A paraffin-based phase-change nanoemulsion and its preparation method and application

Abstract

The invention discloses a paraffin-based phase-change nanoemulsion and a preparation method and application thereof, wherein the preparation method comprises the steps of: configuring 10-30 parts of paraffin phase-change energy storage material, adding 5-15 parts of surfactant and 1-3 parts of nucleating agent, heating to 70-80°C and mixing evenly to obtain an emulsion oil phase material; under stirring conditions, adding 50-100 parts of deionized water or distilled water to the emulsion oil phase material and maintaining the temperature at 70-80°C to obtain an emulsion; after the emulsion is cooled to 25°C, a paraffin-based phase-change nanoemulsion is obtained. The invention provides a paraffin-based phase-change nanoemulsion with good stability, small supercooling, high latent heat of phase change, wide operating temperature, and can be used as an efficient heat dissipation cooling medium; accordingly, a preparation method of the paraffin-based phase-change nanoemulsion with simple process, low cost, and easy industrial amplification is provided, and the phase-change nanoemulsion is applied to the thermal management system of photovoltaic modules to reduce its surface temperature, improve its photoelectric conversion efficiency, and recycle waste heat.

Description

Technical Field

[0001] The present invention relates to the field of energy storage technology, and in particular to a paraffin-based phase-change nanoemulsion and a preparation method and energy storage application thereof. Background Art

[0002] At present, solar photovoltaic power generation technology has achieved great success in my country, but its actual photoelectric conversion efficiency is low, less than 15%. For every 1°C increase in the surface temperature of the photovoltaic module, its photoelectric conversion efficiency will decrease by about 0.5%; at the same time, too high an operating temperature will greatly shorten the service life of the photovoltaic module. Therefore, studying the cooling technology of photovoltaic modules can effectively improve their photoelectric conversion efficiency and service life.

[0003] Common photovoltaic module cooling technologies are divided into active and passive. Passive cooling technology has a simple structure and low cost, but its cooling capacity is poor. Active cooling technology cools and dissipates heat from photovoltaic modules by pumping cooling fluid, and has strong cooling capacity, but from the perspective of economic efficiency, it is necessary to further strengthen the heat dissipation process and the use of waste heat. Therefore, it is very necessary to develop a solar photovoltaic module cooling device based on energy storage.

[0004] As the most common cooling medium, water has a large specific heat capacity, but its heat dissipation power is still limited under high heat flux density. Therefore, currently, a certain mass fraction of organic phase change energy storage materials are dispersed in water, which can undergo phase change within a specific temperature range, thereby absorbing or releasing a large amount of phase change latent heat. Under the same inlet and outlet temperature and flow rate, the heat dissipation power can be further improved.

[0005] Common phase change functional fluids include phase change microcapsule slurries and phase change emulsions. The particles of phase change microcapsules are large, reaching the micron level. The preparation process is complicated and the cost is high. The shell material is easy to break after multiple pumping. At the same time, the shell material increases the thermal resistance and reduces the enhanced heat transfer effect. Phase change emulsions are thermodynamically unstable systems with poor stability. After multiple hot and cold phase change cycles or long-term storage, they are prone to demulsification and phase stratification. In addition, phase change emulsions also have the problem of supercooling. It often requires a temperature 10-15°C below the freezing point to convert the liquid into a solid state. Within the given working temperature, supercooling will cause a large amount of phase change latent heat to be unable to be effectively stored, thereby greatly reducing the heat dissipation power of the phase change emulsion.

[0006] Chinese patent document CN109888430A discloses a phase-change heat transfer medium and its preparation method. However, the preparation method of the phase-change heat transfer medium in the above document is ultrasonic emulsification, and the size and power of the ultrasonic instrument are limited. Currently, this method is only suitable for small-scale laboratory production. Therefore, the existing technology needs to be improved and developed. Summary of the invention

[0007] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a paraffin-based phase change nanoemulsion with good stability, small supercooling, high phase change latent heat, wide operating temperature, and can be used as an efficient heat dissipation cooling medium, as well as a preparation method and application thereof.

