Experimental study of the characteristic curves of 0.5 HP radial pump with constant speed

Abstract

Radial (centrifugal) pumps are commonly used in industry and represent 22% of total consumption of the energy worldwide. The understanding of their operating conditions is important for a proper selection and use, specifically at the Best Efficient Point (BEP). This study analyzed the variation of the operating conditions of a common, small pump when the flow is regulated with a control valve at the pump discharge, keeping the rotational speed constant. The system consists in a closed loop using a turbine meter programmed in Arduino for flowrate measurement. The electric power and energy consumption were provided by an electronic Wattmeter, and the pressure at the suction/discharge of the pump was taken from Bourdon gauges. The minimum submergence of the pump intake was calculated with the Standard ANSI-HI-9.8 and the Bourdon gauges selection followed the recommendations of the Standard ASME B40.100-1998. All the measurements are part of the Energy equation for the pump-motor system (monoblock unit), whose H-Q curve is compared to manufacturer’s curve with reasonable agreement that served as validation. The electric power curve is the evidence that the flow regulation method is unappropriated because the power consumption increases as the flow is regulated. At the end, the efficiency curve of the motor-pump unit was presented, with a maximum value of 12%. The shock and recirculation losses are present, but the electrical losses are evidenced through excessive heating. The test bench will have a better pump and a variable frequency drive for further studies.