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Wyświetlanie 1-15 z 343
Tytuł:
A concrete heat accumulator for use in solar heating systems - a mathematical model and experimental verification
Autorzy:
Sacharczuk, J.
Taler, D.
Powiązania:
https://bibliotekanauki.pl/articles/240260.pdf
Data publikacji:
2014
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
heat storage
solar heating system
control volume finite element method
akumulowanie ciepła
kolektor słoneczny
Opis:
The article presents a numerical model of the concrete heat accumulator for solar heating systems. Model uses control volume finite element method with an explicit solution method for time integration. The use of an explicit method is an essential advantage in the simulation of time-dependent changes in temperature of the air at the accumulator inlet. The study compares the results of numerical model calculations of the accumulator heating with experimental measurements and with computational fluid dynamics modeling. The comparison shows a good correlation between the results of calculation using the model and the results of measurements.
Źródło:
Archives of Thermodynamics; 2014, 35, 3; 281-295
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Galerkin approximation method including space dimensional reduction - applied for solution of a heat conduction equation
Autorzy:
Nakonieczny, K.
Powiązania:
https://bibliotekanauki.pl/articles/118009.pdf
Data publikacji:
2012
Wydawca:
Polskie Towarzystwo Promocji Wiedzy
Tematy:
Galerkin approximation
dimensional reduction
heat conduction
Opis:
A multivariate data fitting procedure, based on the Galerkin minimization method, is studied in this paper. The main idea of the developed approach consists in projecting the set of data points from the original, higher-dimensional space, onto a line section. Then, the approximation problem is solved in the resulting one-dimensional space. The elaborated recipe can be designed so that it is computationally more efficient than the schemes based on the least squares minimization. The performance of the method is studied by comparison with the least squares and the moving least squares procedures in a number of examples, including the solution of the heat diffusion equation.
Źródło:
Applied Computer Science; 2012, 8, 2; 48-58
1895-3735
Pojawia się w:
Applied Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A method to achieve comparable thermal states of car brakes during braking on the road and on a high-speed roll-stand
Metoda osiągania porównywalnych stanów cieplnych hamulców samochodowych podczas hamowania na drodze i na szybkoobrotowym stanowisku rolkowym
Autorzy:
Wolff, A.
Powiązania:
https://bibliotekanauki.pl/articles/224245.pdf
Data publikacji:
2010
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
hamulce samochodowe
skuteczność hamowania
wymiana ciepła
diagnostyka
automative brakes
heat transfer
thermal state of brakes
diagnostics tests
Opis:
The temperature of a brake friction surface influences significantly the braking effectiveness. The paper describes a heat transfer process in car brakes. Using a developed program of finite element method, the temperature distributions in brake rotors (disc and drum brake) of a light truck have been calculated. As a preliminary consistency criterion of the brake thermal state in road and roll-stand braking conditions, a balance of the energy cumulated in the brake rotor has been taken into account. As the most reliable consistency criterion an equality of average temperatures of the friction surface has been assumed. The presented method allows to achieve on a roll-stand the analogical thermal states of automotive brakes, which are observed during braking in road conditions. Basing on this method, it is possible to calculate the braking time and force for a high-speed roll-stand. In contrast to the previous papers of the author, new calculation results have been presented.
Temperatura powierzchni ciernej hamulca w istotny sposób wpływa na skuteczność hamowania. Artykuł opisuje proces wymiany ciepła w hamulcach samochodowych. Stosując opracowany program metody elementów skończonych, wyznaczono rozkłady temperatur w wirnikach hamulców (tarczy i bębna) lekkiego samochodu dostawczego. Jako wstępne kryterium zgodności stanów cieplnych hamulca w warunkach hamowania na drodze i na stanowisku rolkowym założono bilans energii akumulowanej w wirniku hamulca. Jako bardziej wiarygodne kryterium zgodności przyjęto równość średnich temperatur powierzchni ciernej hamulca. Przedstawiona metoda umożliwia uzyskiwanie na stanowisku rolkowym analogicznych stanów cieplnych hamulców samochodowych, jakie występują w warunkach hamowania na drodze. W oparciu o tę metodę możliwe jest obliczenie czasu trwania i siły hamowania na szybkoobrotowym stanowisku rolkowym. W odróżnieniu od poprzednich artykułów autora, przedstawiono tu nowe wyniki obliczeń.
