N2 - 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.
L1 - http://journals.pan.pl/Content/94778/PDF/07_paper.pdf
L2 - http://journals.pan.pl/Content/94778
PY - 2015
IS - No 3 September
EP - 105-121
KW - free convection
KW - Rayleigh number
KW - section bundles
KW - effective thermal conductivity
KW - heat treatment
A1 - Wyczółkowski, Rafał
PB - The Committee of Thermodynamics and Combustion of the Polish Academy of Sciences and The Institute of Fluid-Flow Machinery Polish Academy of Sciences
SP - 105-121
T1 - Analysis of components effecting free convection intensity in steel rectangular sections
DA - 2015[2015.01.01 AD - 2015.12.31 AD]
UR - http://journals.pan.pl/dlibra/publication/edition/94778
T2 - Archives of Thermodynamics
DOI - 10.1515/aoter-2015-0024