Photo-thermal performance optimization method based on aerogel microstructure

Abstract

The invention belongs to the technical field of photo-thermal performance optimization, and relates to a photo-thermal performance optimization method based on an aerogel microstructure. Comprising the following steps: S1, establishing a microcosmic porous structure of aerogel: constructing an aerogel two-dimensional porous structure with a corresponding size based on a four-parameter random growth model; s2, simulating the solar radiation absorption and scattering characteristics of the tabular aerogel: simulating the transmittance of the tabular aerogel based on a Monte Carlo method, and calculating the solar radiation extinction coefficient of the aerogel; s3, simulating the heat transfer process of the aerogel based on a lattice Boltzmann model, and calculating the heat conductivity coefficient of the aerogel; and S4, constructing a dynamic heat transfer model, and simulating the energy consumption performance of the aerogel glass in an actual environment. According to the invention, the photo-thermal performance of the aerogel is accurately simulated, and the dynamic heat transfer model is combined to evaluate the energy consumption performance of the aerogel in an actual environment. By optimizing the microstructure of the aerogel, the photo-thermal performance and the energy efficiency of the aerogel are remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of photothermal performance optimization, and in particular relates to a photothermal performance optimization method based on aerogel microstructure. Background Art

[0002] With the increasing global demand for energy efficiency and environmental protection, the research and development of building energy conservation and green building materials has become an important development direction of the modern construction industry. Global attention to energy efficiency is increasing, especially in the field of construction, where about 40% of energy consumption comes from building heating and cooling systems. Therefore, the use of high-performance thermal insulation materials such as aerogels can significantly reduce building energy consumption and contribute to the realization of energy conservation and emission reduction goals. The application demand for aerogels in building exterior walls, windows, roofs and other parts is growing, among which aerogel glass, as a material with excellent thermal insulation performance and light transmittance, shows a broad market prospect. In particular, in energy-saving window systems such as double-glazed and triple-glazed windows, filling aerogels can greatly improve the thermal resistance of windows, reduce heat loss and heat entry, thereby effectively reducing the air conditioning and heating energy consumption of buildings. In view of the unique advantages of aerogel materials in improving building energy efficiency, promoting the development of green building materials, and meeting the needs of efficient thermal insulation in multiple industries, the present invention aims to further optimize the microstructure of aerogels and improve their photothermal performance to meet the growing market demand for high-performance thermal insulation materials, and promote the rapid development of building energy conservation, special high-efficiency thermal insulation materials and green environmental protection industries. Summary of the invention

[0003] In response to the above problems, the present invention proposes a method for optimizing the photothermal performance based on the microstructure of aerogel, aiming to improve the photothermal performance of aerogel by further optimizing the microstructure of aerogel, so as to meet the market's growing demand for high-performance thermal insulation materials and promote the rapid development of building energy conservation, special high-efficiency thermal insulation materials and green environmental protection industries.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is as follows: A method for optimizing photothermal performance based on aerogel microstructure comprises the following steps:

[0005] S1. Establish the microscopic porous structure of aerogel: construct the two-dimensional porous structure of aerogel of corresponding size based on the four-parameter random growth model. The four parameters of the model include the core distribution probability c d , Direction Growth Probability D i , the porosity P and the intergrowth probability N of the generated structure.

[0006] Because the porous structure of aerogel consists only of silica particles and air, that is, solid phase and gas phase, the probability of cross-growth can be ignored. In the model, first given c d Generate the initial aerogel core distribution, and then according to Di Grow in eight directions (i.e. four vertices and four edges) around it. By changing the core distribution probability c d , Direction Growth Probability D 边缘 , D 顶点 Different aerogel porous structures can be obtained by changing the parameter values.

[0007] S2. Simulate the absorption and scattering characteristics of plate-like aerogel to solar radiation: Based on the Monte Carlo method, the transmittance of plate-like aerogel is simulated and the solar radiation extinction coefficient of aerogel is calculated. The specific steps are as follows:

[0008] S21. A beam of vectorial radiation is randomly emitted in the porous structure of the aerogel to determine whether the radiation collides with the aerogel boundary or the silica particles. If a collision occurs with the aerogel boundary, the radiation overflows and is re-emitted.

[0009] If it collides with silica particles, the random number RND is compared with the transmittance, scattering rate and absorption rate of the material.

[0010] Where 0≤RND≤1.

[0011] S22. Count the amount of radiation transmitted and absorbed, and calculate the average spectral transmittance and solar radiation extinction coefficient of the aerogel.

