CN115010394A - Green energy-saving wall material and preparation method thereof - Google Patents
Green energy-saving wall material and preparation method thereof Download PDFInfo
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- CN115010394A CN115010394A CN202210678964.6A CN202210678964A CN115010394A CN 115010394 A CN115010394 A CN 115010394A CN 202210678964 A CN202210678964 A CN 202210678964A CN 115010394 A CN115010394 A CN 115010394A
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B40/00—Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability
- C04B40/0028—Aspects relating to the mixing step of the mortar preparation
- C04B40/0039—Premixtures of ingredients
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- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- 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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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/14—Thermal energy storage
Abstract
The invention discloses a green energy-saving wall material. The material utilizes a porous matrix adsorption method, takes expanded perlite as a carrier, loads flake graphite as a nucleating agent, and adds Cs x WO 3 CaCl of nanoparticles 2 ·6H 2 And preparing the O inorganic phase-change material. Compared with the prior art, the green energy-saving wall material prepared by the invention has the advantages of low cost, high flame retardance, excellent heat storage capacity and heat insulation performance, and wide application prospect in the field of building energy conservation.
Description
Technical Field
The invention relates to the technical field of wall materials, in particular to a green energy-saving wall material and a preparation method thereof.
Background
Building energy consumption becomes one of three social energy consumption ways, and is driven by industrial and traffic energy consumption. The building energy consumption accounts for about 32 percent of the total energy consumption of China. The wall body is used as a main body part of a building peripheral structure, and the heat insulation performance of the used materials can directly influence the building energy consumption. The building wall in China always adopts materials with larger heat conductivity coefficients, such as a hollow block wall, an aerated concrete wall and the like, to realize building heat preservation. Although the light building envelope widely adopted at present has the function of reducing the energy consumption of the building through heat insulation, the defects of small heat capacity and low heat storage capacity exist, and the indoor temperature fluctuation of the building is large. In order to further improve the energy-saving effect, the use of the novel composite wall body is trending. The phase change material is combined into the light building envelope structure, and the heat capacity of the envelope structure is improved by utilizing the heat stored and released by the phase change material, so that the fluctuation of indoor temperature can be reduced by increasing the thermal inertia of the building, and the phase change material is an effective way for further reducing the building energy consumption. Compared with the traditional building material, the phase-change heat storage building material can reduce the building mass or store more heat energy under the same building mass when storing the same heat, thereby overcoming the defects of small heat capacity and low heat storage capacity of the modern building material.
The phase change material can be divided into an organic phase change material, an inorganic phase change material and a composite phase change material, wherein the organic phase change material comprises paraffin, fatty acid and the like, and the organic phase change material has the advantages of small supercooling degree, no phase separation, no toxicity and the like, but also has the defects of flammability, low heat conductivity and the like; the inorganic phase change material comprises hydrated salt, molten salt and the like, has the advantages of large latent heat, incombustibility, high thermal conductivity and the like, but also has the defects of large supercooling degree, easy phase separation, corrosiveness and the like; the composite phase-change material is formed by compounding an organic material and an inorganic material. Compared with organic phase change materials, the hydrated inorganic salt not only has the advantages of wide raw material source and low cost, but also has no flammability, higher energy storage capacity and larger melting enthalpy, so that the hydrated inorganic salt is more suitable for building envelope structures. However, the defects of supercooling and phase separation inherent in the phase change materials such as hydrated inorganic salts limit the practical application of the phase change materials, and in addition, the poor thermal conductivity of the inorganic phase change materials also causes low charge and discharge rate and limits the overall energy storage efficiency of the phase change materials.
CN103923613A discloses a low-temperature calcium chloride hexahydrate heat storage material and a preparation method thereof, the prepared low-temperature calcium chloride hexahydrate phase change heat storage material is composed of calcium chloride hexahydrate, a nucleating agent and a thickening agent according to mass percentage, wherein the nucleating agent is borax, aluminum oxide or sodium metasilicate nonahydrate, and the thickening agent is sodium carboxymethylcellulose; wherein, calcium chloride hexahydrate is used as a phase change base material, and the using amount is 95 to 98 percent; the low-temperature calcium chloride hexahydrate heat storage material is prepared by respectively adding 1% of borax and 1% of sodium carboxymethylcellulose or 1% of alumina, 4% of sodium carboxymethylcellulose or 1% of sodium metasilicate nonahydrate and 2% of sodium carboxymethylcellulose to modify calcium chloride hexahydrate, wherein the latent heat of phase change of the prepared low-temperature calcium chloride hexahydrate heat storage material is about 150J/g, the phase change temperature is 25-30 ℃, the supercooling degree is less than 2 ℃, and the heat absorption and release performance is stable after 3000 cycles. Has good application prospect in agricultural facilities and residential buildings.
