CN114181665B - High-latent-heat medium-temperature composite phase-change material based on nano heat conduction enhancement and preparation method thereof - Google Patents
High-latent-heat medium-temperature composite phase-change material based on nano heat conduction enhancement and preparation method thereof Download PDFInfo
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- 239000012782 phase change material Substances 0.000 title claims abstract description 46
- 239000002131 composite material Substances 0.000 title claims abstract description 44
- 238000002360 preparation method Methods 0.000 title claims abstract description 21
- 230000005496 eutectics Effects 0.000 claims abstract description 125
- 150000003839 salts Chemical class 0.000 claims abstract description 122
- 238000010587 phase diagram Methods 0.000 claims abstract description 40
- 238000004364 calculation method Methods 0.000 claims abstract description 33
- 239000002105 nanoparticle Substances 0.000 claims abstract description 32
- 238000000034 method Methods 0.000 claims abstract description 21
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 claims abstract description 11
- 239000002052 molecular layer Substances 0.000 claims abstract description 4
- 239000007787 solid Substances 0.000 claims abstract description 4
- 239000000203 mixture Substances 0.000 claims description 61
- 238000010438 heat treatment Methods 0.000 claims description 25
- 230000007704 transition Effects 0.000 claims description 23
- 238000000227 grinding Methods 0.000 claims description 18
- 238000002156 mixing Methods 0.000 claims description 16
- 239000000843 powder Substances 0.000 claims description 15
- 238000005303 weighing Methods 0.000 claims description 13
- 230000008859 change Effects 0.000 claims description 12
- 238000002844 melting Methods 0.000 claims description 11
- 230000008018 melting Effects 0.000 claims description 11
- 239000000725 suspension Substances 0.000 claims description 9
- 230000006872 improvement Effects 0.000 claims description 8
- 239000013078 crystal Substances 0.000 claims description 7
- 239000008367 deionised water Substances 0.000 claims description 7
- 229910021641 deionized water Inorganic materials 0.000 claims description 7
- 230000003993 interaction Effects 0.000 claims description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 7
- 239000002245 particle Substances 0.000 claims description 5
- 230000008569 process Effects 0.000 claims description 5
- 229910002056 binary alloy Inorganic materials 0.000 claims description 4
- -1 fluoride modified carbonate Chemical class 0.000 claims description 4
- 150000004673 fluoride salts Chemical class 0.000 claims description 4
- 239000011833 salt mixture Substances 0.000 claims description 4
- 239000011259 mixed solution Substances 0.000 claims description 2
- 239000012266 salt solution Substances 0.000 claims description 2
- 238000007789 sealing Methods 0.000 claims description 2
- 238000007873 sieving Methods 0.000 claims description 2
- 238000001132 ultrasonic dispersion Methods 0.000 claims description 2
- 238000002924 energy minimization method Methods 0.000 claims 1
- 238000005338 heat storage Methods 0.000 abstract description 26
- 239000011232 storage material Substances 0.000 abstract description 10
- 230000007547 defect Effects 0.000 abstract description 3
- 238000013461 design Methods 0.000 abstract description 3
- 239000012779 reinforcing material Substances 0.000 abstract description 3
- 125000001153 fluoro group Chemical class F* 0.000 abstract 1
- 239000012071 phase Substances 0.000 description 50
- 238000012360 testing method Methods 0.000 description 31
- 239000000919 ceramic Substances 0.000 description 17
- 238000001035 drying Methods 0.000 description 15
- 229910017053 inorganic salt Inorganic materials 0.000 description 13
- 238000001816 cooling Methods 0.000 description 9
- 230000004048 modification Effects 0.000 description 8
- 238000012986 modification Methods 0.000 description 8
- 230000010355 oscillation Effects 0.000 description 7
- 239000000463 material Substances 0.000 description 6
- 230000004580 weight loss Effects 0.000 description 6
- 239000007788 liquid Substances 0.000 description 5
- 239000002114 nanocomposite Substances 0.000 description 5
- 238000001556 precipitation Methods 0.000 description 5
- 239000007790 solid phase Substances 0.000 description 5
- 239000000243 solution Substances 0.000 description 5
- 238000009210 therapy by ultrasound Methods 0.000 description 5
- 238000002411 thermogravimetry Methods 0.000 description 5
- 239000004570 mortar (masonry) Substances 0.000 description 4
- 238000012546 transfer Methods 0.000 description 3
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 2
- 238000000498 ball milling Methods 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000003575 carbonaceous material Substances 0.000 description 1
- 229910010293 ceramic material Inorganic materials 0.000 description 1
- PMHQVHHXPFUNSP-UHFFFAOYSA-M copper(1+);methylsulfanylmethane;bromide Chemical compound Br[Cu].CSC PMHQVHHXPFUNSP-UHFFFAOYSA-M 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 238000001938 differential scanning calorimetry curve Methods 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 239000002923 metal particle Substances 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000004044 response Effects 0.000 description 1
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- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K5/00—Heat-transfer, heat-exchange or heat-storage materials, e.g. refrigerants; Materials for the production of heat or cold by chemical reactions other than by combustion
- C09K5/02—Materials undergoing a change of physical state when used
- C09K5/06—Materials undergoing a change of physical state when used the change of state being from liquid to solid or vice versa
- C09K5/063—Materials absorbing or liberating heat during crystallisation; Heat storage materials
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D15/00—Lithium compounds
- C01D15/04—Halides
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- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D15/00—Lithium compounds
- C01D15/08—Carbonates; Bicarbonates
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- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D7/00—Carbonates of sodium, potassium or alkali metals in general
- C01D7/38—Preparation in the form of granules, pieces or other shaped products
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- C01P2002/00—Crystal-structural characteristics
- C01P2002/80—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70
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- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
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Abstract
The invention discloses a high-latent heat medium-temperature composite phase-change material based on nano heat conduction enhancement and a preparation method thereof, belonging to the field of phase-change heat storage materials; through a theoretical calculation-phase diagram calculation method, a novel eutectic salt system is designed and developed, fluorine salt and carbonate with high latent heat are compounded into high-latent heat multielement eutectic salt, nano AlN with high heat conduction mass and light heat conduction mass is used as a heat conduction reinforcing material, and a solid nano layer on the surface of a nano particle medium can strengthen the heat conduction performance of the eutectic salt. The invention overcomes the defects of complicated preparation method, low efficiency and the like of the traditional trial-and-error method, and reduces the design and preparation cost of eutectic salt; and the prepared phase-change material overcomes the problems of low heat storage density, low heat storage efficiency and the like of the phase-change heat storage material in the prior art.
