Wyniki wyszukiwania - Biblioteka Nauki

1

Sensitivity Analysis of Transient Nonlinear Heat Conduction

100%

Szopa R.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2003

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tom z. 76

279-282

2

Quasifractional approximants for effective conductivity of regular arrays of spheres

63%

Danishevs'kyy V. , Andrianov I. , Tokarzewski S.

Archives of Mechanics

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2000

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tom Vol. 52, nr 2

319-327

EN

We study the effective heat conductivity of regular arrays of perfectly conducting spheres embedded in a matrix with the unit conductivity. Quasifractional approximants allow us to derive an approximate analytical solution, valid for all values of the spheres volume fraction phi belongs to [0; phi[max]] (phi[max] is the maximum limiting volume of a sphere). As the bases we use a perturbation approach for phi --> 0 and an asymptotic solution for phi --> phi[max]. Three different types of the spheres space arrangement (simple, body and face-centred cubic arrays) are considered. The obtained results give a good agreement with numerical data.

3

A contribution to the heat conduction problem in a laminated medium

63%

Łaciński Ł. , Woźniak C.

Prace Naukowe Instytutu Matematyki i Informatyki Politechniki Częstochowskiej

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2005

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tom Vol. 4, nr 1

123-128

EN

In this contribution we are to show that on the boundaries of a laminated medium, which are perpendicular to the laminae interfaces, some near-boundary phenomena related to boundary conditions take place. The aim of this note is to describe and discuss those phenomena. The analysis is carried out in the framework of the tolerance averaging technique, [1]. The obtained model is confronted with the homogenized model. General considerations are illustrated by a certain special problem.

4

An efficient analysis of steady-state heat conduction involving curved line/surface heat sources in two/three-dimensional isotropic media

51%

Mohammadi M. , Hematiyan M. R. , Shiah Y. C.

Journal of Theoretical and Applied Mechanics

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2018

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tom Vol. 56 nr 4

1123--1137

EN

In this paper, a new formulation based on the method of fundamental solutions for two/three- -dimensional steady-state heat conduction problems involving internal curved line/surface heat sources is presented. Arbitrary shapes and non-uniform intensities of the curved heat sources can be modeled by an assemblage of several parts with quadratic variations. The presented mesh-free modeling does not require any internal points as in domain methods. Four numerical examples are studied to verify the validity and efficiency of the proposed method. Our analyses have shown that the presented mesh-free formulation is very efficient in comparison with conventional boundary or domain solution techniques.

5

Numerical analysis of heat conduction influence on SCR aftertreatment systems EFF

51%

Bachanek J. , Rogóż R. , Teodorczyk A.

Journal of KONES

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2018

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tom Vol. 25, No. 3

51--58

EN

Selective Catalytic Reduction (SCR) is well known method for reducing NOx emission in diesel engine exhaust gas. Urea-water solution (UWS) injected into hot stream decomposes due to thermolysis into ammonia and isocyanic acid which hydrolyses further into more ammonia and carbon dioxide. Resultant ammonia is the NOx reductor, producing water vapour and carbon dioxide from the reduction reaction. To provide sufficient NOx reduction efficiency, UWS needs to be properly atomized and mixed with exhaust gas. However, due to more and more restrictive emissions regulations provided by European Union and Close Coupled trend of aftertreatment systems in vehicles the design process is very complex and demanding. Computational Fluid Dynamics (CFD) simulations are integral part of product development, allowing save time and reduce costs of preparing prototypes for further tests. However, it is necessary to understand all the processes and problems connected with NOx reduction in SCR system. Strong turbulent flow of hot stream gas, urea-water solution spray injection, droplets interaction with wall, wallfilm generation are included. The objective of this work is to investigate the impact of heat transfer modelling inside mixing elements of SCR system on urea mixing uniformity and wallfilm deposit on the walls of the system. Simplified and more complex approach is compared with no heat transfer cases. All the simulations were conducted using AVL FIRETM software. Results showed that wall heat transfer might have an impact on mixing efficiency and wallfilm formulation. It is necessary to take into account the effect of mixing elements heat conduction in CFD simulations during the aftertreatment design process.