CN106947434B discloses a hydrated salt-modified expanded graphite composite phase-change material and a preparation method thereof, wherein the hydrated salt-modified expanded graphite composite phase-change material comprises blocky hydrophilic modified expanded graphite and hydrated salt adsorbed in the blocky hydrophilic modified expanded graphite; the density of the block-shaped hydrophilic modified graphite is 300-600 kg/m 3 . According to the composite phase-change material provided by the invention, the hydrophilic modified expanded graphite is used for adsorbing the hydrated salt, so that the adsorption capacity of the expanded graphite to the hydrated salt is obviously improved, and the energy storage density of the composite phase-change material is improved; and the energy storage density of the composite phase change material in unit volume is further improved by adsorbing the hydrated salt by using the blocky modified expanded graphite. Experiments show that the mass fraction of the hydrated salt in the composite phase-change material provided by the invention can reach 85%, and the energy storage density can reach 300MJ/m 3 The thermal conductivity can reach 9.86W/(mK).
Therefore, the development of an inorganic composite phase change material with low cost, high energy storage, nonflammability, low supercooling, difficult phase separation and good thermal conductivity as a green energy-saving wall material is an urgent problem to be solved.
Disclosure of Invention
CaCl 2 ·6H 2 O is a low-cost and flame-retardant hydrated inorganic salt phase-change material, and also has a phase-change temperature of about 28 ℃ and an excellent phase-change potential heat value, so that CaCl is formed 2 ·6H 2 The O has good application prospect in the building field. How to solve CaCl 2 ·6H 2 The defects of large supercooling degree, phase separation, corrosion, liquid leakage and the like of O are one of the research focuses in the direction.
The expanded perlite is considered as an excellent carrier of inorganic phase-change materials due to the advantages of low cost, high porosity, strong adsorption capacity, no toxicity and the like, and is an excellent building heat-insulating material. In addition, because the expanded perlite also has flame retardant property and low heat conductivity coefficient and density, the expanded perlite and the phase-change material are compounded to obtain the expanded perlite-based composite phase-change material with flame retardance, excellent heat storage capacity and heat preservation and insulation capacity, and the expanded perlite-based composite phase-change material has important application prospect in the field of building energy conservation. The cellular porous structure of the expanded perlite ensures that the expanded perlite has excellent adsorption capacity on the phase change material. At present, the reports about the expanded perlite based composite phase change material are mainly organic phase change materials, and the composition of inorganic phase change materials and expanded perlite is rare.
In view of the above defects in the prior art, the invention provides a preparation method of a green energy-saving wall material. The preparation method utilizes a porous matrix adsorption method, takes expanded perlite as a carrier and loads CaCl 2 ·6H 2 The O inorganic phase change material can effectively prevent the liquid leakage problem of the solid-liquid phase change material, inhibit the improvement of the heat conductivity coefficient of the phase change material caused by adding the nucleating agent, and has the advantages of simple process, low cost and the like.
In order to realize the aim, the invention provides a preparation method of a green energy-saving wall material, which comprises the following steps:
(1) adding CaCl 2 ·6H 2 Heating and dissolving O, adding nucleating agent and stirring uniformly to obtain CaCl 2 ·6H 2 Saturated liquid of O;
(2) the CaCl obtained in the step (1) is treated 2 ·6H 2 Dispersing the O saturated liquid by ultrasonic, adding a thickening agent, stirring, and cooling to obtain CaCl 2 ·6H 2 O phase change material;
(3) CaCl obtained in the step (2) 2 ·6H 2 And injecting the O phase-change material into the expanded perlite under the condition of negative pressure, stirring, heating in vacuum, and cooling to room temperature to obtain the green energy-saving wall material.
Specifically, the preparation method of the green energy-saving wall material comprises the following steps:
(1) adding 45-60 parts by weight of solid CaCl 2 ·6H 2 Heating O in a water bath at 50-65 ℃ for 10-20 min, then adding 0.1-0.4 weight part of nucleating agent, and magnetically stirring at a rotating speed of 300-800 r/min for 25-40 min to obtain CaCl 2 ·6H 2 Saturated liquid of O;
(2) at 50-65 ℃, adding CaCl obtained in the step (1) 2 ·6H 2 Ultrasonically dispersing the O saturated liquid for 25-40 min at 20-45 kHz and 200-400W, adding 10-15 parts by weight of thickening agent, stirring for 12-18 min at 1300-1800 r/min, cooling to 15-20 ℃ to obtain CaCl 2 ·6H 2 O phase change material;
(3) CaCl obtained in the step (2) 2 ·6H 2 Slowly injecting the O phase change material into 97-126 parts by weight of expanded perlite under a negative pressure condition, stirring for 25-35 min, vacuum heating for 5-8 min under a negative pressure condition of 45-60 ℃, and cooling to 15-25 ℃ to obtain the green energy-saving wall material.
Preferably, the nucleating agent in the step (1) is SrCl 2 ·6H 2 O、SrCO 2 And borax.