Description
Technical Field
The invention belongs to the field of phase-change heat storage materials, and particularly relates to a high-latency medium-temperature composite phase-change material based on nano heat conduction enhancement and a preparation method thereof.
Background
Along with the development of society, traditional energy is exhausted increasingly, so that the development of new energy and the improvement of energy utilization efficiency are the focus of increasing attention. However, clean energy sources such as solar energy are greatly affected by weather and territories, and have the disadvantages of instability and discontinuity, and the utilization of the clean energy sources is limited by space and time. Therefore, a well-developed heat storage technology is a precondition for efficient use of clean energy. Thermal energy storage technologies include sensible heat storage, phase change heat storage, and thermochemical heat storage. Compared with other two heat storage modes, the phase-change heat storage has the advantages of high heat storage density, stable heat absorption and release and the like, so that the phase-change heat storage is widely studied and applied to various fields.
The core of the phase change heat storage is a phase change material (Phase Change Materials, PCM), and inorganic salt is widely used as the phase change material due to the advantages of low melting point, low vapor pressure, good chemical stability, small pollution and the like. However, the existing inorganic salt system is used as a phase-change heat storage material, has the defects of low heat conductivity, low thermal response rate and the like, influences the heat storage and release rate and the heat transfer capacity of the system, and limits the application of the system to a certain extent. At present, methods of adding high-heat-conductivity metal particles, carbon materials, ceramic materials and the like are often adopted to strengthen heat transfer. But the addition of non-phase change materials results in a reduction in the overall latent heat of phase change of the composite. Therefore, the phase change material with high latent heat is developed, the heat storage and heat transfer performance of the material are considered, and the method has important significance for further expanding the application range of the material.
Disclosure of Invention
The invention provides a high-latent heat medium-temperature composite phase-change material based on nano heat conduction enhancement and a preparation method thereof, wherein a novel eutectic salt system can be accurately designed and developed through a theoretical calculation-phase diagram calculation method, the design and preparation cost of the eutectic salt is reduced, and the prepared phase-change material overcomes the problems of low heat storage density, low heat storage efficiency and the like of a phase-change heat storage material in the prior art.
The high-latency medium-temperature composite phase change material based on nano heat conduction enhancement comprises a multi-element eutectic salt and nano particles, wherein the mass ratio of the multi-element eutectic salt to the nano particles is 100 (0.5-8); the nano particles are used as a heat conduction reinforcing material, and the solid nano layer on the surface of the nano particle medium can strengthen the heat conduction performance of the eutectic salt.
The multi-element eutectic salt is a fluoride modified carbonate system, and the carbonate system is Na 2 CO 3 -Li 2 CO 3 Binary system, fluoride salt is LiF, na in the multi-element eutectic salt system 2 CO 3 55-70% by mass of Li 2 CO 3 The mass percentage of LiF is 10-35%, and the mass percentage of LiF is 10-20%; the nanometer particles are nanometer AlN, and the particle size of the nanometer AlN is 30-100nm.
The preparation method of the high-latency medium-temperature composite phase-change material based on nano heat conduction enhancement comprises the following steps:
step 1: eutectic salt composition determination
The high-latent-heat multielement eutectic salt is adopted to realize the effective regulation and control of the phase transition temperature of the system and the improvement of latent heat;
step 2: component calculation
The method comprises the steps of obtaining the composition of the high-latent-heat multi-element eutectic salt in the step 1 by adopting an energy minimization principle through a phase diagram calculation method;
step 3: eutectic salt blending
Mixing three inorganic salts according to the proportion obtained in the step 2, and preparing ternary eutectic salt by a high-temperature melting method;
step 4: nanoparticle doping
Dispersing the nano particles into ternary eutectic salt solution by an ultrasonic dispersion method to prepare the nano eutectic salt composite phase change material.
