Enhancement of mass transfer at a spherical electrode in pulsating flow

The effect of pulsation on the overall mass transfer coefficient between a sphere and a liquid at low Reynolds number (Re < 6.36) has been studied. When there is no flow reversal, pulsations have a negative effect on the mass transfer coefficient, it being minimum when the dimensionless group α = a/u ₀ = 1. When flow reversal occurs the mass transfer coefficient increases with both frequency, f, and amplitude, a, of the pulse and decreases with the mean fluid velocity, u ₀. The variation of the mass transfer coefficient has been studied with a model based on the quasisteady-state assumption. In this way two correlations have been obtained for the mass transfer coefficient: $$\operatorname{Re} < 20\user1{ }Sh = 1.23Sc^{1/3} \operatorname{Re} ^{0.23} $$ $$\operatorname{Re} < 20\user1{ }Sh = 0.39Sc^{1/3} \operatorname{Re} ^{0.58} $$      

Polymer solubility parameters determined from measurements in a single solvent

The solubility parameter of polyisobutylene has been determined from intrinsic viscosity measurements in a single solvent as a function of temperature. The change in solubility parameter of the solvent as a function of temperature was calculated form the equation \documentclass{article}\pagestyle{empty}\begin{document}$ \frac{{d{\rm}ln \delta s}}{{d{\rm}ln Vs}} = - \frac{{n + 1}}{2} $\end{document} where Vs, the molal volume, changes with temperature. The vlaue for the solubility parameter thus obtained compares well with values reported in the literature for intrinsic viscosity measurements in a series of solvents. Similar measurements were made with an ethylenepropylene copolymer. The solubility parameter of 87 mole % C₂ ethylene-propylene copolymer was determined to be 8.1-8.6 in either toluene or methylcyclohexane.     

Electrical resistivity of layers consisting of large carbon particles as a function of the granulometric composition and applied pressure

A mathematical formula is derived for the electrical resistivity ρ′_s of layers of conducting disperse materials as a function of the particle size d and applied pressure P

Zur kinetik der acrylnitril-polymerisation

The heterogeneous bulk polymerization of acrylonitrile initiated by AIBN has been studied by means of an improved dilatometric technique and a new method of analysis, where the initial reaction rate (v_w)₀ results from the intercept of a straight line in a \documentclass{article}\pagestyle{empty}\begin{document}$ \frac {\ln \left( 1 \hbox{---} {\rm U} \right)} {{\rm e}^{{- 0,5} {\rm k}_{\rm s}{\rm t} \hbox{---} 1}}$\end{document} versus t plot. It has been found that the initial reaction rate is proportional to the square root of the initial catalyst concentration S₀. The ratio of the rate coefficients of propagation and termination\documentclass{article}\pagestyle{empty}\begin{document}$\frac { {\rm k}_{\rm a} } { {\rm k}_{ {\rm w}^{2} } } $\end{document} could be calculated from the slope of a straight line passing through the origin in a plot of (v_w)₀ versus \documentclass{article}\pagestyle{empty}\begin{document}$\sqrt { {\rm S}_{0} }$\end{document} and yielded a value of 280 mol 1^?1.     

Hydrodynamic properties of coal in turbulent fluidized beds

Hydrodynamic properties in turbulent fluidized beds of three different sizes of coal (d _p = 0.507, 0.987, 1.147 mm) have been determined from the pressure fluctuations in a 0.1 m-ID × 3.0 m high Plexiglas column. The transition velocity from the slugging to turbulent flow regimes can be determined from the statistical analysis of pressure fluctuations such as mean amplitude, standard deviation and skewness, the pressure wave velocity, and the bed expansion with gas velocity. The bed expansion in the slugging and turbulent flow regimes cannot be estimated from the two-phase theory. The voids rise velocity and the bed expansion ratio (H/H _mf ) in the turbulent flow regime have been correlated with the relevant dimensionless and operating parameters The ransition velocity to the turbulent flow regime has been determined based on the slug breakdown caused by the inertial force of an upflowing maximum stable slug which overcomes the gravitational force induced by solid refluxing as:      

Characterization of polyvinyl chloride part II. The unperturbed end to end distance values obtained from a new GPC method and viscometry

