Equivalent heat transfer modeling for poplar fiber clusters based on thermography

Abstract

Abstract Poplar fiber mass is a non-uniform medium that is composed of discrete microelements making it an imperative raw material in the production of ultra-thin high-density wood fiberboards. Preheating, therefore, becomes a crucial process in producing ultra-thin boards from poplar fiber masses. This study aims to investigate the thermal conductivity properties of wood fiber pellets with the objective of guiding the process parameters in the preheating section.Basic size and composition of poplar fiber masses were observed using an optical microscope. Measured parameters such as bark content and stacking density were combined with observations to establish the heat transfer unit of poplar fiber masses which were then used to develop a one-dimensional equivalent heat transfer model.The steady-state images of the surface layer of poplar fiber masses were captured under different parameters using infrared thermography. The results indicated that the relationships between thickness, density, and moisture content were negatively correlated with surface layer temperature, while the relationships between bottom heating temperature and surface layer temperature were positively correlated. From these findings, the surface layer temperature of poplar fiber mass was derived, and equivalent thermal conductivity as well as convective heat transfer coefficients were solved.Simulation results showed that the average error of the equivalent heat transfer model of poplar fiber mass was 1.584 indicating that the model is usable. This study contributes to efficient simulation of steady-state heat transfer in wood fiber masses, and could be useful in guiding decision-making processes in the preheating section of ultra-thin high-density fiberboard production.