Hungarian Journal of Industrial Chemistry 

About: Hungarian Journal of Industrial Chemistry is an academic journal published by University of Pannonia. The journal publishes majorly in the area(s): Diesel fuel & Chemistry. It has an ISSN identifier of 0133-0276. It is also open access. Over the lifetime, 478 publications have been published receiving 1517 citations. The journal is also known as: HJIC & Hungarian journal of industrial chemistry (Online).

Comparison of Scalar and Vector Control Strategies of Induction Motors

Abstract: Currently the use of three-phase induction machines is widespread in industrial applications due to several methods available to control the speed and torque of the motor. Many applications require that the same torque be available at all revolutions up to the nominal value. In this paper two control methods are compared: scalar control and vector control. Scalar control is a relatively simple method. The purpose of the technique is to control the magnitude of the chosen control quantities. At the induction motor the technique is used as Volts/Hertz constant control. Vector control is a more complex control technique, the evolution of which was inevitable, too, since scalar control cannot be applied for controlling systems with dynamic behaviour. The vector control technique works with vector quantities, controlling the desired values by using space phasors which contain all the three phase quantities in one phasor. It is also known as field-oriented control because in the course of implementation the identification of the field flux of the motor is required. This paper reports on the changing possibilities of the revolution – torque characteristic curve, and demonstrates the results of the two control methods with simulations. The simulations and the applied equivalent circuit parameters are based on real measurements done with no load, with direct current and with locked-rotor.

Solubility of Gases in Normal-alkanes

Abstract: Solubilities of a number of gaseous were determined in members of the n-pentane n-hexadecane series. Relationships between gas solubilities and physico-chemical properties of members of the series were studied. It was found that gas solubilities varied linearly in the function of reciprocal parachor values of the solvents, and the slopes of the lines were proportional to the sizes and mean polarizabilities of the gases dissolved. An equation was derived solubilities of apolar and moderately polar gases in n-alkanes. The equation is not applicable for polar gases, because the interactions between the gas and liquid molecules cannot be neglected in such cases.

Mechanisms of ammonia-synthesis reaction revisited with the aid of a novel graph-theoretic method for determining candidate mechanisms in deriving the rate law of a catalytic reaction

Abstract: Stoichiometrically exact, candidate pathways, i.e., mechanisms, for deriving the rate law of the catalytic synthesis of ammonia have been determined through the synthesis of networks of known elementary reactions constituting such pathways. This has been undertaken to reassess the validity of available mechanisms and to explore the possible existence of additional ones for the catalytic synthesis of ammonia. Synthesizing the networks of elementary reactions is exceedingly convoluted due to the combinatorial complexity arising from the fact the number of elementary reactions involved usually far exceeds that of available elementary balances, which is only 2 for the ammonia synthesis. Such a complexity can be circumvented by the rigorous and highly efficient, graph-theoretic method adopted in the present contribution. This method follows the general framework of a mathematically exact, combinatorial method established for process-network synthesis. It is based on a unique graph-representation in terms of process graphs (P-graphs), a set of axioms, and a group of combinatorial algorithms. The method renders it possible to generate with dispatch all feasible independent reaction networks, i.e., pathways, only once. The pathways violating any first principle of either stoichiometry or thermodynamics are eliminated. Moreover, the method is capable of directly generating rapidly the acyclic combinations of independent pathways.

Mass Action and Conservation of Current

Abstract: The law of mass action does not force a series of chemical reactions to have the same current flow everywhere. Interruption of far-away current does not stop current everywhere in a series of chemical reactions (analyzed according to the law of mass action), and so does not obey Maxwell’s equations. An additional constraint and equation is needed to enforce global continuity of current. The additional constraint is introduced in this paper in the special case that the chemical reaction describes spatial movement through narrow channels. In that case, a fully consistent treatment is possible using different models of charge movement. The general case must be dealt with by variational methods that enforce consistency of all the physical laws involved. Violations of current continuity arise away from equilibrium, when current flows, and the law of mass action is applied to a nonequilibrium situation, different from the systems considered when the law was originally derived. Device design in the chemical world is difficult because simple laws are not obeyed in that way. Rate constants of the law of mass action are found experimentally to change from one set of conditions to another. The law of mass action is not robust in most cases and cannot serve the same role that circuit models do in our electrical technology. Robust models and device designs in the chemical world will not be possible until continuity of current is embedded in a generalization of the law of mass action using a consistent variational model of energy and dissipation.

Parameter Sensitivity Analysis of an Induction Motor

Abstract: A simple dynamic model of an induction motor is presented in this paper based on engineering principles that describe the mechanical phenomena together with the electrical model. The investigated state space model consists of nonlinear state equations and linear output equations. The model has been verified under the usual controlled operating conditions when the speed is controlled. The effect of load on the controlled induction motor has been analyzed by simulation. The sensitivity analysis of the induction motor and the bridge of the inverter have been applied to determine the model parameters to be estimated.