Wyniki wyszukiwania - BazTech

1

Analysis of components effecting free convection intensity in steel rectangular sections

Wyczółkowski R.

Archives of Thermodynamics

|

2015

|

Vol. 36, no. 3

105--121

EN

Free convection is one of the heat transfer modes which occurs within the heat-treated bundles of steel rectangular section. A comprehensive study of this phenomenon is necessary for optimizing the heating process of this type of charge. The free convection intensity is represented by the Rayleigh number Ra. The value of this criterion depends on the following parameters: the mean section temperature, temperature difference within the section, kinematic coefficient of viscosity, volume expansion coefficient and the Prandtl number. The paper presents the analysis of the impact of these factors on free convection in steel rectangular sections. The starting point for this analysis were the results of experimental examinations. It was found that the highest intensity of this process occurs for the temperature of 100°C. This is mainly caused by changes in the temperature difference observed in the area of sections and changes in kinematic coefficient of viscosity of air. The increase in the value of the Rayleigh number criterion at the initial stage is attributable to changes in the parameter of temperature difference within the section. After exceeding 100°C, the main effect on convection is from changes in air viscosity. Thus, with further increase in temperature, the Rayleigh number starts to decline rapidly despite further rise in the difference in temperature.

2

Experimental tests for the occurence of convective heat transfer within the bed of rectangular steel profiles

Wyczółkowski R., Musiał D.

Archives of Thermodynamics

|

2012

|

Vol. 33, no. 3

89-100

EN

The paper describes tests intended to examine the occurrence of natural convection within the space occupied by 40x20 mm rectangular steel sections. Within these tests the bed of four layers of section was heated by the electric palate heater. Depending on the manner in which the heater was positioned, the tests were divided into two series. In the case of heating from above, the heat flowing through the bed is transferred only by conduction and radiation. When heating the bed from below, in addition to conduction and radiation, also a convective heat transfer will occur. Should this be the case, it will result in the intensification of the heat exchange. The results of measurements carried out have not demonstrated that the occurrence of any possible natural convection would influence the development of a temperature field in this type of charge.

3

An approximate solution of the Lorenz equations

Icha A.

Zeszyty Naukowe Katedry Mechaniki Stosowanej / Politechnika Śląska

|

1998

|

z. 7

447-452

EN

In this paper the renormalization group approach is applied to ordinary differential equations . The method is developed on the basis of the classical theory of envelope and it is used for getting asymptotic behavior of solutions in Lorenz problem. As the result , an aproximate but global solution of the Lorenz model is obtained near origin steady state (0,0,0) for a reduced Rayleigh number r ~ 1 .

PL

W pracy zastosowano metodę grupy renormalizacji w celu analizy układów równań różniczkowych zwyczajnych . Wykorzystując geometryczne sformułowanie tej metody , oparte na pojęciu obwiedni rodziny krzywych, określono asymptotyczne zachowanie się rozwiązań równań Lorenza . W rezultacie , otrzymano przybliżone , globalne rozwiązanie modelu Lorenza w otoczeniu punktu stałego (0,0,0 ) przy liczbie Rayleigha r ~ 1 .