Roll coating of purely viscous liquids

Experimental measurements are reported for the flow of Newtonian liquids through the nip of two co- and counter-rotating rolls of various size and speed ratios. Results are presented in a dimensionless form for the total volumetric flux through the nip and for the distribution of this flux between the two rolls. Simple correlations have been developed and these should be useful in the design and analysis of roll coating equipment.Some preliminary data are also presented for a shear thinning inelastic non-Newtonian liquid. The forms of the correlating equations developed for the Newtonian systems are still applicable but the constants in the equations are slightly modified.     

Free coating of pseudoplastic liquids onto a vertical surface

The coating of pseudoplastic liquids onto a vertical surface continuously withdrawn from the liquid bath is considered. The problem is treated in a two-dimensional nonlinear approach incorporating the inertial effects. The model gives a relationship between the dimensionless film thickness, T, and the Capillary number, Ca, as a function of the fluid physical properties and the parameteres of the power-law model. The comparison with the experimental data is satisfactory.     

Flow of generalized newtonian liquids through fixed beds of nonspherical particles

The flow of generalized Newtonian liquids through a random fixed bed of particles has been investigated and a universal method of calculation of the creeping flow was suggested. The usefulness of this method has been verified experimentally for the flow of power law, Ellis and Sutterby liquids through fixed beds of different nonspherical particles.     

Method for determining diffusion coefficients of slightly soluble gases in liquids

A method is described, according to which the diffusion coefficient of a slightly soluble gas in a liquid is calculated from the volume of gas absorbed per unit of time from a gas bubble of constant size. The gas bubble is fixed on the top of a needle of a syringe. This top is ground in the shape of a truncated cone. The centre of the gas bubble coincides with the hypothetical top of this cone. Through the needle, the gas is continuously supplied to such an extent that, in spite of the gas absorption, the bubble diameter remains constant. In this paper, this method is mentioned constant bubble size method and is referred to as the CBS-method.It has been investigated what precautions have to be taken during the measurements to prevent convection and other error sources.Further, it has been shown why the decreasing bubble size method, referred to as the DBS-method, which has been described in the literature, generally leads to unreliable results.Experiments have been conducted with the hydrogen—water system, at about 1 bar in the range of 20–60°C. Results are given and compared both with literature data and values calculated from some diffusion coefficient predicting equations.     

Entrainment of air into liquids by a high speed continuous solid surface

The paper reports a wide range of experimental data on air entrainment velocities and apparent dynamic contact angles, were a continuous surface entersThe main dimensional correlation took the form:

for variables in the range:

However, due to the limited range of fluid densities used (0.785-1.26 * 10³kg.m³), a simpler correlation for air entrainment velocity was found

for the case of the entrainment of air by a plunging solid surface where 0.2 <(ηs/η9u)>< 3.2m.sec^-1 was found to be the corresponding rThe critical capillary number Ca_c was found to lie in the range 0.2 <Ca_c< 1.26 which agrees very well with a recent study due to GuThe investigation also showed that anomalous behaviour could occur with charged surfaces or surfaces with significant roughness. Surfactant type was al     

Heat transfer from a plane sufrace to liquids and to liquids-solid fluidised beds

Heat transfer coefficients have been measured for transfer between a small immersed electrically heated surface and both liquids and liquid-solid fluidised beds. Fluid viscosity, and hence Prandtl number, has been varied approximately 600 fold. Experimental results for liquids have been expressed in terms of Nusselt, Reynolds and Prandtl numbers and for the fluidised systems in terms of Stanton number, particle Reynolds number for free falling conditions, and bed voidage. Maxima in the heat transfer coefficient-voidage relations are satisfactorily predicted.     

Correlation for second virial coefficients of polar compounds

A new correlation has been developed for calculation of second virial coefficients of polar compounds. The new procedure uses superimposition of the sq interaction. Parameters for this new correlation have been determined for 13 polar compounds. Using these parameters, the second virial coefficients we 3.46%. This compares favorably with the mean standard deviation of Stockmayer's correlation at 31.3 cm³/g mole or 3.36%.     

Measurements of diffusivities in liquids by the dispersion method

A combination of convective and diffusive mass transfer is advantageous when molecular diffusion in liquid systems is investigated because the measurements can be made in a relatively short time, with small concentration differences, and in a wide range of temperatures and pressures. The principle of the experimental method, the apparatus and the possibilities of data evaluation are discussed. The results of test measurements are presented.     

