Experimental data on the average mass transfer liquid film coefficient ( k L ) in an aerated tank stirred by Rushton turbine and in bubble column are presented. Liquid media were used as 0.8 M sodium sulphite solution, pure or with the addition of Sokrat 44 (copolymer of acrylonitrile and acrylic acid) or short-fiber carboxymethylcellulose (CMC) for the Newtonian and long-fiber CMC for the non-Newtonian viscosity enhancement and ocenol ( cis -9-octadecen-1-ol) or polyethylenglycol (PEG) 1000 for surface tension change. Volumetric mass transfer coefficient ( k L a ) and specific interfacial area ( a ) were measured by the Danckwerts’ plot method. Coefficients k L measured by pure oxygen absorption in pure sulphite solution and Newtonian viscous liquids are well fitted by the “eddy” model in the form of k L = 0.448 ( e v / ρ ) 0.25 ( D / v ) 0.5 with a mean deviation of 20%. Surface-active agents (ocenol and PEG) and non-Newtonian additive (long-fiber CMC) reduced k L value significantly but their effect was not described satisfactorily neither by surface tension nor by surface pressure. It is shown that the decisive quantity to correlate k L in the stirred tank and bubble column is power dissipated in the liquid phase rather than the bubble diameter and the slip velocity. Absorption of air did not yield correct k L data, which did not depend on or slightly decreased with increasing power. This is due to the application of an improper gas phase mixing model for absorption data evaluation.

Mechanism of mass transfer from bubbles in dispersions: Part II: Mass transfer coefficients in stirred gas–liquid reactor and bubble column

Application of the Danckwerts method in a bubble column

Influence of sodium polyacrylate on the rheology of aqueous Laponite dispersions.

Rheology of titanium oxide based gels: determination of gelation time versus temperature

Mechanism of gas absorption enhancement in presence of fine solid particles in mechanically agitated gas–liquid dispersion. Effect of molecular diffusivity

This paper presents an efficient and objective procedure for the outcome-based assessment of engineering final year projects (FYP). The procedure, consisting of 6 steps, can easily be customized for different engineering curricula. A User Guide has been developed to help institutions create their own FYP assessment system. The guide includes the assessment procedure and aids for its implementation. Particularly, a set of FYP-oriented observable descriptors for Tuning outcomes was defined. The end-products of the proposed assessment procedure are a set of assessment reports that the evaluator agent/s must fulfil per milestone, marking the level reached by the student at every descriptor (0: unacceptable, 1: minimum acceptable, 2: good, 3: excellent). These marks are then gathered together in an overall assessment sheet showing, for every learning outcome, the evolution along the assessment milestones of the level reached by the student at any descriptor. This sheet is a very powerful tool for setting the final mark. All assessment agents use the same list of descriptors and the same levels of acquisition, thus improving the consistency, traceability and global quality of the assessment process.

/pdf/guidelines-for-the-final-year-project-assessment-in-4x3zic8i8w.pdf

Guidelines for the final year project assessment in engineering

Discrimination of the effects of surfactants in gas absorption

The use of membranes for gas separation is a relatively recent but rapidly growing technique. There are polymeric membranes for gas separations, but they are chemically and thermally unstable for some applications. Ceramic membranes can provide stability under drastic conditions, and for combustion gas purification they are probably the only useful membranes. The sol-gel technique facilitates preparation of thin ceramic layers with controlled pore size. Ceramic membranes were made by slip-casting sols on a support which was composed of two ceramic layers. Membranes made of pure Al 2 O 3 , a mixture of Al 2 O 3 TiO 2 , and a mixture of Al 2 O 3 SiO 2 were tested for their ability to separate the gas mixtures N 2 O 2 , N 2 CO 2 and N 2 SO 2 . The mechanisms of flow through the porous membranes are discussed in relation to their efficiency of gas separation.

Ceramic membranes from sol-gel technology

Viscoelastic properties in the course of hydrolysis and condensation reactions of modified titanium alkozides leading to gelation

Alumina sols were obtained by hydrolysis of aluminium sec-butoxide according to Yoldas method. Peptization was carried out with two different quantities of HCl and at two different temperatures. The four sols obtained were stored at 40°C, and their rheological behaviour was determined for times to 1 year. Rheological measurements were fitted to a slightly modified Casson model. Evolution of adjusting parameters, yield stress, consistency index and flow index, with aging time, are discussed. Samples with higher HCl give a yield stress from the day of preparation. Samples with lower HCl display a Newtonian behaviour initially and shear thinning behaviour with increasing viscosity with aging time.

Rheology of alumina sols

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