In the above step, the phase transition temperature of the eutectic salt with high latent heat in the step 1 is higher than 300 o C is less than 500 o C；
The multi-element eutectic salt in the step 1 is a fluoride salt modified carbonate system; the carbonate system and the fluoride are substances with highest phase change latent heat in each range, wherein the carbonate system is Na 2 CO 3 -Li 2 CO 3 Binary eutectic salt system, fluoride salt is LiF with highest phase change latent heat in inorganic salt, and Na is modified by adding LiF with high latent heat 2 CO 3 -Li 2 CO 3 The binary system effectively reduces the phase transition temperature and further improves the latent heat of the eutectic salt system;
the step 2 is to achieve thermodynamic equilibrium of the system in a closed system, the total energy achieves the minimum value, and the equilibrium state of the system is determined mainly by two methods of a Gibbs free energy minimum method and an isochemical potential method, and specifically comprises the following steps:
according to each terminal component, namely Na 2 CO 3 、Li 2 CO 3 Selecting a thermodynamic model according to the crystal characteristics of LiF, and selecting, analyzing and evaluating corresponding experimental data; continuously optimizing interaction parameters of each phase by means of phase diagram calculation software to finally obtain Na 2 CO 3 -Li 2 CO 3 The thermodynamic database of the LiF ternary system, and further the eutectic point temperature and the corresponding proportion of the novel high-latent heat eutectic salt are predicted according to the phase diagram calculation result;
in the step 2, the specific Phase Diagram calculation process is that a Phase diagnostic module of the Phase Diagram is selected, an FT-demo database is selected, a ternary component to be calculated is input, units of temperature, pressure and quality parameters are set, and the Phase Diagram calculation is carried out on the ternary system, so that the lowest eutectic point of the ternary system and the component proportion at the temperature are obtained;
the step 3 specifically comprises the following steps: three inorganic salts Na 2 CO 3 、Li 2 CO 3 Weighing pure salt of each component according to the proportion obtained in the step 2 after LiF is dried; mixing and grinding the weighed three salts, and sieving to obtain a uniformly mixed salt mixture; the mixture is mixed at 500-600 o C, melting for 2-4 hours at high temperature to obtain fully melted ternary eutectic salt, grinding the ternary eutectic salt into powder, and sealing and preserving the ternary eutectic salt;
in the step 3, the three salt mixtures are preferably ball-milling mixtures, the speed of the ball mill is 300RPM, and the ball-milling time is 1-2h; the drying time is 24 h, and the drying temperature is 120 ℃; placing the uniformly mixed salt mixture into a muffle furnace, and heating the muffle furnaceThe speed is less than or equal to 10 o C /min；
The specific operation process of the step 4 is as follows: weighing nanometer AlN according to the mass ratio of the multi-element eutectic salt to the nanometer particles of 100 (0.5-8), adding deionized water, and carrying out ultrasonic vibration for 1h to form a uniformly dispersed suspension; adding eutectic salt into the nanometer AlN suspension, and carrying out ultrasonic vibration on the mixture for 1h to uniformly mix the eutectic salt with the nanometer AlN; drying the mixed solution, cooling and grinding the sample into powder;
in the process of the step 4, the ultrasonic oscillation frequency is 45 kHz, the drying temperature is 200 ℃, and the drying time is 24 h.
The beneficial effects are that: the invention provides a high-latent heat medium-temperature composite phase-change material based on nano heat conduction enhancement and a preparation method thereof, wherein a eutectic salt system can be accurately designed and developed through a theoretical calculation-phase diagram calculation method, the defects of complicated traditional trial-and-error method-preparation method, low efficiency and the like are overcome, and the design and preparation cost of the eutectic salt is reduced; the eutectic salt system has the advantages of simple and safe preparation process, easy operation and control, short preparation period and wide application range. The performance is excellent, the heat storage density is high, and the latent heat value is high; the invention adopts the nano aluminum nitride as the heat conduction base material, has stable performance, high temperature resistance and corrosion resistance, effectively improves the heat conduction performance of the eutectic salt system, has faster heat absorption and release rate, and the enthalpy value of the prepared eutectic salt material is up to 390+/-21 kJ/kg, and the melting temperature is 443+/-1 o C, specific heat capacity of 1.4987J/(g.K), 50-500 o The thermal weight loss rate in the C interval was 0.47%, and the thermal conductivity was 0.71. 0.71W/(mK). The average specific heat capacity of the nano eutectic salt composite phase-change material is 1.5138-1.6126J/(g.K), which is improved by 1.0-7.6% compared with the eutectic salt material, wherein the thermal conductivity of the composite phase-change material is 0.92W/(m.K) when the mass ratio of the multi-element eutectic salt to the nano particles is 100:3, and is improved by 30.1% compared with the eutectic salt material.