[0012] S3. Simulate the heat transfer process of aerogel based on the lattice Boltzmann model and calculate the thermal conductivity of aerogel: The specific steps are as follows:

[0013] S31. The temperature distribution function and heat flux of aerogel are solved based on the two-dimensional nine-speed D2Q9 lattice Boltzmann model.

[0014] S32. Finally, the thermal conductivity of the plate-like aerogel is calculated according to Fourier's law of thermal conductivity.

[0015] S4. Construct a dynamic heat transfer model to simulate the energy consumption performance of aerogel glass in actual environment, which specifically includes the following steps:

[0016] S41. Fill the aerogel between the double layers of glass to form aerogel glass.

[0017] S42. A dynamic heat transfer differential equation is constructed by combining the convective heat transfer between the two sides of the glass and the external environment, the long-wave radiation heat transfer, the heat transfer between the glass layers, and the heat generated by the glass absorbing solar radiation.

[0018] S43. Evaluate the thermal performance of aerogel glass under different environmental conditions by calculating the indoor heat gain.

[0019] S5. Based on the above simulation results, the microstructure of aerogel is optimized to improve its photothermal performance and energy efficiency.

[0020] Furthermore, in S22, the calculation formula of the spectral average transmittance of the aerogel is:

[0021]

[0022] Where θ is the spectral transmittance; τ is the wavelength, ranging from 300-2500nm; E is the solar radiation intensity, W / m 2 .

[0023] Furthermore, the solar radiation extinction coefficient ω of the aerogel is obtained according to the Boolean law, and the specific calculation formula is:

[0024] ω=-lnθ / S

[0025] Where S is the optical path length of the aerogel in nm.

[0026] Furthermore, in S3, during the heat transfer process of the aerogel, the heat conduction energy equation of the aerogel porous structure is:

[0027]

[0028] Where ε is the density, kg / m 3 ;c p is the specific heat capacity, J / (kg·k); T is the temperature at the position (m, n) at time t, °C; γ is the thermal conductivity of the medium, W / (m·k); subscript q indicates gas; subscript e indicates solid;

[0029] The temperature evolution equation is:

[0030]

[0031] Among them, g a is the temperature distribution function; is the equilibrium distribution function;

[0032] μ is the dimensionless relaxation time, which is determined by the thermal conductivity of the respective phase as follows:

[0033]

[0034] Among them, b a represents discrete speed, specifically,

[0035]

[0036] The lattice Boltzmann differential equation form is obtained:

[0037]

[0038] Since heat transfer occurs only by thermal diffusion, the equilibrium distribution function can be expressed as follows:

[0039]

[0040] Where X a Represents the weight factor:

[0041]

[0042] The temperature T and heat flux are then calculated according to the following formula:

[0043] T=∑ a g a

[0044]

[0045] Furthermore, the thermal conductivity of the plate-like aerogel is calculated according to Fourier's thermal conductivity law. The specific formula is as follows:

[0046]

[0047] Where, λ is the thermal conductivity of the plate aerogel, W / (m·K); δ is the distance of heat conduction; ΔT represents the temperature difference between the cold surface and the hot surface; and A is the area of ​​the cross-section of the aerogel through which heat passes.

[0048] Further, in S5, the pore distribution and particle size of the aerogel are adjusted to optimize its solar radiation extinction coefficient and thermal conductivity.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] 1. The present invention adopts a four-parameter random growth method to construct the microstructure model of aerogel. By adjusting the core distribution probability (c d ), direction growth probability (D 边缘 , D 顶点 ) and other parameters to generate aerogel structures with different pore distributions and particle sizes.

[0051] Optical performance simulation: Based on the Monte Carlo method, the absorption and scattering characteristics of aerogel to solar radiation are simulated, and the extinction coefficient, transmittance and absorptivity are calculated.

[0052] Heat transfer performance simulation: The heat transfer process of aerogels was simulated based on the lattice Boltzmann model (LBM) and the thermal conductivity was calculated.

[0053] By combining the four-parameter random growth method, the Monte Carlo method and the lattice Boltzmann model, a multi-scale simulation of aerogel microstructure, optical properties and thermal transfer performance is achieved. This method significantly improves the calculation speed and accuracy, and provides comprehensive theoretical support for the optimization of aerogel photothermal performance.