A new gel permeation chromatography (GPC) method is proposed for determining the unperturbed end-to-end distance, \documentclass{article}\pagestyle{empty}\begin{document}$ \left({\frac{{r_0 ^2 }}{M}} \right)^{0.5} $\end{document}, of polymers of known molecular weights, Mn and Mw. This method requires the value of \documentclass{article}\pagestyle{empty}\begin{document}$ \left({\frac{{r_0 ^2 }}{M}} \right)^{0.5} _{{\rm ps}} $\end{document} of polystyrene which was determined through viscometry to be 0.735 \documentclass{article}\pagestyle{empty}\begin{document}$ \left({\frac{{{\rm {\AA}}^2-{\rm mole}}}{{gm}}} \right)^{0.5} $\end{document} Polyvinyl chloride (PVC) was chosen to illustrate the method and \documentclass{article}\pagestyle{empty}\begin{document}$ \left({\frac{{r_0 ^2}}{M}} \right)^{0.5} _{pvc} $\end{document} was found to be 0.99 from GPC data which is in agreement with the result obtained from viscometry, \documentclass{article}\pagestyle{empty}\begin{document}$ \left({\frac{{r_0 ^2}}{M}} \right)^{0.5} _{pvc} $\end{document} = 1.01. All \documentclass{article}\pagestyle{empty}\begin{document}$ \left({\frac{{r_0 ^2 }}{M}} \right)^{0.5} $\end{document} values were determined at 30°C. The advantage to this method lies in its speed and economy of materials.     

A study of the fatigue behavior of fiber reinforced nylons

A phenomenological model combining a Weibull distribution function with a kinetic equation for flaw growth has been used to describe the static tensile strengths and fatigue lives of short graphite-fiber reinforced nylon 66 materials. A simple Weibull function of the form \documentclass{article}\pagestyle{empty}\begin{document}$ P\left( {\sigma _b } \right) = \exp - \left( {{{\sigma _b } \mathord{\left/ {\vphantom {{\sigma _b } {\hat \sigma }}} \right. \kern-\nulldelimiterspace} {\hat \sigma }}} \right)^{9.5} $\end{document} described the distribution of static strengths. The scale factor \documentclass{article}\pagestyle{empty}\begin{document}$ {\hat \sigma } $\end{document} varies with the annealing treatment and, in general, is a function of environmental variables. The cumulative distribution of breaking times in fatigue can be characterized by a translated three parameter Weibull function \documentclass{article}\pagestyle{empty}\begin{document}$ P\left( {t_B } \right) = \exp - \left\{ {\left. {\left( {\frac{{\sigma _{\max } }}{{\hat \sigma }}} \right)^{16} + \frac{{t_B }}{{\hat t}}} \right\}} \right.^{0.59} . $\end{document} The average time to break (which is related to the time scale factor \documentclass{article}\pagestyle{empty}\begin{document}$ {\hat t} $\end{document}), appears to be a function of the flaw growth rate. The distribution equation has been found to predict the number of half cycle failures and is thus a valid model for the proof testing of large populations. An electrical resistivity method was developed to measure flaw growth rates in prenotched cantilever beams. Experimental data fit the following equation: ln (Δa/Δn) = ?88.88 + (12.46 ± 5.68) ln (K_eff)_max. The correlation coefficient was 0.81. From curve fitting of fatigue data it appeared that flaw growth rate varied with the ninth power of flaw length (Δa/Δn) = Ma⁹. The direct measure of flaw growth rate using electrical resistance gave Δa/Δn = Ma^6.23±2.84 with 90 percent confidence. The two measurements overlap within the 90 percent confidence bands, but predictions of fatigue life using the flaw propagation data were not good. Scanning electron microscope studies showed that specimens with a short fatigue life have glassy, fibrillated fracture surfaces while specimens with a long fatigue life exhibit a high degree of ductility in portions of the fracture surface. These differences are traced to differences in the size and shape of flaws.     

