Prijenos topline tijekom hlađenja vrućih površina pomoću vodenih sapnica

Method of cooling in a secondary zone of continuous casting of steel has a significant influence on a quality of continuously cast products mainly from the point of view of internal and surface defects as well as zonal segregations. At the department of thermal engineering, a physical model of the secondary zone has been developed, which enables testing of both water and water-air nozzles. During laboratory measurements cooling effects of a cone nozzle have been expressed by means of three parameters. Most commonly used parameter is an admission characteristic, infrequently heat transfer coefficient is determined and newly a measuring of dynamic impact of the cooling water has been introduced.Tijekom kontinuiranog lijevanja čelika, hlađenje sekundarne zone od značajnog je utjecaja na kvalitetu odljevaka sa aspekta unutrašnjih i površinskih pogrešaka te u kontekstu zonske segregacije u materijalu. U odjelu za termoenergetiku razvijen je fizikalni model sekundarne zone, kojim je omogućeno ispitivanje vodenih sapnica i sapnica za hlađenje mješavinom vode i zraka. Tijekom laboratorijskih mjerenja, efekti hlađenja koničnom sapnicom izraženi su trima parametrima. Nejčešći je pritom parameter admisijske karakteristike, ponekad se određuje i koeficijent prijelaza topline a recentno je uvedeno mjerenje dinamičkog utjecaja rashladne vode

Modernization of Charpy 's intpact test stand

W artykule zaproponowano koncepcję modernizacji stanowiska do pomiaru udarności stali metodą Charpy'ego. Modernizacja ma na celu rejestrację siły w trakcie udaru i wyznaczenie strzałki ugięcia w momencie zerwania próbki. W pierwszych dwóch rozdziałach pokrótce opisano przyczyny pękania stali w okolicy spoin i wynikającą stąd potrzebę badania jej udarności. W następnych dwóch opisano metodę modernizacji stanowiska i przedstawiono osprzęt pomiarowy służący temu celowi. Doraźne korzyści wynikające z modernizacji to zwiększenie dokładności wyznaczania udarności stali oraz wizualizacja próby laboratoryjnej dla celów dydaktycznych. Docelowe korzyści to uzyskanie wyników analizy matematycznej z przebiegu impulsu siły łamiącej próbkę w czasie udaru. Wyniki z próby udarowej i atest materiałowy stali stanowić będą komputerowe archiwum dla przyszłych ekspertyz porównawczych.The preliminary conception of additional equipment for the Charpy's impact test stand is presented. It enables successive measurement of impulse force curve and deflection of steel specimen during strike tests. After mathematic process data are stored in computer archive files and can be used in future evaluation of fragile breaking. The realised test stand is also very helpful in educational process and enables students to be full acquainted with the modern laboratory equipment

Measurement of impact force and deflection in Charpy impact test

Tradycyjna próba Charpy'ego wyznacza jedynie współczynnik udarności stali. W artykule przedstawiono modernizację stanowiska umożliwiającą pomiar dodatkowych wielkości, to jest siły udaru oraz strzałki ugięcia badanej próbki.The paper presents modernization of the Charpy impact test machine. The machine determines the energy absorbed by a test piece of steel during fracture. The impact force and deflection are measured during the test on the modernized laboratory stand. The historical introduction to the welding technology is described, too

Heat transfer during cooling of hot surfaces by water nozzles

Method of cooling in a secondary zone of continuous casting of steel has a significant influence on a quality of continuously cast products mainly from the point of view of internal and surface defects as well as zonal segregations. At the department of thermal engineering, a physical model of the secondary zone has been developed, which enables testing of both water and water-air nozzles. During laboratory measurements cooling effects of a cone nozzle have been expressed by means of three parameters. Most commonly used parameter is an admission characteristic, infrequently heat transfer coefficient is determined and newly a measuring of dynamic impact of the cooling water has been introduced

The Influence Of Calcite On The Ash Flow Temperature For Semi-Anthracite Coal From Donbas District

