Determination of effective thermal conductivity and specific heat capacity of wood pellets

Abstract

Effective thermal conductivity and specific heat capacity are important properties for studying the self-heating during wood pellets storage. A modified line heat source within a wood pellets container was used to determine the thermal conductivity and specific heat capacity of wood pellets with moisture content ranging from 1.4% to 9%w.b. A second order partial differential equation describing transient temperature distribution within the test container was numerically solved for temporal and spatial temperatures. The difference between experimental and numerical temperatures was minimized to estimate an effective thermal conductivity and specific heat capacity for the bulk pellets. The estimated thermal conductivity ranged from 0.146 to 0.192W/(mK) increasing with moisture content. An empirical relationship among effective thermal conductivity, moisture content and porosity was developed. The dependence of effective thermal conductivity on pellets size was negligible. The estimated specific heat capacity of pellets ranged from 1.074 to 1.253kJ/(kgK) in the tested range. A relation between specific heat capacity and moisture content was developed for general wood pellets.