A phase-change nano-emulsion and use thereof

Abstract

This invention belongs to the field of cooling materials technology and relates to a phase change nanoemulsion and its applications. The phase change nanoemulsion is prepared by a method including the following steps: (1) mixing raw materials containing phase change materials, nonionic surfactants, and polyols under a certain temperature to obtain a uniform gel phase; (2) adding water dropwise to the uniform gel phase under a certain temperature and stirring to trigger a spontaneous phase transition and obtain an oil-in-water nanoemulsion; (3) cooling the oil-in-water nanoemulsion to obtain a phase change nanoemulsion with a particle size in the submicron range. The phase change nanoemulsion of this invention can be prepared at low cost and on a large scale, and has both high heat storage density and excellent fluidity, thus it can be applied to many fields, especially as a cooling medium in new energy vehicles, high-density artificial intelligence data centers, and advanced thermal energy storage.

Description

Specification 1 A Phase Change Nanoemulsion and Its Application Technical Field This invention belongs to the field of cooling materials technology, and relates to a phase change nanoemulsion and its application. Background Art Currently, the performance requirements of cooling media in fields such as new energy vehicles, high-density artificial intelligence data centers, and advanced thermal energy storage are continuously increasing, and existing technologies are no longer sufficient to meet the demands, mainly in the following aspects. First, the volumetric heat capacity of traditional single-phase coolants (such as water / ethylene glycol mixtures) has a physical upper limit. Under extreme conditions where the critical heat flux exceeds 100 W / cm², its heat dissipation capacity has reached its limit. With the popularization of new-generation AI accelerator chips and high-power power battery systems, the heat density continues to rise, and traditional single-phase coolants can no longer maintain the system's stable operation within a safe temperature window, posing a risk of thermal runaway. Second, although existing microencapsulated phase change material slurries (MPCM slurries) introduce latent heat of phase change to improve heat storage density, their core defect lies in the structure of using a polymer shell to encapsulate the phase change material. In practical engineering dynamic pumping cycles, the capsule shell is easily ruptured by shear forces, leading to leakage of phase change materials, severe particle agglomeration, and pipeline blockage. The system reliability and service life are insufficient to meet industrial application requirements. Third, the preparation of traditional nanoemulsions relies on high-energy mechanical shearing methods such as high-pressure homogenizers (HPH) or ultrasonic emulsification, with typical preparation energy consumption reaching the order of 10¹⁰ W / kg. This places extremely high demands on equipment investment and process costs, severely restricting the industrial-scale production and commercial promotion of phase change nanoemulsions. The existence of these three major technical bottlenecks urgently necessitates the development of a novel phase change nanoemulsion that combines high heat storage density, excellent flowability, and low-cost, scalable preparation. Furthermore, when using high-melting-point paraffin (such as 50# paraffin, Tm ≈ 50°C) as a phase change material to prepare nanoemulsions, the traditional PIT method presents a thermodynamic conflict: to obtain nanoscale particles (<500 nm), a high surfactant concentration (>15%) must be used; however, increasing the surfactant concentration significantly reduces the system's phase transition temperature (PIT). Successful PIT emulsification requires the PIT point to be approximately 25°C higher than the melting point of paraffin. For 50# paraffin, this means the PIT needs to reach 75°C, but this is almost impossible to achieve at high surfactant concentrations. HK 30138783 A Specification 2 Summary of the Invention The primary objective of this invention is to provide a phase change nanoemulsion that can be prepared at low cost and on a large scale, while also possessing high heat storage density and excellent flowability.To achieve this objective, in a basic implementation scheme, the present invention provides a phase change nanoemulsion, which is prepared by a preparation method including the following steps: (1) mixing raw materials containing phase change material, nonionic surfactant and polyol under a certain temperature to obtain a uniform gel phase; (2) adding water dropwise to the uniform gel phase under a certain temperature and stirring to trigger a spontaneous phase transition to obtain an oil-in-water nanoemulsion; (3) cooling the oil-in-water nanoemulsion to obtain a phase change nanoemulsion with a particle size in the submicron range, wherein the preparation method does not require a high-pressure