[0008] The technical solution of the present invention is as follows:

[0009] A method for preparing a paraffin-based phase-change nanoemulsion, comprising the steps of:

[0010] Prepare 10-30 parts of paraffin phase change energy storage material, add 5-15 parts of surfactant and 1-3 parts of nucleating agent, heat to 70-80°C and mix evenly to prepare emulsion oil phase material;

[0011] Under stirring conditions, adding 50-100 parts of deionized water or distilled water to the emulsion oil phase material and maintaining the temperature at 70-80° C. to obtain an emulsion;

[0012] After the emulsion is cooled to 25° C., a paraffin-based phase-change nanoemulsion is obtained.

[0013] The preparation method of the paraffin-based phase-change nanoemulsion, wherein the phase change temperature of the paraffin phase-change energy storage material is 18-70°C.

[0014] The method for preparing the paraffin-based phase-change nanoemulsion, wherein the paraffin phase-change energy storage material comprises at least one of alkanes with carbon atoms of 16-30 and at least one of paraffins with a carbon number of 20-70.

[0015] The method for preparing the paraffin-based phase-change nanoemulsion comprises the following steps: the surfactant is a compound of surfactant A and surfactant B, wherein the mass fraction of surfactant A is not less than 50%.

[0016] The preparation method of the paraffin-based phase-change nanoemulsion, wherein the surfactant A is lauryl alcohol polyoxyethylene ether; the surfactant B is selected from one of Tween-20, Tween-40, Tween-60, Tween-80, polyethylene glycol monohexadecyl ether, polyoxyethylene lauryl ether, polyoxyethylene stearate, polyethylene glycol 12 hydroxystearate, ethoxylated C16-18-alcohol, polyoxyethylene castor oil series with an HLB value greater than 14, and polyoxyethylene hydrogenated castor oil series with an HLB value greater than 14.

[0017] The method for preparing the paraffin-based phase-change nanoemulsion, wherein the nucleating agent is at least one of polyethylene-block-poly(ethylene glycol), paraffin, nano-alumina dispersion, nano-zinc oxide dispersion, and nano-silicon oxide dispersion.

[0018] The method for preparing the paraffin-based phase-change nanoemulsion, wherein the dispersed particle size of the paraffin-based phase-change nanoemulsion is less than 100 nm.

[0019] A paraffin-based phase-change nanoemulsion is prepared by the preparation method of the paraffin-based phase-change nanoemulsion of the present invention.

[0020] An application of a paraffin-based phase-change nanoemulsion, wherein the paraffin-based phase-change nanoemulsion of the invention is used in a thermal management system of a solar photovoltaic module.

[0021] The application of the paraffin-based phase-change nanoemulsion, wherein the thermal management system includes a heat exchange coil arranged on a solar photovoltaic panel assembly, the heat exchange coil is provided with the paraffin-based phase-change nanoemulsion circulating, and the heat exchange coil is connected to a heat exchanger.

[0022] Beneficial effects: The present invention provides a paraffin-based phase change nanoemulsion which has good stability, small supercooling, high phase change latent heat, and wide operating temperature, and can be used as an efficient heat dissipation cooling medium; accordingly, a preparation method of the paraffin-based phase change nanoemulsion which has a simple process, low cost, and is easy for industrial scale-up is provided, and the phase change nanoemulsion is applied to the thermal management system of photovoltaic components to reduce their surface temperature, improve their photoelectric conversion efficiency, and recycle waste heat. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The present invention is a flow chart of a method for preparing a paraffin-based phase-change nanoemulsion.

[0024] Figure 2 Schematic diagram of the differential scanning calorimetry result curve of the phase change nanoemulsion prepared in Example 1 of the present invention.

