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ENCIT 2020
18th Brazilian Congress of Thermal Sciences and Engineering
INFLUENCE OF ROUGHNESS ON THE TUBE HEAT TRANSFER SUBMITTED TO QUENCHING
Submission Author:
Felipe Raul Ponce Arrieta , MG
Co-Authors:
Fernanda Machado, Felipe Raul Ponce Arrieta
Presenter: Felipe Raul Ponce Arrieta
doi://10.26678/ABCM.ENCIT2020.CIT20-0472
Abstract
This work aimed aimed to analyze, on a permanent basis, the influence of the surface finish on the heat transfer of a steel tube, submitted to the immersion tempering process. The proposed methodology consisted of heating a steel tube internally using electrical resistors with a maximum power of 36 kW. The tests were conducted under rotations varying between 10 and 60 rpm, water temperature equals to 25°C and surface temperature of the tube varying between 90 and 115ºC. The experimental data were evaluated using correlations proposed in the literature. Initially, it was seen that the roughness increase implies a more efficient thermal exchange, however with the temperature increase this influence was reduced to all rotations. In addition, the influence of roughness increased with the speed of rotation of the test tube. From the preliminary evaluation of the experimental data, through correlations provided in the literature, it was possible to propose two correlations for the mixed convection, which are better suited to the empirical data. These equations presented Emed equals to 3.8% and 2.3%. Correlations were estimated from experimental data with Re ranging between 100,610 - 229,116 and Gr ranging between 7.2x109 – 1.63x1010.
Keywords
Heat transfer coefficient, surface roughness, quenching
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