Tibor Alpár

Modeling the shear rate and pressure drop in a hydrodynamic cavitation reactor with experimental validation based on KI decomposition studies

A mathematical model describing the shear rate and pressure variation in a complex flow field created in a hydrodynamic cavitation reactor (stator and rotor assembly) has been depicted in the present study. The design of the reactor is such that the rotor is provided with surface indentations and cavitational events are expected to occur on the surface of the rotor as well as within the indentations. The flow characteristics of the fluid have been investigated on the basis of high accuracy compact difference schemes and Navier-Stokes method. The evolution of streamlining structures during rotation, pressure field and shear rate of a Newtonian fluid flow have been numerically established. The simulation results suggest that the characteristics of shear rate and pressure area are quite different based on the magnitude of the rotation velocity of the rotor. It was observed that area of the high shear zone at the indentation leading edge shrinks with an increase in the rotational speed of the rotor, although the magnitude of the shear rate increases linearly. It is therefore concluded that higher rotational speeds of the rotor, tends to stabilize the flow, which in turn results into less cavitational activity compared to that observed around 2200-2500RPM. Experiments were carried out with initial concentration of KI as 2000ppm. Maximum of 50ppm of iodine liberation was observed at 2200RPM. Experimental as well as simulation results indicate that the maximum cavitational activity can be seen when rotation speed is around 2200-2500RPM.

General waste handling and recycling in particleboard production

This paper aims to analyze general waste handling in Hungarian particleboard production and give solutions based on experimental researches. During our research reuse of waste in Hungarian particleboard production was studied. A wood industrial branch, which can be considered as both a waste “producer” and a waste “re‐user”, recycler was mapped. This allowed an examination and analysis of both sides of waste handling. In the experimental work the effect of recycling dried impregnated decor paper in particleboard production was evaluated. The primary goal was to work out technologies for recycling non‐dangerous materials such as washing water, production and process waste from the cutting of boards. With these technologies general techniques for waste handling in the particleboard industry can be developed. The results of the experiments with impregnated paper showed that by adding crushed impregnated paper the strength of the particleboards can be increased or the same board properties can be achieved with reduced amounts of applied adhesive (UF). Based on this case study the waste handling in Hungarian particleboard companies can be worked out. More experimental researches should be made to give solutions on every waste handling needs. Solutions and advices for the particleboard industry to work in an environmental friendly and economical way are practical implications of the research. This paper was created based on a case study and researches at the University of West Hungary and Hungarian particleboard companies.