Study On The Emission Mass Transfer Characteristics Of Pollutants From Materials In Vehicle And Indoor Environment

Since the new century, the automotive and construction industries in China have made great progress, which facilitates people’s daily lives but brings serious air pollution problems as well. The volatile organic compounds(VOC) emitted from materials in vehicle and indoor environment is treated as one of the main reasons causing poor air quality. Researches have shown that the emission behaviors are characterized by three key parameters, i.e., the initial emittable concentration(C0), the diffusion coefficient(Dm) and the partition coefficient(K). Determination of the key parameters is the foundation for emission prediction as well as for exposure evaluation. At present, the rapid determination method to the emission key parameters is lacking and the impacts of environmental factors such as temperature and relative humidity on the above parameters are not very clear, which make it difficult to effectively predict and control the emission characteristics of VOC. This thesis studied the addressed problems and the main academic contributions are as follows:Firstly, we develop an analytical model for VOC emission in ventilated chamber and propose a novel method based on the concentration trajectory to simultaneously determine C0 and Dm. For this method, an initial K value is pre-assumed, and then by measuring the concentration trajectory in the chamber and performing linear curve fitting, C0 and Dm can be obtained from the slope and intercept of the regression results. Experiments are taken to determine the key parameters of 7 VOCs emitted from one typical vehicular material and the result indicated that this method has a relatively high accuracy.Secondly, the effect law of environmental factors(temperature, relative humility) have on the emission characteristics of VOC from materials is studied. The result indicates that for the 7 VOCs tested, the values of C0 and Dm increase with the increase of temperature. When the temperature increases from 35℃ to 50℃, the values of C0 and Dm increase by 41.9% and 26.4%. But the impact of the relative humility on VOC emission is different. When the relative humility increases from 50% to 80%, the values of C0 increases but the values of Dm have a reduction.Finally, a correlation between the steady state cabin VOC concentration(C) and temperature(T) as well as ventilation rate(Q) is derived. The result indicates that when Q remains constant, the logarithm of C/T0.75 is in a linear relationship with the reciprocal of T; while when T remains constant, the logarithm of C/T0.75 is in a linear relationship with the logarithm of Q. By the experimental data in the literature the effectiveness of this developed relationship is validated. Once the parameters in the derived correlations are determined, the correlations can then be applied to predict the VOC concentrations under certain temperature or ventilation rate conditions.