Kinetic study of the hydrolysis of cellulose acetate in the pH range of 2–10

A kinetic study of the hydrolysis of 39.8 wt.-% acetyl cellulose acetate has been made as a function of pH and temperature over the pH range of 2.2–10 and temperature range of 23–95°C. The hydrolysis reaction was carried out on highly porous membranes under quasihomogeneous conditions and the data have been treated as a pseudo-first-order reaction in acetyl concentration. The reaction can be represented by the equation \documentclass{article}\pagestyle{empty}\begin{document}$k_1 {\rm = }\;k_{\rm H ^ +} \left[ {{\rm H^+}} \right]{\rm +}k_{\rm OH^-}\left[ {{\rm OH}^ - } \right] + k_{\rm H_2O} $\end{document}, and where \documentclass{article}\pagestyle{empty}\begin{document}$k_{\rm H} ^ + {\rm = 5}{\rm .24}\;{\rm x 10}^{\rm 5} {\rm exp }\left\{ {{\rm ‐ 16}{\rm .4 x 10}^{\rm 3} /RT} \right\},{\rm }k_{{\rm OH}} ^ ‐ {\rm = 1}{\rm .55}\;{\rm x 10}^{\rm 4} {\rm exp }\left\{ {{\rm ‐ 8}{\rm .1 x 10}^{\rm 3} /RT} \right\}$\end{document}, and \documentclass{article}\pagestyle{empty}\begin{document}$k_{\rm H_2O} {= 4.25\;\times 10}^{- 2} {\rm exp }\left\{ {{- 11.5 \times 10^3 /RT}} \right\}$\end{document} (where the quantities in brackets are activities of the ions shown).     

Modified response surface methodology (MRSM) for phase equilibrium-application

Attempts are being made to predict multicomponent azeotropic mixtures from the physical property of pure component and compositions of the constituting binary combination pairs. A modified response surface methodology (MRSM) model has been proposed which correlates boiling temperatures of binary, ternary and quaternary mixtures directly with the compositions of vapor and liquid phases. The generalized MRSM-2 models for liquid and vapor phases are proposed as follows: (for liquid phase) (for vapor phase) These models require normal boiling point of the pure components, T, and group-group parameters A_ij B_ij & C_ij which can be estimated by the group-group concepts of the constituent components. Therefore, this methodology is applied for the system of three and four components by the computer simulation. No experimental data is required for seeking of composition and temperature of the multicomponent azeotropic mixtures. By means of this methodology, MRSM, it is possible to depict an isothermal line map, temperature contours of the individual phase of the constituting ternaries for each quaternary system. Furthermore, it is possible to predict the azeotropic behaviors, maximum, minimum, saddle or any other type of azeotropic mixtures by examining the graphic contours obtained by computer graphics in the triangular coordinate for ternary and tetrahedron for quaternary. The proposed methodology (MRSM model) has been tested and compared successfully with previously reported azeotropic data in various journals for several ternary and quaternary multicomponent systems. Two azeotropic mixtures are newly found for each of two different quaternary tetrahedrons. The composition, temperature and type of the newly found azeotropes are reported.     

Coalescence of an emulsion in a fibrous bed: Part I. Theory

A model of a fibrous bed coalescer is presented which relates the collision frequency between particles and fibers to the overall coalescence frequency. The model will predict the ratio of outlet to inlet particle number densities (Y) and takes into account the mean inlet particle size, mean fiber size, void fraction of the bed, superficial velocity through the bed, degree of bed saturation, and bed length. The ratio of outlet to inlet particle number density, in terms of these parameters, is given by \documentclass{article}\pagestyle{empty}\begin{document} \[Y = \exp \left\{{- \frac{{3(1 - \in)S(1 + d_{10} /d_f)}} {{4d_f (1 - S)}}\eta _e L} \right\} \] \end{document} where η is defined as the coalescence efficiency and varies between 0 and 1 with the fiber Reynolds number.     

Effect of turnover rate on the change of concentration of an unstable compound in a dip coating bath

The effect of turnover rate on the change of concentration of unstable (degradable) compounds in a dip coating bath during a continuous coating process was theoretically calculated as a function of the degradation rate of the compound. It is assumed that the bath is replenished by the same coating material as that in the original bath to maintain the volume of the material in the bath constant. The results show that the fraction of the unstable compound in the bath at the end of the nth day is given by where t is the number of days for one turnover and where P is the fraction of the compound remaining undegraded in the bath per day. The equilibrium fraction of the compound after infinite coating days is given by The concentration of the compound in the replenishing material (C_r) to maintain the original concentration in the bath (C_o) constant is given by.     