[0025] Figure 3 This is the dispersed phase droplet size distribution curve of the nanoemulsion prepared in Example 1 of the present invention.

[0026] Figure 4 The following are the appearance comparison photos of the nanoemulsion prepared in Example 1 of the present invention after being bottled. Figure 4 It can be seen that after one year of storage, the appearance of the nanoemulsion did not change significantly.

[0027] Figure 5 is a schematic diagram of the differential scanning calorimetry result curve of the phase change nanoemulsion prepared in Example 3 of the present invention, Figure 5 It can be seen that after adding the nucleating agent, the solidification temperature of the phase change nanoemulsion increased by 5°C and the supercooling degree was significantly reduced.

[0028] Figure 6 This is a schematic diagram of a solar photovoltaic component cooling and heat collection device based on energy storage in Example 8 of the present invention.

[0029] Figure 7 This is a schematic diagram of the structure of the U-shaped heat exchange coil in Example 8 of the present invention. DETAILED DESCRIPTION

[0030] The present invention provides a paraffin-based phase-change nanoemulsion and a preparation method and application thereof. To make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0031] See also Figure 1 , Figure 1 The present invention provides a process flow chart of a paraffin-based phase-change nanoemulsion, as shown in the figure, which comprises the steps of:

[0032] S10, prepare 10-30 parts of paraffin phase change energy storage material, add 5-15 parts of surfactant and 1-3 parts of nucleating agent, heat to 70-80° C. and mix evenly to obtain an emulsion oil phase material;

[0033] S20, adding 50-100 parts of deionized water or distilled water to the emulsion oil phase material under stirring and maintaining the temperature at 70-80° C. to obtain an emulsion;

[0034] S30, cooling the emulsion to 25° C. to obtain a paraffin-based phase-change nanoemulsion.

[0035] Specifically, the preparation method of the paraffin-based phase-change nanoemulsion provided by the present invention has simple procedures, low cost, and is easy to scale up industrially. The paraffin phase-change material and surfactant are preferably industrial-grade agents. In addition, by adding a new polymer nucleating agent polyethylene-block-poly (ethylene glycol), not only can the supercooling degree of the phase-change nanoemulsion be effectively reduced, but also its stability can be improved. Compared with conventional solid-phase nano oxide particles, the nano oxide dispersion as a nucleating agent is easier to disperse and embed. The prepared phase-change nanoemulsion is light blue and transparent, and the particle size of the dispersed droplets is less than 1 00nm; if the properties of the paraffin-based phase-change nanoemulsion change, it can be slowly stirred and heated to 70-80°C, and cooled to 20-30°C to restore its original properties; the paraffin-based phase-change nanoemulsion prepared by the present invention has no significant change in performance after hundreds of phase-change cycles or storage for more than one year, so it is superior to existing phase-change microcapsule slurries and phase-change emulsions in terms of application; the prepared paraffin-based phase-change nanoemulsion is applied to the thermal management system of solar photovoltaic modules. Within the phase-change temperature range, the paraffin in the phase-change nanoemulsion can absorb or release a large amount of heat energy. Compared with water, the surface temperature of the photovoltaic module is further reduced, and its photoelectric conversion efficiency is improved.

[0036] In some embodiments, the phase change temperature of the paraffin phase change energy storage material is 18-70°C, and the paraffin phase change energy storage material includes at least one of alkanes with carbon atoms of 16-30 and at least one of paraffins with a carbon number of 20-70, but is not limited thereto. For example, the paraffin phase change energy storage material may also include other paraffin materials.

[0037] In some embodiments, the surfactant is a compound of surfactant A and surfactant B, wherein the mass fraction of surfactant A is not less than 50%; the surfactant A is lauryl alcohol polyoxyethylene ether; the surfactant B is selected from Tween-20, Tween-40, Tween-60, Tween-80, polyethylene glycol monohexadecyl ether, polyoxyethylene lauryl ether, polyoxyethylene stearate, polyethylene glycol 12 hydroxystearate, ethoxylated C16-18-alcohol, polyoxyethylene castor oil series with HLB value greater than 14, and polyoxyethylene hydrogenated castor oil series with HLB value greater than 14.