A generalized corresponding states method for the prediction of the thermal conductivity of liquids and liquid mixtures

We have recently developed an extension of the three parameter corresponding states principle based on the properties of two non-spherical reference fluids for the viscosity of liquids and liquid mixtures. We extend the method here to the thermal conductivity. We have tested the method for a large number of binary liquid mixtures using the two pure components in each case as our reference fluids. Good agreement between predicted and experimental thermal conductivities was obtained using only the data for the pure components. This agreement becomes excellent if a single binary interaction consta independent of temperature and composition, is used in the mixture calculations. If the pure component reference properties are not available, then the may he obtained from the properties of two similar fluids.     

Interfacial area and liquid side mass transfer coefficient in trickle bed reactors operating with organic liquids

Interfacial area and liquid-side mass transfer coefficients measured in a 5cm diameter trickle-bed reactor operating with organic liquids are presented d_p≤ 2.4 mm and cylindrical catalyst of size 0.9 mm × 5 mm. A few data concern also 5.9 and 6.4 mm Raschig rings. Gas and liquid flowrates a Mass transfer parameters have been determined by the chemical technique using the carbamation of the reactants cyclohexylamine, monoethanolamine or die results obtained at low gas-liquid interaction with low liquid flowrate are reported for the ionic aqueous systems CO₂-NaOH and O₂-Na₂SO₃. The variation of the mass transfer data, the gas pressure drop and the liquid holdup with the gas and liquid flowrates show that there exists a strong connection between these parameters. This has led to correlate the with the liquid-solid friction factor within a $\text{+}$30% accuracy.     

The transient response of a CSTR containing porous catalyst pellets: Asymptotic solutions

Transient response of a CSTR containing porous catalyst pellets is analyzed theoretically using a matched asymptotic expansion technique. This singular perturbation technique leads directly to the conditions under which the minima of reservoir concentration occur. The existence of the minima may be used to estimate some inherent parameters of the catalyst pellet.     

Transient response of continuous-flow stirred reactors containing heterogeneous systems for catalysis or sorption

Time domain solutions are presented for the transient response of an isothermal CFSR with one-dimensional diffusion and first-order irreversible chemical reaction in catalyst particles or liquid pools of regular geometry and with mass transfer resistance at the fluid-catalyst interface. Three different cases of feed perturbations have been considered, namely, step input, impulse input and the sudden introduction of pellets into the reactor. The solutions have been derived in a general manner, without specifying the particle shape, and are in terms of characteristic functions defined for each of the three particle geometries considered, i.e. slab with sealed edges, cylinder with sealed ends, and sphere. Asymptotic solutions suitable for large Thiele parameters (gf≥3) have also been derived and are particularly convenient when the series solutions converge slowly. Experimental verification of the exact and asymptotic solutions for a specific case of absorption and diffusion in a liquid pool is presented.     

The poisoning of noble metal catalysts by phosphorus compounds—II the kinetics of poisoning and a mathematical model

The kinetic data of the poisoning of a porous noble metal carrier-type catalyst by phosphorus were determined during the total oxidation of ethane with air. An appropriate mathematical model for the reaction system including internal diffusion in the porous pellet was developed. The experimentally-obtained data were used in computations to prove that the mathematical model properly describes experimental poisoning within the limits of error.     

The electrode properties of polycrystalline SnO2 containing up to 10% Sb or Ru oxides

Thin tin dioxide films containing up to ca. 10% Sb or Ru oxides were prepared by the hydrolysis of SnCl₄/SbCl₅ or SnCl₄/RuO₄ vapour mixtures at 420°C, on conducting substrates. The distribution of electronic states in the band gap of the semiconducting materials was determined by UPS (ultraviolet photoelectron spectroscopy). The films were then used as electrodes and the electrode kinetics of the redox-systems Fe^{2 + /3+} and Ce^{3 + /4+} were determined. By correlating the UPS and the electrochemical results, a model for the charge-transfer mechanisms is suggested in which electrons can pass the narrow semiconductor space charge barrier by mediation of the deep donor states in the band gap being introduced by the dopants.     

Azo-hydrazone tautomerism of hydroxyazo compounds—a review

The phenomenon of azo-hydrazone tautomerism of hydroxyazo compounds is reviewed in relation to structural factors such as the degree of annellation and the type and position of substituents, as well as environmental factors which are determined by the medium containing the tautomeric entity. Media effects are discussed with reference to studies in solution, polymeric substrates, the crystalline solid state and the gas phase. The influence of the state of the tautomeric equilibrium on the chemical reactivity is considered with an emphasis on the practically important aspects of photochemistry and acid-base behaviour of tautomeric hydroxyazo dyestuffs.