6

Zastosowanie operacji symbolicznych do wyznaczania funkcji Trefftza dla falowego równania przewodnictwa ciepła

51%

Ciałkowski M. , Frąckowiak A.

Zeszyty Naukowe Politechniki Poznańskiej. Maszyny Robocze i Transport

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2004

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tom Nr 57

85-92

PL

Rozwój technik komputerowych pozwala na wykorzystanie operacji symbolicznych do jawnego przedstawienia ciągu funkcji tożsamościowo spełniających różnego rodzaju liniowe równania różniczkowe cząstkowe. W artykule przedstawiono zastosowanie techniki operacji symbolicznych do wyprowadzenia wzorów rekurencyjnych dla funkcji cieplnych dla falowego równania przewodnictwa ciepła. Postać rekurencyjna pozwala wyznaczać wartości funkcji cieplnych z bardzo dużą dokładnością. Funkcje cieplne mogą być stosowane jako funkcje bazowe w metodzie elementów skończonych.

EN

In the paper has been presented an application of the variable separation method for deriving the Trefftz functions for hyperbolic heat conduction equation. For the deriving the Trefftz functions the method of symbolic calculations has been employed. The advantage of this method is the simple way to obtain these functions which can be subsequently used in the finite element method for shape functions generation. In the paper has been shown some remarks about error estimation for the approximation with using of Trefftz functions.

7

On spatial vs referential isotropic fourier’s law in finite deformation thermomechanics

51%

Wcisło B. , Pamin J. , Rose L. , Menzel A.

Engineering Transactions

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2023

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tom Vol. 71, iss.1

111--140

EN

This paper deals with the issue of isotropic heat conduction in thermomechanical largestrain problems. The aim of the paper is a comparison of different variants of Fourier’s law used in the literature for a large strain problem. In particular, Fourier’s law is specified either in the reference or in the deformed configuration by using different options of heat flux density vectors which are presented and discussed. The paper includes working examples to illustrate the presented theory. Moreover, different formulations of Fourier’s law are tested by using the finite element method to investigate the influence of the applied variant on simulation results. The analysis reveals that in a strongly deformed area the temperature distribution varies.

8

A one-dimensional model for the heat conduction in ring-like body

51%

Ecsedi I. , Baksa A.

Archive of Mechanical Engineering

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2013

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tom Vol. LX, nr 4

495–-508

EN

A one-dimensional model based on the Fourier’s theory of heat conduction is developed for ring-like bodies. The ring-like body is an incomplete or complete torus with arbitrary cross section. The thermal properties of considered rings are independent of the polar angle. Examples illustrate the application of model presented.

PL

Opracowano jednowymiarowy model przewodnictwa cieplnego dla ciał o kształcie pierścieniowym oparty o fourierowską teorię przewodnictwa. Rozważane ciała mają kształt pełnego lub niepełnego torusa o dowolnym przekroju. Właściwości cieplne rozważanych ciał są niezależne od kąta biegunowego. Przedstawiono przykłady ilustrujące zastosowanie modelu.

9

A Galerkin approximation method including space dimensional reduction - applied for solution of a heat conduction equation

51%

Nakonieczny K.

Applied Computer Science

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2012

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tom Vol. 8, no 2

48--58

EN

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.

10

Heat flow through a thin cooled pipe filled with a micropolar fluid

51%

Beneš M. , Pažanin I. , Suárez-Grau F. J.