Źródło:
Archives of Transport; 2010, 22, 2; 259-273
0866-9546
2300-8830
Pojawia się w:
Archives of Transport
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A method to improve repeatability and reproducibility of the results of examination of the rate of heat released by shipbuilding materials
Autorzy:
Sychta, K.
Powiązania:
https://bibliotekanauki.pl/articles/258830.pdf
Data publikacji:
2014
Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Tematy:
intensity of the secretion of the warmth
dynamic measurements
dynamic error
Opis:
A specialised integrated research rig has been designed and built to validate the method of heat release dynamic error correction based on the FTP Code, part 5, and to control the rig operation and calibration. The basic rig component is a programmed gas burner with an option to select the function and parameters of burner’s operation. The use of the programmed burner increased the level of consistency (reproducibility and correlation) of the results of heat release rate measurements.
Źródło:
Polish Maritime Research; 2014, 1; 70-76
1233-2585
Pojawia się w:
Polish Maritime Research
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Method to Make Classification of the Heat Treatment Processes Performed on Bronze Using Incomplete Knowledge
Autorzy:
Kluska-Nawarecka, S.
Górny, Z.
Regulski, K.
Wilk-Kołodziejczyk, D.
Jančíková, Z.
David, J.
Powiązania:
https://bibliotekanauki.pl/articles/947501.pdf
Data publikacji:
2014
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
information technology
foundry industry
heat treatment
classification algorithms
rough sets
data mining
technologia informacyjna
przemysł odlewniczy
obróbka cieplna
algorytmy klasyfikacyjne
zbiory przybliżone
Opis:
The article describes the problem of selection of heat treatment parameters to obtain the required mechanical properties in heat- treated bronzes. A methodology for the construction of a classification model based on rough set theory is presented. A model of this type allows the construction of inference rules also in the case when our knowledge of the existing phenomena is incomplete, and this is situation commonly encountered when new materials enter the market. In the case of new test materials, such as the grade of bronze described in this article, we still lack full knowledge and the choice of heat treatment parameters is based on a fragmentary knowledge resulting from experimental studies. The measurement results can be useful in building of a model, this model, however, cannot be deterministic, but can only approximate the stochastic nature of phenomena. The use of rough set theory allows for efficient inference also in areas that are not yet fully explored.
Źródło:
Archives of Foundry Engineering; 2014, 14, 2; 69-72
1897-3310
2299-2944
Pojawia się w:
Archives of Foundry Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A new method for calculation of high-temperature capacitors thermal resistance
Autorzy:
Hapka, A.
Powiązania:
https://bibliotekanauki.pl/articles/118564.pdf
Data publikacji:
2016
Wydawca:
Politechnika Koszalińska. Wydawnictwo Uczelniane
Tematy:
high-temperature capacitors
heat profiles
thermal resistance
kondensatory wysokotemperaturowe
profile cieplne
rezystancja termiczna
Opis:
In this paper, issues related to the self-heating phenomenon in high-temperature capacitors are described. Measurements of capacitance and parasitic resistance, as a function of frequency and ambient temperature of considered capacitors are presented. Novel procedures for calculation of internal temperature changes are proposed and a novel method for acquiring thermal resistance values is developed and its numerical error is estimated.
W niniejszej pracy, opisano zagadnienia związane ze zjawiskiem samonagrzewania w kondensatorach wysokotemperaturowych. Przedstawiono wyniki pomiarów pojemności i oporności pasożytniczej wybranych kondensatorów w funkcji częstotliwości i temperatury otoczenia. Zaproponowano nową metodę obliczania zmian temperatury wewnątrz elementu oraz wyznaczania jego rezystancji termicznej. Oszacowano błędy numeryczne proponowanej metody.
Źródło:
Zeszyty Naukowe Wydziału Elektroniki i Informatyki Politechniki Koszalińskiej; 2016, 9; 99-106
1897-7421
Pojawia się w:
Zeszyty Naukowe Wydziału Elektroniki i Informatyki Politechniki Koszalińskiej
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A new method for determining allowable medium temperature during transient operation of thick-walled elements in a supercritical power plant
Autorzy:
Duda, P.
Rząsa, D.