[0054] 2. The present invention fills aerogel between double-layer glass to construct a dynamic heat transfer model of aerogel glass. Comprehensively consider various heat transfer mechanisms such as radiation, convection and thermal conduction to simulate the energy consumption performance of aerogel glass in actual environment. By introducing a dynamic heat transfer model, comprehensive consideration of various heat transfer mechanisms such as radiation, convection and thermal conduction can be made to accurately evaluate the energy efficiency of aerogel glass, especially its performance under dynamic environmental changes, thereby comprehensively evaluating the energy consumption performance of aerogel glass in actual environment.

[0055] 3. The present invention significantly improves the energy efficiency of building envelopes by optimizing the photothermal performance of aerogels, provides technical support for green buildings and energy-saving renovations, and helps reduce the energy consumption of air conditioning and heating systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 The two-dimensional porous structure of the aerogel in the embodiment of the present invention;

[0057] Figure 2 It is the lattice Boltzmann model D2Q9. DETAILED DESCRIPTION

[0058] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0059] like Figure 1 , Figure 2 Shown is a method for optimizing photothermal performance based on aerogel microstructure.

[0060] The steps include:

[0061] S1. Establishment of the microscopic porous structure of aerogel: A two-dimensional porous structure of aerogel of corresponding size is constructed based on a four-parameter random growth model. The four parameters of the model include the core distribution probability (c d ), direction growth probability (D i ), the porosity (P) and the probability of cross-growth (N) of the generated structure. Since the porous structure of aerogels consists only of silica particles and air, i.e., solid and gas phases, the probability of cross-growth can be ignored. In the model, we first give c dGenerate the initial aerogel core distribution, and then according to D i Grow in eight directions (i.e. four vertices and four edges) around it. By changing the core distribution probability c d , Direction Growth Probability D 边缘 , D 顶点 Different aerogel porous structures can be obtained by changing the parameter values.

[0062] Among them, the four-parameter random growth model is based on the random growth algorithm. It generates a two-dimensional porous structure of aerogel with specific pores by simulating the random aggregation and growth behavior of aerogel particles during the formation process.

[0063] It should be noted that the initial parameter core distribution probability c d , determines the number and location of core points in the aerogel structure. Directional growth probability D 边缘 , D 顶点 , is the probability of the aerogel extending toward the edge or vertex during growth. These parameters control the shape of the aerogel structure and the distribution of pores.

[0064] The four edge directions are the growth probabilities of the aerogel in the four edge directions (such as up, down, left, and right). These parameters affect the symmetry and anisotropy of the aerogel structure.

[0065] The four vertex directions are the growth probabilities of the aerogel in the four vertex directions (such as the diagonal directions). These parameters further regulate the complexity of the aerogel structure and the connectivity of the pores.

[0066] The four-parameter random growth model is used to construct the microstructure of the aerogel, providing a basis for the subsequent simulation of optical properties (Monte Carlo method) and thermal transfer properties (lattice Boltzmann model). By adjusting the four parameters, aerogel structures with different pore distributions and particle sizes can be generated, thereby optimizing their photothermal properties.

[0067] Compared with the traditional random model, the four-parameter random growth model can more accurately control the morphology and pore distribution of the aerogel structure by introducing directional growth probability and edge / vertex direction growth probability, providing more accurate theoretical support for the optimization of material properties.

[0068] S2. Simulate the absorption and scattering characteristics of plate-like aerogel to solar radiation: Based on the Monte Carlo method, the transmittance of plate-like aerogel is simulated and the solar radiation extinction coefficient of aerogel is calculated. The specific steps are as follows:

[0069] S21. A beam of vectorial radiation is randomly emitted in the porous structure of the aerogel to determine whether the radiation collides with the aerogel boundary or the silica particles. If a collision occurs with the aerogel boundary, the radiation overflows and is re-emitted.

[0070] If it collides with silica particles, the random number RND is compared with the transmittance, scattering rate and absorption rate of the material, where 0≤RND≤1.

[0071] Specifically, if the RND is less than the transmittance, the radiation passes through the particle;

[0072] If RND is within the sum of transmittance and scattering rate and is greater than transmittance, the radiation is scattered;

[0073] If the RND is greater than the sum of the transmittance and the scattering rate, the radiation is absorbed.

[0074] S22, counting the amount of radiation transmitted and absorbed, and calculating the average spectral transmittance and solar radiation extinction coefficient of the aerogel. Specifically, the amount of radiation transmitted and absorbed is counted based on the result of S21.