Journal of Theoretical and Applied Mechanics

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2015

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tom Vol. 53 nr 3

569--579

EN

In this paper, a non-isothermal flow of a micropolar fluid in a thin pipe with circular cross- -section is considered. The fluid in the pipe is cooled by the exterior medium and the heat exchange on the lateral part of the boundary is described by Newton’s cooling condition. Assuming that the hydrodynamic part of the system is provided, we seek for the micropolar effects on the heat flow using the standard perturbation technique. Different asymptotic models are deduced depending on the magnitude of the Reynolds number with respect to the pipe thickness. The critical case is identified and the explicit approximation for the fluid temperature is built improving the known result for the classical Newtonian flow as well. The obtained results are illustrated by some numerical simulations.

11

Two methods to solve a fractional single phase moving boundary problem

51%

Li X. , Wang S. , Zhao M.

Open Physics

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2013

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tom 11

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nr 10

1387-1391

EN

A moving boundary problem of a melting problem is considered in this study. A mathematical model using the Caputo fractional derivative heat equation is proposed in the paper. Since moving boundary problems are difficult to solve for the exact solution, two methods are presented to approximate the evolution of the temperature. To simplify the computation, a similarity variable is adopted in order to reduce the partial differential equations to ordinary ones.

12

Method for solving inverse problems encountered in monitoring of thermal stresses

51%

Duda P.

Archives of Thermodynamics

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2000

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tom Vol. 21, nr 3-4

25-39

EN

A method for solving one- and multidimesional inverse problems of transient heat conduction is presented. The method is formulated in a matrix form, so problems with large numbers of unknown boundary parameters in bodies of complex geometry can be solved. Three examples illustrate the accuracy of presented method.

13

Modelling and analysis of the heat conduction in a certain functionally graded material

51%

Michalak B. , Ostrowski P.

Zeszyty Naukowe Politechniki Świętokrzyskiej. Nauki Techniczne

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2007

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tom Z. 6

25-34

EN

The subject of this contribution is an analysis of the heat conduction in a two-phase microheterogeneous rigid heat conductor with smoothly space-varying effective properties. The aim of the contribution is application of derived macroscopic model to analysis of heat conduction in a certain rigid conductor. The general results are illustrated by numerical calculations.

PL

Przedmiotem rozważań pracy jest analiza przewodnictwa cieplnego w dwufazowym mikroniejednorodnym przewodniku ciepła ze zmiennymi własnościami efektywnymi. Celem pracy jest zastosowanie wyprowadzonego modelu makroskopowego do analizy przewodnictwa w tym przewodniku. Pewne ogólne wyniki pokazano na obliczeniach numerycznych.

14

On hyperbolic heat conduction in periodic lattice structures

51%

Borowska-Szymczyk J.

Zeszyty Naukowe Politechniki Świętokrzyskiej. Nauki Techniczne

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2007

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tom Z. 6

17-24

EN

The aim of this contribution is to propose two kinds of simplified mathematical models for the analysis of hyperbolic problems describing heat transfer in dense periodic lattice-type conductors of an arbitrary form. We begin with a special description of the periodic lattice geometry which leads to the heat conduction model governed by the system of ordinary differential equations which have a finite difference form with respect to the spatial coordinates. The continuum models are derived from the finite difference equations by using the principle of stationary action. The considerations are based on the Cattaneo-type constitutive heat transfer law. The paper contains some of results obtained in [5, 8].

PL

Celem tej pracy jest przedstawienie alternatywnego podejścia do modelowania hiperbolicznych zagadnień przewodnictwa ciepła w siatkach periodycznych o dowolnej złożonej strukturze. Punktem wyjścia jest pewien szczególny opis geometrii struktury siatkowej, który prowadzi do modelu opisanego układem równań różnicowych. Fizyczną bazę rozważań stanowi prawo konstytutywne Cattaneo, [1]. W procedurze modelowania wykorzystano pewne wyniki zamieszczone w pracach [5, 8].

15

A few remarks on micro/macro transitions and Gassmann relations for poroelastic materials

51%

Wilmański K.

