Flow of aqueous suspensions of fine particles in diffusers

The flow of dilute aqueous suspensions of micron-size carbon black particle s in diffusers was studied by visualization and by measurements of pressure drop. For particle concentrations from 0.1 to 1.0% by weight and for conic al diffusers with half angles of 5 and 11 degrees, the measurements show th at pressure recovery was less than that for plain water. The reductions wer e of order 10% and increased with particle concentration. To understand thi s effect, the flow was visualized in a two-dimensional diffuser, using comp uted sonography because of liquid opacity. The sonographic images show that the flow separated earlier than it did with water, which explains the redu ced pressure recovery. At the same time, it is not understood how such minu te particles at such small concentrations affect flow separation. (C) 2000 Elsevier Science Ltd. All rights reserved.