Heat transfer calculation on viscous-gravitational fluid flow inside vertical and inclined tubes

In this paper is presented a new procedure for the calculation of the heat transfer in vertical and inclines tubes, with presence of viscous-gravitational flow. Three models, one for inclines tubes and two for vertical tubes with presence of downward and upward flow were developed. The first model was development for coincident directions and 12 different fluids, included water and organic liquids, shows a correlation adjustment with a mean error of 12.75% in 81.51 % of the available experimental data in the interval of validity 7.5 × 105 ≤ Ra < 2.75 × 1011 and 0.9 < Pr ≤ 3.5 × 104. The second model was development for not coincident directions and 10 different fluids, included water and organic liquids, shows a correlation adjustment with a mean error of 13.04% in 83.09 % of the available experimental data in the interval of validity 7.6 × 105 ≤ Ra < 1.45 × 1011 and 0.8 < Pr ≤ 3.9 × 104. The third model was development for inclined tubes, it is valid for 10 different fluids included water and organic liquids, shows a correlation adjustment with a mean error of 16.12%, in 81.08% of the available experimental data in the interval of validity 7.9 × 105 ≤ Ra < 6.98 × 1010, 0.9 < Pr ≤ 2.1 × 104 and angle of inclination with respect to horizontal line 1° ≤ θ ≤ 88°. The objective of this paper is to make a procedure of analysis that enables considering the influence of the gravitational effects in the laminar flow regimen and to decrease the average uncertainty of the models and that additionally has a larger range of applicability. © 2020 WITPress. All rights reserved.