homogenizer or ultrasonic emulsification equipment throughout the process, and the emulsification process relies on the spontaneous phase structure transition induced by the dilution of the gel phase. The relevant principles of this invention are as follows: This invention provides a high latent heat pumpable phase change nanoemulsion, which is composed of phase change material (e.g., paraffin-based phase change material, PCM) nanodroplets uniformly dispersed in a continuous aqueous phase. It can simultaneously transfer sensible and latent heat, possessing both high heat storage density and water-like flow characteristics, and can directly replace the traditional coolant in existing liquid cooling systems. The preparation process of this nanoemulsion includes the following steps: (a) mixing phase change material, nonionic surfactant, and polyol under heating conditions to form a uniform gel phase composed of phase change material uniformly dispersed in a surfactant-polyol system; (b) adding an aqueous phase dropwise to the uniform gel phase at a controlled rate under stirring conditions to trigger a spontaneous phase transition, obtaining an oil-in-water nanoemulsion; (c) cooling to obtain a phase change nanoemulsion with a particle size in the submicron range. The preparation process does not require a high-pressure homogenizer or ultrasonic emulsification equipment. The core technological innovation of this invention lies in the use of a low-energy emulsification method to prepare the nanoemulsion. This method utilizes dilution-induced phase transformation and reduced interfacial tension to achieve low-energy emulsification, eliminating the need for high-pressure homogenizers or ultrasonic equipment throughout the process. The specific operation consists of three steps: First, phase change material, nonionic surfactant, and polyol are thoroughly mixed under specific temperature conditions to form a homogeneous gel phase with a three-dimensional network structure. Within this network, a dual stabilization mechanism of "electrostatic repulsion + steric hindrance" is constructed by precisely adjusting the HLB value of the surfactant and introducing trace additives, giving the emulsion excellent long-term stability. Second, the aqueous phase is added dropwise to the homogeneous gel phase at a controlled rate, triggering a spontaneous phase transformation. The gel phase network spontaneously swells and uniformly encapsulates and disperses the phase change material droplets within the aqueous phase. Third, the system spontaneously splits under conditions requiring only conventional low-speed stirring, without the need for high-pressure homogenization or ultrasonic high-energy mechanical shearing, forming a homogeneous nanoemulsion with a particle size of approximately 300-600 nm. After cooling, the final product is obtained.The energy consumption of the above preparation process is significantly lower than that of high-pressure homogenization or ultrasonic emulsification methods; within the phase change temperature range of 40–60 ℃, the volumetric latent heat storage capacity of the obtained emulsion is approximately 1.5 times that of water; it exhibits near-Newtonian fluid characteristics with minimal viscosity change within the working shear rate range (viscosity remains at approximately 20 mPa·s at shear rates of 10–100 s⁻¹, significantly lower than that of traditional PCM slurries, meeting conventional pumping requirements), and is compatible with existing pumping pipelines; thermal cycling verification showed no demulsification or Ostwald ripening phenomenon; supercooling was controlled within ΔT < 5°C; and the particle size did not significantly increase after thermal cycling. In a preferred embodiment, the present invention provides a phase change nanoemulsion, wherein in step (1), the phase change material is a long-chain alkane phase change material, selected from paraffin wax with a melting point of 20–60°C, or a eutectic compound formed from one or more straight-chain or branched alkanes having 18–28 carbon atoms; and / or the nonionic surfactant is selected from a compound system of two of polyoxyethylene lauryl ether, polyethylene glycol monooleate, polyoxyethylene hydrogenated castor oil, cetearyl alcohol polyether, glyceryl monostearate, Tween 20 / 60 / 80, and Span 20 / 60 / 80; and / or the polyol is selected from one or more of glycerol, ethylene glycol, 1,3-butanediol, 1,4-butanediol, and propylene glycol. In a preferred embodiment, the present invention provides a phase change nanoemulsion, wherein in step (1), the mass percentage content of the phase change material, the nonionic surfactant, and the polyol in the preparation raw materials are 10-40 wt%, 4.0-7.0 wt%, and 2.0-4.0 wt%, respectively. In a preferred embodiment, the present invention provides a phase change nanoemulsion, wherein in step (1), the preparation raw materials further contain 0.01-0.10 wt% of anionic surfactant and / or 0.1-0.5 wt% of water-soluble polymeric stabilizer. The anionic surfactant described