Coupled heat and formaldehyde migration in dry porous building materials

Abstract

Due to a lack of accurate description of the coupled heat and formaldehyde migration in dry porous building materials, the characteristics of the heat and mass transfer have not been fully revealed. An improved model of coupled heat and formaldehyde migration is developed and analyzed to investigate the transport features in dry porous building materials. Based on the theory of non-equilibrium thermodynamics and molecular kinetics, the mechanisms of the heat and formaldehyde migration process in dry porous building materials are discussed. The effect of temperature on the transfer coefficients, such as the infiltration coefficient, migration coefficient, apparent thermal conductivity and thermal infiltration coefficient is also presented. The coupled heat and formaldehyde migration process in an ordinary particle board is simulated using a finite difference method. The simulated results indicate that the effect of temperature on the formaldehyde migration in dry porous building materials is obvious. In contrast to the formaldehyde diffusion process, the heat transfer process in the particle board approaches to a steady state more quickly. The formaldehyde emission levels from the particle board in the early stage increase with the increasing temperature gradient, while the formaldehyde concentration remained in the particle board decreases with the increasing temperature gradient. The peak concentration in the chamber increases with the increase of the initial formaldehyde concentration. The reasonability of the present model is verified by the similarity between the numerical results and the experimental data available in the literatures.