Determining thermal physical properties of pyrolyzing New Zealand medium density fibreboard (MDF)

Abstract

For modelling the burning behaviour of New Zealand medium density fibreboard (MDF), thermal physical properties of both virgin and charred material have been experimentally investigated. An empirical equation is proposed to predict the vertical density profile along the MDF panel thickness. Then a simplified model is developed to determine the specific heat based on the experimental data obtained from differential scanning calorimetry (DSC). The measurements for thermal conductivity have been conducted using the transient plane source (TPS) method and the experimental results are compared to the literature values. Finally a set of one dimensional heat transfer experiments have been carried out to validate the proposed models. The comparison of different modelling schemes shows that a combination of the non-uniform vertical density model, the specific heat obtained using DSC and thermal conductivity model of Von Haas and Haselein gives the best predictions to the experimental results for the temperature range assessed.Compared to virgin MDF, the density distribution along the charred material is more even, leading to a 330kg/m3 local density which is comparable to the measured bulk densities of 305 and 303kg/m3. The overall volume reduction caused by shrinkage is measured as 40% vertically and 20% horizontally. Experimental investigations show that MDF char has similar thermal physical properties as softwood char. The specific heat of MDF char is measured to be 600–800J/kg/K from 40 to 110°C and the experimental measured thermal conductivity of MDF char is 0.09W/m/K.