Measurement of the Diffusion Coefficient of Miscible Fluids using Moiré Deflectometry
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Date
2012-02
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Addis Ababa University
Abstract
Measurements of the diffusion coefficient of two miscible liquids are reported.
The liquids are various combinations of sodium chloride (NaCl) and pure water.
The liquids were placed in a diffusion cell such that the interface is initially
horizontal. As the fluids diffuse, the profile of the index of refraction near the
interface is time dependent and is related to the local concentration of the
diffusing fluids. The concentration gradient profile was measured, the
experimental details and theoretical analysis for obtaining the magnitude of
diffusion coefficient using the Moiré fringe patterns are described.
In this report the Moiré defelectometery method is applied for measuring the
diffusion coefficient of NaCl in pure water at room temperature. The average
diffusion coefficient was obtained by analysis of the measured concentration
gradient profile, assuming that the diffusion process is one-dimensional and is
characterized by a constant value of the diffusion coefficient (D). The value of
s
D m
2
9 1.58( 0.05) 10 is obtained for diffusion of NaCl molecules in pure
water and it is in good agreement with the reported value in literatures
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Keywords
Using Moiré Deflectometry