Though same as general salt hydrate phase change materials, CaCl 2 ·6H 2 O has the disadvantages of supercooling and phase segregation, hindering its practical application, but studies have found that this problem can be solved to some extent by the addition of nucleating agents and thickeners. CaCl prevention by using thickening agent in the invention 2 ·6H 2 Separation of O during phase change, using nucleating agent to reduce CaCl in phase change material 2 ·6H 2 The supercooling degree of O utilizes the expanded perlite to inhibit the increase of the heat conductivity coefficient of the phase-change material caused by the addition of the nucleating agent to a certain extent. The invention discovers that the CaCl inhibition by using the flake graphite as the nucleating agent 2 ·6H 2 The supercooling degree and the heat conductivity coefficient of O are increased more effectively, the negative influence of the nucleating agent on the heat conductivity coefficient of the phase-change material can be weakened, and the heat conductivity coefficient of the wall material is further improved.
Further preferably, the nucleating agent in the step (1) is flake graphite.
Preferably, the thickener in step (2) is one of hydroxyethyl cellulose, polyacrylamide and sodium polyacrylate.
Further preferably, the thickener in the step (2) is sodium polyacrylate.
Preferably, the negative pressure condition in the step (3) is 80-98 kPa.
More preferably, the negative pressure condition of step (3) is 88.1 kPa.
Due to CaCl 2 ·6H 2 Modified CaCl with O phase transition temperature within 22-28 ℃ of human body thermal comfort 2 ·6H 2 O has great potential in building for energy storage and regulation of indoor temperature. The inventors have found that Cs is x WO 3 Dispersing nanoparticles into CaCl 2 ·6H 2 The O phase change material can be used for preparing a novel solar energy storage wall material, and can further reduce indoor temperature fluctuation.
In the whole spectrum of sunlight, only visible light can influence the indoor temperature, and the near infrared with the waveform range of 780-2500 nm accounts for more than 50% of solar energy and is called as a heat source. Therefore, the present inventors combined a near infrared absorber with a phase change material to improve the utilization efficiency of solar energy, thereby preventing more solar heat from entering a building. And Cs x WO 3 Is a near-infrared shading nano particle and has excellent near-infrared shielding performance. If it is to mix Cs x WO 3 Nanoparticles with CaCl 2 ·6H 2 The O phase change material is combined, and the prepared material can fully utilize near infrared solar energy and can obviously reduce indoor temperature fluctuation.
Further preferably, the preparation method of the green energy-saving wall material comprises the following steps:
(1) adding CaCl 2 ·6H 2 Heating and dissolving O, adding nucleating agent and stirring uniformly to obtain CaCl 2 ·6H 2 Saturated liquid of O;
(2) adding CaCl obtained in the step (1) 2 ·6H 2 Adding Cs into O saturated solution x WO 3 Dispersing nanoparticles and dispersant by ultrasonic wave, stirring, adding thickener, stirring, and cooling to obtain the final productTo CaCl 2 ·6H 2 O phase change material;
(3) CaCl obtained in the step (2) 2 ·6H 2 And injecting the O phase-change material into the expanded perlite under the condition of negative pressure, stirring, heating in vacuum, and cooling to room temperature to obtain the green energy-saving wall material.
Specifically, the preparation method of the green energy-saving wall material comprises the following steps:
(1) 45-60 parts by weight of solid CaCl 2 ·6H 2 Heating O in a water bath at 50-65 ℃ for 10-20 min, then adding 0.1-0.4 weight part of nucleating agent, and magnetically stirring at a rotating speed of 300-800 r/min for 25-40 min to obtain CaCl 2 ·6H 2 Saturated liquid of O;
(2) adding CaCl obtained in the step (1) at 50-65 DEG C 2 ·6H 2 Adding 0.78-0.86 weight part of Cs into the O saturated solution x WO 3 Ultrasonically dispersing a mixture of nano particles and a dispersing agent for 25-40 min under the conditions of 20-45 kHz and 200-400W, stirring for 15-25 min at 28-35 ℃, adding 10-15 parts by weight of a thickening agent, stirring for 12-18 min at 1300-1800 r/min, cooling to 15-20 ℃ to obtain CaCl 2 ·6H 2 O phase change material;
(3) CaCl obtained in the step (2) 2 ·6H 2 Slowly injecting the O phase change material into 97-126 parts by weight of expanded perlite under a negative pressure condition, stirring for 25-35 min, vacuum heating for 5-8 min under a negative pressure condition of 45-60 ℃, and cooling to 15-25 ℃ to obtain the green energy-saving wall material.
Preferably, the Cs described in step (2) x WO 3 The mixture of the nano particles and the dispersing agent is Cs x WO 3 The nano particles and the dispersing agent are mixed according to the mass ratio of 1 (1.1-1.3).
Preferably, the dispersant in step (2) is cetyl trimethyl ammonium bromide.
The invention also provides a green energy-saving wall material which is prepared according to the preparation method.
