A Mass Transfer Model for Simulating Voc Sorption on Building Materials

The sorption of VOCs by different building materials can significantly affect VOC concentrations in indoor environments. In this paper, a new model has been developed for simulating VOC sorption and desorption rates of homogeneous building materials with constant diffusion coefficients and material-air partition coefficients. The model analytically solves the VOC sorption rate at the material-air interface. It can be used as a “wall function” in combination with more complex gas-phase models that account for non-uniform mixing to predict sorption process. It can also be used in conjunction with broader indoor air quality studies to simulate VOC exposure in buildings. Key word index: Numerical model, indoor air quality, diffusion coefficient, partition coefficient, environmental chamber, gypsum board. Nomenclature Ca air phase VOC concentration [mg m] Cad adsorbed VOC concentration on the material surface [mg m] Cm VOC concentration in the material film [mg m] Da VOC diffusion coefficient in the air [m s] Dm VOC diffusion coefficient in the material [m s] gi component i of the gravitation vector [m s] Kl Langmuir sorption coefficient [-] Kma material-air partition coefficient [-] Lm thickness of the sorption material [m] M maximum number of roots for sorption Mw molecular weight of the compound [g mol] P VOC vapor pressure [mmHg] Pa air pressure [Pa] Pr Prandtl number q VOC sorption rate [mg ms] Q VOC emission or sorption rate in the Laplace domain s Laplace operator Sc VOC Schmidt number Sφ source term for φ T absolute temperature [K] * Corresponding author. Tel.: +305-284-3456; fax: +305-284-3492. E-mail address: [email protected] Yang, X., Chen, Q., Zeng, J., Zhang, J.S., and Shaw, C.Y. 2001. “A mass transfer model for simulating VOC sorption on building materials,” Atmospheric Environment, 35(7), 1291-1299.