Comparação entre métodos de cálculo de vazão de projeto em instalações hidráulicas prediais de água fria: Estudo de caso em edificação residencial

Abstract

NBR 5626 (ABNT, 2020) removed the recommendation for the use of the fixture unit method for the design flow rate calculation of cold water installations, as outlined in the 1998 version of the same standard, and left the choice of an empirical or probabilistic method, properly substantiated, to the discretion of the designer. In this context, the study conducted a bibliographic review with the aim of identifying methods for this purpose recommended nationally and internationally. Among them, the methods from NBR 5626 (1998), IPC (2024), EN 806-3 (2006), as well as Gonçalves' method (1986), were selected for application in a case study, which was conducted in a four-story building with four apartments on each floor. The IPC (2024) method establishes a direct conversion of load units to flow, resulting in high flow values, nominal diameters (ND), and head losses. The other methods showed similar results to each other in terms of flow and ND. The NBR 5626 (1998) method uses fixture units based on the type of sanitary appliance to estimate probable demand. Gonçalves' method (1986) considers variables related to the building’s consumption profile, requiring more input parameters defined by the designer. With the established data, Gonçalves' method (1986) presented intermediate flows, placing them between the values obtained by NBR 5626 (1998) and EN 806-3 (2006). Meanwhile, the EN 806-3 (2006) method uses an abacus that considers both the total flow rate in loading units and the highest single value load unit. This method resulted in the lowest flow rates and ND values among those considered. The residual pressure in the system was verified, and the IPC method recorded the highest pressures, while the EN 806-3 (2006) method showed the lowest. Head losses in hydrometers were calculated for distinct types of hydrometers, and it was found that these losses are extremely sensitive to flow rate. Therefore, it is concluded that selecting appropriate flow rate is crucial to meet demand, ensure the hydraulic functionality of the system, and choose the proper hydrometer.