Annular flow entrainment rate experiment in a small vertical pipe

Two-fluid model predictions of film dryout in annular flow, leading to nuclear reactor fuel failure, are limited by the uncertainties in the constitutive relations for the entrainment rate of droplets from the liquid film. The main cause of these uncertainties is the lack of separate-effects experimental data in the range of the operating conditions in nuclear power reactors. An air–water experiment has been performed to measure the entrainment rate in a small pipe. The current data extend the available database in the literature to higher gas and liquid flows and also to higher pressures. The measurements were made with the film extraction technique. A mechanistic model was obtained based on Kelvin–Helmholtz' instability theory. The dimensionless model includes the Weber number of the gas and the liquid film Reynolds number. Kataoka and Ishii's correlation (Kataoka, I., Ishii, M., 1982. NUREG/CR-2885, ANL-82-44) is modified based on this model and the new data. The new correlation collapses the present air–water data and Cousins and Hewitt's data (Cousins, L.B., Hewitt, G.F., 1968. UKAEA Report AERE-R5657) The effects of pressure and surface tension were considered in the derivation so it may be applied for boiling water reactor operating conditions.     

Vapour—liquid equilibria of the systems acetone—benzene,benzene—cyclohexane and acetone—cyclohexane at 25°C

Vapour—liquid equilibrium data for the binary systems acetone—benzene, benzene—cyclohexane and acetone—cyclohexane have been determined experimentally at 25°C. The reduction producers based on P - x - y as well as on P - x isothermal data sets, which incorporate usual thermodynamically consistent models expressing the dependence of activity coefficients of liquid composition, have been examined for representing the reported results. Nonideal behaviour of the both phases has been taken into account. Thermodynamic consistency of the data has been shown by comparing of the experimentally obtained vapour compositions with those calculated from P - x data using the best of the examined models for activity coefficients.     

Simulation of fuel ethanol production from potato tubers

Semi-continuous fuel ethanol production (FEP), based on the utilization of potato overstocks, including either acid (process I) or enzymatic (process II) hydrolysis of potato starch on the industrial scale was developed. The FEP simulations were developed by help of the Aspen Plus^® software using both experimental and literature data. The main goals were to analyze the influence of starch conversion kinetics on overall process design, to compare two FEP processes with respect to their technical benefits and limitations, to use the mass and energy balances for determining the consumption of materials and energy and to evaluate FEP environmental impact. From the technical assessment, both processes were shown to be feasible for producing high quality fuel ethanol. The analysis showed that the process I was less complex since it required fewest and smallest process equipment units than the process II, making it a competitive alternative for commercial FEP form potato overstocks.     

A kinetic study of quicklime-catalyzed sunflower oil methanolysis

The quicklime-catalyzed sunflower oil methanolysis was studied at mild reaction conditions. Quicklime (calcined at 550 °C for 4 h) in amounts of 1.0, 2.5, 5.0 and 10.0% (based on the oil weight) and different molar ratios of methanol-to-oil (6:1, 12:1 and 18:1) were employed to investigate their influence on the methyl esters content and the kinetics of the methanolysis reaction. The optimal methanol-to-oil molar ratio and quicklime amount for achieving the highest fatty acid methyl esters content were established to be 12:1 and 5% (based on the oil weight), respectively. The sigmoidal kinetics of quicklime-catalyzed methanolysis reaction was described by a model which included the changing mechanism of the reaction and the triacylglycerols mass transfer limitation. The kinetic parameters were determined and correlated with the process variables. A good agreement between the kinetic model and the experimental data for all applied reaction conditions was observed.     

Structural simulation and protein engineering to convert an endo-chitosanase to an exo-chitosanase

To obtain an enzyme for the production of chito-disaccharides (GlcN(2)) by converting endo-chitosanase to exo-chitosanase, we chose an endo-chitosanase from Bacillus circulans MH-K1 (Csn) as the candidate for protein engineering. Using molecular modeling, two peptides with five amino acids (PCLGG) and six amino acids (SRTCKP) were designed and inserted after the positions of D(115) and T(222) of Csn, respectively. The inserted fragments are expected to form loops that might protrude from opposite walls of the substrate-binding cleft, thus forming a 'roof' over the catalytic site that might alter the product specificity. The chimeric chitosanase (Chim-Csn) and wild-type chitosanase (WT-Csn) were both over-expressed in Escherichia coli and purified nearly to homogeneity. The products formed from chitosan were analyzed by ESI-MS (electrospray ionization-mass spectrometry). A mixture of GlcN(2), GlcN(3) and GlcN(4) was obtained with WT-Csn, whereas Chim-Csn formed, with a smaller catalytic rate (3% of WT-Csn activity), GlcN(2) as the dominant product. Measurements of viscosity showed that, with similar amounts of enzyme activity, Chim-Csn catalyzed the hydrolysis of chitosan with a smaller rate of viscosity decrease than WT-Csn. The results indicate that, on inserting two surface loops, the endo-type chitosanase was converted into an exo-type chitosanase, which to our knowledge is the first chitosanase that releases GlcN(2) from chitosan as the dominant product.