Design Of Electromagnetic Anti-Fouling Device And Experimental Study Of Anti-Fouling Mechanism

Fouling results in tremendous loss to design and operation of heat exchangers and becomes of a major unsolved problem in heat transfer field. Recently, advanced electromagnetic anti-fouling technology (EAF) has got more attention in research and application. This thesis focuses on the design of EAF device, EAF effect and its mechanism with a detailed experimental study. The main jobs are as follows. The EAF device was designed and made to generate square wave and sweeping square wave, which voltage amplitude and frequency could be adjusted continuously. This device has simple structure and high precision, so it can satisfy the experimental study. We built the static and dynamic anti-fouling experimental system and simulated circulating water system. The fouling process and anti-fouling effect were investigated with different concentration, flow velocity, temperature, and electromagnetic signal. The physical and chemical parameters were obtained through chemical analysis method and heat transfer measurements; moreover, the fouling shape and particle diameter could be observed by Scanning Electron Microscope photos and Dynamics Laser Scattering technology respectively. The experimental results are as follows. Under low temperature, the solution's conductance and concentration of calcium ion with EAF treatment are hardly different from those without EAF treatment, and all crystals are calcite. Under high temperature, the solution's concentration of calcium ion with EAF treatment is a little higher than that without EAF treatment, which indicates electromagnetic field can restrain fouling on a certain extent. Usually, calcium carbonate is composed of aragonite that is a harder and denser deposit; with EAF treatment it can be changed into an unshaped flat structure that is easy to be wiped off. Also, the signal with frequency of 500Hz and current of 0.2A has a better anti-fouling effect under the same conditions. And the EAF treatment could prolong the delay time of fouling effectively on heat transfer surface, and slower the fouling process.