Without any other dispersion mechanism, the axial spreading would continue over time, increasingly dispersing over the length of the tube and resulting in an asymmetric concentration distribution.ĭiffusion is often considered to be a spreading mechanism due to the transfer of solute molecules from higher concentration regions to lower concentration regions. The pulse’s front and back ends start out as sharp interfaces, becoming parabolic in shape because of the laminar flow of the fluid. The solute pulse spreads axially along the direction of flow, which is known as convection. Axial spreading of the solute due to convection. Figure 1 shows the effect of this velocity distribution on the profile of an injected solute pulse.įigure 1. The flow of a pressure-driven fluid in a cylindrical tube under Poiseuille laminar conditions experiences a drop in the velocity of the fluid radially from a maximum, u max, at the center of the cylinder to a minimum, u min, at the cylinder walls. The method was further developed by Aris when he took into account the longitudinal diffusion of the molecules.Īccording to Taylor, convection as a result of the fluid’s cross-sectional velocity and the radial diffusion of the molecules make the solute to disperse. Taylor described the TDA method for the first time in his classic paper, which covered the measurement of the dispersion of an injected solute pulse into a flowing fluid in a capillary. From the diffusion coefficient values, hydrodynamic radii of the molecules can be determined. Taylor Dispersion Analysis (TDA), or Taylor-Aris dispersion, is a technique for rapidly determining the diffusion coefficients of molecules. Sponsored by Malvern Panalytical Jul 2 2015
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