Powiązania:
https://bibliotekanauki.pl/articles/240343.pdf
Data publikacji:
2010
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
kocioł parowy
naprężenia całkowite
optymalizacja
wymiana ciepła
heat transfer
optimization
steam boilers
total stresses
Opis:
Construction elements of supercritical power plants are subjected to high working pressures and high temperatures while operating. Under these conditions high stresses in the construction are created. In order to operate safely, it is important to monitor stresses, especially during start-up and shut-down processes. The maximum stresses in the construction elements should not exceed the allowable stress limit. The goal is to find optimum operating parameters that can assure safe heating and cooling processes [1-5]. The optimum parameters should guarantee that the allowable stresses are not exceeded and the entire process is conducted in the shortest time. In this work new numerical method for determining optimum working parameters is presented. Based on these parameters heating operations were conducted. Stresses were monitored during the entire processes. The results obtained were compared with the German boiler regulations - Technische Regeln fur Dampfkessel 301.
Źródło:
Archives of Thermodynamics; 2010, 31, 3; 55-72
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A new method for optimum heating of pressure components in supercritical steam power blocks
Autorzy:
Rząsa, D.
Duda, P.
Powiązania:
https://bibliotekanauki.pl/articles/240145.pdf
Data publikacji:
2012
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
kotły parowe
metody optymalizacji
wymiana ciepła
heat transfer
optimization methods
steam boilers
total stresses
Opis:
One of the major concerns of the power energy industries is a proper operation of steam power blocks. Pressurized working medium and high temperature cause very high stresses in the construction elements such as collectors, separators or steam valves. They are exposed to sudden temperature and pressure changes that cause high stresses at certain points. Additionally, the cyclic character of loading causes material fatigue, known as low-cyclic fatigue, which may lead to the formation of fracture. Thus, methodologies offered by many companies should ensure reliable and safe operation of steam power blocks. The advanced numerical solutions for determining time-optimum medium temperature changes are presented. They are based on Levenberg-Marquardt and nonlinear programming by quadratic Lagrangian methods. The methods allow us to find parameters for start-up and shut-down operation that can reduce total stresses to limits governed by European regulations. Furthermore, the heating and cooling operations are conducted in a shortest time possible.
Źródło:
Archives of Thermodynamics; 2012, 33, 3; 133-145
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Novel Identification Method of Thermal Resistances of Thermoelectric Modules Combining Electrical Characterization Under Constant Temperature and Heat Flow Conditions
Autorzy:
Siouane, S.
Jovanović, S.
Poure, P.
Powiązania:
https://bibliotekanauki.pl/articles/136156.pdf
Data publikacji:
2016
Wydawca:
EEEIC International Barbara Leonowicz Szabłowska
Tematy:
Thermoelectric Module (TEM)
thermal resistance
contact thermal resistance
electrical characterization
identification
electrical models
Opis:
The efficiency of a Thermoelectric Module (TEM) is not only influenced by the material properties, but also by the heat losses due to the internal and contact thermal resistances. In the literature, the material properties are mostly discussed, mainly to increase the well-known thermoelectric figure of merit ZT. Nevertheless, when a TEM is considered, the separate characterization of the materials of the p and n elements is not enough to have a suitable TEM electrical model and evaluate more precisely its efficiency. Only a few recent papers deal with thermal resistances and their influence on the TEM efficiency; mostly, the minimization of these resistances is recommended, without giving a way to determine their values. The aim of the present paper is to identify the internal and contact thermal resistances of a TEM by electrical characterization. Depending on the applications, the TEM can be used either under constant temperature gradient or constant heat flow conditions. The proposed identification approach is based on the theoretical electrical modeling of the TEM, in both conditions. It is simple to implement, because it is based only on open circuit test conditions. A single electrical measurement under both conditions (constant-temperature and constant-heat) is needed. Based on the theoretical electrical models, one can identify the internal and thermal resistances.
Źródło:
Transactions on Environment and Electrical Engineering; 2016, 1, 4; 44-49
2450-5730
Pojawia się w:
Transactions on Environment and Electrical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A numerical examination of an unsteady nonlinear MHD flow in the presence of thermal radiation and heat generation
Autorzy:
Agbaje, T. M.
Leach, P. G. L.
Powiązania:
https://bibliotekanauki.pl/articles/1839890.pdf
Data publikacji:
2021
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
przepływ MHD
promieniowanie cieplne
wytwarzanie ciepła
unsteady MHD flow
spectral perturbation method
spectral relaxation method
thermal radiation
heat generation
Opis:
In this study, the spectral perturbation method and the spectral relaxation method are used to solve the nonlinear differential equations of an unsteady nonlinear MHD flow in the presence of thermal radiation and heat generation. The SPM is mainly based on series expansion, generating series approximation coupled with the Chebyshev spectral method. The numerical results generated using the spectral perturbation method were compared with those found in the literature, and the two results were in good agreement.
