High efficiency and low required area for the pulsed columns are interesting and useful especially in nuclear industries in spite of exposure and radiation protection requirements. In this research, dispersion coefficient in a typical disc and doughnut pulsed column in a two phase system (water and kerosene) was determined via radiotracer technique. In the radiotracer method, two Geiger-Mueller detectors at the top and bottom of the active section of the pulsed column and 99mTc in the form of NaTcO4 as radiotracer are used. dispersion is introduced by Pecletdimensionless number which is inversely propotional to the dispersion coefficient. The continuous and dispersed phase flow rate, amplitude and frequency of pulse as the effective parameters on Axial mixing and dispersion coefficient magnitude have been studied. Experimental results indicate that by increasing the continuous phase flow rate, the dispersion coefficient decreases. Also, by increasing the dispersion phase flow rate as well as the amplitude and frequency of the pulse, the dispersion coefficient will increase.

A simple method which is suitable for determining with reasonable precision the parameters of gas flow system has been proposed. An inverse boundary-value problem is considered. The model of gas flow with the Danckwert’ s boundary conditions in a real measurement system has been analyzed and solved. The tracer technique was applied to determine Axial dispersion coefficient of gas phase and Pè clet number. These parameters are commonly used to characterize the flow behavior of fluids. Axial dispersion coefficients were estimated by comparing model solution with recorded TCD signal (an inverse problem as a method for model parameter estimation) employing the Laplace transform technique. The Gaver-Stehfest algorithm for the solution of the mathematical model has been applied. The proposed model of gas show a good agreement with the experimental data. The obtained results show that under operation conditions in the studied system the flow behaviour is neither plug flow nor perfect mixing. The described method is very fast in both experimental and computational part. Simple and errorless derivation of sophisticated model formulas has been possible by application of the Computer Algebra System-type program. The program also simplifies computations. Mathematical manipulations and computations were performed using program Maple® .

In this work, a packed bed reactor of methyl acetate hydrolysis process has been studied. First, mass transfer limitations from bulk fluid to catalyst surface and then from surface into catalyst body were investigated quantitatively. Whereas diffusion had no any limitation on the overall rate of reaction, a pseudo homogeneous one dimensional model considering Axial dispersion coefficients was developed. A LHHW kinetic model for rate of reaction and a Longmuir model for equilibrium adsorption of species on the catalyst, developed experimentally, were used in the mathematical model. An experiment of pulse-input feed to reactor was performed and concentration of reactor product versus time was determined. The model were solved by the numerical method of lines and the absolute difference between calculated concentration profile and those measured experimentally was defined as the objective function which was optimized by Levenberg-Marquardt optimization algorithm. A comparison of our model with ideal Plug Flow model and also with previous model in literature shows that this model is more accurate and more comprehensive than the others and can be used in many comparable industrial cases.

In this study, the mass transfer performance of the Horizontal pulsed sieve plate column for the extraction of uranium from Bandar Abbas sulfate leach solution with Alamine 336 was investigated using a dispersion model. The organic phase contained 6% (v/v) Alamine 336 as extractant and 5% (v/v) isodecanol as a modifier in kerosene as diluent. The sulfate solution of Bandar Abbas containing 0. 22 M sulfate and 250 ppm Uranium was used as the aqueous phase. The Axial dispersion model was used to determine the mass transfer parameters and modeling of this system. Also, the effect of operating parameters such as pulsation intensity, the rate of phases flow on the volumetric overall mass transfer parameters was investigated; namely total volumetric coefficients of continuous phase mass transfer (Koca) and Axial scattering coefficients of continuous and scattered phase (Ec and Ed). The obtained results showed that the mass transfer parameters are strongly dependent on the pulse intensity and turbulence degree of the system. In addition, the mass transfer performance of this column is high for the uranium extraction from sulfate leach liquors. Moreover, the practical and novel correlations have been determined for prognostication of mass transfer parameters which are closely matched with the experimental results in the horizontal pulsed column.

An optimal system of Lie infinitesimals has been used in an investigation to find a solution to the (2+1)-dimensional Bogoyavlensky-Konopelchenko equation (BKE). This investigation was conducted to characterize certain fantastic characteristics of plasma-particle dispersion. A careful investigation into the Lie space with an unlimited number of dimensions was carried out to locate the relevant arbitrary functions. When developing accurate solutions for the BKE, it was necessary to establish an optimum system that could be employed in single, double, and triple combination forms.There were some fantastic wave solutions developed, and these were depicted visually. The Optimal Lie system demonstrates that it can obtain many accurate solutions to evolution equations.

The current paper reports on a new theory developed by modifying the basic Moore-Greitzer model, which can predict the performance of a compression system during the instabilities in more details. The general assumptions such as the compression system layout, the lags in the entrance and exit ducts, the compressor axisymmetric characteristic and the small disturbances are similar to those of Moore-Gereitzer model. However, a second order hysteresis is used in the current work for the pressure rise of the rotor and stator rows. As a result, some new parameters are added to the governing equations, such as the stall cell acceleration ( ), second derivative of the mean Axial flow coefficient ( ), second derivative of the disturbance amplitude ( ) and slope of the compressor characteristic curve. This gives the modified model new capabilities, like investigating the transient speed of the stall cell or the effect of the throttling rate on the instabilities, which are discussed in details in the current paper.

This paper is concerned with the introduction of PDM2, a 2D curvilinear model of dispersion of pollutants in rivers of variable geometry. The model can handle rivers with variable width, depth and path and is capable of grid generation, input data preparation and the processing of output results. The governing two-dimensional advection-dispersion equation is solved numerically, using a finite difference technique. The numerical scheme used is second order accurate in time and space and is unconditionally stable. Pollutant dispersion is assumed to be unsteady. Considering the present gap of knowledge about the mechanics of mixing in rivers and the uncertainties in the proposed equations for mixing coefficients, the model makes use of a number of simplifying assumptions in order to reduce the amount of input data. These are the assumptions of steady river flow and constant depth across the river. The formulation and structure of the model, along with an illustrative example, are discussed in this paper.