Determining effects of spacer orientations on channel hydraulic conditions using PIV

Feed spacer orientation affects the velocity pattern and pressure drop of spacer-filled channels such as those encountered in Spiral-wound Membrane (SWM) modules of Reverse Osmosis (RO). However, there are only limited numbers of experimental studies on this topic. This study sets out to reveal more detailed information on the pressure drop and velocity patterns of spacer-filled channels. Particle Image Velocimetry (PIV) is used to provide high-resolution velocity maps for three commercial feed spacers of different thicknesses at a flow attack angle of 45 degrees and 90 degrees. The pressure drop is measured for the applied operational conditions (Re < 250). Results showed higher pressure losses, a better mixing of flow, a lower variation of temporal velocity, and a smaller variation of velocity over the channel height in the orientation with a flow attack angle of 45 degrees as compared to 90 degrees. The results presented here can be used to validate numerical studies, determine the fouling-sensitive regions in a spacer-filled channel and consequently, design the optimal spacer with respect to its orientation and thickness.