热风加热沥青路面冲击射流共轭传热特性

Conjugate heat-transfer characteristics of impinging jet for hot air heating asphalt pavement

为提高热风加热沥青路面的就地再生加热效果,基于热风冲击射流对流换热和沥青路面内部导热的共轭传热过程,建立了热风加热沥青路面的冲击射流共轭传热理论模型,选取有限容积法得到了共轭传热模型的通用离散方程,采用压力-速度耦合半隐式算法(semi-implicit method for pressure linked equations,SIMPLE)获得了整个求解域内温度场分布,选取平均热流密度和平均换热系数反映沥青路面加热效果,通过正交试验研究了热风出口速度和热风出口温度对路面加热效果的影响程度。仿真和试验结果表明:理论计算与实验温度场分布趋势吻合度高,两者平均误差为8.4%;平均热流密度和平均换热系数在加热初期均从最大值急剧下降,而后下降幅度逐渐减小趋于平衡,两者的仿真计算与实验结果趋势相同,平均误差分别为6.4%和7.8%;热风出口速度和热风出口温度对平均热流密度均有显著影响,热风出口速度对平均换热系数有显著影响,热风出口温度对平均换热系数的影响相较于平均热流密度指标表现为不显著。研究结果为后续沥青路面就地热再生热风加热温度控制和加热器设计提供了理论依据。

To improve the heating effect of hot air heating on asphalt pavement during hot in-place recycling(HIR),the hot-air impinging jet convective heat transfer and the heat conduction were regarded as conjugate heat-transfer process,and a theoretical model of conjugate heat-transfer for impinging jet for hot air heating asphalt pavement was established.Based on the finite volume method,the general discrete equation of conjugate heat-transfer model was presented.The temperature field distribution in the whole solution domain was obtained by using the pressure/velocity coupled semi-implicit algorithm(SIMPLE).The average heat flux and average heat-transfer coefficient were selected to reflect the heating effect on the asphalt pavement.The influence degree of hot-air outlet velocity and hot-air outlet temperature on heating effect was studied by orthogonal experiments.The simulation and experimental results show that there is a high degree of agreement between the theoretical calculation and the experiment temperature distribution,with an average error of 8.4%.Both average heat flux and average heat-transfer coefficient decrease sharply from the maximum value at the beginning of heating,and then gradually decrease to equilibrium.The simulation and the experiment of both average heat flux and average heat-transfer coefficient have the same trend,and the average errors are 6.4% and 7.8%,respectively.Both the velocity and the temperature of hot-air outlet have a significant effect on the average heat flux,while the hot-air outlet velocity has a significant effect on the average heat-transfer coefficient.However,the influence of hot-air outlet temperature on the average heat-transfer coefficient is relatively insignificant compared to the average heat flux.The research results provide a theoretical basis for temperature control and the design of hot-air heating equipment during HIR.