in HK 30138783 A specification 4 is selected from one or more of sodium dodecyl sulfate (SDS) and sodium stearoyl lactylate (SSL), and the water-soluble polymeric stabilizer is selected from one or more of polyvinyl alcohol (PVA), polyethylene glycol (PEG), and PE-b-PEG diblock copolymer. Preferably, the raw materials used in the preparation also include 0.05 wt% sodium dodecyl sulfate and / or 0.2-0.3 wt% polyvinyl alcohol. The anionic surfactant and the water-soluble polymeric stabilizer can synergistically form a dual stabilizing network of electrostatic repulsion and steric hindrance. Thus, after steps (2) and (3), the resulting emulsion exhibits low viscosity near-Newtonian fluid characteristics at the actual working shear rate, and the particle size remains stable after multiple thermal cycles, with supercooling effectively suppressed.In a preferred embodiment, the present invention provides a phase change nanoemulsion, wherein in step (1), the raw materials for preparation further include 0.1-0.3 wt% of a nucleating agent, wherein the nucleating agent is selected from one or more of nano silica, homologous high-melting-point paraffin (e.g., 58# or 65# paraffin), stearic acid, and myristic acid; in step (2), the water added is the remaining water in the formula. After adding the nucleating agent, supercooling can be suppressed; with sufficient PCM content, the emulsion maintains a high latent heat of fusion, while maintaining supercooling ΔT ≤ 5°C. In a preferred embodiment, the present invention provides a phase change nanoemulsion, wherein in step (1), the stirring and mixing temperature is 75-85°C, the stirring speed is 300-700 rpm, and the time is 15-30 min. In a preferred embodiment, the present invention provides a phase change nanoemulsion, wherein in step (2), the certain temperature is 75-85℃; and / or the stirring speed is 300-700 rpm; and / or the water dropping rate is 0.5-2 mL / min; and / or the volume ratio of the gel phase to the water is 1:2-4. In a preferred embodiment, the present invention provides a phase change nanoemulsion, wherein in step (3), the cooling is to a temperature of 20-25℃. A second object of the present invention is to provide the use of the phase change nanoemulsion as described above, wherein the phase change nanoemulsion is used as a cooling medium in at least one of the following fields or systems: hydrogen fuel cell cooling, synergistic thermal management of low-temperature or medium-low-temperature solid hydrogen storage materials, thermal management of power batteries for new energy vehicles, liquid cooling of high-density data centers, chip heat dissipation and thermal management, building HVAC thermal energy storage, and cold chain logistics. The beneficial effects of this invention are that the phase change nanoemulsion can be prepared at low cost and on a large scale, and possesses both high heat storage density and excellent fluidity, thus making it applicable to many fields, especially as a cooling medium in new energy vehicles, high-density artificial intelligence data centers, and advanced thermal energy storage. The phase change nanoemulsion of this invention has broad commercial application potential across industries, and its technological advantages can be transformed into significant competitive barriers in several high-value markets. In the fields of new energy vehicles and hydrogen energy, this invention can serve as a direct replacement for the coolant in the thermal management system of power batteries. Its phase change latent heat characteristics can effectively maintain the battery operating temperature within the optimal range, suppress the risk of thermal runaway, and are expected to improve thermal uniformity, reduce the risk of thermal runaway, and enhance system energy efficiency. Furthermore, its dual-functional characteristics can simultaneously meet the synergistic thermal management needs of hydrogen fuel cell cooling and solid-state hydrogen storage tank activation heat supply, providing an integrated thermal management solution for hydrogen fuel cell vehicles.In the field of artificial intelligence data centers, as the thermal density of next-generation AI chips continues to break through the heat dissipation limits of traditional liquid cooling media, the latent heat buffering characteristics of this invention can effectively absorb the instantaneous heat peaks of GPUs / NPUs, and are expected to serve as a candidate alternative medium in existing cold plate / CDU circuits, improving overall heat dissipation margin and system stability. In the fields of HVAC and cold chain energy storage, this invention can be integrated into building heating and cooling energy storage systems and logistics cold chain equipment, utilizing the latent heat of phase change to achieve peak shaving and valley filling of electricity, reducing the overall energy consumption of the system. In addition, this nanoemulsion platform can also be extended to the fields of medicine and cosmetics, serving as a nano-delivery carrier for