Análise comparativa de metodologias para a determinação da vazão em sistemas de bombeamento de água

Abstract

In the search for greater precision in the data related to the flow of a fluid and its determination in the field, it is essential to use methods that minimize possible errors and present errors, including different means, easy installation and low cost. Flow rate measurements are considered important for better control of irrigation practice. Thus, it is essential to obtain this variable, using alternative methods, which are characterized by indirect estimation. These methods will allow to determine the flow rate, from information easily measured or readily available. Given the above, the present study aims to perform a comparative analysis between different methodologies to determine the flow rate available in water pumping systems. The study was carried out in a water pumping system, located in the Hydraulics Laboratory of the Rural Sciences Center of the Federal University of Santa Maria. Seven different methodologies were used based on hydraulic, pressure and level parameters. Different opening points were tested in the drawer register to control and vary the flow rate. Thirteen test sequences were performed, three for adjustment and ten for testing the equations, divided through a draw. Values obtained by a hydrometer were adopted as the observed flow rate, and estimated values obtained by the methodologies. It was verified if there is a correlation between the observed flow rate and the parameters under study. The behavior of the results was analyzed using the values of the coefficients of determination (R²), angular and linear coefficient. To analyze and compare the results, different statistical indicators were used (Ip, Ic, Id, RMSD and NSE). A cost survey was carried out for each instrument used in the study. After analyzing the results, it was confirmed that the flow rate can be determined using the methodologies employed. The permanent flow rate control can be performed by monitoring the variation of the pressure measurement, both at the entrance and at the exit of the system. Among the tested parameters, the pressure one showed better performance compared to the others, with the best results according to the statistical indicators. The Tensiometer, Bourdon Vacuometer and the “U” tube vacuum gauge were the methodologies that presented the best overall performance in determining the flow rate. The values for the acquisition of this equipment ranged from R$ 120.00 to R$ 750.00, considered low cost, in relation to the others for determining the flow rate.