a melting point and solidification point of 54.78 and 55.15°C, and an encapsulation rate of up to 80.63%. The average particle size is about 88.3 nm. TGA and 500 hot and cold cycle results show that octadecyl alcohol@polystyrene has excellent thermal stability, anti-leakage performance and cyclic stability. Figure 5 This is a dispersion stability diagram of a phase-change nanocapsule-based latent heat functional thermal fluid in Example 1. Figure 6 The results show that the latent heat functional thermal fluid containing 10wt% phase change nanocapsules has excellent photothermal conversion efficiency (up to 64.91%), excellent dispersion stability (zeta potential 39.17mV) and thermal storage capacity (peak specific heat capacity 5.72J·g -1 ·K -1). Under the influence of solar radiation, the temperature rise curve of the latent heat functional thermal fluid shows a faster initial heating rate after reaching the melting point of the phase change nanocapsules, followed by a plateau period of about 76 minutes, and its photothermal conversion efficiency is about 2.18 times that of water. The experimental results show that the latent heat functional thermal fluid based on octadecyl alcohol@polystyrene phase change nanocapsules has potential application value in the solar thermal industry.

[0128] Figure 7 , Figure 8 , Fig. 9 and Fig.10 The results show that the size-controlled octadecyl alcohol@silica phase-change nanocapsules have an average particle size of 27.13 nm, melting enthalpy and solidification enthalpy are 235.1 and 229.9 J / g, melting point and solidification point are 55.53 and 54.77°C, respectively, and the encapsulation rate is about 85.12%. The results of TGA and 500 hot and cold cycles show that the octadecyl alcohol@silica phase-change nanocapsules have excellent thermal stability, good anti-leakage and cycle stability. Fig.11 and Fig.12 The results show that under solar radiation, the latent heat functional thermal fluid containing 10wt% octadecyl alcohol@silica phase change nanocapsules has excellent dispersion stability (zeta potential 35.63mV), heat storage capacity (peak specific heat capacity 5.11J·g -1 ·K -1 ) and excellent photothermal conversion efficiency (up to 98.09%), which is about 3.29 times that of water. Specifically, the temperature rise curve of the latent heat functional thermal fluid shows a phase change plateau of about 62min, even with only 7g of octadecanol@silica phase change nanocapsules. The experimental results show that the latent heat functional thermal fluid based on octadecanol@silica phase change nanocapsules has potential application prospects in the solar thermal industry.

[0129] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0130] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in the field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A phase change nanocapsule, characterized in that: It is a core-shell structure with controllable size, including a core structure and a shell structure; wherein the mass percentage of the core structure is 55.68%-85.12% based on the phase-change nanocapsule; and / or, the core structure is an alcohol material having a phase transition temperature of 20-80°C; And / or, the shell structure is polystyrene or silicon dioxide.

2. The phase-change nanocapsule according to claim 1, characterized in that: The average particle size of the phase-change nanocapsules is about 27.13-167.3 nm, and the particle size can be regulated by any one of an emulsifier, an initiator and a cross-linking agent; And / or, the phase change temperature of the phase change nanocapsule is 20-80°C.

3. A method for preparing a phase-change nanocapsule-based latent heat functional thermal fluid, characterized in that: Dispersing the phase change nanocapsules described in claim 1 or 2 in deionized water containing modified multi-walled carbon nanotubes, and mixing them uniformly to form the stable functional thermal fluid through the action of an emulsifier; The preparation method of the phase change nanocapsule with polystyrene as the shell structure includes: preparing a water phase by mixing an emulsifier and deionized water evenly; preparing an oil phase by mixing a core structure material with polystyrene, an initiator, a crosslinking agent and a comonomer evenly; and subjecting the water phase and the oil phase to a polymerization reaction.

4. The preparation method according to claim 3, characterized in that: The emulsifier comprises sodium lauryl sulfate and octylphenol polyoxyethylene-10 in a mass ratio of (1:3)-(3:1); And / or, the mass fraction of the material of the shell structure is 100 parts, and the mass fraction of the emulsifier is 6-14 parts.

5. The preparation method according to claim 3, characterized in that: The mass ratio of the material of the core structure to the material of the shell structure is (1:2)-(3:1); And / or, the initiator comprises potassium persulfate or azobisisobutyronitrile; and / or, the cross-linking agent comprises n-dodecyl mercaptan or ethylene glycol dimethacrylate; and / or, the comonomer comprises acrylic acid, acrylamide, butyl acrylate or methyl methacrylate; And / or, the mass fraction of the material of the shell structure is 100 parts, the mass fraction of the initiator is 1.2-2.8 parts; the mass fraction of the cross-linking agent is 1.2-2.8 parts; the mass fraction of the comonomer is 0-1.2 parts; And / or, the mass fraction of the deionized water is 100 parts, the mass fraction of the phase change nanocapsules is 5-15 parts; and the mass fraction of the modified multi-walled carbon nanotubes is 0.1 parts.

6. The preparation method according to any one of claims 3 to 5, characterized in that: The water phase and the oil phase are dispersed at a high speed of 3000-8000 rpm for 5-10 minutes to complete fine emulsification; And / or, the polymerization reaction is carried out under a protective atmosphere; And / or, the polymerization reaction conditions are: temperature of 30-100°C; stirring speed of 150-500rpm; time of 6-10h; And / or, after the polymerization reaction is completed, filtering, washing and drying are performed to obtain the phase change nanocapsules with polystyrene as the shell structure.

7. The preparation method according to claim 3, characterized in that: The method for preparing a phase-change nanocapsule with a silicon dioxide shell structure comprises the steps of uniformly mixing a core material, an emulsifier and deionized water to prepare a first mixed solution; uniformly mixing an initiator and silicon dioxide to prepare a second mixed solution; and dropwise adding the second mixed solution to the first mixed solution to produce a polycondensation reaction. And / or, when the phase-change nanocapsules are dispersed in deionized water containing modified multi-walled carbon nanotubes, the deionized water further contains ethylene glycol.

8. The preparation method according to claim 7, characterized in that: The emulsifier includes Tween-80 and Span-80 in a mass ratio of (1:3) to (3:1); And / or, based on the mass fraction of the deionized water being 100 parts, the weight fraction of the emulsifier is 5.3 parts; And / or, based on the mass fraction of the deionized water being 100 parts, the mass fraction of the shell structure material being 6 parts; the weight fraction of the initiator being 1.6-3.0 parts; And / or, the mass ratio of the material of the core structure to the material of the shell structure is (5:9)-(20:9); and / or, the second mixed solution is added dropwise to the first mixed solution and magnetically stirred at 400-800 rpm to complete fine emulsification; And / or, the polycondensation reaction temperature is 30-100°C and the time is 6-10h; And / or, after the polycondensation reaction is completed, filtering, washing and drying are performed to obtain the phase change nanocapsules with silicon dioxide as the shell structure.

9. A phase-change nanocapsule-based latent heat functional thermal fluid, characterized in that: The functional thermal fluid is obtained by the preparation method described in any one of claims 3 to 8, wherein the eta potential of the functional thermal fluid is 31.8-39.87 mV.

10. Application of the functional thermal fluid described in claim 9 in the field of solar thermal energy.

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