Research And Experiment On Hot Air Heating Process Of Asphalt Pavement

The heating of asphalt pavement is the key link of in place heat regeneration,which has an important impact on the construction speed and quality of in place heat regeneration of asphalt pavement.The characteristics of controllable hot air heating power make it widely used in the heating of asphalt pavement regeneration.In order to further accurately control the heating power and improve the heating quality of asphalt pavement,it is necessary to study the heat transfer characteristics and heating uniformity of hot air heating asphalt pavement.Based on the school enterprise cooperation project "Research on hot air heating technology of asphalt pavement",based on the enhanced convective heat transfer theory of hot air heating,this paper has studied the factors affecting the heat transfer characteristics and heating uniformity of hot air heating asphalt pavement.The fluid structure coupling model of asphalt pavement heated by hot air from a circular single nozzle was established.The heat transfer process between hot air and asphalt pavement under different wind speed and temperature conditions was simulated by FLUENT software.The hot air heating simulation test device and test device for asphalt pavement were developed,and the heat transfer characteristics of asphalt pavement heated by hot air from a single nozzle were studied.The fluid structure coupling model of asphalt pavement heated by hot air from hot air heating wall with round nozzles arranged in triangle was established.The effects of nozzle spacing,nozzle diameter and height from the ground on the heating uniformity of asphalt pavement heated by hot air were studied by software simulation.The results show that: wind speed and wind temperature affect the heat exchange between hot air and asphalt pavement,and wind speed affects the heat exchange between hot air and asphalt pavement by changing the heat exchange coefficient.The higher the wind speed is,the greater the heat exchange is.After the wind speed exceeds 10m/s,the increase rate of heat exchange with the increase of hot air speed becomes slower,and the heating efficiency decreases.Heating the old asphalt pavement with the wind speed of 10 m / s can ensure the high utilization rate of hot air energy.By increasing the energy contained in the hot air,the heat exchange capacity of the thermal boundary layer is enhanced,so as to increase the heat exchange between the hot air and asphalt pavement.The larger the nozzle diameter is,the stronger the heat transfer ability is for the hot air heater with triangular arrangement of nozzles,but the heating uniformity becomes worse with the increase of nozzle diameter.When the nozzle spacing is 60 mm,70mm,80 mm,90mm and 100 mm respectively,the smaller the nozzle diameter is,the better the heating uniformity is when the nozzle spacing is 10 mm,20mm and30 m respectively.As the distance from the ground increases,the heat transfer between the hot air and the road surface decreases.The experimental value of heat flux between hot air and asphalt pavement is close to the simulation value,and the change trend is consistent,which shows that the simulation results can provide reference for the adjustment of hot air parameters and machine parameters in actual engineering construction.