Method for determining phase change material category and use layer for asphalt pavement

Abstract

The application provides a method for determining the type and use layer of a phase change material for asphalt pavement, and belongs to the field of phase change asphalt pavement. The method combines the temperature field of the asphalt pavement and the thermal physical parameters of the composite shaped phase change material, calculates the phase change completion degree and the absolute temperature difference of the phase change material, preliminarily screens the phase change material, calculates the cooling contribution rate, and uses the cooling contribution rate to represent the effect of the phase change material on each layer of the pavement. The method for determining the molecular weight of the phase change material for asphalt pavement and the use layer can reasonably preliminarily screen the phase change material, and scientifically add the phase change material to the layer of the asphalt pavement.

Description

Technical Field

[0001] This invention belongs to the field of phase change asphalt pavement, specifically relating to a method for determining the type and application layer of phase change material for asphalt pavement. Background Technology

[0002] Asphalt pavements are widely used due to their advantages such as driving safety, high smoothness, and ease of maintenance. However, because asphalt materials are temperature sensitive, high temperatures can lead to thermal stability problems such as rutting, shoving, and rutting, which reduce the durability and driving stability of asphalt pavements and increase the risk of traffic accidents. At the same time, the radiant energy absorbed by asphalt pavements accumulates and is released into the surrounding environment, causing near-surface air temperatures to rise, exacerbating the urban heat island effect, increasing building energy consumption in urban areas, and reducing pedestrian comfort.

[0003] To mitigate the negative impacts of high-temperature asphalt pavements, researchers both domestically and internationally have adopted several main approaches, including permeable pavements, water-retaining pavements, thermally resistive pavements, and heat-reflective coatings. While these methods have been proven effective in reducing heat, they also have limitations. For instance, permeable and water-retaining asphalt pavements have relatively low mechanical properties and require sufficient moisture retention to dissipate heat through evaporation. Thermally resistive asphalt pavements cause heat to accumulate in the surface layer, generating longitudinal temperature stress and reducing pavement performance. Heat-reflective coatings reduce skid resistance, increase traffic risks, and also present durability issues such as peeling and cracking. Therefore, finding an active and efficient method for cooling pavements has become urgent.

[0004] In recent years, the emergence of phase change materials (PCMs) has offered the possibility of actively reducing high temperatures on pavements. The application of PCMs in building insulation is relatively mature, mainly concentrated in cement concrete structures and gypsum board and other building insulation materials. They regulate temperature by absorbing or releasing heat through phase changes (solid, liquid, and gas phases). However, research on incorporating PCMs into asphalt concrete to reduce high temperatures in asphalt pavements is still in the exploratory stage. Currently, research on incorporating PCMs into asphalt pavements lacks a theoretical basis, and the internal temperature gradient generated in asphalt pavements due to the lag in temperature transfer requires further analysis regarding the selection of phase change temperatures for PCMs used in pavements.

[0005] Therefore, this invention provides a method for determining the type and application layer of phase change material for asphalt pavement. By screening phase change materials and calculating their cooling contribution rate, the type and application layer of phase change materials can be determined more rationally. Summary of the Invention

[0006] To address the aforementioned shortcomings in existing technologies, this invention provides a method for determining the type and application layer of phase change materials (PCMs) for asphalt pavements. By calculating the completion degree of phase change and the absolute temperature difference to screen PCMs and calculating their contribution to cooling, the method can more rationally determine the type of PCM and the layer in which PCMs are incorporated.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] This solution provides a method for determining the type and application layer of phase change material for asphalt pavement, including the following steps:

[0009] S1. Using ANSYS Fluent software, an asphalt pavement structure model was established and the model network was divided. Boundary conditions of the asphalt pavement model were set, and the temperature field and longitudinal temperature gradient of the asphalt pavement under typical summer high temperature weather were simulated.

[0010] S2. Prepare composite shaped phase change material samples and use thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) to test the prepared phase change material samples according to standard procedures to obtain the thermal stability and related thermal performance parameters of the composite shaped phase change material.

