Hyo Seon Kim

INSTABILITIES INDUCED BY AN ELECTROSTATIC FIELD OVER THE FILM FLOW DOWN AN INCLINED PLANE

A study of the instabilities in the interaction of an electrostatic field with a thin liquid film flowing under gravity down an inclined plane is presented. First, the long-wave stability conditions are studied by perturbing the evolution equation of film height about its steady-state solution. Three limits of flow systems are considered, i.e., static state, Reynolds number Re = 0(1) and Re = 0(1/ξ). Here ξ(≪1) is the ratio of the characteristic length scale parallel to the flow to the primary film thickness. Next, the long-wave behavior of the thin film flow is examined with the electrostatic potential of a Gaussian function in the two limits of Reynolds number, i.e., Re = 0(1) and Re =0(l/≪). These results are also compared with those from a full-scale explicit calculation. Finally, wave-growth rates are calculated from the Orr-Sommerfeld equation to show the stability to wave number with and without the electric field. The effect of the electric field is to lessen the range of the wave number in which the thin film flow remains stable.

Valorization of galactose into levulinic acid via acid catalysis

We applied methanesulfonic acid (MSA) as a green catalyst to produce levulinic acid (LA) from monomeric sugars. To optimize reaction factors and assess the effect of reciprocal interactions, a statistical experimental design was applied. Optimized result of 40.7% LA yield was obtained under the following conditions: 60 g/L galactose, 0.4M MSA at 188 °C for 26.7 min. On the other hand, 66.1% LA yield was achieved under 60 g/L fructose and 0.4M MSA at 188 °C for 36 min conditions. For the effect of combined severity factor on the LA yield from galactose, the LA yield showed a peaked pattern, which was linearly increased until a CSF 3.2 and then diminished with a high CSF. Moreover, it was closely fitted to a non-linear Gaussian peak pattern with a high regression value of 0.989. These results suggest that MSA and galactose, derived from marine red macro-algae, can potentially be applied for the conversion into platform chemicals.