Investigation of instantaneous and local transmembrane pressure in rotating and vibrating filtration (RVF) module: Comparison of three impellers

Abstract The instantaneous and local pressure at membrane surface was experimentally investigated in a dynamic filtration module, named Rotating and Vibrating Filtration (RVF) module. The present paper focuses mainly on the pressure fluctuations in turbulent regime. To this end, the instantaneous pressure is decomposed into its time-averaged and fluctuating quantities using Statistical Analysis (SA), Probability Distribution Function (PDF) and Fast Fourier Transform (FFT). The effects of back pressure, flowrate, rotation frequency and radial position at the membrane on the magnitude of the pressure fluctuations are studied for three different impellers (Imp 1, 2 and 3). For mixing pressure, Imp 2 (6 blades) exhibits a larger core velocity coefficient than Imp 1 and Imp 3 (3 blades). For pressure fluctuation, the extracted variables from SA (standard deviations), PDF (peak-to-peak values) and FFT (amplitudes) confirm that the magnitude of Imp 1 > Imp 3 > Imp 2. Considering SA at 20 Hz, standard deviation of Imp 1 exceeds 100 mbar (up to 25% of TMP), while these values are negligible (