[0011] S3. Based on the temperature field of asphalt pavement and the thermal performance parameters of composite shape-stabilized phase change materials, the phase change completion degree and absolute temperature difference formulas are used to calculate the phase change completion degree and absolute temperature difference of phase change materials with different molecular weights at different depths of the pavement surface layer. Combining these two indicators, composite shape-stabilized phase change materials with high phase change completion degree and small absolute temperature difference in each layer of asphalt pavement are selected.

[0012] S4. Based on the preliminary screening of phase change materials, confirm the layer in which the phase change materials are used in the phase change asphalt pavement, and combine the physical property parameters of the composite phase change asphalt pavement to simulate the relationship curve between the road surface cooling rate and depth.

[0013] S5. Based on the curve of the relationship between the cooling amplitude and depth of the road surface, obtain the contribution rate of the asphalt concrete in the layer where phase change material is used to the cooling of the road surface layer, and characterize the effect of phase change material on each layer of the road surface.

[0014] Further, step S1 includes the following steps:

[0015] S101. Use ANASYS software to build an asphalt road structure model and perform mesh generation to obtain a high-quality and high-quantity mesh.

[0016] S102. Define the physical property parameters of each layer of the road surface model, including density, specific heat capacity and thermal conductivity.

[0017] S103. Define the boundary conditions of the model, and then simulate the temperature field and longitudinal temperature gradient of asphalt pavement under typical summer high temperature weather.

[0018] Further, step S3 includes the following steps:

[0019] S301. Calculate the phase change completion degree according to the formula, and determine the phase change completion degree of the phase change material at different depths of the road surface layer.

[0020] S302. Calculate the absolute temperature difference according to the formula to determine the absolute temperature difference of the phase change material at the midpoint of each road surface layer.

[0021] S303. Based on the phase change completion degree and absolute temperature difference, composite shape-stabilized phase change materials with high phase change completion degree and adaptability in various layers of asphalt pavement are selected.

[0022] Furthermore, the formula expression for the phase transition completion degree in step S302 is as follows:

[0023]

[0024] Among them, P c T represents the degree of phase transition completion. peak T represents the peak temperature of the asphalt pavement. start T represents the phase transition initiation temperature. end This indicates the temperature at which the phase transition ends.

[0025] Furthermore, the formula for the absolute temperature difference in step S303 is as follows:

[0026] T ad =|T peak -T phase |

[0027] Among them, T ad T represents the absolute temperature difference. peak T represents the peak temperature of the asphalt pavement. phase This indicates the peak phase transition temperature of the phase change material.

[0028] Furthermore, the formula for the phase transition contribution rate in step S5 is as follows:

[0029]

[0030] S 总 =∑S i

[0031] Among them, C i S represents the contribution rate to cooling. i S represents the temperature drop magnitude of the corresponding stratum and the area enclosed by the horizontal axis. 总This represents the total area of ​​the top, middle, and bottom layers.

[0032] The beneficial effects of this invention are:

[0033] (1) This invention uses the phase change completion degree and temperature absolute formula to conduct preliminary screening of phase change materials, which can supplement the theoretical basis for the selection of phase change materials for asphalt pavement.

[0034] (2) This invention quantitatively describes the effect of phase change materials by plotting the relationship curve between the cooling range and depth of the road surface and the contribution rate of phase change materials to each road surface layer.

[0035] (3) The method for determining the type and application layer of phase change material for asphalt pavement proposed in this invention can help determine the type of composite shape-fixed phase change material and add it to the road pavement layer in a scientific and reasonable manner. Attached Figure Description

[0036] Figure 1 This is a flowchart of the method of the present invention.

[0037] Figure 2 This embodiment shows a schematic diagram of the asphalt pavement structure and its grid division.

[0038] Figure 3 Thermogravimetric analysis results of PEG6000 / SiO2 in this embodiment.

[0039] Figure 4 The PEG / SiO2 heating DSC curve in this embodiment.

[0040] Figure 5 The degree of PEG / SiO2 phase transformation completion at the midpoint of each surface layer of the road in this embodiment.

[0041] Figure 6 The absolute temperature difference in this embodiment.