The invention has the following beneficial effects:
the invention provides a green energy-saving wall materialThe preparation method of the material adopts a porous matrix adsorption method, takes expanded perlite as a carrier and loads CaCl 2 ·6H 2 The inorganic phase-change material is prepared by mixing CaCl with expanded perlite in porous honeycomb structure and good hydrophilicity 2 ·6H 2 O is uniformly adsorbed in the pore structure and at the edges of the pores of the expanded perlite and is CaCl 2 ·6H 2 The O crystal provides a site for attachment and growth, so that CaCl is prepared 2 ·6H 2 The O/expanded perlite composite phase change material has reliable structural stability, can effectively prevent the liquid leakage problem of the solid-liquid phase change material, inhibits the improvement of the heat conductivity coefficient of the phase change material caused by adding a nucleating agent, and has the advantages of simple process, low cost and the like.
In order to weaken the negative influence of the nucleating agent on the heat conductivity of the phase-change material and further improve the heat conductivity of the wall material, the invention takes the flake graphite as the nucleating agent to reduce CaCl 2 ·6H 2 Degree of supercooling of O. The surface of the flake graphite is modified by some oxygen-containing functional groups, plays an important role in the crystal attachment process and accelerates CaCl in the cooling process 2 ·6H 2 Crystallization of O, thereby reducing CaCl 2 ·6H 2 Supercooling of O. CaCl 2 ·6H 2 O also takes the flake graphite as a main site for crystal attachment and growth, and further reduces CaCl 2 ·6H 2 Supercooling degree and thermal conductivity of O. In addition, the addition of flake graphite can cause the increase of solution viscosity and the contraction of molecular motion region, thereby causing CaCl 2 ·6H 2 The crystallization speed of O is accelerated, and the supercooling degree is reduced.
Due to CaCl 2 ·6H 2 The O phase transition temperature is within the range of 22-28 ℃ of human thermal comfort, and the CaCl prepared by the method 2 ·6H 2 The O/expanded perlite has great potential for storing energy and regulating indoor temperature in buildings. By reducing CaCl 2 ·6H 2 The supercooling degree and the heat conductivity coefficient of the O/expanded perlite phase-change material are improved to improve the phase-change enthalpy of CaCl 2 ·6H 2 The capability of the O/expanded perlite phase change material to reduce indoor temperature fluctuation. In addition, CaCl 2 ·6H 2 The O/expanded perlite is relatively economical and can be applied to a plurality of fields such as solar energy, building energy conservation and the like.
The invention also designs and prepares a novel green energy-saving wall material for solar energy storage, which takes flake graphite as a nucleating agent and CaCl 2 ·6H 2 O/expanded perlite is used as a core phase change material, and added Cs is added through a dispersing agent x WO 3 The nanoparticles are uniformly distributed in the phase-change material, and the interaction force between the nanoparticles and the hydrated salt is strengthened, so that the collision frequency between the components is faster, and the phase-change time is shortened. As the nano particles can be used as a nucleating agent, heterogeneous nucleation is promoted, the crystallization process is further accelerated, and the nano particles can be used for preparing flake graphite and Cs x WO 3 Under the combined action of the nanoparticles, CaCl 2 ·6H 2 The supercooling degree of O is suppressed to 0.61 ℃.
Although the heat transfer rate of the metal nanoparticles is greater, due to the low mass fraction of Cs x WO 3 The enhancement of the heat conductivity coefficient of the nano particles is offset by the interface resistance among the components, so that the heat conductivity coefficient of the green energy-saving wall material is reduced. In addition, the dispersant may increase the viscosity of the solution, uniformly distribute the precipitated crystals, thereby preventing phase separation during phase transition, reducing the heat transfer rate, and maintaining thermal properties. In CaCl 2 ·6H 2 Cs with good dispersion in O salt hydrate x WO 3 The nano particles can absorb 90% of near-infrared solar radiation, the photo-thermal conversion rate and the thermal adsorption performance of the green wall material are enhanced, the fluctuation of indoor temperature in the daytime is reduced, and the indoor temperature fluctuation is further reduced by effectively blocking the sunlight irradiation in a near-infrared region. Cs x WO 3 The addition of the nano particles also enhances the thermal inertia of the green wall material, and reduces the indoor temperature fluctuation by releasing the collected solar energy at night, so that the indoor temperature is kept within 22-28 ℃ for a long time. The green energy-saving wall material is very suitable for areas with strong solar radiation in daytime and low temperature at night.
In conclusion, the green energy-saving wall material prepared by the invention has low cost and high flame retardance, has excellent heat storage capacity and heat insulation performance, and has wide application prospect in the field of building energy conservation.
Detailed Description
Some raw material introductions in this application:
expanded perlite, density 180kg/m 3 The hydrophobicity was 98%.