Partition characteristics of close-boiling components in a chromatographic column

Partition characteristics of three close-boiling components (dichloromethane, diethylether, and dimethoxymethane) were investigated with dinonylphthaiate-coated Chromosorb A and helium as the carrier. The outlet stream from the Chromatographic column was monitored continuously. Partition coefficients were experimentally determined at various column temperatures for the three components. With the assumption of uniform film thickness, two parameters were estimated by Fourier analysis of the response curves. The Peclet number for particle was expressed in terms of the Reynolds number and the Schmidt number as: $$\frac{1}{{Pe,p}} = \frac{{0.87}}{{\operatorname{Re} \cdot Sc}} + 0.5$$ Intraparticle diffusion coefficient of each component was also determined in the form of the dimensionless group. P_i. The theoretical response curve in time domain was in good agreement with the observed one. From the sensitivity analysis, it is concluded that the liquid film resistance was small and the diffusion in the liquid phase was not a rate-determining step.     

Influence of temperature on the electro-dissolution of tin in NaCl aqueous solution at pH4

The influence of temperature in the range 25 to 80°C on the dissolution of tin was investigated in an acidic solution at pH4 containing 0.1 to 1m NaCl. The corrosion current is slightly dependent on both the temperature and the Cl^– ion concentration. The main dissolution characteristics of tin are

Characterization of polyvinyl chloride. Part III. An alternative GPC method for measuring the radii of gyration,and the degree of long-chain branching of polydispersed polymers

A method for measuring the unperturbed radius of gyration and the degree of long-chain branching in Gaussian-distribution polymers is proposed. Polyvinyl chloride (PVC) and polyvinyl acetate (PVAc) were selected to illustrate the method. It was observed that PVC samples prepared by homogeneous and heterogeneous polymerizations exhibit the same degree of long-chain branching. This conclusion is supported by viscometric data. The polydispersity ratios (M_w/M_n) indicate that both types of polymerizations would yield a very small amount of total branching (long chain and short chain.) The calculated unperturbed radius of gyration of linear PVC samples was found to be 0.185 \documentclass{article}\pagestyle{empty}\begin{document}$ \left( {\frac{{{\rm \dot A}^{\rm 2} {\rm mole}}}{{{\rm gm}}}} \right) $\end{document}, and that of PVAc was determined to be 0.107 \documentclass{article}\pagestyle{empty}\begin{document}$ \left( {\frac{{{\rm \dot A}^{\rm 2} {\rm mole}}}{{{\rm gm}}}} \right) $\end{document}. The value obtained for PVC is shown to be in agreement with the value determined from the viscometric method as described in our previous work.     

Vapor-liquid equilibria of the acetylacetone-1,3-dioxolane system

Isobaric vapor-liquid equilibrium data on the mixture acetylacetone-1,3-dioxolane were obtained at P = 40, 66.67 and 98.67 kPa. Both keto and enol tautomers of acetylacetone were taken into account when checking the thermodynamic consistency of the data with the area test. The integral \documentclass{article}\pagestyle{empty}\begin{document}$ I = \int_{x_B = 1}^{x_B = 1} {\ln \left({\gamma _A /\gamma _B} \right)dx_B} $\end{document} is not zero and is higher than the estimated error of I, ΔI. Specific interactions among the tautomers and 1,3-dioxolane are hypothesized to explain the non random deviations of I from the expected zero value.     

Dropwise condensation of different steam-air mixtures on various substrate materials

Dropwise condensation of different steam-air mixtures on three substrate materials (copper, aluminium and nickel) is studied. For each steam-air mixture, the heat flux, the heat transfer coefficient and the surface temperature are observed to be highest on copper and lowest on nickel substrates for the same identical test conditions. The above heat transfer variables are related to the bulk properties of the substrate. It is concluded that the presence of non-condensable gases is an inhibiting influence on the heat transfer performance in the condensation of steam. The normalized variables \documentclass{article}\pagestyle{empty}\begin{document}$ \frac{{h_i \left(\eta \right)}}{{h_i \left(o \right)}} $\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ \frac{{T_{si} \left(\eta \right)}}{{T_{si} \left(o \right)}} $\end{document} are found to be functions of the air concentration only.     