Drawings
FIG. 1 is a DSC curve of a eutectic salt composite phase change material;
FIG. 2 is a graph of the fit of the specific heat capacities of eutectic salt composite phase change materials;
FIG. 3 is a TG plot of eutectic salt composite phase change material;
FIG. 4 is a graph of the fit of the specific heat capacities of the nano-eutectic salt composites in example 1;
FIG. 5 is a graph of the fit of the specific heat capacities of the nano-eutectic salt composites in example 2;
FIG. 6 is a plot of the specific heat capacity fit of the nano-eutectic salt composite in example 3;
FIG. 7 is a plot of the specific heat capacity fit of the nano-eutectic salt composite of example 4;
FIG. 8 is a graph of the fit of the specific heat capacities of the nano-eutectic salt composites in example 5.
Detailed Description
The invention is described in detail below with reference to the attached drawings and the specific embodiments:
example 1
The preparation method of the high-latency intermediate-temperature composite phase-change material based on nano heat conduction enhancement comprises the following steps of:
step 1: eutectic salt composition determination
Modification of carbonate Na with high latent heat inorganic salt LiF 2 CO 3 -Li 2 CO 3 The system realizes effective regulation and control of the phase transition temperature of the system and improvement of latent heat;
step 2: component calculation
According to each terminal component Na 2 CO 3 、Li 2 CO 3 The crystal characteristics and thermodynamic parameters of LiF, selecting Phase Diagram module of Factsag, selecting FT-demo database, inputting the ternary component to be calculated, setting the units of temperature, pressure and quality parameters, respectively selecting pure solid Phase component and solid-liquid precipitation Phase for product and solution Phase, performing Phase Diagram calculation on the ternary system, continuously optimizing interaction parameters of each Phase by means of Phase Diagram calculation software, and further obtaining Na according to the Phase Diagram calculation result 2 CO 3 -Li 2 CO 3 -lowest eutectic point of LiF ternary system and composition ratio at that temperature;
step 3: inorganic salt blending
Na is mixed with 2 CO 3 、Li 2 CO 3 Placing LiF salt in an oven, and drying at 200 ℃ for 24 hours to remove the influence of moisture for later use; according to the phase diagram calculation result, selecting the proportion at the eutectic point according to 57:32:11 corresponding mass ratio of Na 2 CO 3 、Li 2 CO 3 Separately weighing LiF, mixing, and grinding in a mortar sufficiently; the mixture was placed in a ball mill at 300rpm, ball milled for 1-2 hours and then sieved. Pouring the mixture into a ceramic crucible, and placing in a muffle furnace to be less than or equal to 10 o C/min is heated from room temperature to 500-600 ℃, the temperature is kept at 2-4h, the mixture is cooled to room temperature, and the mixture is ground into powder, thus obtaining a novel high-latent heat eutectic salt system;
step 4: nanoparticle doping
According to the mass ratio of the ternary eutectic salt to the nano particles of 100:0.5 g of nanometer AlN is weighed, 30 ml deionized water is added, and the mixture is put into an ultrasonic oscillator for ultrasonic treatment at the oscillation frequency of 45 kHz for 1h, so as to prepare a uniformly dispersed suspension; adding 5g novel high-latent heat eutectic salt, and carrying out ultrasonic oscillation for 1h to uniformly mix the eutectic salt with the nano particles; finally, put it in an oven, 200 o Drying 24-h under the condition of C, cooling, and grinding the sample into powder to obtain the nano eutectic salt composite phase change material; the nano particles in the obtained phase change material are used as a heat conduction reinforcing material, and the solid nano layer on the surface of the nano particle medium can strengthen the heat conduction performance of the eutectic salt.
And testing the phase transition temperature and the phase transition latent heat of the obtained eutectic salt by using LabsysEvo, and setting test parameters: n (N) 2 Atmosphere, heating rate of 10 o C/min, test range 25 o C-500 o C。
The specific heat of the sample was measured using DSC 131 Evo, test parameters were set: n (N) 2 Atmosphere, heating rate of 10 o C/min, test range is 25-400 ℃.
TG analysis was performed on the samples using an SDT-Q600 simultaneous thermal analyzer manufactured by TA corporation, usa, test parameters were set: n (N) 2 Atmosphere, heating rate of 10 o C/min, test range of 50-500 o C。
The thermal diffusivity of the sample at 25℃was determined using LFA.
The performance parameters of the nano composite phase change heat storage material prepared by the embodiment are as follows:
the phase transition latent heat of the ternary eutectic salt is 390+/-21 kJ/kg, and the melting temperature is 443+/-1 o C, the specific heat capacity is 1.4987J/(g.K), the weight loss of the sample from room temperature to 500 ℃ is 0.47%, and the thermal conductivity is 0.7W/(m.K). The specific heat capacity of the 100:0.5 nano eutectic salt composite phase change material is 1.5138J/(g.K), which is improved by 1.01% compared with ternary eutectic salt.
