| Asphalt is an important organic cementing material used in road construction.Because it is a high-viscosity non-Newtonian fluid,it needs to be heated from 80℃ to 150℃ in the mixing station to be applied to the production of asphalt concrete.The existing asphalt heating technology in the industry consumes a lot of fossil energy every year.,emits a lot of polluting gases such as CO2,SOx and NOx.At present,the world is in a period of lack of energy supply,which brings severe challenges to the asphalt concrete production industry.In order to solve this problem,this paper proposes to use trough solar collectors as asphalt heating heat sources,which greatly reduces the use of fossil energy and realizes the emission production of asphalt heating,which not only meets the new requirements of energy conservation and emission reduction under the current situation,but also my country’s development.Important practice of solar energy in industrial thermal utilization.The law that the thermal efficiency of trough solar collectors is affected by the meteorological conditions in Zhengzhou is carried out.On this basis,the optimal design of the asphalt heating tank is completed,and the relevant experiments and numerical simulation analysis are carried out.The main research work and contents of this paper are as follows:(1)The relationship between the angle of solar radiation was studied,the geometric,optical and heat transfer modeling of the trough solar collector was completed,and the heat collection efficiency model was obtained.In order to quickly complete the calculation of the heat collection efficiency and heat loss,a program was compiled by using Matlab software,and it was obtained that the optical parameters and the vacuum degree of the glass sleeve had a great influence on the optical efficiency of the trough solar collector and the loss of the heat unit length of the collector.The study found that the solar radiation was the strongest in the 1.5h period before and after 12 o’clock,and it was necessary to make full use of the solar energy during this period.(2)A trough solar collector system was built,and a concentrating heat collection experiment was carried out in Zhengzhou,and the influence of different meteorological conditions on the collector efficiency was studied.The heat collection efficiency decreases accordingly with the decrease of the ambient temperature;when the solar radiation intensity increases from 229 W·m-2,the heat collection efficiency increases with the increase of the solar radiation intensity.The thermal efficiency of the collector reaches a peak around 700 W·m-2,but with the increase of solar radiation intensity,the output useful energy of the collector continues to increase;the ambient wind speed is 0.5～8.3 m·s-1,and the heat collection efficiency varies between 0.58～0.65.With the increase of ambient wind speed,the heat collection efficiency will decrease accordingly.(3)Based on the MCRT ray tracing method,Soltrace software is used to calculate the photothermal data,and then the actual heating capacity of PTSC is determined through models and experiments,the asphalt heating tank is optimized,and the trough solar heating asphalt experiment is carried out.The flow rate of the working medium is 2 m·s-1,the asphalt was heated from 80℃ to 150℃,and the required time is 3.7 hours,which meets the production time requirements of the mixing station.Four groups of mixer speed heating asphalt experiments were carried out,and the heating time decreased accordingly with the increase of the mixer speed,but this trend is unsustainable.(4)The temperature rise process of asphalt was studied by CFD method,and a threedimensional numerical heat transfer model of the asphalt heating system was established with the help of Solidworks.The asphalt heating simulation was carried out in Ansys Fluent,and the numerical simulation results were in good agreement with the experiment.Subsequently,the thermal fluid flow rates of 1.5,2.0,2.5 and 3.0 m·s-1 were simulated in Fluent,and the relationship between the Nussel number Nu and the pressure drop ΔP after the simulation was read.It is concluded that increasing the flow rate of heat transfer oil can shorten the heating time of asphalt,but the increase of the flow rate of working fluid will make the pressure drop rise rapidly.To sum up,this paper studies the law of high-efficiency heating of asphalt by trough solar energy through theory and experiments,which provides a reference for large-scale application of solar energy technology to heat asphalt. |
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