Elaboração de uma equação empírica para estimar o número de potência de um impelidor de pás retas

Abstract

Still nowadays, the project of industrial agitators essentially depends on empirical relations. Thus, experimental works are widely used as a reference to calculate the power consumption of agitation systems. So this work’s main objective is the preparation of an empirical equation to calculate the power number of a pitched blade impeller, through the analysis of experimental data obtained by Silva (2019) in turbulent regime, through the model of Nagata (1975). To achieve this goal, the power number was analyzed as a function of the variation of the Reynolds Number and the geometric parameters (relations between impeller diameter and tank diameter, Di/T; the impeller width and impeller diameter, w/Di; and pitch blade angle, θ), and also the power consumed by the impeller as a function of rotational speed. The experimental data was gathered by Silva (2019) in a 50 L tank, with configurations of three and four baffles and without baffles. One hundred and twenty impellers were studied, organized in groups of five variations of the impeller blade width (w/ Di = 0.14; 0.17; 0.20; 0.25 and 0.30), in each group there were impellers with six different diameters (Di/T = 0.25; 0.33; 0.40; 0.45; 0.55 and 0.70) and each group of impellers with different diameters had four different blade angles (30°, 45°, 60° and 90°), for each type of configuration adopted. For measuring torque, which is necessary to calculate power consumption, a torquemeter was used. The power number and Reynolds number data were listed in tables for the elaboration of graphs, and analyzing the trends in the curves, the model I-342 was chosen for the elaboration of the equation. The main contribution of this work is the development of a more specific equation for an impeller based on its geometric relations for power estimation, which satisfactorily describes the power number profile in the turbulent regime.