[0038] In some embodiments, the nucleating agent is at least one of polyethylene-block-poly(ethylene glycol), paraffin, nano-alumina dispersion, nano-zinc oxide dispersion, and nano-silicon oxide dispersion. Preferably, the nucleating agent is a novel polymer nucleating agent polyethylene-block-poly(ethylene glycol), which can not only effectively reduce the supercooling of the paraffin-based phase-change nanoemulsion, but also improve its stability. More preferably, a combination of polyethylene-block-poly(ethylene glycol) and paraffin, or a combination of polyethylene-block-poly(ethylene glycol) and nano-metal oxide dispersion (e.g., nano-alumina dispersion) is used as a nucleating agent, which can reduce the supercooling of the paraffin-based phase-change nanoemulsion, improve its stability, and enhance its embedding rate in the oil phase.

[0039] In some embodiments, a paraffin-based phase-change nanoemulsion is also provided, which is prepared by the preparation method of the paraffin-based phase-change nanoemulsion of the present invention.

[0040] In some embodiments, there is also an application of a paraffin-based phase change nanoemulsion, where the paraffin-based phase change nanoemulsion of the present invention is used in a thermal management system of a solar photovoltaic module, wherein the thermal management system includes a heat exchange coil arranged on a solar photovoltaic panel assembly, wherein the heat exchange coil is provided with the paraffin-based phase change nanoemulsion circulating therein, and the heat exchange coil is connected to a heat exchanger. Within the phase change temperature range, the paraffin in the paraffin-based phase change nanoemulsion can absorb or release a large amount of heat energy. Compared with water, the surface temperature of the photovoltaic module is further reduced, and its photoelectric conversion efficiency is improved. The present invention is further explained below through specific embodiments:

[0041] Example 1

[0042] Weigh 2g of paraffin phase change material OP44, add 1.05g of lauryl alcohol polyoxyethylene ether, 0.45g of ethoxylated C16-18-alcohol, and 0.2g of polyethylene-block-poly(ethylene glycol), heat to 80°C, and stir evenly at 400rpm; then slowly add 10g of distilled water and cool it to 25°C to obtain a phase change nanoemulsion with a phase change temperature of 40°C, a small degree of supercooling, and a dispersed droplet size of less than 100nm.

[0043] Figure 2 The diagram is a schematic diagram of the differential scanning calorimetry result curve of the nano phase change emulsion with a phase change temperature of 40° C. prepared by the preparation method of the present invention in Example 1. Its phase change enthalpy is 22 J / g, which is about 5 times the sensible heat of water.

[0044] Figure 3 This is the droplet size distribution curve of the dispersed phase of the phase change nanoemulsion prepared by the preparation method of the present invention in Example 1. The average particle size is 48 nm, and the droplets are concentrated within 100 nm.

[0045] Figure 4 This is a photograph of the appearance of the phase change nanoemulsion prepared in Example 1 using the preparation method of the present invention. Figure 4 (a) shows the prepared light blue transparent phase change nanoemulsion; Figure 4 (b) shows the phase change nanoemulsion after being stored for one year. It can be seen from the figure that there is no obvious change in appearance.

[0046] Example 2

[0047] Weigh 2g of paraffin phase change material OP18, add 0.6g of lauryl alcohol polyoxyethylene ether, 0.35g of Tween-60, and 0.2g of paraffin material OP65, heat to 70°C, and stir evenly at 400rpm; then slowly add 7g of distilled water and cool it to 25°C to obtain a phase change nanoemulsion with a phase change temperature of 15°C, a small degree of supercooling, and an average particle size of dispersed droplets less than 100nm.