Źródło:
International Journal of Applied Mechanics and Engineering; 2021, 26, 1; 1-17
1734-4492
2353-9003
Pojawia się w:
International Journal of Applied Mechanics and Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A numerical method for viscous flow in a driven cavity with heat and concentration sources placed on its side wall
Autorzy:
Ambethkar, V.
Basumatary, L. R.
Powiązania:
https://bibliotekanauki.pl/articles/122794.pdf
Data publikacji:
2018
Wydawca:
Politechnika Częstochowska. Wydawnictwo Politechniki Częstochowskiej
Tematy:
numerical method
viscous flow
heat source
concentration source
driven square cavity
general algorithm
stability conditions
isotherms
streamlines
geometric center
heat and mass transfer
metoda numeryczna
lepki przepływ
źródło ciepła
warunki stabilności
izotermy
transfer ciepła
transfer masy
Opis:
This paper proposes a method to numerically study viscous incompressible two-dimensional steady flow in a driven square cavity with heat and concentration sources placed on its side wall. The method proposed here is based on streamfunction-vorticity (Ψ-ξ) formulation. We have modified this formulation in such a way that it suits to solve the continuity, x and y-momentum, energy and mass transfer equations which are the governing equations of the problem under investigation in this study. No-slip and slip wall boundary conditions for velocity, temperature and concentration are defined on walls of a driven square cavity. In order to numerically compute the streamfunction Ψ, vorticityfunction ξ , temperature θ, concentration C and pressure P at different low, moderate and high Reynolds numbers, a general algorithm was proposed. The sequence of steps involved in this general algorithm are executed in a computer code, developed and run in a C compiler. We propose that, with the help of this code, one can easily compute the numerical solutions of the flow variables such as velocity, pressure, temperature, concentration, streamfunction, vorticityfunction and thereby depict and analyze streamlines, vortex lines, isotherms and isobars, in the driven square cavity for low, moderate and high Reynolds numbers. We have chosen suitable Prandtl and Schmidt numbers that enables us to define the average Nusselt and Sherwood numbers to study the heat ad mass transfer rates from the left wall of the cavity. The stability criterion of the numerical method used for solving the Poisson, vorticity transportation, energy and mass transfer has been given. Based on this criterion, we ought to choose appropriate time and space steps in numerical computations and thereby, we may obtain the desired accurate numerical solutions. The nature of the steady state solutions of the flow variables along the horizontal and vertical lines through the geometric center of the square cavity has been discussed and analyzed. To check the validity of the computer code used and corresponding numerical solutions of the flow variables obtained from this study, we have to compare these with established steady state solutions existing in the literature and they have to be found in good agreement.
Źródło:
Journal of Applied Mathematics and Computational Mechanics; 2018, 17, 3; 17-30
2299-9965
Pojawia się w:
Journal of Applied Mathematics and Computational Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Predictive Method for the Heat of Explosion of Non-ideal Aluminized Explosives
Autorzy:
Zhang, Q.
Chang, Y.
Powiązania:
https://bibliotekanauki.pl/articles/358737.pdf
Data publikacji:
2013
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Tematy:
aluminized explosives
heat of explosion
thermodynamic
nonideal explosives
high energy materials
Opis:
The heat of explosion is one of the most important thermodynamic parameters of aluminized explosives. Two improvements in numerical calculations to predict the behaviour of the explosion of non-ideal aluminized explosives were completed in this work. The chemical reaction between aluminum and the C-J detonation products of high energy ingredients was determined and the equation of state for the detonation products of high energy ingredients was revised. The constant k in the BKW equation was revised to obtain perfect results for predicting the C-J parameters for high energy ingredients. The predicted results show that the heats and temperatures of aluminized explosives become maximized when the mass fraction of aluminum powder is 30%, which is in good agreement with the results obtained by empirical formulae.
Źródło:
Central European Journal of Energetic Materials; 2013, 10, 4; 541-554
1733-7178
Pojawia się w:
Central European Journal of Energetic Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A sequential and global method of solving an inverse problem of heat conduction equation
Sekwencyjna i globalna metoda rozwiązania zagadnienia odwrotnego dla równania przewodnictwa ciepła
Autorzy:
Ciałkowski, M.
Grysa, K.
