Browsing by Author "kebede, Alemu"

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    Determination of Diffilsion Coefficient of Transparent Liquid Solutions using Moire Deflectometry and online Monitoring of Liquid Quality by Ray Defectionand Online
    (Addis Ababa University, 2006-06) kebede, Alemu
    In this thesis the diffusion coefficients of coffee, caffeine and sugar were investigated. The technique cmployed is Moire deflectometry. New technique of on-line monitoring of the quality of liquor in the process of manufacturing is also introduced. The diffusion coefficient of caffeine was found to decrease with an increase in the caffeine concentration at constant temperature. The diffusion coefficient of grinded and sieved raw coffee at a concentration of 4.11mg/ml in distilled water, at temperature of 22°C was (3.05±0.16) x JO.6cm2/s. This value of diffusion coefficient is less than the value of the diffusion coefficient of caffeine at the same concentration and temperature, in distilled water, which is (6.13±0.16)xl0·6cm2/s. The main factors that are expected to have contributed to this difference are the fact that coffee is a mixture of many ingredients, as wcll as the particle size of the grinded raw coffee. Diffusion coefficient of 10% sugar solution in distilled water at a room temperature of 24°C was also measured and the value found is (6.68 ± 0.07) xlO·6cnfls. On-line monitoring of a liquid quality in the process of manufacturing is also found applicable in controlling a liquid quality. This was applied to sugar solution that was made to flow through a horizontal diffusion tank and expected result was found. The qualitative aspect about any change in the index of refraction of liquid that passes through a horizontal tank with diffusion column can easily be observed by a person at work; only by referring to ray deflections that correspond to the optical density of the medium Key words: coffee, caffeine Moire deflectometry, diffusion coefficient, and index of refraction