Experimental study on fouling inhibition characteristics of a variable frequency electromagnetic field on the CaCO3 fouling of a heat transfer surface

Forced convective heat transfer and CaCO3 deposition experiments were performed to investigate fouling inhibition characteristics of a variable frequency electromagnetic field on the CaCO3 fouling of a heat transfer surface and three indicators, namely, fouling resistance, conductivity, and scanning electron microscope (SEM), were analyzed. Experimental results indicated that the variable frequency electromagnetic field could effectively inhibit the CaCO3 fouling deposition on the heat transfer surface and slow down the growth rate of CaCO3 fouling by influencing aqueous solution and fouling forming ions. Moreover, the variable frequency electromagnetic field could reduce the conductivity of the test fluid, increase both the total precipitation and the bulk precipitation, and promote the CaCO3 crystallization in aragonite rather than calcite to form muddy soft fouling that was readily washed off by the fluid flow. An evaluation model was proposed to better define the fouling inhibition effect of the variable frequency electromagnetic field in the whole period of CaCO3 deposition. The fouling inhibition characteristics of the variable frequency electromagnetic field presented an extremum feature. The minimum fouling resistance was 1.1 x 10(-4) m(2)center dot K/W obtained at 1 kHz, during which the fouling inhibition rate was 64.7% and the average growth rate of CaCO3 fouling dramatically decreased by 61.0% compared with that of the blank test. This work can provide sound theoretical guidance for future application of electromagnetic fouling inhibition technology in the heat transfer enhancement. (c) 2022 Elsevier Ltd. All rights reserved.

Automated summary

Forced convective heat transfer and CaCO3 deposition experiments were conducted to investigate the fouling inhibition characteristics of a variable frequency electromagnetic field. The results showed that the electromagnetic field effectively inhibited the CaCO3 fouling deposition and decreased the growth rate of fouling. It also reduced the conductivity of the test fluid and promoted the crystallization of CaCO3 in aragonite, resulting in easily removable soft fouling. An evaluation model was proposed to better define the fouling inhibition effect of the variable frequency electromagnetic field.