Heat transfer mechanism of microwave heating asphalt concrete based on multi-physical field

The poor thermal conductivity of traditional asphalt concrete will lead to the problems of poor temperature uniformity and small depth of microwave heating. In order to explore the factors that affect the heat transfer performance, a heat transfer model was established based on Maxwell equation and Fourier equation by numerical simulation method. The effects of electromagnetic field, material dielectric constant and heat conduction structure on the heat transfer performance of asphalt concrete during microwave heating were analyzed. The results show that the electromagnetic field is the external factor affecting the temperature increasing rate and heat transfer performance of the model during microwave heating. The larger the electromagnetic field intensity, the higher the microwave heating temperature, the more the area, and the better the temperature uniformity of the model. The TCOV(temperature coefficient of varation) of the double waveguide structure model is about 16% lower than that of the single waveguide structure model. For the internal factors, the higher the dielectric constant will increase the microwave heating rate, but the temperature uniformity will become worse. The addition of the heat conduction structure can significantly improve the heat transfer performance of the model. When the heat conduction structure is located near the microwave emission source, the temperature uniformity of the model is the best compared with that of other layout methods, and the TCOV of the model can be increased by 17.5% compared with the ordinary asphalt concrete model. In conclusion, in the case of a certain external electromagnetic field, the heat transfer performance of asphalt concrete can be improved by changing its dielectric constant and constructing a high heat conduction structure inside. © 2021, Central South University Press. All right reserved.