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Research on Multi-phase Mass Transfer Model and Characteristic Parameters of TVOC Emission from Wood

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Tutor: ShenZuo
School: Northeast Forestry University
Course: Wood Science and Technology
Keywords: Wood-based Panels,volatile organic compounds,multiphase mass transfer model,rele
CLC: TS653
Type: PhD thesis
Year:  2013
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Abstract:
Along with the enhancement of social environmental protection consciousness, more and more people pay attention to volatile organic compounds (TVOC) quality problem in indoor air. Extensive use of wood based panels indoor decorating makes them to be the main sources of TVOC. To improve economic environment in the room, the mechanism of TVOC release from Wood based panels and its influence factors must be fully understood and researched. In this paper, these questions of the common material of wood based panels in the market are discussed. The multi-phase mass transfer models for TVOC emission from Wood based panels are established, and temperature and relative humidity influence on TVOC emission from Wood based panels and their characteristic parameters are researched. The prediction models and methods for TVOC emission are also given.This article researchs in release characteristics of TVOC from wood based panels for use of indoor decorating. By using the method of theory analysis and experiment release of TVOC from wood based panels are discussed. Main research contents are as follows:1. The wood based panels TVOC release multiphase mass transfer model are establishedNotice the wood based panels for use of indoor decorating are the most common porous materials, their internal are the multiphase mixture of solid skeleton and fluids. By using Fick¡¯s law it estabishs volatile organic compounds release multiphase multidimensional mass transfer model of Wood based panels. Based on the peculiarity that wood-based panels are thin in the geometry, the multiphase multidimensional mass transfer model for the release of TVOC from wood-based panels is reduced to a one-dimensional multi-phase mass transfer model, which is solved and numerically simulated. The work adopts the domestic medium density fiberboard for some plant to perform multiphase mass transfer model verification.2. Providing a Method to Estimate the Parameters of TVOC Release from Wood-based PanelsEstimation model for Wood based panels release parameters is established. By using two steps estimation, TVOC release parameter estimation method is given. First using integral approximation and Taylor expansion method for partial differential equations of heat conduction, it inverses the order of magnitude estimate for TVOC release charasteristics parameters of wood based panels indoor decorating including separation coefficient, initial concentration of TVOC and the mass transfer coefficient. Then, based on the TVOC release mass transfer model and the given magnitude of release parameters, The second step estimations of the release parameter including diffusion coefficient, separation coefficient, initial concentration of TVOC and the mass transfer coefficient diffusion coefficient are given by means of least square method. Of someone domestic particleboard measuring, and using the estimation method of the model, particieboard TVOC release parameter diffusion coefficient magnitude is10-9-10-11m2/s, separation coefficient magnitude is103-104. the mass transfer coefficient diffusion coefficient magnitude is10-4-103m/s. They are roughly the same order of magnitude of experience value magnitude.3. Impact of Temperature in the Research Environment on the TVOC Release From Wood-based PanelsThe particleboard PI, P2, P3and P4made by several domestic manufacturers are set as research objects, and the TVOC release from the particleboard is measured at temperatures configured atl5¡æ,20¡æ,25¡æ,30¡æand35¡æ. The separation coefficient, the mass transfer coefficient and the initial TVOC concentration of the panel are estimated at different temperatures by the estimation method for TVOC release parameters. The least squares method is used to fit the estimated values and the pattern of impact of temperature on the parameters of release characteristics is obtained.The results showed that when the temperature rises, the initial TVOC concentrations of the particleboard P1, P2, P3and P4increase significantly. The separation coefficient of particleboard P1, P2, P3and P4decreases with the rise of temperature. And those enhance the capability of the free-state TVOC in the particleboard to diffuse to the chamber. In short, the rise of temperature enhances the release of TVOC from particleboardP1, P2, P3and P4.4. Impact of Relative Humidity in the Research Environment on the TVOC Release from Wood-based PanelsThe particleboard P1, P2, P3and P4made by several domestic manufacturers are set as research objects, and the TVOC release from the particleboard is measure with relative humidity configured at30%,45%,60%and75%. The separation coefficient, the convective mass transfer coefficient and the initial TVOC concentration in the particleboard of the parameters of the release characteristics under different humidity are provided. The linear correlation analysis method is used to discuss the impact of relative humidity on the parameters of release characteristics. The results showed that when the relative humidity in the indoor environment rises, initial TVOC concentration in the particleboard increases, and the mass transfer coefficient of TVOC in the air also significantly increases, accelerating the diffusion of TVOC in the air, while the separation factor K varies with different particleboard as the humidity rises. However, in general, the release rate of TVOC in the particleboard increases with the rise of relative humidity. In the experimental results, this is shown by the rise of TVOC concentration in the same particleboard in the chamber as the relative humidity increases.5. Prediction Model for the TVOC Release from Wood-based PanelsFrom the convenient and practical point of view, the paper offers the rapid prediction model for the TVOC release from wood-based panels, and the long-term prediction model for the TVOC release from wood-based panels. The rapid prediction model using one test point is effective on the release of TVOC from wood-based panels within a short term, for example, a few days, but prone to considerable errors over long-term releases. The longer-termmodel can predict the TVOC concentration in the chamber over a longer period of time. The results as it predicts the TVOC releases from particleboard made by several domestic manufacturers are consistent with those obtained in the experiment. The prediction model for the TVOC release from wood-based panels provides ways for the forecast and control of indoor air quality and a theoretical basis for further improving indoor air quality.
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