Example 1
A green energy-saving wall material is prepared by the following steps:
(1) 50g of solid CaCl 2 ·6H 2 O was heated in a 60 ℃ water bath for 15min, followed by the addition of 0.25g SrCl 2 ·6H 2 O, magnetically stirring for 30min at the rotating speed of 500r/min to obtain CaCl 2 ·6H 2 Saturated liquid of O;
(2) at 60 ℃, adding CaCl obtained in the step (1) 2 ·6H 2 Ultrasonically dispersing the saturated O solution at 25kHz and 400W for 30min, adding 12g of sodium polyacrylate, stirring at 1500r/min for 15min, cooling to 20 deg.C to obtain CaCl 2 ·6H 2 O phase change material;
(3) CaCl obtained in the step (2) 2 ·6H 2 Slowly injecting the O phase change material into 100g of expanded perlite under the negative pressure condition of 88.1kPa, stirring for 30min, heating in vacuum for 5min under the negative pressure condition of 88.1kPa at 50 ℃, and cooling to 20 ℃ to obtain the green energy-saving wall material.
Example 2
A green energy-saving wall material is prepared by the following steps:
(1) 50g of solid CaCl 2 ·6H 2 Heating O in 60 deg.C water bath for 15min, adding 0.25g flake graphite, and magnetically stirring at 500r/min for 30min to obtain CaCl 2 ·6H 2 Saturated liquid of O;
(2) at 60 ℃, adding CaCl obtained in the step (1) 2 ·6H 2 Ultrasonically dispersing the saturated O solution at 25kHz and 400W for 30min, adding 12g of sodium polyacrylate, stirring at 1500r/min for 15min, cooling to 20 deg.C to obtain CaCl 2 ·6H 2 O phase change material;
(3) CaCl obtained in the step (2) 2 ·6H 2 O phase change materialSlowly injecting the material into 100g of expanded perlite under the negative pressure condition of 88.1kPa, stirring for 30min, heating for 5min under the vacuum condition of 50 ℃ and the negative pressure condition of 88.1kPa, and cooling to 20 ℃ to obtain the green energy-saving wall material.
Example 3
A green energy-saving wall material is prepared by the following steps:
(1) 50g of solid CaCl 2 ·6H 2 Heating O in 60 deg.C water bath for 15min, adding 0.25g flake graphite, and magnetically stirring at 500r/min for 30min to obtain CaCl 2 ·6H 2 Saturated liquid of O;
(2) adding CaCl obtained in step (1) at 60 deg.C 2 ·6H 2 0.375g of Cs is added into the O saturated liquid x WO 3 Dispersing nanoparticles and 0.45g hexadecyl trimethyl ammonium bromide with 25kHz and 400W ultrasound for 30min, stirring at 30 deg.C for 20min, adding 12g sodium polyacrylate, stirring at 1500r/min for 15min, cooling to 20 deg.C to obtain CaCl 2 ·6H 2 O phase change material;
(3) CaCl obtained in the step (2) 2 ·6H 2 Slowly injecting the O phase change material into 100g of expanded perlite under the negative pressure condition of 88.1kPa, stirring for 30min, heating in vacuum for 5min under the negative pressure condition of 88.1kPa at 50 ℃, and cooling to 20 ℃ to obtain the green energy-saving wall material.
Comparative example 1
A green energy-saving wall material is prepared by the following steps:
(1) 50g of solid CaCl 2 ·6H 2 Heating O in 60 deg.C water bath for 15min, magnetically stirring at 500r/min for 30min to obtain CaCl 2 ·6H 2 O saturated liquid;
(2) at 60 ℃, adding CaCl obtained in the step (1) 2 ·6H 2 Ultrasonically dispersing the O saturated solution at 25kHz and 400W for 30min, adding 12g of sodium polyacrylate, stirring at 1500r/min for 15min, cooling to 20 ℃ to obtain CaCl 2 ·6H 2 O phase change material;
(3) CaCl obtained in the step (2) 2 ·6H 2 The O phase-change material is slowly injected into 100g of expanded perlite under the negative pressure condition of 88.1kPa and stirredStirring for 30min, vacuum heating at 50 deg.C under 88.1kPa for 5min, and cooling to 20 deg.C to obtain green energy-saving wall material.
Comparative example 2
A green energy-saving wall material is prepared by the following steps:
(1) 50g of solid CaCl 2 ·6H 2 Heating O in water bath at 60 deg.C for 15min, adding 0.25g flake graphite, and magnetically stirring at 500r/min for 30min to obtain CaCl 2 ·6H 2 O saturated liquid;
(2) at 60 ℃, adding CaCl obtained in the step (1) 2 ·6H 2 Ultrasonically dispersing the saturated O solution at 25kHz and 400W for 30min, adding 12g of sodium polyacrylate, stirring at 1500r/min for 15min, cooling to 20 deg.C to obtain CaCl 2 ·6H 2 O phase-change material, namely green energy-saving wall material.
Comparative example 3
A green energy-saving wall material is prepared by the following steps:
(1) 50g of solid CaCl 2 ·6H 2 Heating O in 60 deg.C water bath for 15min, adding 0.25g flake graphite, and magnetically stirring at 500r/min for 30min to obtain CaCl 2 ·6H 2 Saturated liquid of O;
(2) adding CaCl obtained in step (1) at 60 deg.C 2 ·6H 2 Adding 0.45g hexadecyl trimethyl ammonium bromide into O saturated solution, ultrasonically dispersing at 25kHz and 400W for 30min, stirring at 30 ℃ for 20min, adding 12g sodium polyacrylate, stirring at 1500r/min for 15min, cooling to 20 ℃ to obtain CaCl 2 ·6H 2 O phase change material;
(3) CaCl obtained in the step (2) 2 ·6H 2 Slowly injecting the O phase change material into 100g of expanded perlite under the negative pressure condition of 88.1kPa, stirring for 30min, heating in vacuum for 5min under the negative pressure condition of 88.1kPa at 50 ℃, and cooling to 20 ℃ to obtain the green energy-saving wall material.
