| With the progress of urbanization,artificial underlying surfaces such as hardened road surfaces have greatly enhanced the city’s heat absorption and heat storage capacity,and have also deteriorated the urban thermal environment.Currently,there are many roads that utilize high reflectivity or water permeability,which are some technical applications to alleviate the urban heat island effect,but most of the existing pavements still use traditional paving materials.Therefore,the most direct and effective way to improve the present road thermal environment is immediate water-spraying.Due to the lack of basic research,the application of the technology of hardened road surface water cooling technology still lacks specific technical guidance.Thus,this paper explores the energy balance and heat and moisture migration mechanism under the condition of hardened road surface water-spraying.Based on the thermal environment research and evaluation of the advantages and disadvantages of the water-spraying scheme,it aims to provide a scientific basis for the specific implementation and application of the water cooling technology.In this paper,the distribution and transfer mechanism of heat and moisture in asphalt pavement system in hot and humid zones are explored through experimental experiments.The variation rules under different water-spraying schemes are preliminarily obtained.Then the thermal-wet coupling simulation method based on COMSOL Multiphysics is constructed and its reliability is verified.Finally,through simulation,the variation law of road surface thermal environment under different watering methods and watering timing is explored,and optimized watering strategies are proposed.The main research and findings of the paper are as follows:(1)According to the relevant road pavement standards,the pavement test boxes are made to measure the temperature and water content of the surface and internal layers under the action of water-spraying within one day.The results show that the lowest temperature that can be reached by the water spray is the most relevant to the long-wave radiation and the total solar radiation intensity,and the appearance time is mostly 10~20 minutes after watering.The average surface temperature after watering is reduced by 5.13°C~8.53°C,and the average temperature difference with air is reduced to 0.43°C~7.42°C.The surface temperature is lower than the air temperature after the period of 16pm to 17pm.(2)Based on the software COMSOL Multiphysics,a numerical simulation method for road heat and moisture transfer under the action of water spray is constructed.The software physical field interface and boundary conditions are corrected by the relevant physical equations.The spraying and non-spraying conditions are selected for simulation,considering the hourly and minute-by-minute meteorological parameters and comparing with the measured results.The results show that the simulated values and the measured values have good consistency and similarity,and the root mean square error is within 2°C.(3)Based on the typical summer weather data in summer,the influence of different water spray methods on the road thermal environment is analyzed.The results show that there is a maximum critical water volume at a certain water-spraying interval.For example,the interval is 45 minutes corresponding to 0.4kg/m~2,and the continuous increase of water volume will not significantly enhance the cooling effect.After stopping the watering,the residual cooling effect can be maintained for 1~2 hours.When the water-spraying method is adjusted according to a certain combination of the water-spraying interval and water volume,the way of increasing the amount of sprayed water has a better cooling effect than the method of reducing the water-spraying interval.This paper is of great significance to improve the technical system of road water cooling and cooling and alleviate the urban heat island effect. |
