Abstract
Comparing with the traditional chemical and physical method, the electromagnetic water treatment technology draws more attention of researchers for its advantages of easy application, small investment, low cost, and being pollution free in recent years. However, due to the less study of the formation process and adhesion of fouling on the surface of heat exchange equipment, the electromagnetic anti-fouling performance cannot be well evaluated. This paper studies the numerical simulation of the flow states of circulating cooling water in heat exchange tubes with a straight shape and U-shaped ones and analyzes the experimental data of fouling resistance on heat transfer surface under the action of 0.5, 0.75, 1, and 1.5 kHz electromagnetic fields. The variations in the velocity field and pressure field at various points in heat exchange tubes declare that the velocity of the circulating cooling water is smaller in the outlet of the pipeline. The change of the circulating cooling water flow state with the pipeline shape causes a certain impact on fluid velocity, and the pressure value at the outlet is larger. It is obtained that the flow velocity in the area with high surface pressure of circulating cooling water is relatively small. The experimental results indicate that the fouling resistance on the surface of the magnetic heat exchange tube is smaller than that of the nonmagnetic one. The anti-fouling efficiency in 0.5, 0.75, 1, and 1.5 kHz magnetic and contrast experiments are 46.8, 84.8, 91.2, and 63.6%, respectively. Better anti-fouling performances are obtained under the action of about 1 kHz electromagnetic frequency. The induction period of fouling on the heat exchange surface is lengthened under electromagnetic fields. All these studies are of significant importance to further understand the formation process and adhesion of fouling on the surface of heat exchange equipment, as well as to better evaluate the electromagnetic anti-fouling performance.