Test example 1
The green energy-saving wall materials prepared in the embodiments 1 to 3 and the comparative examples 1 to 3 are subjected to thermal characteristic analysis, and the building energy-saving performance of the wall material is evaluated through three aspects of thermal physical property analysis, supercooling degree test, heat conductivity coefficient test and the like.
And (3) thermal physical property analysis: according to the differential scanning calorimetry, the green energy-saving wall materials prepared in the examples 1-3 and the comparative examples 1-3 and CaCl are subjected to differential scanning calorimetry by using a Q20 differential scanning calorimeter of TAInstructor company in America 2 ·6H 2 And O, carrying out thermophysical property analysis, and testing the specific heat capacity of the material required by the experiment. Wherein the phase transition temperature and enthalpy of the sample are measured by N 2 Atmosphere, N 2 The flow rate is 50mL/min, the mass of each test material is 10mg, the test materials are packaged in an aluminum plate for heating, the heating rate is 3 ℃/min, the temperature rise/temperature drop range is-5-50 ℃, and the test results are shown in table 1.
And (3) supercooling degree test: the green energy-saving wall materials prepared in examples 1-3 and comparative examples 1-3 and CaCl were measured by using a constant temperature oil bath, a temperature acquisition system and a thermal energy storage test unit 2 ·6H 2 And obtaining the supercooling degree of the O. The temperature of the oil bath is regulated and controlled by a temperature control system, and the test unit is subjected to the following processes of temperature rise and temperature reduction after being put into the oil bath. The temperature raising and lowering procedure is as follows: heating the silicone oil from room temperature to 50 ℃ at the heating rate of 1 ℃/min, and keeping the temperature for 10 min; then, cooling the silicone oil to-5 ℃ at a cooling rate of 1 ℃/min, and keeping the temperature for 10 min; finally, the silicone oil is heated to 50 ℃ at a heating rate of 1 ℃/min and is kept for 10 min. In the processes of temperature rise and temperature drop, two K-type thermocouples in a temperature acquisition system are used for monitoring the temperature change of each sample, and temperature data are collected through an Agilent34970A data acquisition system. The thermal energy storage testing unit in the device consists of a testing sample and a test tube. Test tubes of 12cm length, 5cm diameter and 2mm thickness were loaded with test samples and then placed in an oil bath. Before testing, CaCl was added 2 ·6H 2 The O sample was heated and stirred uniformly, the mass of the sample loaded into the tube was 35. + -. 0.15g, and the position of the thermocouple probe was kept 2cm from the bottom of the tube, and the test results are shown in Table 1.
And (3) testing the heat conductivity coefficient: the thermal conductivity coefficient of the green energy-saving wall materials prepared in the examples 1 to 3 and the comparative examples 1 to 3 was tested by a transient heat source method at room temperature by using a TPS2500 thermal conductivity coefficient analyzer of Hot Disk of Sweden. Using a cylindrical die with a diameter of 4cm and a height of 1cm at 100kg/cm 2 Pressing the green energy-saving wall materials prepared in the examples 1-3 and the comparative examples 1-3 into cylindrical sheets under pressure; the 7577 sensor probe with a radius of 2.01mm was then placed between two sheets of the press formed test material for measurement. For comparison, molten CaCl 2 ·6H 2 The O and the expanded perlite are respectively poured into a cylindrical die for tabletting, and the respective thermal conductivity coefficients are respectively measured, and the test results are shown in table 1.
TABLE 1 thermal characteristic analysis results of green energy-saving wall material
As shown in table 1, compared with comparative example 2, the green energy-saving wall material prepared in example 2 has a suitable phase transition temperature, a higher phase transition enthalpy value, a lower supercooling degree and a lower thermal conductivity. This is due to the porous cellular structure and good hydrophilicity of the expanded perlite, the CaCl 2 ·6H 2 The O is uniformly adsorbed in the pore structure and on the pore edge of the expanded perlite and is CaCl 2 ·6H 2 The O crystal provides a site for attachment and growth, so that CaCl is prepared 2 ·6H 2 The O/expanded perlite composite phase change material has reliable structural stability, can effectively prevent the liquid leakage problem of the solid-liquid phase change material, inhibits the improvement of the heat conductivity coefficient of the phase change material caused by adding a nucleating agent, and has the advantages of simple process, low cost and the like.
