| Abstract |
Improving mass transfer in membrane modules is always desirable, but not easily achieved under laminar regime. Pulsatile flow induced by a solenoid valve was investigated as a technique to improve mass transfer in membrane modules with spacer-filled channels. Mass transfer coefficients were measured by the limiting current technique in open and spacer-filled narrow rectangular channels, both for steady-state flow and pulsatile flow, at Reynolds numbers ranging from 10 to 50 (based on the channel height). The Lest cell had a narrow rectangular channel (170 min x 15 mm x 2 mm) and 8 consecutive nickel electrodes (11.2 mm long and 10 mm wide) fitted in the Lop wall, with and without spacer inside the flow channel. The pulsatile flow followed a step function with three different frequencies (1, 10 and 50 Hz) and two different duty cycles (fraction of time during which the valve is closed in each pulse) 0125\% and 50\%. The results show that pulsatile flow generated with solenoid valves with frequencies between 10 Hz and 50 Hz can increase up to 50\% the mass-transfer coefficient in membranes modules with spacer-filled channels, operating in laminar flow. The effect is particularly intense near the channel outlet, close to the solenoid valve, but vanishes for large distances from the channel outlet. (C) 2014 Elsevier Ltd. All rights reserved. |