Example 2
The preparation method of the high-latency medium-temperature composite phase-change material based on nano heat conduction enhancement comprises the following steps:
step 1: eutectic salt composition determination
Modification of carbonate Na with high latent heat inorganic salt LiF 2 CO 3 -Li 2 CO 3 The system realizes effective regulation and control of the phase transition temperature of the system and improvement of latent heat;
step 2: component calculation
According to each terminal component Na 2 CO 3 、Li 2 CO 3 The crystal characteristics and thermodynamic parameters of LiF, selecting Phase Diagram module of Factsag, selecting FT-demo database, inputting the ternary component to be calculated, setting the units of temperature, pressure and quality parameters, respectively selecting pure solid Phase component and solid-liquid precipitation Phase for product and solution Phase, performing Phase Diagram calculation on the ternary system, continuously optimizing interaction parameters of each Phase by means of Phase Diagram calculation software, and further obtaining Na according to the Phase Diagram calculation result 2 CO 3 -Li 2 CO 3 Lowest eutectic point of LiF ternary system and component proportion at the temperature
Step 3: inorganic salt blending
Na is mixed with 2 CO 3 、Li 2 CO 3 Placing LiF salt in an oven, and drying at 200 ℃ for 24 hours to remove the influence of moisture for later use; according to the phase diagram calculation result, selecting the proportion at the eutectic point according to 57:32:11 corresponding mass ratio of Na 2 CO 3 、Li 2 CO 3 Separately weighing LiF, mixing, and grinding in a mortarGrinding fully; the mixture was placed in a ball mill at 300rpm, ball milled for 1-2 hours and then sieved. Pouring the mixture into a ceramic crucible, placing the ceramic crucible into a muffle furnace, heating the ceramic crucible to 500-600 ℃ from room temperature at a heating rate less than or equal to 10 ℃/min, keeping the temperature at 2-4h, cooling the ceramic crucible to room temperature, and grinding the ceramic crucible into powder to obtain the novel high-latent heat eutectic salt system.
Step 4: nanoparticle doping
Weighing 0.05g of nano AlN according to the mass ratio of the ternary eutectic salt to the nano particles of 100:1, adding 30 ml deionized water, and placing the mixture into an ultrasonic oscillator to carry out ultrasonic treatment on the mixture for 1h at the oscillation frequency of 45 kHz to prepare a uniformly dispersed suspension; adding 5g novel high-latent heat eutectic salt, and carrying out ultrasonic vibration for 1h to uniformly mix the eutectic salt and the nano particles; and finally, placing the mixture in an oven, drying the mixture at 200 ℃ for 24 h, cooling the mixture, and grinding the mixture into powder to obtain the nano eutectic salt composite phase change material.
The phase transition temperature and the phase transition latent heat of the eutectic salt are tested by LabsysEvo, and the test parameters are set: n (N) 2 Atmosphere, heating rate of 10 o C/min, test range 25 o C-500 o C。
The specific heat of the sample was measured using DSC 131 Evo, test parameters were set: n (N) 2 Atmosphere, heating rate of 10 o C/min, test range is 25-400 ℃.
The sample was subjected to TG analysis using an SDT-Q600 simultaneous thermal analyzer manufactured by TA company of America. And (3) setting test parameters: n (N) 2 Atmosphere, heating rate of 10 o C/min, the test range is 50-500 ℃.
The thermal diffusivity of the sample at 25℃was determined using LFA.
The performance parameters of the nano composite phase change heat storage material prepared by the embodiment are as follows:
the phase change latent heat of the ternary eutectic salt is 390+/-21 kJ/kg, and the melting temperature is 443+/-1 o C, specific heat capacity is 1.4987J/(g.K), and the weight loss of the sample is 0.47% from room temperature to 500 ℃. The specific heat capacity of the 100:0.5 nano eutectic salt composite phase change material is 1.5636J/(g.K), which is improved by 4.33% compared with ternary eutectic salt.
Example 3
The preparation method of the high-latency medium-temperature composite phase-change material based on nano heat conduction enhancement comprises the following steps:
step 1: eutectic salt composition determination
Modification of carbonate Na with high latent heat inorganic salt LiF 2 CO 3 -Li 2 CO 3 The system realizes the effective regulation and control of the phase transition temperature of the system and the improvement of latent heat.
Step 2: component calculation
According to each terminal component Na 2 CO 3 、Li 2 CO 3 The crystal characteristics and thermodynamic parameters of LiF, selecting Phase Diagram module of Factsag, selecting FT-demo database, inputting the ternary component to be calculated, setting the units of temperature, pressure and quality parameters, respectively selecting pure solid Phase component and solid-liquid precipitation Phase for product and solution Phase, performing Phase Diagram calculation on the ternary system, continuously optimizing interaction parameters of each Phase by means of Phase Diagram calculation software, and further obtaining Na according to the Phase Diagram calculation result 2 CO 3 -Li 2 CO 3 Lowest eutectic point of LiF ternary system and component proportion at the temperature
Step 3: inorganic salt blending
Na is mixed with 2 CO 3 、Li 2 CO 3 Placing LiF salt in an oven, and drying at 200 ℃ for 24 hours to remove the influence of moisture for later use; according to the phase diagram calculation result, selecting the proportion at the eutectic point according to 57:32:11 corresponding mass ratio of Na 2 CO 3 、Li 2 CO 3 Separately weighing LiF, mixing, and grinding in a mortar sufficiently; the mixture was placed in a ball mill at 300rpm, ball milled for 1-2 hours and then sieved. Pouring the mixture into a ceramic crucible, placing the ceramic crucible into a muffle furnace, heating the ceramic crucible to 500-600 ℃ from room temperature at a heating rate less than or equal to 10 ℃/min, keeping the temperature at 2-4h, cooling the ceramic crucible to room temperature, and grinding the ceramic crucible into powder to obtain the novel high-latent heat eutectic salt system.
