화학공학소재연구정보센터
Polymer Engineering and Science, Vol.33, No.23, 1540-1547, 1993
Experimental-Study of Film Thickness and Free-Surface Velocity Around a Rotating Roll for Non-Newtonian Fluids
Measurements are performed on film thickness and free surface velocity around a rotating roll for Newtonian, non-Newtonian inelastic, and viscoelastic fluids by using noncontact methods of a capacitance probe and a laser Doppler velocimeter probe. The film thickness decreases with increasing inspection angle for Newtonian fluids. For non-Newtonian fluids, it retains an approximately constant value, owing to shear-thinning of viscosity, except for a meniscus region development, which is dependent on fluid elasticity. Comparison of current results with the film thickness from a previous work is also made. With the increment of inspection angle, the free surface velocity increases rapidly in the meniscus region and maintains a constant value almost equal to a roll speed in the other region for viscoelastic fluids, while it increases linearly for Newtonian fluids. The shear rate at a roll surface is presented assuming that the velocity distribution in the liquid film is a polynomial equation. It is found that viscoelastic fluids exhibit different behavior from that of Newtonian and non-Newtonian inelastic fluids. Evaluation of the force acting on the liquid film for Newtonian fluids implies that the velocity gradient at a roll surface in an ascending region may be steeper than the parabolic form assumed in this study.