## 3 Results
### Scale Inhibition Rate Analysis  
The effect of AEFT on the scale inhibition rate was nonlinear with the concentration of magnesium ions in the circulating cooling water. When the concentrations of magnesium chloride were 0 and 4 mmol/L, the effect of promoting adherent scale formation was exhibited to a different extent, and the magnesium ion concentration showed a strong inhibitory effect when it was 6 mmol/L. Table 2 shows the quality of the adherent scale, the mass scale inhibition rate \(\eta_{m}\) obtained by Equation (6), and the average scale inhibition rate \(\eta_{average}\) obtained by Equation (5). The differences in the quality of the adherent scale between Nos. 1, 2, and 3 experimental groups and Nos.1, 2, and 3 control groups were 0.19, 2.08, and \(-\)0.61 g, respectively. This finding indicated that AEFT exhibited different effects at different concentrations of magnesium ions. It further indicated that the AEFT in this experiment slightly promoted the growth of the adherent scale when the magnesium ion concentration was 0 mmol/L, which significantly promoted the adherent scale growth when magnesium ion concentration was 4 mmol/L, and stronger inhibition of the adherent scale growth when magnesium ion concentration was 6 mmol/L. The scale inhibition rate obtained by the mass method of Nos. 1 and 3 experimental groups were close to the average scale inhibition rate obtained by the fouling resistance method. However, a large gap was observed in the No. 2 experimental group, which may be due to accidental errors during weighing and the like. Therefore, the average scale inhibition rate obtained by the fouling resistance method was more reliable compared with. Real-time scale inhibition rate \(\eta_{t}\) was obtained from Equation (4) and shown in Figure 5. The AEFT exhibited a great difference in the scale inhibition effects of the three experimental groups. The scale inhibition rate of No. 1 experimental group was relatively stable and always close to the position below the zero mark. The scale inhibition rate was negative most of the time, indicating that AEFT promotes the growth of adherent scale. The scale inhibition rate of the No. 3 experimental group was always kept above zero, and it remained basically stable without large fluctuations. \begin{table}
\begin{tabular}{l c c c} \hline \hline
**Group** & **Adherent Scale Quantity (g)** & \(\eta_{m}\)(\%) & \(\eta_{average}\)(\%) \\ \hline
1 experimental group & 1.03 & \(-\)22.27 & \(-\)23.96 \\
2 experimental group & 2.60 & \(-\)403.09 & \(-\)107.86 \\
3 experimental group & 0.37 & 62.17 & 59.11 \\
1 control group & 0.84 & - & - \\
2 control group & 0.52 & - & - \\
3 control group & 0.98 & - & - \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Adherent scale quality and scale inhibition rate. At the higher magnesium ion concentration of No. 3 experimental group, AEFT showed a significant inhibitory effect on the growth of the adherent scale. This finding indicates that a higher magnesium ion concentration is beneficial to the alternating electric field to better exert the scale inhibition effect. The average scale inhibition rate of the No. 1 experimental group was \(-\)23.96%, and that of the No. 2 experimental group was \(-\)107.86%. For the No. 2 experimental group, the generation of aragonite may be promoted under experimental conditions. The deposition of aragonite on the heat exchanger resulted in an increase in fouling resistance. Aragonite and calcite are two types of calcium carbonate crystals; on the surface of the heat exchanger, the aragonite is denser and firmer than the calcite deposit; hence, aragonite is more difficult to remove than the calcite [24]. An increase in aragonite was observed in the XRD result analysis and SEM photographs of the No. 2 experimental group. The average scale inhibition rate of the No. 3 experimental group was 59.11%, which inhibited the formation of adherent scale and demonstrated a better scale inhibition effect.