The effects of turbulence promotion and flux enhancement for ultrafiltration in a zigzag spacer-filled cross-flow channel were tested experimentally for feed solutions containing dextran, silica and reconstituted whey protein concentrate, For cross-how velocities between 0.1 and 0.8 m/s, the spacer-filled channel achieved flux enhancements over the empty channel of up to three times for dextran and silica ultrafiltration. Flux enhancements of up to two times were measured for reconstituted whey protein concentrate. The zigzag spacer was operating in the upper transition fluid mechanics region. Processing costs were reduced by 60% per unit volume of permeate for dextran and silica and by 35% for reconstituted whey protein concentrate.