Experimental Study And Numerical Simulation Of Heat Transfer And Flow Characteristics Of Asphalt

As a by-product of the crude oil refining process,asphalt is an important road engineering material.The general production area is far away from the user's location,and the asphalt needs to undergo a long transportation process.Asphalt is a non-Newtonian fluid with a large difference in morphology at different temperatures.When the transportation time is long,the heat dissipation to the external environment causes the temperature of the asphalt to decrease,and the asphalt in the tanker condenses into a solid-state.At this time,the flowability of the asphalt deteriorates and cannot be directly unloaded,and it is required to have a certain fluidity before the unloading can be performed.Different from the general Newtonian fluid,the viscosity of asphalt will change drastically during heating,and it has more complicated heat transfer characteristics.Studying the heat transfer and flow characteristics of asphalt are of great significance for the transportation,heating,and use of asphalt.In this paper,70#road asphalt is taken as the research object,and the heating process in the tanker is studied.The main research work and results are as follows:1.Asphalt is a non-Newtonian fluid,the physical properties of asphalt were analyzed and the important influencing factors of asphalt viscosity were introduced in detail.The relationship between viscosity and temperature and the relationship of viscosity at different shear rates were obtained.At the same time,the existing main heating methods of asphalt are compared and analyzed in terms of heat transfer characteristics and economy.2.The electric heating experiment of asphalt in the tank was designed and the experimental results were analyzed.The heat transfer process characteristics of asphalt were obtained.The natural convection phenomenon was very weak at the beginning of heating process of high viscosity asphalt.With the increase of asphalt temperature,the viscosity of asphalt decreased,and the natural convection increased.The effect of heat source on the heating process was studied when it was located in the middle part of the space.The results showed that the heating process could not be accelerated by arranging heat source in the middle of the tank.The influence of the number of tube layouts at the bottom of the tank on the heating process is studied,A smaller number of heating tubes can be used at the same power.3.The Fluent numerical simulation software was used to simulate the unsteady heating process of asphalt in the tank.A new asphalt viscosity-temperature model was used,and the obtained simulation results were compared with the experimental results:during the heating process,the temperature distribution of the asphalt obtained by the experiment and the simulation is the same,and the deviation of the Nu number is small;the difference between the Ra number of the experiment and the simulation is small.The flow state is the same throughout the heating process.4.The electric heating system of GL70 asphalt tank is designed and the heating process of asphalt in tank is numerically simulated by using the new simulation method.The temperature distribution of asphalt and the completion time of heating were obtained.The calculation results provided a reference for the design of electric heating system of asphalt tanker.