Analysis of Nusselt Number for Natural Convection in Package of Square Steel Sections

R. Wyczółkowskia, J. Szmidlaa, M. Gałaa, V. Bagdasaryanb aCzęstochowa University of Technology, 42-201 Częstochowa, Poland bWarsaw University of Life Sciences - SGGW, 02-787 Warsaw, Poland

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The paper analyses the Nusselt number for natural convection in the inner area of square 40, 60 and 80 mm sections in the temperature range 20-700°. The obtained values of the Nu number are in the range 1.5-7.2. For each section the maximum value of the Nu occurs at a temperature amounting to approximately 60-90°. This is the effect of the simultaneous influence of the temperature difference within the section Δt, the kinematic viscosity and the coefficient of thermal expansion of air. The natural convection depending on the section size increases the heat transfer within gas from 1.5 to 4.3 times upon averaging for the whole temperature range.

DOI:10.12693/APhysPolA.139.548 topics: natural convection, steel section, heat treatment, Nusselt number