8 research outputs found
Wp艂yw modelu metody element贸w sko艅czonych na wsp贸艂czynnika wymiany ciep艂a wyznaczany z rozwi膮zania odwrotnego procesu laminarnego ch艂odzenia p艂yty metalowej
The industrial hot rolling mills are equipped with systems for controlled cooling of hot steel products. In the case of strip rolling mills the main cooling system is situated at run-out table to ensure the required strip temperature before coiling. One of the most important system is laminar jets cooling. In this system water is falling down on the upper strip surface. The proper cooling rate affects the final mechanical properties of steel which strongly dependent on microstructure evolution processes. Numerical simulations can be used to determine the water flux which should be applied in order to control strip temperature. The heat transfer boundary condition in case of laminar jets cooling is defined by the heat transfer coefficient, cooling water temperature and strip surface temperature. Due to the complex nature of the cooling process the existing heat transfer models are not accurate enough. The heat transfer coefficient cannot be measured directly and the boundary inverse heat conduction problem should be formulated in order to determine the heat transfer coefficient as a function of cooling parameters and strip surface temperature. In inverse algorithm various heat conduction models and boundary condition models can be implemented. In the present study two three dimensional finite element models based on linear and non-linear shape functions have been tested in the inverse algorithm. Further, two heat transfer boundary condition models have been employed in order to determine the heat transfer coefficient distribution at the hot plate cooled by laminar jets. In the first model heat transfer coefficient distribution over the cooled surface has been approximated by the witch of Agnesi type function with the expansion in time of the approximation parameters. In the second model heat transfer coefficient distribution over the cooled plate surface has been approximated by the surface elements serendipity family with parabolic shape functions. The heat transfer coefficient values at surface element nodes have been expanded in time by the cubic-spline functions. The numerical tests have shown that in the case of heat conduction model based on linear shape functions inverse solution differs significantly from the searched boundary condition. The dedicated finite element heat conduction model based on non-linear shape functions has been developed to ensure inverse determination of heat transfer coefficient distribution over the cooled surface in the time of cooling. The heat transfer coefficient model based on surface elements serendipity family is not limited to a particular form of the heat flux distribution. The solution has been achieved for measured temperatures of the steel plate cooled by 9 laminar jets.Nowoczesne linie walcowania blach na gor膮co posiadaj膮 instalacje do wymuszonego ch艂odzenia. Jego celem jest kontrolowanie szybko艣ci zmian temperatury blachy w ca艂ej obj臋to艣ci zapewniaj膮c tym wymagan膮 struktur臋 i w艂asno艣ci mechaniczne. Ch艂odzenie jest prowadzone w ko艅cowej cz臋艣ci linii technologicznej, w kt贸rej nad g贸rn膮 i pod doln膮 powierzchni膮 gor膮cego pasma umieszczone s膮 urz膮dzenia dostarczaj膮ce wod臋 ch艂odz膮c膮. Z uwagi na spos贸b podawania wody ch艂odz膮cej mo偶na je podzieli膰 na trzy g艂贸wne systemy: ch艂odzenie laminarne, ch艂odzenie z u偶yciem kurtyn wodnych oraz ch艂odzenie natryskiem wodnym. W istniej膮cych liniach walcowniczych mo偶na spotka膰 kombinacje poszczeg贸lnych system贸w. Projektowanie system贸w ch艂odniczych jest trudne i musi by膰 wspomagane przez modele matematyczne i numeryczne wymiany ciep艂a mi臋dzy gor膮c膮 powierzchni膮 blachy a wod膮 i otoczeniem. Podstawowe znaczenie dla symulacji procesu ma przyj臋cie poprawnych warto艣ci wsp贸艂czynnik贸w wymiany ciep艂a, kt贸rych znajomo艣膰 w du偶ej mierze determinuje dok艂adno艣膰 oblicze艅. Wsp贸艂czynnik wymiany ciep艂a nie mo偶e by膰 zmierzony bezpo艣rednio i konieczne jest zastosowanie rozwi膮za艅 odwrotnych zagadnienia przewodzenia ciep艂a. W algorytmach odwrotnych mo偶liwe jest u偶ycie r贸偶nych modeli do rozwi膮zania r贸wnania przewodzenia ciep艂a. Zastosowane modele w istotnym stopniu wp艂ywaj膮 na jako艣膰 rozwi膮zania odwrotnego. W pracy przedstawiono wyniki test贸w dw贸ch modeli przewodzenia ciep艂a opartych na liniowych i nieliniowych funkcjach kszta艂tu w algorytmie metody element贸w sko艅czonych. Testowano r贸wnie偶 dwa modele aproksymacji warunku brzegowego. Wybrany model warunku brzegowego i model metody element贸w sko艅czonych wykorzystuj膮cy nieliniowe funkcje kszta艂tu zastosowano do wyznaczenia wsp贸艂czynnika wymiany ciep艂a w procesie ch艂odzenia gor膮cej p艂yty stalowej 9 strumieniami wody swobodnie opadaj膮cej na jej powierzchnie. Uzyskano rozwi膮zanie przedstawiajace rozk艂ad wsp贸艂czynnika wymiany ciep艂a i g臋sto艣ci strumienia ciep艂a na powierzchni p艂yty w czasie jej chodzenia