Zeszyty Naukowe Politechniki Świętokrzyskiej. Nauki Techniczne

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2007

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tom Z. 6

191-204

EN

In order to evaluate experimental results on porous materials, one has to know relations between partial mass densities, macroscopic compressibility moduli, coupling parameters on the one hand-side, and real (true) mass densities, real compressibility parameters and porosity, on the other hand. Such relations for a linear static model of soils were derived by Gassmann ([1]).For the Biot model, similar considerations were presented by Biot and Willis ([2]). Recently a systematic micro/macro derivation was constructed ([7]). In this paper, we present the derivation for a two-component linear model of poroelastic material following from general thermodynamical considerations. We present a "flow chart" of the micro/macro transition for saturated materials. It consists of the solution of a homogeneous "field" problem and the subsequent use of boundary conditions following from Gedankenexperiments. The main purpose is the demonstration of the new procedure of derivation in order to apply it in more complex problems such as unsaturated materials.

PL

W celu wykorzystania wyników eksperymentalnych dla ośrodków porowatych potrzebne są związki pomiędzy parcjalnymi gęstościami masy, makroskopowymi modułami ściśliwości, parametrami sprzężeń z jednej strony i rzeczywistymi gęstościami masy, modułami ściśliwości i porowatością z drugiej strony. Takie związki dla statycznego modelu liniowego zostały wyprowadzone przez Gassmanna ([1]). Dla modelu Biota podobne rozważania były przedstawione przez Biota i Willisa ([2]). Niedawno skonstruowano systematyczne wyprowadzenie mikro/makro ([7]). W tej pracy wykorzystujemy dwuskładnikowy liniowy model materiału porosprężystego wynikający z ogólnych rozważań termodynamicznych. Przedstawiamy schemat blokowy przejścia mikro/makro dla materiałów nasyconych. Składa się on z rozwiązania jednorodnego problemu “polowego” i wykorzystania warunków brzegowych wynikających z eksperymentów myślowych. Głównym celem jest demonstracja metody wyprowadzenia umożliwiająca jej zastosowanie w bardziej złożonych problemach takich, jak materiały nienasycone.

16

Diffusion problems on fractional nonlocal media

51%

Sapora A. , Cornetti P. , Carpinteri A.

Open Physics

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2013

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tom 11

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nr 10

1255-1261

EN

In this paper, the nonlocal diffusion in one-dimensional continua is investigated by means of a fractional calculus approach. The problem is set on finite spatial domains and it is faced numerically by means of fractional finite differences, both for what concerns the transient and the steady-state regimes. Nonlinear deviations from classical solutions are observed. Furthermore, it is shown that fractional operators possess a clear physical-mechanical meaning, representing conductors, whose conductance decays as a power-law of the distance, connecting non-adjacent points of the body.

17

Micro-macro model for prediction of local temperature distribution in heterogeneous and two-phase media

51%

Seredyński M. , Łapka P. , Furmański P. , Banaszek J.

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18

Optimal choice of integral parameter in a process of solving the inverse problem for heat equation

51%

Joachimiak M. , Ciałkowski M.

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19

On the modelling of a certain quasi-linear heat conduction problem in a two-phased laminated medium

51%

Siedlecka U. , Woźniak C.

Prace Naukowe Instytutu Matematyki i Informatyki Politechniki Częstochowskiej

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2008

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tom Vol. 7, nr 1

181-184

EN

The aim of the contribution is to obtain a macroscopic model equation for the quasi-linear heat conduction in a two phased-laminated medium. The analysis will be based on the tolerance averaging technique.

20

Temperature distribution in a circular plate heated by a moving heat source

51%

Kidawa-Kukla J.

Prace Naukowe Instytutu Matematyki i Informatyki Politechniki Częstochowskiej

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2008

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tom Vol. 7, nr 1

71-76

EN

This paper concerns the heat conduction problem in a circular thin plate subjected to the activity of a heat source which changes its place on the plate surface with time. The heat source moves along an circular trajectory round centre of the plate with constant angular velocity. The solution of the problem is obtained in an analytical form by using the Green's function method.