Compared with the comparative example 1 and the example 1, the green energy-saving wall material prepared in the example 2 has proper phase transition temperature, higher phase transition enthalpy value, lower supercooling degree and lower heat conductivity coefficient. This is probably because the surface of the flake graphite is modified by some oxygen-containing functional groups, which plays an important role in the crystal attachment process and accelerates CaCl during the cooling process 2 ·6H 2 Crystallization of O, thereby reducing CaCl 2 ·6H 2 The supercooling and heat conductivity coefficient of O improves the phase change enthalpy. CaCl 2 ·6H 2 O also takes the flake graphite as a main site for crystal attachment and growth, and further reduces CaCl 2 ·6H 2 Supercooling degree and thermal conductivity of O. In addition, the addition of flake graphite can cause the increase of solution viscosity and the contraction of molecular motion region, thereby causing CaCl 2 ·6H 2 The crystallization speed of O is accelerated, and the supercooling degree is reduced. Uses flake graphite as nucleating agent to reduce CaCl 2 ·6H 2 The supercooling degree and the heat conductivity coefficient of the O/expanded perlite phase change material improve the phase change enthalpy, and further improve the capacity of the green wall material for stabilizing the indoor temperature.
Compared with the embodiment 2 and the comparative example 3, the solar energy storage green energy-saving wall material prepared in the embodiment 3 has proper phase change temperature, higher phase change enthalpy value, lower supercooling degree and heat conductivity coefficient. This is probably due to the addition of Cs by the dispersant x WO 3 The nano particles are uniformly distributed in the phase-change material, and the interaction force between the nano particles and the hydrated salt is strong, so that the collision frequency between the components is higher, the phase-change time is shortened, and the phase-change enthalpy is increased. As the nano particles can be used as a nucleating agent, heterogeneous nucleation is promoted, the crystallization process is further accelerated, and the nano particles can be used for preparing flake graphite and Cs x WO 3 Under the combined action of the nano-particles, CaCl 2 ·6H 2 The supercooling degree of O was suppressed to 0.61 ℃. Although the heat transfer rate of the metal nanoparticles is greater, due to the low mass fraction of Cs x WO 3 The enhancement of the heat conductivity coefficient of the nano particles is offset by the interface resistance among the components, so that the heat conductivity coefficient of the green energy-saving wall material is reduced. In addition, the dispersant may increase the viscosity of the solution, uniformly distribute the precipitated crystals, thereby preventing phase separation during phase transition, reducing the heat transfer rate, and maintaining thermal properties.
Test example 2
Testing thermal regulation performance: in order to evaluate the feasibility of the green energy-saving wall materials prepared in examples 1 to 3 and comparative example 3 in reducing indoor temperature fluctuation under solar irradiation, each group of experiments was equipped with a small house model according to each sample material to study the thermal regulation performance of each sample. The details of the small house model construction are shown in table 2, wherein the blank control does not contain one of the green energy-saving wall materials prepared in the 5mm embodiments 1-3 and the comparative example 3. 200W sunlight irradiation was simulated by CEL-HXUV300 solar simulation equipment, AM1.5 filter. Thermocouples are respectively arranged in the middle of the small house model and on the outer surface of the irradiation surface wall and used for monitoring the temperature. The experiment is carried out at the environment temperature of 19 ℃, the experiment is closed after the simulated sunlight is irradiated for 2 hours, the temperature of the middle of the small house model and the temperature of the outer surface of the irradiated surface wall at 2 hours and 4 hours are measured, and the test results are shown in table 2.
TABLE 2 details of the construction of the small house model
Table 3 green energy-saving wall material thermal regulation performance test results
As can be seen from table 3, as the result of the thermal characteristic analysis, the higher the enthalpy of phase change, the lower the thermal conductivity, and the smaller the fluctuation range of the indoor central temperature. Thus, the use of expanded perlite for loading CaCl is illustrated 2 ·6H 2 O phase-change material, using flake graphite as nucleating agent and adding Cs x WO 3 The nano particles can reduce the supercooling degree and the heat conductivity coefficient of the green energy-saving wall material and improve the phase change enthalpy of the wall material so as to improve the capability of stabilizing the indoor temperature fluctuation.
Compared with the blank control, examples 1-2 and comparative example 3, the temperature of the outer wall surface prepared by the green energy-saving wall material in example 3 is always higher than that of the outer wall surface prepared by the groups in examples 1-2 and comparative example 3, which is probably due to Cs x WO 3 The near infrared light absorption capacity of the nano particles enhances the photo-thermal conversion rate and the thermal adsorption performance. However, the indoor central temperature of the group of example 3 was kept lower than that of the groups of examples 1-2 and comparative example 3 during the simulated solar irradiation, thereby showing that the green energy-saving wall material prepared in example 3 indeed has the functions of reducing the indoor peak temperature and increasing the thermal inertia. This is probably due to the presence of CaCl 2 ·6H 2 Cs with good dispersion in O salt hydrate x WO 3 The nano particles can absorb 90% of near-infrared solar radiation, the photo-thermal conversion rate and the thermal adsorption performance of the green wall material are enhanced, the fluctuation of indoor temperature in the daytime is reduced, and the indoor temperature fluctuation is further reduced by effectively blocking the sunlight irradiation of a near-infrared region, so that the indoor temperature of the group of the embodiment 3 can be kept at 22-28 ℃ within a long time. Thus illustrating CaCl 2 ·6H 2 O/expanded perlite phase change material and Cs x WO 3 The synergistic effect of nanoparticles plays a key role in the cooling requirements for solar energy storage and building energy conservation.