[0042] Figure 7 The relationship between the cooling range and depth of PEG6000 / SiO2 in this embodiment. Detailed Implementation

[0043] The present invention is described in detail with reference to specific embodiments to enable those skilled in the art to understand the invention. However, it should be understood that the invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0044] Example

[0045] This invention provides a method for determining the type and application layer of phase change material for asphalt pavement, the implementation method of which is as follows:

[0046] S1. Using ANSYS Fluent software, an asphalt pavement structure model was established and the model network was divided. Boundary conditions of the asphalt pavement model were set, and the temperature field and longitudinal temperature gradient of the asphalt pavement under typical summer high-temperature weather were simulated. The method is as follows:

[0047] S101. Use ANASYS software to build an asphalt road structure model and perform mesh generation to obtain a high-quality and high-quantity mesh.

[0048] S102. Define the physical property parameters of each layer of the road surface model, including density, specific heat capacity and thermal conductivity.

[0049] S103. Define the boundary conditions of the model, and then simulate the temperature field and longitudinal temperature gradient of asphalt pavement under typical summer high temperature weather.

[0050] In this embodiment, ANSYS Fluent software is used to build an asphalt road structure model and perform mesh generation, such as... Figure 2 As shown.

[0051] The simulation obtained the temperature field and longitudinal temperature gradient of asphalt pavement under typical summer high-temperature weather. The schematic diagram of the asphalt pavement structure and the mesh division are shown below. Figure 2 As shown in Table 1, the physical properties of each layer of the road pavement model are defined. The boundary conditions of the model are defined, mainly including convective heat transfer and radiative heat transfer, thereby simulating the temperature field and longitudinal temperature gradient of the asphalt pavement under typical summer high-temperature weather.

[0052] Table 1 Thermophysical properties of asphalt concrete materials

[0053]

[0054] S2. Prepare composite shaped phase change material samples and use thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) to test the prepared phase change material samples according to standard procedures to obtain the thermal stability and related thermal performance parameters of the composite shaped phase change material.

[0055] In this embodiment, the composite qualitative phase change material is selected as PEG / SiO2, and the PEG / SiO2 composite qualitative phase change material is prepared according to the sol-gel method, wherein the SiO2 content in the SiO2 sol is 30%, and the PEG:SiO2 ratio is 7:3. TG and DSC tests were performed on the composite qualitative phase change materials of various molecular weights to obtain... Figure 3 The thermogravimetric analysis curves shown are Figure 4The heating DSC curves shown are used to obtain the thermal stability and related thermal performance parameters of the composite shape-stabilized phase change material.

[0056] S3. Based on the temperature field of asphalt pavement and the thermal performance parameters of composite shape-stabilized phase change materials, the phase change completion degree and absolute temperature difference formulas are used to calculate the phase change completion degree and absolute temperature difference of phase change materials with different molecular weights at different depths in the pavement surface layer. Combining these two indicators, composite shape-stabilized phase change materials with high phase change completion degree and small absolute temperature difference in various layers of asphalt pavement are selected. The implementation method is as follows:

[0057] S301. Calculate the phase change completion degree according to the formula, and determine the phase change completion degree of the phase change material at different depths of the road surface layer.

[0058] S302. Calculate the absolute temperature difference according to the formula to determine the absolute temperature difference of the phase change material at the midpoint of each road surface layer.

[0059] S303. Based on the phase transformation completion degree and absolute temperature difference, composite shape-stabilized phase change materials with high phase transformation completion degree and small absolute temperature difference in each layer of asphalt pavement are selected.

[0060] In this embodiment, the thermal stability and related thermal performance parameters of the composite shape-stabilized phase change material are first combined with the temperature field data of the asphalt pavement. Then, the phase change completion formula is used. The phase change completion degree of the phase change material in the layer where it is used in the road pavement is calculated, and the results are obtained. Figure 5 The degree of PEG / SiO2 phase transition completion at the midpoint of each surface layer of the road surface is shown, and then calculated using the absolute temperature difference formula T. ad =|T peak -T phase | Calculate the absolute temperature difference of the phase change material at the midpoint of each pavement layer to obtain Figure 6 The absolute temperature difference shown indicates that PEG / SiO2 with molecular weights of 8000, 6000, and 4000 has a higher compatibility with the surface layer of the road, PEG / SiO2 with molecular weights of 2000 and 1500 has a higher compatibility with the middle layer of the road, and PEG / SiO2 with molecular weights of 1500 and 1000 has a higher compatibility with the lower layer of the road.

