Fibre suspension character - isation using heat transfer measurements with model synthetic fibres in flowing suspension

摘要

Heat transfer data were obtained for a wide range of synthetic fibre suspensions flowing in a specially designed flow loop with an annular test section. The heating rod located coaxially in the test section comprised an embedded heating element, four thermocouples set immediately below the surface beyond the heater, and a calming extension. Heat transfer data were obtained for various synthetic fibre suspensions at a fixed concentration (0.4% by mass) and flow velocity (1.5m/s). Various fibre properties such as fibre length L, length-to-perimeter (L/P) ratio, fibre stiffness, fibre moment of inertia, relative fibre number, and coarseness (mass per unit length), were plotted against heat transfer coefficient h_c values. The results in general validated findings for wood pulp fibre suspensions obtained from a previous pipeline study when there was close correspondence with fibre physical dimensions. Heat transfer coefficient h_c appears to be affected by the interaction between physical and material parameters of the fibres. In general the stiffer fibres are associated with a higher heat transfer coefficient values, most likely due to the increased ability of these fibres to transmit momentum and thermal energy between neighbouring eddies and eddies adjacent to the boundary layer. Further experiments are required with a greater range of synthetic fibres of different dimensions to extend the range of the correlations.