Step 4: nanoparticle doping
Weighing 0.15g of nano AlN according to the mass ratio of the ternary eutectic salt to the nano particles of 100:3, adding 30 ml deionized water, and placing the mixture into an ultrasonic oscillator to carry out ultrasonic treatment on the mixture for 1h at the oscillation frequency of 45 kHz to prepare a uniformly dispersed suspension; adding 5g novel high-latent heat eutectic salt, and carrying out ultrasonic vibration for 1h to uniformly mix the eutectic salt and the nano particles; and finally, placing the mixture in an oven, drying the mixture at 200 ℃ for 24 h, cooling the mixture, and grinding the mixture into powder to obtain the nano eutectic salt composite phase change material.
The eutectic salt phase transition temperature and latent heat of phase transition were tested using LabsysEvo. And (3) setting test parameters: n (N) 2 Atmosphere, heating rate of 10 o C/min, test range 25 o C-500 o C。
The specific heat of the sample was measured using DSC 131 Evo, test parameters were set: n (N) 2 Atmosphere, heating rate of 10 o C/min, test range is 25-400 ℃.
The sample was subjected to TG analysis using an SDT-Q600 simultaneous thermal analyzer manufactured by TA company of America. And (3) setting test parameters: n (N) 2 Atmosphere, heating rate of 10 o C/min, the test range is 50-500 ℃.
The thermal diffusivity of the sample at 25℃was determined using LFA.
The performance parameters of the nano composite phase change heat storage material prepared by the embodiment are as follows:
the phase transition latent heat of the ternary eutectic salt is 390+/-21 kJ/kg, and the melting temperature is 443+/-1 o C, specific heat capacity is 1.4987J/(g.K), and the weight loss of the sample is 0.47% from room temperature to 500 ℃. The ratio of eutectic salt to nano particles is 100:3, the specific heat capacity of the composite phase change material is 1.6126J/(g.K), and the ratio is improved by 7.60% compared with ternary eutectic salt.
Example 4
The preparation method of the high-latency medium-temperature composite phase-change material based on nano heat conduction enhancement comprises the following steps:
step 1: eutectic salt composition determination
Modification of carbonate Na with high latent heat inorganic salt LiF 2 CO 3 -Li 2 CO 3 The system realizes the effective regulation and control of the phase transition temperature of the system and the improvement of latent heat.
Step 2: component calculation
According to each terminal component Na 2 CO 3 、Li 2 CO 3 The crystal characteristics and thermodynamic parameters of LiF, selecting Phase Diagram module of Factsag, selecting FT-demo database, inputting the ternary component to be calculated, setting the units of temperature, pressure and quality parameters, respectively selecting pure solid Phase component and solid-liquid precipitation Phase for product and solution Phase, performing Phase Diagram calculation on the ternary system, continuously optimizing interaction parameters of each Phase by means of Phase Diagram calculation software, and further obtaining Na according to the Phase Diagram calculation result 2 CO 3 -Li 2 CO 3 Lowest eutectic point of LiF ternary system and component proportion at the temperature
Step 3: inorganic salt blending
Na is mixed with 2 CO 3 、Li 2 CO 3 Placing LiF salt in an oven, and drying at 200 ℃ for 24 hours to remove the influence of moisture for later use; according to the phase diagram calculation result, selecting the proportion at the eutectic point according to 57:32:11 corresponding mass ratio of Na 2 CO 3 、Li 2 CO 3 Separately weighing LiF, mixing, and grinding in a mortar sufficiently; the mixture was placed in a ball mill at 300rpm, ball milled for 1-2 hours and then sieved. Pouring the mixture into a ceramic crucible, and placing in a muffle furnace to be less than or equal to 10 o The heating rate of C/min is increased from room temperature to 500-600 ℃, the temperature is kept constant for 2-4h, the mixture is cooled to room temperature, and the mixture is ground into powder, thus obtaining the novel high-latent heat eutectic salt system.
Step 4: nanoparticle doping
Weighing 0.25g of nano AlN according to the mass ratio of the ternary eutectic salt to the nano particles of 100:5, adding 30 ml deionized water, and placing the mixture into an ultrasonic oscillator to carry out ultrasonic treatment on the mixture for 1h at the oscillation frequency of 45 kHz to prepare a uniformly dispersed suspension; adding 5g novel high-latent heat eutectic salt, and carrying out ultrasonic vibration for 1h to uniformly mix the eutectic salt and the nano particles; and finally, placing the mixture in an oven, drying the mixture at 200 ℃ for 24 h, cooling the mixture, and grinding the mixture into powder to obtain the nano eutectic salt composite phase change material.