[0048] Example 3

[0049] Weigh 2g of n-hexadecane, add 0.6g of lauryl alcohol polyoxyethylene ether, 0.4g of Tween-80, 0.1g of polyethylene-block-poly(ethylene glycol), and 0.2g of n-dotriacontane, heat to 70°C, and stir evenly at 400rpm; then slowly add 7g of distilled water, and cool it to 25°C to obtain a phase change nanoemulsion with a phase change temperature of 15°C, a small degree of supercooling, and an average particle size of dispersed droplets less than 100nm.

[0050] At the same time, a phase change nanoemulsion without a nucleating agent was prepared as a control: 2 g of n-hexadecane was weighed, 0.6 g of lauryl alcohol polyoxyethylene ether, 0.4 g of Tween-80 were added, heated to 70°C, and stirred evenly at 400 rpm; then 7 g of distilled water was slowly added and cooled to 25°C to obtain a phase change nanoemulsion with a phase change temperature of 15°C and an average particle size of dispersed droplets less than 100 nm.

[0051] Figure 5 3 is a schematic diagram of the differential scanning calorimetry result curve of the phase change nanoemulsion prepared by the preparation method of the present invention in Example 3. It can be seen from the figure that after adding the nucleating agent, the solidification point of the phase change nanoemulsion is increased by 5° C. and the supercooling degree is significantly reduced.

[0052] Example 4

[0053] Weigh 2g of n-tetracosane, add 0.7g of lauryl alcohol polyoxyethylene ether, 0.3g of polyoxyethylene lauryl ether, 0.25g of polyethylene-block-poly(ethylene glycol), and 0.05g of nano-silica dispersion, heat to 80°C, and stir evenly at 400rpm; then slowly add 9g of distilled water, and cool it to 25°C to obtain a phase change nanoemulsion with a phase change temperature of 48°C, a small degree of supercooling, and an average particle size of dispersed droplets less than 100nm.

[0054] Example 5

[0055] Weigh 0.5g paraffin phase change material OP28, 1.5g paraffin phase change material OP44, add 0.6g lauryl alcohol polyoxyethylene ether, 0.4g polyethylene glycol monohexadecyl ether, 0.2g n-octacosane, 0.02g nano alumina dispersion, heat to 70°C, and stir evenly at 400rpm; then slowly add 10g distilled water, and cool it to 25°C to obtain a phase change nanoemulsion with a phase change temperature of 35°C, a small degree of supercooling, and an average particle size of dispersed droplets less than 100nm.

[0056] Example 6

[0057] Weigh 2g of industrial-grade paraffin (melting point 54-56°C), add 0.85g of lauryl alcohol polyoxyethylene ether, 0.4g of ethoxylated C16-18-alcohol, 0.2g of polyethylene-block-poly(ethylene glycol), and 0.05g of nano zinc oxide dispersion, heat to 80°C, and stir evenly at 400rpm; then slowly add 10g of distilled water, and cool it to 25°C to obtain a phase change nanoemulsion with a phase change temperature of 52°C, a small degree of supercooling, and an average particle size of dispersed droplets less than 100nm.

[0058] Example 7

[0059] Weigh 2g of paraffin phase change material OP65, add 1.1g of lauryl alcohol polyoxyethylene ether, 0.5g of Tween-20, 0.1g of polyethylene-block-poly(ethylene glycol), and 0.1g of nano-alumina dispersion, heat to 80°C, and stir evenly at 400rpm; then slowly add 10g of distilled water and cool it to 25°C to obtain a phase change nanoemulsion with a phase change temperature of 62°C, a small degree of supercooling, and a dispersed droplet size of less than 100nm.

[0060] Based on the preparation method of the present invention, a variety of surfactants and nucleating agents are used to obtain phase-change nanoemulsions with different working temperatures (15-65°C), small supercooling, and dispersed droplet average particle size less than 100nm. Therefore, the phase-change nanoemulsion prepared by the preparation method of the present invention solves the problems of poor stability and high supercooling of conventional phase-change emulsions.