[0075] The calculation formula of the spectral average transmittance of aerogel is:

[0076]

[0077] Where θ is the spectral transmittance; τ is the wavelength, ranging from 300-2500nm; E is the solar radiation intensity, W / m 2 Furthermore, the solar radiation extinction coefficient ω of the aerogel is obtained according to the Boolean law, and the specific calculation formula is:

[0078] ω=-lnθ / S

[0079] Where S is the optical path length of the aerogel in nm.

[0080] It should be noted that aerogel transmittance, absorptivity and extinction coefficient are the core parameters of aerogel optical properties, which directly affect the response of aerogel glass to solar radiation. The above data provide input parameters for the dynamic heat transfer model in S4, which is used to simulate the heat absorption and transfer behavior of aerogel glass under solar radiation. The energy consumption performance of aerogel glass is closely related to its absorption and scattering characteristics of solar radiation. The above results help quantify the optical performance of aerogel glass under different spectra, thereby providing a basis for the subsequent evaluation of the energy consumption performance of aerogel glass.

[0081] S3. Simulate the heat transfer process of aerogel based on the lattice Boltzmann model and calculate the thermal conductivity of aerogel: The specific steps are as follows:

[0082] S31. The temperature distribution function and heat flux of aerogel are solved based on the two-dimensional nine-speed D2Q9 lattice Boltzmann model.

[0083] S32. Finally, the thermal conductivity of the plate-like aerogel is calculated according to Fourier's law of thermal conductivity.

[0084] In S3, during the heat transfer process of aerogel, the heat conduction energy equation of the aerogel porous structure is:

[0085]

[0086] Where ε is the density, kg / m 3 ;c p is the specific heat capacity, J / (kg·k); T is the temperature at the position (m, n) at time t, °C; γ is the thermal conductivity of the medium, W / (m·k); subscript q indicates gas; subscript e indicates solid;

[0087] The temperature evolution equation is:

[0088]

[0089] Among them, g a is the temperature distribution function; is the equilibrium distribution function;

[0090] μ is the dimensionless relaxation time, which is determined by the thermal conductivity of the respective phase as follows:

[0091]

[0092] Among them, b a represents discrete speed, specifically,

[0093]

[0094] The lattice Boltzmann differential equation form is obtained:

[0095]

[0096] Since heat transfer occurs only by thermal diffusion, the equilibrium distribution function can be expressed as follows:

[0097]

[0098] Where X a Represents the weight factor:

[0099]

[0100] The temperature T and heat flux are then calculated according to the following formula:

[0101] T=∑ a g a

[0102]

[0103] Then the thermal conductivity of the plate-like aerogel is calculated according to Fourier's thermal conductivity law. The specific formula is as follows:

[0104]

[0105] Where, λ is the thermal conductivity of the plate aerogel, W / (m·K); δ is the distance of heat conduction; ΔT represents the temperature difference between the cold surface and the hot surface; and A is the area of ​​the cross-section of the aerogel through which heat passes.

[0106] It should be noted that the thermal conductivity (λ) calculated in the above results is a key parameter of the heat transfer performance of aerogels and directly affects the thermal insulation effect of aerogel glass.

[0107] These data provide input parameters for the dynamic heat transfer model in step 4, which is used to simulate the performance of aerogel glass under heat transfer mechanisms such as heat conduction, convection and radiation.

[0108] S4. Construct a dynamic heat transfer model to simulate the energy consumption performance of aerogel glass in actual environment, which specifically includes the following steps:

[0109] S41. Fill the aerogel between the double layers of glass to form aerogel glass.

[0110] S42. A dynamic heat transfer differential equation is constructed by combining the convective heat transfer between the two sides of the glass and the external environment, the long-wave radiation heat transfer, the heat transfer between the glass layers, and the heat generated by the glass absorbing solar radiation.

[0111] S43. Evaluate the thermal performance of aerogel glass under different environmental conditions by calculating the indoor heat gain.

[0112] S5. Based on the above simulation results, the microstructure of aerogel is optimized to improve its photothermal performance and energy efficiency.

[0113] Among them, in S5, the pore distribution and particle size of the aerogel are adjusted to optimize its solar radiation extinction coefficient and thermal conductivity.

[0114] The above technical solution uses multi-scale modeling and simulation methods to accurately simulate the photothermal performance of aerogels, and combines dynamic heat transfer models to evaluate their energy consumption performance in actual environments. By optimizing the microstructure of aerogels, their photothermal performance and energy efficiency are significantly improved, providing important technical support for building energy conservation and green buildings.

