Validation of an electronic anti-fouling technology in a single-tube heat exchanger

The objective of the present study was to investigate the validity of an electronic anti-fouling (EAF) technology in the mitigation of precipitation fouling in a once-through flow system with a single-tube heat exchanger. Effects of flow velocity and water hardness on the effectiveness of the EAF technology were experimentally studied. The water hardness varied from 7.5 to 10 mol m(-3) as CaCO3. For both 7.5 and 10 mol m(-3) solutions, the EAF treatment reduced fouling resistance by 20-38% at a flow velocity between 0.52 and 0.78 m s(-1). As the velocity decreased to 0.28 m s(-1), the EAF treatment was not helpful in reducing fouling. SEM photographs of scale produced from the 10 mol m-3 solution at 0.78 m s(-1) indicated that calcium carbonate scales without the EAF treatment were needle-shaped aragonite, which is sticky, dense, and difficult to remove. Scales with the EAF treatment showed a cluster of elliptic shape crystals. Both the heat transfer test results and SEM photographs obtained in the present study support the validity of the EAF technology in mitigating precipitation fouling. (C) 1998 Elsevier Science Ltd. All rights reserved.