[0061] S4. Based on the preliminary screening of phase change materials, confirm the layer in which the phase change materials are used in the phase change asphalt pavement, and combine the physical property parameters of the composite phase change asphalt pavement to simulate the relationship curve between the road surface cooling rate and depth.

[0062] In this embodiment, a PEG / SiO2 phase change material with a molecular weight of 6000 was selected. The layer in the phase change asphalt pavement where the phase change material is used was confirmed to be the top layer. The relationship between the road surface cooling rate and depth was simulated. Figure 7 .

[0063] S5. Based on the curve of the relationship between the cooling amplitude and depth of the road surface, obtain the contribution rate of the asphalt concrete in the layer where phase change material is used to the cooling of the road surface layer, and characterize the effect of phase change material on each layer of the road surface.

[0064] In this embodiment, the relationship between the cooling amplitude and depth of the road surface is analyzed using the cooling contribution rate calculation formula. and S 总 =∑S i The phase change material with a molecular weight of 6000, when used in the surface layer of road pavement, contributed 31.4%, 39.3%, and 29.3% to the cooling of each surface layer, respectively. The results show that when the phase change material is added to the surface layer, the middle layer contributes the most to the cooling, followed by the surface layer, while the bottom layer contributes the least.

Claims

1. A method for determining the type and application layer of phase change material for asphalt pavement, characterized in that, Includes the following steps: S1. Using ANSYS Fluent software, the temperature field and longitudinal temperature gradient of asphalt pavement under typical summer high temperature weather were simulated and obtained. S2. Thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) were used to test the phase change material samples to obtain the thermal stability and related thermal performance parameters of the composite shaped phase change material. S3. Based on the temperature field of asphalt pavement and the thermal performance parameters of composite shape-stabilized phase change materials, the phase change completion degree and absolute temperature difference formula are used to calculate the phase change completion degree and absolute temperature difference of phase change materials with different molecular weights at different depths of the pavement surface layer. Combining these two indicators, composite shape-stabilized phase change materials with high phase change completion degree and small absolute temperature difference in each layer of asphalt pavement are selected. S4. Based on the preliminary screening of phase change materials, confirm the layer in which the phase change materials are used in the phase change asphalt pavement, and combine the physical property parameters of the composite phase change asphalt pavement to simulate the relationship curve between the cooling range and depth of the road surface. S5. Based on the curve of the relationship between the cooling amplitude and depth of the road surface, obtain the contribution rate of the asphalt concrete in the layer where phase change material is used to the cooling of the road surface layer, and characterize the effect of phase change material on each layer of the road surface.

2. The method for determining the type and application layer of phase change material for asphalt pavement according to claim 1, characterized in that, The formula for the phase transition completion degree in step S3 is: Among them, P c T represents the degree of phase transition completion. peak T represents the peak temperature of the asphalt pavement. start T represents the phase transition initiation temperature. end This indicates the temperature at which the phase transition ends.

3. The method for determining the type and application layer of phase change material for asphalt pavement according to claim 1, characterized in that, The formula for the absolute temperature difference in step S3 is: T ad =|T peak -T phase | Among them, T ad T represents the absolute temperature difference. peak T represents the peak temperature of the asphalt pavement. phase This indicates the peak phase transition temperature of the phase change material.

4. The method for determining the type and application layer of phase change material for asphalt pavement according to claim 1, characterized in that, The cooling contribution rate in step S5 is determined by... Calculate, where, C i S represents the contribution rate to cooling. i This represents the temperature drop magnitude of the corresponding stratum and the area enclosed by the horizontal axis. This represents the total area of ​​the top, middle, and bottom layers.

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