Wykorzystanie techniki SEM do analizy chemicznej materia艂贸w ogniotrwa艂ych
In Polish industry, especially in the iron and steel industry, uses large amounts of refractory materials. Waste materials are disposed of through a common storage. For altemative methods of waste management of refractory materials, it is necessary to carry out several studies. One of the basie research include determine the chemical composition of refractory materials exposed to li膮uid steel. This paper presents the results of microscopic examination of changes in the concentration of refractory elements in new and used.W polskim przemy艣le, zw艂aszcza w hutnictwie 偶elaza i stali, wykorzystuje si臋 du偶e ilo艣ci materia艂贸w ogniotrwa艂ych. Zu偶yte materia艂y s膮 bardzo cz臋sto unieszkodliwiane przez sk艂adowanie. Zastosowanie innych metod zagospodarowania odpadowych materia艂贸w ogniotrwa艂ych wi膮偶臋 si臋 z konieczno艣ci膮 przeprowadzenia wielu bada艅. Jednym z podstawowych bada艅 jest m.in. okre艣lenie zmiany sk艂adu chemicznego materia艂贸w ogniotrwa艂ych nara偶onych na kontakt z ciek艂膮 stal膮. W niniejszym artykule przedstawiono wyniki bada艅 mikroskopowych dotycz膮cych zmiany st臋偶enia pierwiastk贸w w materia艂ach ogniotrwa艂ych nowych i zu偶ytyc
Badania numeryczne spalania gazu ziemnego w piecu przepychowym
The paper presents results of the preliminary numerical model of the natural gas combustion in the furnace. The production technology requirements strongly limit the possibility of any action interfering in the process, which could improve the gas pollutants emission. The optimization of the pollutants generation, which strongly depends on the parameters of the process, is important aim to understand concerning the environmental protection regulations. The simple model of methane com-bustion mechanism has been studied taking into account nitrogen oxides formation. The model, using Eddy Dissipation Model, calculates the concentration of gas pollutants. The input data (e.g. geometry, flows, furnace zoning, types of applied burners etc.) were taking from real device (the pusher fumace from the rolling mill). The calculations were not included the presence of the charge in the process. The emission of pollutants from modeling of methane combustion has been presented. Although the results do not correspond with real condition of the furnace, no charge in the furnace, this first step of modeling allows the extension of the model taking into account the heat exchange in the atmosphere of the furnace.W artykule przedstawiono wyniki oblicze艅 uzyskanych na podstawie zaprojektowanego numerycznego modelu spalania gazu ziemnego w piecu przemys艂owym. Wymagania technologii produkcji stali mocno ograniczaj膮 mo偶liwo艣ci ingerencji w proces spalania. Modyfikowanie przebiegu procesu spalania mo偶e prowadzi膰 do ograniczenia emisji zanieczyszcze艅 gazowych. W ograniczeniu emisji zanieczyszcze艅, kt贸ra w du偶ym stopniu zale偶y od parametr贸w procesu, istotne jest uwzgl臋dnienie przepis贸w ochrony 艣rodowiska. Zastosowany model mechanizmu spalania metanu badano, uwzgl臋dniaj膮c formowanie si臋 tlenk贸w azotu, kt贸re s膮 szkodliwe dla 艣rodowiska naturalnego. Do oblicze艅 st臋偶e艅 zanieczyszcze艅 gazowych wykorzystano model EDM. Dane wej艣ciowe (np. geometria, przep艂ywy, strefy pieca, rodzaje zastosowanych palnik贸w itp.) oparte s膮 na parametrach rzeczywistych (piec przepychowy z walcowni). W artykule przedstawiono wyniki oblicze艅 emisji zanieczyszcze艅 gazowych z procesu spalania gazu ziemnego
Wp艂yw modelu promieniowania na rozk艂ad g臋sto艣ci strumienia ciep艂a w piecu przepychowym