The eutectic salt phase transition temperature and latent heat of phase transition were tested using LabsysEvo. And (3) setting test parameters: n (N) 2 Atmosphere, heating rate of 10 o C/min, test range 25 o C-500 o C。
The specific heat of the sample was measured using DSC 131 Evo, test parameters were set: n (N) 2 Atmosphere, heating rate of 10 o C/min, test range is 25-400 ℃.
The sample was subjected to TG analysis using an SDT-Q600 simultaneous thermal analyzer manufactured by TA company of America. And (3) setting test parameters: n (N) 2 Atmosphere, heating rate of 10 o C/min, the test range is 50-500 ℃.
The thermal diffusivity of the sample at 25℃was determined using LFA.
The performance parameters of the nano composite phase change heat storage material prepared by the embodiment are as follows:
the phase transition latent heat of the ternary eutectic salt is 390+/-21 kJ/kg, and the melting temperature is 443+/-1 o C, specific heat capacity is 1.4987J/(g.K), and the weight loss of the sample is 0.47% from room temperature to 500 ℃. The specific heat capacity of the 100:3 nano eutectic salt composite phase change material is 1.5508J/(g.K), which is improved by 3.48% compared with ternary eutectic salt.
Example 5
The preparation method of the high-latency medium-temperature composite phase-change material based on nano heat conduction enhancement comprises the following steps:
step 1: eutectic salt composition determination
Modification of carbonate Na with high latent heat inorganic salt fluoride 2 CO 3 -Li 2 CO 3 LiF system, realizing effective regulation and control of phase transition temperature and improvement of latent heat.
Step 2: component calculation
According to each terminal component Na 2 CO 3 、Li 2 CO 3 The crystal characteristics and thermodynamic parameters of LiF, selecting Phase Diagram module of Factsag, selecting FT-demo database, inputting the ternary component to be calculated, setting the units of temperature, pressure and quality parameters, respectively selecting pure solid Phase component and solid-liquid precipitation Phase for product and solution Phase, performing Phase Diagram calculation on the ternary system, continuously optimizing interaction parameters of each Phase by means of Phase Diagram calculation software, and further obtaining Na according to the Phase Diagram calculation result 2 CO 3 -Li 2 CO 3 Lowest eutectic point of LiF ternary system and temperatureComponent ratio under the degree
Step 3: inorganic salt blending
Na is mixed with 2 CO 3 、Li 2 CO 3 Placing LiF salt in an oven, and drying at 200 ℃ for 24 hours to remove the influence of moisture for later use; according to the phase diagram calculation result, selecting the proportion at the eutectic point according to 57:32:11 corresponding mass ratio of Na 2 CO 3 、Li 2 CO 3 Separately weighing LiF, mixing, and grinding in a mortar sufficiently; the mixture was placed in a ball mill at 300rpm, ball milled for 1-2 hours and then sieved. Pouring the mixture into a ceramic crucible, placing the ceramic crucible into a muffle furnace, heating the ceramic crucible to 500-600 ℃ from room temperature at a heating rate less than or equal to 10 ℃/min, keeping the temperature at 2-4h, cooling the ceramic crucible to room temperature, and grinding the ceramic crucible into powder to obtain the novel high-latent heat eutectic salt system.
Step 4: nanoparticle doping
Weighing 0.4g of nano AlN according to the mass ratio of the ternary eutectic salt to the nano particles of 100:8, adding 30 ml deionized water, and placing the mixture into an ultrasonic oscillator to carry out ultrasonic treatment on the mixture for 1h at the oscillation frequency of 45 kHz to prepare a uniformly dispersed suspension; adding 5g novel high-latent heat eutectic salt, and carrying out ultrasonic vibration for 1h to uniformly mix the eutectic salt and the nano particles; and finally, placing the mixture in an oven, drying the mixture at 200 ℃ for 24 h, cooling the mixture, and grinding the mixture into powder to obtain the nano eutectic salt composite phase change material.
The eutectic salt phase transition temperature and latent heat of phase transition were tested using LabsysEvo. And (3) setting test parameters: n (N) 2 Atmosphere, heating rate of 10 o C/min, test range 25 o C-500 o C。
The specific heat of the sample was measured using DSC 131 Evo, test parameters were set: n (N) 2 Atmosphere, heating rate of 10 o C/min, test range is 25-400 ℃.
The sample was subjected to TG analysis using an SDT-Q600 simultaneous thermal analyzer manufactured by TA company of America. And (3) setting test parameters: n (N) 2 Atmosphere, heating rate of 10 o C/min, the test range is 50-500 ℃.
The thermal diffusivity of the sample at 25℃was determined using LFA.
The performance parameters of the nano composite phase change heat storage material prepared by the embodiment are as follows:
the phase transition latent heat of the ternary eutectic salt is 390+/-21 kJ/kg, and the melting temperature is 443+/-1 o C, specific heat capacity is 1.4987J/(g.K), and the weight loss of the sample is 0.47% from room temperature to 500 ℃. The specific heat capacity of the 100:3 nano eutectic salt composite phase change material is 1.5225J/(g.K), which is improved by 1.59% compared with ternary eutectic salt.
