Transient computational fluid dynamics modelling of the melting process in thermal bonding of porous fibrous media

A continuum model of the melting process in porous fibrous media is introduced. The fluid flow, heat transfer and phase change within the porous nonwoven web is numerically solved using computational fluid dynamics. Boundary conditions from an experimentally validated whole system model of a typical industrial machine, producing fibrous webs are incorporated. The presented model shows the capability to investigate the phase change during heating of the thermoplastic fibres during nonwoven web formation. Moreover, the fibres' geometrical information and constitutive equations, describing the material behaviour are included. The approach considers the fibre thickness, sheath fraction, and thermophysical properties like melting temperature, latent heat of fusion and the liquid fraction, enabling the assessment of different fibre types and to determine the properties of the fabric. The model results reveal that the web porosity has the most significant effect on the melting process among the considered parameters. Thermal gradients that occur inside the web are due to the combined convection and latent heat of fusion effect, which stores heat to melt the fibres. The model is applicable to a wide variety of systems ranging from textiles, fibrous beds, ceramics, membranes and porous composite materials. © IMechE 2012 Reprints and permissions: sagepub.co.uk/ journalsPermissions.nav.