This paper presents the results of research focused on the lowering of ash flow temperature at semianthracite coal from Donbas district by means of additive (calcite) dosing. Ash fusion temperatures were set for two coal samples (A, B) and for five various states (samples of ash without any additives, with 1%, with 3%, with 5% and with 7% of the additive) in total. The macroscopicphotographic method was used for identifying all specific temperatures. Obtained outputs prove that A type coal has a lower value of sphere temperature than B type coal in the whole scope of percentage representation of the additive. The flow temperature dropped in total from 1489°C to 1280°C, i.e. by 14% during the test of coal of type A with 7% of the additive; while it was near 10% for coal of type B (from 1450°C to 1308°C). Numerical simulations of the process showed that it is not effective to add an additive with a grain size lower than 280 μm by means of wastevapour burners

The invasive ambrosia beetle, Gnathotrichus materiarius (Coleoptera: Curculionidae), in Central Europe

Gnathotrichus materiarius Fitch, 1858 is an invasive bark beetle that colonizes conifers and has spread widely in Europe. The beetle was introduced from North America to Western Europe, where it was first detected in France in 1933. In countries of Western and Northern Europe, the first detections were found at ports or airports, which probably served as sources of further spread. Gnathotrichus materiarius spread eastward to the Czech Republic and other countries in Central Europe from Germany and Poland and spread northward from Italy to Slovenia. The presence of wilting spruces, outbreaks dominated by Ips typographus Linnaeus, 1758, and the subsequent transport of timber have probably accelerated the spread of G. materiarius. It is possible that G. materiarius was imported with timber to Austria, the Czech Republic, and Poland. Although G. materiarius has been present in Europe for almost 100 yr, and even though its host trees include Picea and Pinus spp., which are abundant in Central European forests, no significant damage caused by this beetle has been detected or reported. Gnathotrichus materiarius is a typical secondary pest in that it multiplies on decaying trees or trees already infested and killed by other bark beetle species. It has 2 generations a year in Central Europe. The beetles of G. materiarius occur the whole year, but the flight of adults starts in early May and the offspring beetles emerge in mid-July. The adults of F2 generation overwinter in wood. The best method for monitoring and detecting the presence of G. materiarius is the use of ethanol-baited traps. © 2024 The Author(s). Published by Oxford University Press on behalf of Entomological Society of America

Determination of permeability and inertial resistance coefficient of filter inserts used in the cleaning of natural gas

The article describes a methodology for determination of permeability and inertial resistance coefficient of filter inserts used for the separation of solid and liquid impurities in natural gas. The parameters of the filter inserts are described by analytical relations and their real values are obtained experimentally. The realized experiment was focused on the measurement of the pressure drop in the insert, with which both permeability and inertial resistance coefficient were possible to be expressed. The experiment was performed on the reduced physical model of the filter separator, which was constructed at a scale of 1:127. During the experimental measuring the working medium was pressure air. In a real filter separator there is compressed natural gas used as the working medium. The reduced model, therefore, had to meet the basic requirement of similarity of flowing in the model and the real object, which was based on equality of the Reynolds criteria for the work and the model.Web of Science26111110

Verification of pollutant creation model at dendromass combustion

Results of verification of two mathematical models presenting the creation of three pollutants at wood combustion in a low power pellet boiler are published in this article. The type of boiler used in the experiment was EKO-KARBON ÚSPOR-AUTOMAT with nominal power of 18 kW. Nitrogen oxides, carbon oxide, and total organic carbon were tested. The models elaborated on the basic theory of dimensional analysis. In the first model, the emissions produced in the wood combustion process were described under the condition that the combustion product temperature in boiler outlet is one relevant parameter in the mathematical model. Combustion air volume flow, combustion air temperature, combustion product temperature, boiler power, and wood calorific power are other parameters in the model. The second model describes the mutual coherence of the same pollutants, provided that flame temperature, instead of combustion product temperature, is incorporated into the model. The outputs obtained from both models are subjected to the same combustion conditions.Web of Science26124169416