Experimental Study And Numerical Simulation Of Natural Convection Heat Transfer Characteristics Of Asphalt

In recent years,the rapid development of highway traffic construction has greatly promoted the development of asphalt industry.Asphalt is an important road engineering material.The production,storage,transportation and use of asphalt are accompanied by a lot of heat exchange and energy loss.At the same time,the asphalt is a non-Newtonian fluid and exhibits different rheological properties as the temperature changes.After long-distance transportation,the flow and thermal conductivity of asphalt become worse along with the lower temperature.While the subsequent heating process will have a direct impact on asphalt physical properties and energy consumption.Therefore,it is of great significance to study the heat transfer characteristics of asphalt and optimize the design of asphalt transportation and heating equipment.Taking non-Newtonian fluid asphalt as the research object,this paper analyzes the heat transfer characteristics of natural convection process in a finite space by means of theoretical analysis,experimental research and numerical simulation.Then the design of the heating system has been optimized.The main research work and results are as follows:1.Make the theoretical calculations on the heat transfer process by electric heating and fire tube heating.Then implement an experiment of heating on a small-scale asphalt tank by electric radiant tubes.By analyzing the temperature distribution in the experiment,the heat transfer characteristics of asphalt is obtained:the fluidity is poor at low temperature,and the heating process is slow.When the temperature exceeds 60?,the natural convection becomes intense.Ra increased slowly at first and then increased rapidly,while the Nu increased linearly.The effect of viscosity on the heat transfer is also analyzed:based on the experimental data,an empirical criterion expression of Nu under the natural convection of asphalt is given.2.Establish the numerical model of the experiment by Fluent software,and make the comparison between simulation and experimental results,and then do the numerical model correction.In this paper,the variable viscosity method is proposed to simulate the natural convection process of asphalt.The specific approach is using UDF to supplement the viscosity of asphalt with temperature change.The results show that the Nu deviation between the experimental and simulated is small,and the temperature field gets good agreement as well.Therefore the model and simulation method are got verified.3.Optimize the fire pipe structure in the asphalt tank by using the Matlab genetic algorithm.Compared with the original 8-root canal model,the heating time of the 5-canal scheme is 8.29h shorter.The optimization method and results of fire pipe plays an equally significance role to other existing asphalt heating methods.