Research On Indoor Formaldehyde Pollution And Thermal Comfort Of Bus Cabins In Plateau City

Yunnan is a major tourism province,and the city bus is one of the main means of transportation to transport tourists and passengers;The solar radiation of plateau city is large,and the ultraviolet radiation is strong,which has a great impact on indoor environment of bus cabins.Cabin air pollution and thermal comfort are related to the indoor air quality of buses and the health of drivers and passengers.It is of great practical significance to study the indoor formaldehyde pollution and thermal comfort of bus cabins in plateau cities.According to the detection standard on vehicle indoor air pollution of China,the indoor air environment in 35 bus cabins operated in summer was measured on the spot.The measurement parameters included formaldehyde concentration,air temperature,relative humidity and air volume.In terms of the air quality standard of China,Japan and South Korea,the formaldehyde pollution was evaluated objectively,and the maximum rate over the standard control level was 25.7%.According to the thermal comfort requirements of ASHRAE standard 55-2017,with or without solar radiation,the thermal comfort of six cases,including three behaviors such as driver driving,passenger sitting in silence and passenger relying,is calculated.When there is solar radiation,the cabin is hot,and the maximum temperature to be reduced is 17.5 ? if the optimal comfort is achieved through air conditioning.According to the actual driving environment of plateau city buses,a real bus model for flow and heat transfer calculation was established,and the mesh separation and mesh independence of the model were verified.The influence of solar radiation and human model on the flow and heat transfer in a bus was considered,and the convergence of numerical simulation was monitored and analyzed.In terms of the calculation model by using FLUENT software,with 10 kinds of operating conditions such as different speed,temperature and angle of air supply,the distribution characteristics and differences of velocity field,temperature field and formaldehyde pollution concentration in bus cabins were researched.The region size of each working condition,where the formaldehyde pollution level exceeds the standard control level,was compared,and the advantages and disadvantages of different air supply schemes were evaluated using the contaminant removal efficiency index.The UDF file was written in C language to solve the thermal comfort evaluation index of PMV-PPD/PD,and the research on thermal comfort of human body in bus cabins with different speeds and temperature conditions of air supply were achieved.Finally,the validity and reliability of the model are verified by comparing the measured data with the simulation results.In this paper,through the field measurement and CFD numerical simulation technology,the present status of formaldehyde pollution in bus cabins in plateau cities and the distribution law of different air supply conditions on the formaldehyde pollution and thermal comfort are determined,which provides a certain reference for improving indoor air quality of coach cabins.