In addition, after the simulated light was turned off, the indoor center temperature of the group of examples 3 was kept higher than that of the groups of examples 1 to 2 and comparative example 3, with the temperature fluctuation range being minimized. This may be due to Cs x WO 3 The addition of the nano particles also enhances the thermal inertia of the green wall material, and reduces the indoor temperature fluctuation by releasing the collected solar energy in the absence of illumination, so that the indoor temperature is kept within 22-28 ℃ for a long time. The green energy-saving wall material is very suitable for areas with strong solar radiation in daytime and low temperature at night.
Claims (10)
1. The preparation method of the green energy-saving wall material is characterized by comprising the following steps of:
(1) adding CaCl 2 ·6H 2 Heating and dissolving O, adding nucleating agent and stirring uniformly to obtain CaCl 2 ·6H 2 Saturated liquid of O;
(2) the CaCl obtained in the step (1) is treated 2 ·6H 2 Dispersing the saturated O solution by ultrasonic, adding a thickening agent and stirringStirring and cooling to obtain CaCl 2 ·6H 2 O phase change material;
(3) CaCl obtained in the step (2) 2 ·6H 2 And injecting the O phase-change material into the expanded perlite under the condition of negative pressure, stirring, heating in vacuum, and cooling to room temperature to obtain the green energy-saving wall material.
2. The preparation method of the green energy-saving wall material as claimed in claim 1, characterized by comprising the following steps:
(1) adding 45-60 parts by weight of solid CaCl 2 ·6H 2 Heating O in a water bath at 50-65 ℃ for 10-20 min, then adding 0.1-0.4 part by weight of nucleating agent, and magnetically stirring at the rotating speed of 300-800 r/min for 25-40 min to obtain CaCl 2 ·6H 2 Saturated liquid of O;
(2) at 50-65 ℃, adding CaCl obtained in the step (1) 2 ·6H 2 Ultrasonically dispersing the O saturated liquid for 25-40 min at 20-45 kHz and 200-400W, adding 10-15 parts by weight of thickening agent, stirring for 12-18 min at 1300-1800 r/min, cooling to 15-20 ℃ to obtain CaCl 2 ·6H 2 O phase change material;
(3) CaCl obtained in the step (2) 2 ·6H 2 Slowly injecting the O phase change material into 97-126 parts by weight of expanded perlite under a negative pressure condition, stirring for 25-35 min, vacuum heating for 5-8 min under a negative pressure condition of 45-60 ℃, and cooling to 15-25 ℃ to obtain the green energy-saving wall material.
3. The method for preparing green energy-saving wall material according to claim 1 or 2, wherein the nucleating agent in the step (1) is SrCl 2 ·6H 2 O、SrCO 2 One of borax and flake graphite.
4. The method for preparing green energy-saving wall material according to claim 3, wherein the nucleating agent is flake graphite.
5. The method for preparing green energy-saving wall material according to claim 1 or 2, wherein the thickener in the step (2) is one of hydroxyethyl cellulose, polyacrylamide and sodium polyacrylate.
6. The preparation method of the green energy-saving wall material as claimed in claim 1 or 2, wherein the negative pressure condition in the step (3) is 80-98 kPa.
7. The preparation method of the green energy-saving wall material as claimed in claim 1, characterized by comprising the following steps:
(1) adding CaCl 2 ·6H 2 Heating and dissolving O, adding nucleating agent and stirring uniformly to obtain CaCl 2 ·6H 2 Saturated liquid of O;
(2) adding CaCl obtained in the step (1) 2 ·6H 2 Adding Cs into O saturated solution x WO 3 The mixture of the nano particles and the dispersant is stirred after ultrasonic dispersion, then the thickener is added for stirring, and CaCl is obtained after cooling 2 ·6H 2 O phase change material;
(3) CaCl obtained in the step (2) 2 ·6H 2 And injecting the O phase-change material into the expanded perlite under the condition of negative pressure, stirring, heating in vacuum, and cooling to room temperature to obtain the green energy-saving wall material.
8. The preparation method of the green energy-saving wall material as claimed in claim 7, characterized in that: cs described in step (2) x WO 3 The mixture of the nano particles and the dispersing agent is Cs x WO 3 The nano particles and the dispersing agent are mixed according to the mass ratio of 1 (1.1-1.3).
9. The preparation method of the green energy-saving wall material as claimed in claim 7, characterized in that: the dispersant in the step (2) is cetyl trimethyl ammonium bromide.
10. A green energy-saving wall material prepared by the method of any one of claims 1 to 9.
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