high-value bioactive ingredients. Figure 1 is a photograph of the phase change nanoemulsion prepared in Example 1 at room temperature. Figure 2 is a viscosity-shear rate curve of the phase change nanoemulsion prepared in Example 1 and the prior art. Figure 3 is a graph showing the 32-day particle size stability test results of the phase change nanoemulsion prepared in Example 1. Detailed Description of Embodiments To better understand the technical solutions and advantages of the present invention, the present invention will be further described below through embodiments and accompanying drawings (HK 30138783 A Specification 6). Example 1: Preparation of Phase Change Nanoemulsion The preparation method of the phase change nanoemulsion in this example includes the following steps: (1) The phase change material, nonionic surfactant, polyol, anionic surfactant, water-soluble polymer stabilizer and nucleating agent are mixed at 80°C and 300-700 rpm for a period of 15-30 min until a uniform and transparent viscous gel phase is formed (the gel phase is an isotropic or gel-like surfactant phase formed by surfactant, polyol and phase change material); (2) At a certain temperature, water is added dropwise to the gel phase under stirring, thereby triggering a spontaneous phase change, and the system spontaneously changes from gel state to emulsion state to obtain an oil-in-water nanoemulsion; (3) The oil-in-water nanoemulsion is in liquid nanoemulsion state when it is above the melting point of PCM, and forms a phase change nanodispersion containing solid phase change particles after cooling.In step (1), the phase change material accounts for 10-40 wt% of the raw materials, which is 50# paraffin wax with a melting point of about 50℃; the nonionic surfactant accounts for 4.0-7.0 wt% of the raw materials, which is a mixture of polyoxyethylene lauryl ether and cetearyl alcohol polyether in a mass ratio of 1:1.5-1:2; the polyol accounts for 2.0-4.0 wt% of the raw materials, which is glycerol; the anionic surfactant accounts for 0.05 wt% of the raw materials, which is sodium dodecyl sulfate; the water-soluble polymeric stabilizer accounts for 0.2-0.3 wt% of the raw materials, which is polyvinyl alcohol (viscosity average molecular weight of about 70,000-80,000 g / mol); and the nucleating agent accounts for 0.1-0.3 wt% of the raw materials, which is nano-silica. In step (2), the temperature is 75-85℃, the stirring speed is 300-700rpm, the water drop rate is 2 mL / min, and the volume ratio of gel phase to water is 1:2-4. In step (3), the temperature is naturally cooled to 20-25℃, and the cooling rate is not particularly limited. The energy consumption of the above preparation process is about 10² W / kg. The actual photograph of the phase change nanoemulsion prepared in this example at room temperature is shown in Figure 1, which shows that the emulsion is translucent to milky white at room temperature, has good fluidity, and no obvious residue on the bottle wall, proving its low viscosity and good fluidity. Example 2: Detection of phase change nanoemulsion The phase change nanoemulsion prepared in Example 1 was subjected to relevant tests, and the results are as follows. HK 30138783 A Specification 7 Example 1 A phase change nanoemulsion product with an average particle size of 402nm was obtained. The particle size distribution was determined by dynamic light scattering (DLS), and the particle size remained stable at <600 nm with a storage stability period of ≥32 days. The phase transition enthalpy and supercooling were determined by differential scanning calorimetry (DSC), with ΔT = 2.54°C (lower than the 3.42°C of pure bulk paraffin). The viscosity was confirmed to be 20 mPa·s at the working shear rate (10-100 s⁻¹), exhibiting near-Newtonian fluid characteristics. Accelerated thermal cycling tests confirmed the absence of demulsification or Ostwald ripening. Furthermore, by plotting shear rate (s⁻¹) on the x-axis and viscosity (mPa·s) on the y-axis, the viscosity-shear rate relationship curves of the phase change nanoemulsion were compared. Specifically, the rheological behavior of the conventional micron-sized PCM slurry (PCS50) and the nanoemulsion of this invention (N84, prepared in Example 1) were compared. The results are shown in Figure 2, indicating that the viscosity of the sample in Example 1 remained stable at approximately 20 mPa·s within the typical working shear rate range (10-100 s⁻¹), exhibiting near-Newtonian fluid characteristics, which is much lower than the initial viscosity of the conventional slurry (>300 mPa·s).Furthermore, the 32-day particle size stability of the phase change nanoemulsion prepared in Example 1 was examined. The particle size changes under room temperature (25°C) and thermal aging (60°C) conditions were compared, with error bars (mean ± SD, n=3). The results are shown in Figure 3 (the dashed line in the figure marks the 600 nm stability threshold), indicating that the particle size of the emulsion of the present invention remained below 600 nm under both storage