The foregoing description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, and various modifications can be made to the above-described embodiment of the present invention. The present invention is subject to various changes and modifications without departing from the spirit and scope thereof, and such changes and modifications fall within the scope of the invention as hereinafter claimed. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (8)
1. The high-latency medium-temperature composite phase change material based on nano heat conduction enhancement is characterized by comprising a multi-element eutectic salt and nano particles, wherein the mass ratio of the multi-element eutectic salt to the nano particles is 100 (0.5-8); the solid nano layer on the surface of the nano particle medium can strengthen the heat conducting property of the eutectic salt; the multi-element eutectic salt is a fluoride modified carbonate system, and the carbonate system is Na 2 CO 3 -Li 2 CO 3 Binary system, wherein the fluoride salt is LiF, and the Na is 2 CO 3 55-70% by mass of Li 2 CO 3 The mass percentage of LiF is 10-35%, and the mass percentage of LiF is 10-20%; the nano-particles are nano AlN.
2. The nano-heat conduction enhanced high-latency medium-temperature composite phase change material according to claim 1, wherein the multi-element eutectic salt phase change temperature is higher than 300 o C is less than 500 o C。
3. The nano-heat conduction enhanced high-latent heat medium-temperature composite phase-change material according to claim 1, wherein the nano AlN particle size is 30-100nm.
4. The preparation method of the high-latency medium-temperature composite phase-change material based on nano heat conduction enhancement comprises the following steps:
step 1: eutectic salt composition determination
The high-latent-heat multielement eutectic salt is adopted to realize the effective regulation and control of the phase transition temperature of the system and the improvement of latent heat;
step 2: component calculation
The method comprises the steps of determining the equilibrium state of a system by using an energy minimization principle through a Gibbs free energy minimization method and an isochemical potential method, and obtaining the composition of the high-latent-heat multi-element eutectic salt in the step 1 through a phase diagram calculation method, wherein the multi-element eutectic salt is a fluoride salt modified carbonate system, and the carbonate system is Na 2 CO 3 -Li 2 CO 3 Binary system, wherein the fluoride salt is LiF, and the Na is 2 CO 3 55-70% by mass of Li 2 CO 3 The mass percentage of LiF is 10-35%, and the mass percentage of LiF is 10-20%;
step 3: eutectic salt blending
Mixing three inorganic salts in proportion according to the result of the step 2, and preparing ternary eutectic salt by a high-temperature melting method;
step 4: nanoparticle doping
Dispersing the nano particles into ternary eutectic salt solution by an ultrasonic dispersion method to prepare the nano eutectic salt composite phase change material.
5. The method for preparing the nano-heat conduction enhanced-based high-latent heat medium-temperature composite phase change material according to claim 4, wherein the step 2 specifically comprises the following steps:
according to each terminal component, namely Na 2 CO 3 、Li 2 CO 3 Selecting a corresponding thermodynamic model according to the crystal characteristics of LiF, and carefully selecting, analyzing and evaluating corresponding experimental data; continuously optimizing interaction parameters of each phase by means of phase diagram calculation software to finally obtain Na 2 CO 3 -Li 2 CO 3 Ternary LiFAnd a thermodynamic database of the system, so that the eutectic point temperature and the corresponding proportion of the high-latent heat eutectic salt are predicted and obtained according to a phase diagram calculation result.
6. The method for preparing the nano heat conduction enhanced-based high-latency intermediate-temperature composite Phase change material according to claim 4 or 5, wherein the specific process of Phase Diagram calculation in step 2 is to select a Phase Diagram module of Factsag, select an FT-demo database, input a ternary component to be calculated, set a unit of temperature, pressure and quality parameters, and perform Phase Diagram calculation on the ternary system to obtain the lowest eutectic point of the ternary system and the component proportion at the temperature.
7. The method for preparing the nano-heat conduction enhanced-based high-latent heat medium-temperature composite phase change material according to claim 4, wherein the step 3 specifically comprises the following steps: three inorganic salts Na 2 CO 3 、Li 2 CO 3 Weighing pure salt of each component according to the proportion obtained in the step 2 after LiF is dried; mixing and grinding the weighed three salts, and sieving to obtain a uniformly mixed salt mixture; heating the mixture to 500-600 ℃ at a heating rate of less than or equal to 10 ℃/min, and carrying out high-temperature melting for 2-4h to obtain fully melted ternary eutectic salt, grinding the ternary eutectic salt into powder, and sealing and preserving the powder.
8. The preparation method of the nano-heat conduction enhanced-based high-latent heat medium-temperature composite phase change material according to claim 4, wherein the specific operation process of the step 4 is as follows: weighing nanometer AlN according to the mass ratio of the multi-element eutectic salt to the nanometer particles of 100 (0.5-8), adding deionized water, and carrying out ultrasonic vibration for 1h to form a uniformly dispersed suspension; adding eutectic salt into the nanometer AlN suspension, and carrying out ultrasonic vibration on the mixture for 1h to uniformly mix the eutectic salt with the nanometer AlN; the mixed solution was dried, cooled and the sample was ground into a powder.
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