A three dimensional numerical model of the heat exchange during a charge heating process in a pusher furnace, using the finite element method, was used in this study. The radiative heat exchange in the furnace chamber was carried out based on two methods: the zone method and the method of basing on the average configuration ratio. In the zone method the flux of radiation energy reaching the surface of the heated charge was determined by performing calculations of brightness in a multi-surface closed system which is the pusher furnace chamber filled with an emitting-absorbing medium. In the second case an average configuration ratio was used by setting the radiation energy flux through linking the walls temperature with the furnace atmosphere temperature.W pracy wykorzystano tr贸jwymiarowy model numeryczny wymiany ciep艂a w czasie nagrzewania wsadu w piecu przepychowym przy zastosowaniu metody element贸w sko艅czonych. Radiacyjna wymian臋 ciep艂a w komorze pieca realizowano w oparciu o dwie metody: metod臋 strefowa oraz w oparciu o 艣redni wsp贸艂czynnik konfiguracji. W metodzie strefowej strumie艅 energii radiacyjnej docieraj膮cej do powierzchni nagrzewanego wsadu wyznaczano prowadz膮c obliczenia jasno艣ci w wielo-powierzchniowym uk艂adzie zamkni臋tym jakim jest komora pieca przepychowego wype艂nionego o艣rodkiem emituj膮co-poch艂aniaj膮cym. W drugim przypadku wykorzystano 艣redni wsp贸艂czynnik konfiguracji wyznaczaj膮c strumie energii radiacyjnej poprzez powiazanie temperatury 艣cian z temperatura atmosfery pieca
Wp艂yw usytuowania palnik贸w w piecu grzewczym na pole temperatury nagrzewanego wsadu do przer贸bki plastycznej
Charge heating in industrial furnaces is a difficult and complex process. There are many physical phenomena which influence heat transfer. At the charge surface heat transfer takes place by radiation and convection. In order to ensure correct operation of the technological system, it is necessary to achieve the required charge temperature in the whole volume and ensure its uniformity. The influence of selected burner locations inside the furnace on the charge temperature has been analysed. The temperature field and its uniformity in the round charge made of steel for hot open die forging have been analysed. The model and numerical calculations were performed with the ANSYS-Fluent 14.5 package.Nagrzewanie wsadu w piecach przemys艂owych jest trudnym i z艂o偶onym procesem. Celem zapewnienia prawid艂owej pracy ci膮gu technologicznego konieczne jest osi膮gni臋cie przez wsad wymaganej temperatury w ca艂ej obj臋to艣ci, oraz zapewnienie odpowiedniej r贸wnomierno艣ci nagrzewania. W pracy okre艣lono wp艂yw sposobu nagrzewania wsadu w piecu komorowym dla wybranych wariant贸w usytuowania palnik贸w grzewczych. Analizie poddano pole temperatury i jego jednorodno艣膰 w nagrzewanym wsadzie stalowym przeznaczonym do przer贸bki plastycznej. Model i obliczenia wykonano pakietem numerycznym ANSYS-Fluent 14.5
Modelling of Heat Transfer at the Solid to Solid Interface
In technological process of steel industry heat transfer is a very important factor. Heat transfer plays an essential role especially in rolling and forging processes. Heat flux between a tool and work piece is a function of temperature, pressure and time. A methodology for the determination of the heat transfer at solid to solid interface has been developed. It involves physical experiment and numerical methods. The first one requires measurements of the temperature variations at specified points in the two samples brought into contact. Samples made of C45 and NC6 steels have been employed in physical experiment. One of the samples was heated to an initial temperature of: 800掳C, 1000掳C and 1100掳C. The second sample has been kept at room temperature. The numerical part makes use of the inverse method for calculating the heat flux and at the interface. The method involves the temperature field simulation in the axially symmetrical samples. The objective function is bulled up as a dimensionless error norm between measured and computed temperatures. The variable metric method is employed in the objective function minimization. The heat transfer coefficient variation in time at the boundary surface is approximated by cubic spline functions.
The influence of pressure and temperature on the heat flux has been analysed. The problem has been solved by applying the inverse procedure and finite element method for the temperature field simulations. The self-developed software has been used. The simulation results, along with their analysis, have been presented
Numerical Evaluation of Gear Ring Behavior During Various Cooling Conditions
The phase transformation model incorporated via the user subroutines to the commercial finite element software to accurately predict changes occurring during cooling of metallic components is presented in the paper. The cooling process of steel rings used in airplanes was selected as a case study. Particular attention was put on heterogeneities occurring in temperature field, which influence phase transformations and eventually residual stresses. Developed model was used in the present work to evaluate influence of different cooling conditions on ring behaviour