Polymerization of olefins through heterogeneous catalysis. II. Kinetics of gas phase propylene polymerization with Ziegler–Natta catalysts

Propylene was polymerized in gas phase over a \documentclass{article}\pagestyle{empty}\begin{document}${\rm TiCl}_3 \cdot \frac{1}{3}{\rm AlCl}_3$\end{document} (Stauffer Type AA) Catalyst with AlEt₂Cl cocatalyst both with and without H₂ present. The effects of polymerization temperature, monomer concentration, catalyst composition, and hydrogen were investigated. The experiments were carried out at operating conditions approaching industrial practice.     

Massenspektrometrische Fragmentierung cis/trans-isomerer tert. Butylcycloheptanole

Mass Spectrometric Fragmentation of cis-trans Isomeric tert. Butylcycloheptanols The mass spectra of six cis-trans isomeric tert. butylcycloheptanole 1 – 6 are discussed The fragmentation of the tert. butylcycloheptanols is similar to that observed for the corresponding cyclohexanes. The quotient \documentclass{article}\pagestyle{empty}\begin{document}$ \frac{{[{\rm M \hbox{---} M}_{\rm 2} {\rm O}]^{+ _ \bullet}}}{{{\rm M}^{{\rm +}_ \bullet}}} $\end{document} is found to be characteristic for the different geometric isomers. But the differences observed between flexible tert. butylcycloheptanols are much smaller than those calculated for the rigid tert. butylcyclohexanols.     

Graft polymerization of methyl methacrylate onto wool initiated by a hydrogen peroxide-sodium thiosulphate redox system. Part II kinetics and mechanism of the grafting reaction

Methyl methacrylate was grafted onto wool in the presence of an aqueous dioxane solution with a hydrogen peroxide-sodium thiosulphate initiator system, using the optimum conditions found in our previous paper¹⁹. It was stated that up to 90% conversion for the rate of reaction the following equation holds: \documentclass{article}\pagestyle{empty}\begin{document}${\rm R}_{\rm p} = - \frac{{{\rm d}\left[ {\rm M} \right]}} {{{\rm dt}}} = {\rm K} \cdot \left[ {\rm M} \right]^{1.5}$\end{document} where R_p is the overall rate of the graft polymerization, and [M] is the monomer concentration at the time t. The degree of polymerization of the isolated poly(methyl methacrylate) was found to be linearly proportional with the monomer concentration [M]. Investigations of the effect of the ratio of solvent to monomer concentration [S]/[M] on the reciprocal of the degree of polymerization showed that there was no chain transfer caused by the solvent dioxane. The number average molecular weight M?_n of the polymer separated from the grafted wool was found to be within the range of 3–15.9 × 10⁶ as determined by viscosimetry. The molecular weight distribution of the isolated poly(methyl methacrylate) samples was determined by turbidimetric titration. The following relationship was established between the volume fraction of the non-solvent, γ and the number average molecular weight M?ⁿ. of poly(methyl methacrylate): \documentclass{article}\pagestyle{empty}\begin{document}$\gamma = - 0.0285 + \frac{{50.54}}{{\sqrt[3]{{\overline M _n }}}}. $\end{document} The molecular weight distribution curves were found to be rather homogeneous indicating approximately the same chain length of the grafted poly(methy1 methacrylate) on the wool backbone. It was stated before³³ that the number average molecular weight could be determined from the inflection point of the turbidimetric curves. This method can be used for determining the molecular weight of all kinds of poly(methy1 methacrylate) occurring in practice.     

Characteristic velocity and mass transfer in rotating impeller column

The effects of system variables on flow characteristics and mass transfer rate were studied in a rotating impeller column using a ternary system of water (continuous phase)-acetone (solute)-cyclohexane (dispersed phase). The characteristic velocity, Peclet numbers in both phases and mass transfer coefficient between phases were correlated as; $$\begin{gathered} \bar U_o = 6.3(10^2 )(Nd_I )^{ - 2.1} Z_C^{0.83} \hfill \\ \frac{{\bar U_C L}}{{D_C }} = 1.26N^{ - 1.11} d_I ^{ - 2.17} Z_C^{0.59} \bar F_C^{1.9} \hfill \\ \frac{{\bar U_d L}}{{D_d }} = 20.5N^{ - 0.78} d_I ^{ - 1.36} Z_C^{0.25} \bar F_C^{0.09} \hfill \\ \frac{{k_{OC} aL}}{{\bar U_d }} = 13.2N^{ - 1.33} d_I ^{0.74} Z_C^{0.93} \bar F_C^{0.78} \hfill \\ \end{gathered} $$