VOC source and sink behaviour of porous building materials: Part II effects of Reynolds number and temperature

This study theoretically investigates the impact of air velocity and temperature on the sourceand sink behaviour of porous building materials, by applying the analytical model proposedin Part I. The impact of air velocity on the source and sink behaviour was investigated forvarious levels of material properties. The Reynolds number was varied from 102 to 105,which is equivalent to an air velocity from almost stagnant to 0.34 m/s when the material is4.5 m long. The results of the extensive parametric study showed that the effect of airvelocity depends on the effective diffusion coefficient and the thickness of the porousmaterial. As the diffusion resistance of the material increases (effective diffusion coefficientdecreases and/or the thickness increases), the effect of air velocity decreases up to a certainlimit, beyond which no effect is observed.Unlike air velocity, the temperature affects material properties and transport properties likegas diffusion coefficient and kinematic viscosity of air. The effects of temperature wasinvestigated using the material properties of carpet obtained by Zhang et al. (2001) at threedifferent temperature namely 10.5, 23 and 35C. The effect of temperature was noticeable inall five VOCs considered, but the impact varied from one compound to another. The changesin the convective mass transfer coefficient relative to that of 23C are less than 5%; hence,changes in the material properties are a major contributing factor.