[0061] Example 8

[0062] 4 kg of phase change nanoemulsion (working temperature 35-40° C.) was prepared according to the ratio and preparation method in Example 1 (or Example 5), and applied to the thermal management system of solar photovoltaic modules. Figure 6 This is a schematic diagram of the solar photovoltaic module cooling and heat collection device based on energy storage. The U-shaped heat exchange coil is installed on the back of the solar photovoltaic module. The phase change nanoemulsion flowing in the pipe absorbs a large amount of heat, significantly reducing the surface temperature of the photovoltaic module; compared with water, the surface temperature of the photovoltaic module is further reduced by 10%. In addition, through the plate heat exchanger, a large amount of latent heat in the phase change nanoemulsion can be recycled to provide the energy required for domestic hot water. Figure 7 The schematic diagram of the structure of the U-shaped heat exchange coil is shown in Figure 1. The temperature of the phase-change nanoemulsion at the inlet is low, and the coil distribution is relatively sparse. The temperature of the phase-change nanoemulsion at the outlet is high, the coil distribution is relatively dense, and the temperature distribution is more uniform.

[0063] It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for preparing a paraffin-based phase-change nanoemulsion, characterized in that: Includes steps: Weigh 2g of paraffin phase change material OP44, add 1.05g of lauryl alcohol polyoxyethylene ether, 0.45g of ethoxylated C16-18-alcohol, and 0.2g of polyethylene-block-poly(ethylene glycol), heat to 80°C, and stir evenly at 400rpm; then add 10g of distilled water, and cool to 25°C to obtain a paraffin-based phase change nanoemulsion; The dispersed particle size of the paraffin-based phase-change nanoemulsion is less than 100 nm.

2. A method for preparing a paraffin-based phase-change nanoemulsion, characterized in that: Includes steps: Weigh 2 g of industrial grade paraffin with a melting point of 54-56°C, add 0.85 g of lauryl alcohol polyoxyethylene ether, 0.4 g of ethoxylated C16-18-alcohol, and 0.2 g of polyethylene-block-poly(ethylene glycol). 0.05g of nano zinc oxide dispersion was heated to 80°C and stirred at 400rpm; then 10g of distilled water was added and cooled to 25°C to obtain a paraffin-based phase change nanoemulsion; The dispersed particle size of the paraffin-based phase-change nanoemulsion is less than 100 nm.

3. A method for preparing a paraffin-based phase-change nanoemulsion, characterized in that: Includes steps: Weigh 2g of paraffin phase change material OP65, add 1.1g of lauryl alcohol polyoxyethylene ether, 0.5g of Tween-20, 0.1g of polyethylene-block-poly(ethylene glycol), and 0.1g of nano-alumina dispersion, heat to 80°C, and stir evenly at 400rpm; then add 10g of distilled water, and cool to 25°C to obtain a paraffin-based phase change nanoemulsion; The dispersed particle size of the paraffin-based phase-change nanoemulsion is less than 100 nm.

4. A paraffin-based phase-change nanoemulsion, characterized in that: The nanoemulsion is prepared by the method for preparing the paraffin-based phase-change nanoemulsion according to any one of claims 1 to 3.

5. An application of a paraffin-based phase-change nanoemulsion, characterized in that: The paraffin-based phase-change nanoemulsion described in claim 4 is used in a thermal management system of a solar photovoltaic module.

6. The use of the paraffin-based phase-change nanoemulsion according to claim 5, characterized in that: The thermal management system comprises a heat exchange coil arranged on a solar photovoltaic panel assembly, wherein the paraffin-based phase-change nanoemulsion is circulated in the heat exchange coil, and the heat exchange coil is communicated with a heat exchanger.

Images