[0115] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art may still modify the technical solutions described in the aforementioned embodiments, or perform equivalent substitutions on some of the technical features. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for optimizing photothermal performance based on aerogel microstructure, characterized in that: The steps include: S1. Establish the microscopic porous structure of aerogel: construct the two-dimensional porous structure of aerogel of corresponding size based on the four-parameter random growth model. The four parameters of the model include the core distribution probability c d , Direction Growth Probability D i , the porosity P and the probability of intergrowth N of the generated structure, and different aerogel porous structures are obtained by changing the parameter values; S2. Simulate the absorption and scattering characteristics of plate-like aerogel to solar radiation: Based on the Monte Carlo method, the transmittance of plate-like aerogel is simulated and the solar radiation extinction coefficient of aerogel is calculated. The specific steps are as follows: S21, randomly emitting a beam of vectorial radiation in the porous structure of the aerogel, and determining whether the radiation collides with the aerogel boundary or the silica particles. If the radiation collides with the aerogel boundary, the radiation overflows and is re-emitted; If it collides with silica particles, the random number RND is compared with the transmittance, scattering rate and absorption rate of the material. Where 0≤RND≤1; S22, counting the amount of radiation transmitted and absorbed, and calculating the average spectral transmittance and solar radiation extinction coefficient of the aerogel; S3. Simulate the heat transfer process of aerogel based on the lattice Boltzmann model and calculate the thermal conductivity of aerogel: The specific steps are as follows: S31, solve the temperature distribution function and heat flux of aerogel based on the two-dimensional nine-speed D2Q9 lattice Boltzmann model; S32, finally calculating the thermal conductivity of the plate-like aerogel according to Fourier's thermal conductivity law; S4. Construct a dynamic heat transfer model to simulate the energy consumption performance of aerogel glass in actual environment, which specifically includes the following steps: S41, filling aerogel between double-layer glass to form aerogel glass; S42. Construct a dynamic heat transfer differential equation by combining the convection heat transfer between the two sides of the glass and the external environment, the long-wave radiation heat transfer, the heat transfer between the glass layers, and the heat generated by the glass absorbing solar radiation; S43. Evaluate the thermal performance of aerogel glass under different environmental conditions by calculating the indoor heat gain of aerogel glass; S5. Based on the above simulation results, the microstructure of aerogel is optimized to improve its photothermal performance and energy efficiency.

2. The method for optimizing photothermal performance based on aerogel microstructure according to claim 1, characterized in that: In S22, the calculation formula of the spectral average transmittance of aerogel is: Where θ is the spectral transmittance; τ is the wavelength, ranging from 300-2500nm; E is the solar radiation intensity, W / m 2 .

3. The method for optimizing photothermal performance based on aerogel microstructure according to claim 2, characterized in that: According to Boole's law, the solar radiation extinction coefficient ω of aerogel is obtained, and the specific calculation formula is: ω=-lnθ / S Where S is the optical path length of the aerogel in nm.

4. The method for optimizing photothermal performance based on aerogel microstructure according to claim 1, characterized in that: In S3, during the heat transfer process of aerogel, the heat conduction energy equation of the aerogel porous structure is: Where ε is the density, kg / m 3 ;c p is the specific heat capacity, J / (kg·k); T is the temperature at the position (m, n) at time t, °C; γ is the thermal conductivity of the medium, W / (m·k); subscript q indicates gas; subscript e indicates solid; The temperature evolution equation is: Among them, g a is the temperature distribution function; is the equilibrium distribution function; μ is the dimensionless relaxation time, which is determined by the thermal conductivity of the respective phase as follows: Among them, b a represents discrete speed, specifically, The lattice Boltzmann differential equation form is obtained: Since heat transfer occurs only by thermal diffusion, the equilibrium distribution function can be expressed as follows: Where X a Represents the weight factor: The temperature T and heat flux are then calculated according to the following formula: T=∑ a g a 5. The method for optimizing photothermal performance based on aerogel microstructure according to claim 4, characterized in that: The thermal conductivity of plate-like aerogel is calculated according to Fourier's thermal conductivity law. The specific formula is as follows: Where, λ is the thermal conductivity of the plate aerogel, W / (m·K); δ is the distance of heat conduction; ΔT represents the temperature difference between the cold surface and the hot surface; and A is the area of ​​the cross-section of the aerogel through which heat passes.

6. The method for optimizing photothermal performance based on aerogel microstructure according to claim 1, characterized in that: In S5, the pore distribution and particle size of the aerogel are adjusted to optimize its solar radiation extinction coefficient and thermal conductivity.

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