Powiązania:
https://bibliotekanauki.pl/articles/280136.pdf
Data publikacji:
2010
Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Tematy:
inverse problem
heat conduction
sequential method
global method
Opis:
The paper presents a solution to an inverse problem based on the analy- tical form of the direct problem solution in the convolutional form. The analytical form T (r, t) is a surface that is fitted to temperature patterns measured (and charged with errors) at the internal points. In the case of quickly-varying patterns, the solution to the inverse problem is highly sen- sitive to measurement errors (short sampling times). In order to obtain reliable results, the method of sequential (step by step) and global solving of the inverse problem was used together with smoothing the measurement results with the help of hyperbolic spline functions. The numerical results confirm effectiveness of the methods presented in the paper.
W pracy przedstawiono rozwiązanie zagadnienia odwrotnego w oparciu o analityczną postać rozwiązania zagadnienia prostego w postaci splotowej. Ta postać analityczna T (r, t) jest powierzchnią, która jest dopasowywana do przebiegów temperatury pomierzonej (obciążonej błędem) w punktach wewnętrznych. Dla przebiegów szybkozmiennych rozwiązanie zagadnienia odwrotnego jest bardzo wrażliwe na błędy pomiarów (małe czasy próbkowania). Dla otrzymania wiarygodnych wyników zastosowano metodę sekwencyjnego (z kroku na krok) i globalnego rozwiązywania zagadnienia odwrotnego w połączeniu z wygładzaniem wyników pomiarowych za pomocą hiperbolicznych funkcji sklejanych. Wyniki obliczeń numerycznych potwierdzają efektywność przedstawionych metod.
Źródło:
Journal of Theoretical and Applied Mechanics; 2010, 48, 1; 111-134
1429-2955
Pojawia się w:
Journal of Theoretical and Applied Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Simple and Reliable Method for Predicting the Detonation Velocity of CHNOFCl and Aluminized Explosives
Autorzy:
Keshavarz, M. H.
Zamani, A.
Powiązania:
https://bibliotekanauki.pl/articles/951480.pdf
Data publikacji:
2015
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Tematy:
decomposition reaction
heat of detonation
detonation velocity
CHNOFClAl explosive
loading density
Opis:
A reliable method is introduced for predicting the detonation velocity of CHNOFClAl explosives through suitable decomposition paths. The predicted decomposition products are used to estimate the heat of detonation (decomposition) and the detonation velocity. For non-ideal aluminized explosives, the Chapman-Jouguet detonation velocities are significantly different from those expected from existing thermodynamic computer codes for equilibrium and steady state calculations. The predicted detonation velocities give more reliable results for CHNO explosives than one of the best available empirical methods over a wide range of loading densities. The new model provides better agreement with respect to experimental values for aluminized explosives than the computed results from the BKWS equation of state using full and partial equilibrium of aluminium.
Źródło:
Central European Journal of Energetic Materials; 2015, 12, 1; 13-33
1733-7178
Pojawia się w:
Central European Journal of Energetic Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A study on magneto hydrodynamics Jeffery-Hamel flow with heat transfer problem in Eyring-Powell fluid using differential transform method
Autorzy:
Meher, Ramakanta
Patel, N. D.
Powiązania:
https://bibliotekanauki.pl/articles/122591.pdf
Data publikacji:
2019
Wydawca:
Politechnika Częstochowska. Wydawnictwo Politechniki Częstochowskiej
Tematy:
Differential Transform Method
Jeffery-Hamel flow
Eyring-Powell fluid
heat transfer
metoda transformacji różnicowej
przepływ Jeffery-Hamela
przenikanie ciepła
płyn Eyringa-Powella
Opis:
In this paper, we study and analyse the variations of velocity profiles for different values of the Reynolds number, Eckert number, Prandtl number and Hartmann number in the Magneto Hydrodynamics Jeffery-Hamel flow with heat transfer in Eyring-Powell fluid in both divergent and convergent channels. The Differential Transform Method (DTM) is used to obtain an analytical solution of the Jeffery Hamel flow problem and to determine the velocity profiles of the fluid flow. Finally, the efficiency of DTM has been shown, and the results have been validated by comparing the obtained results with the numerical results (fourth order RK method) in both convergent and divergent channels.
Źródło:
Journal of Applied Mathematics and Computational Mechanics; 2019, 18, 3; 57-68
2299-9965
Pojawia się w:
Journal of Applied Mathematics and Computational Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
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