Mesoscopic Simulation of VOCs’ Migration in Porous Building Materials with Different Spatial Scale

Abstract

Volatile organic compounds (VOCs) emission from building materials are the main pollution sources of indoor air quality (IAQ). The migration characteristics of VOCs in porous building materials are important to control VOCs concentration level in indoor environment. In this study, we examined VOCs desorbed from matrix of building material and diffused in pore of porous building material using lattice Boltzmann method (LBM) with different spatial scale. In pore scale of porous building materials, the LBM model of gas diffusion was developed, which is based on the theory of binary mixtures proposed by Luo Lishi. The quartet structure generation set (QSGS) proposed by Wang moran is used to construct the random porous building material. The unsteady binary gas diffusion with third boundary condition in channel was simulated with this model. The results of simulation were compared with analytical solution. The effective mass diffusion coefficient of gas diffusion through random porous media was calculated in this chapter. The comparison of effective mass diffusion coefficient shows that the numerical simulation results agree with the traditional empirical model, so reliability of this model was verified. Based on the assumption of Henry law, an approach for disposing boundary conditions of adsorbed gas was proposed. The process of VOC emitted from porous media was investigated with different partition coefficient. It is concluded that transient concentration in porous media of VOC will be increased with the increase in partition coefficient. In representative elementary volume (REV) scale, the VOC emission rate of porous building material to static chamber was simulated by LBM in static chamber. VOC concentration of static chamber in emission process agrees with analytical method very well.