conditions. Obviously, those skilled in the art can make various modifications and variations to the present invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of the present invention and their equivalents, the present invention also intends to include these modifications and variations. The above embodiments or implementations are merely illustrative examples of the present invention, and the present invention can also be implemented in other specific ways or other specific forms without departing from the gist or essential characteristics of the invention. Therefore, the described embodiments should be considered illustrative rather than limiting in any respect. The scope of this invention shall be defined by the appended claims, and any variations equivalent to the intent and scope of the claims shall also be included within the scope of this invention. HK 30138783 A Claims 1 1. A phase change nanoemulsion, characterized in that the phase change nanoemulsion is prepared by a preparation method comprising the following steps: (1) mixing raw materials comprising phase change material, nonionic surfactant and polyol under a certain temperature condition to obtain a uniform gel phase; (2) adding water dropwise to the uniform gel phase under a certain temperature and stirring to trigger a spontaneous phase transition to obtain an oil-in-water nanoemulsion; (3) cooling the oil-in-water nanoemulsion to obtain a phase change nanoemulsion with a particle size in the submicron range, wherein the preparation method does not require a high-pressure homogenizer or ultrasonic emulsification equipment throughout the process, and the emulsification process relies on the spontaneous phase structure transition induced by the dilution of the gel phase. 2. The phase change nanoemulsion according to claim 1, characterized in that: in step (1), the phase change material is a long-chain alkane phase change material, selected from paraffin with a melting point of 20–60℃, or a eutectic compound formed from one or more straight-chain or branched alkanes having 18-28 carbon atoms; and / or the nonionic surfactant is selected from a compound system of two of polyoxyethylene lauryl ether, polyethylene glycol monooleate, polyoxyethylene hydrogenated castor oil, cetearyl alcohol polyether, glyceryl monostearate, Tween 20 / 60 / 80, and Span 20 / 60 / 80; and / or the polyol is selected from one or more of glycerol, ethylene glycol, 1,3-butanediol, 1,4-butanediol, and propylene glycol.3. The phase change nanoemulsion according to claim 1, characterized in that: in step (1), the mass percentage content of the phase change material, the nonionic surfactant, and the polyol in the preparation raw materials are 10-40 wt%, 4.0-7.0 wt%, and 2.0-4.0 wt%, respectively. 4. The phase change nanoemulsion according to claim 1, characterized in that: in step (1), the preparation raw materials further contain 0.01-0.10 wt% of anionic surfactant and / or 0.1-0.5 wt% of water-soluble polymeric stabilizer, wherein the anionic surfactant in claim 2 of HK 30138783 A is selected from one or more of sodium dodecyl sulfate and sodium stearoyl lactylate, and the water-soluble polymeric stabilizer is selected from one or more of polyvinyl alcohol, polyethylene glycol, and PE-b-PEG diblock copolymer. 5. The phase change nanoemulsion according to claim 4, characterized in that: in step (1), the raw materials for preparation further include 0.1-0.3 wt% of a nucleating agent, wherein the nucleating agent is selected from one or more of nano-silica, homologous high-melting-point paraffin, stearic acid, and myristic acid; in step (2), the water added is the remaining water in the formula. 6. The phase change nanoemulsion according to claim 1, characterized in that: in step (1), the stirring and mixing temperature is 75-85℃, the stirring speed is 300-700 rpm, and the time is 15-30 min. 7. The phase change nanoemulsion according to claim 1, characterized in that: in step (2), the specific temperature is 75-85℃; and / or the stirring speed is 300-700 rpm; and / or the rate of water addition is 0.5-2 mL / min; and / or the volume ratio of the gel phase to the water is 1:2-4. 8. The phase change nanoemulsion according to claim 1, characterized in that: in step (3), the cooling is to a temperature of 20-25℃. 9. The use of the phase change nanoemulsion according to any one of claims 1-8, characterized in that: the use is for the phase change nanoemulsion as a cooling medium in at least one of the following fields or systems: hydrogen fuel cell cooling, synergistic thermal management of low-temperature or medium-low-temperature solid hydrogen storage materials, thermal management of power batteries for new energy vehicles, liquid cooling of high-density data centers, chip heat dissipation and thermal management, building HVAC thermal energy storage, and cold chain logistics. HK 30138783 A Specification Drawings 1 Figure 1 Figure 2 HK 30138783 A Specification Drawings 2 Figure 3 HK 30138783 A.

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