## 4 Results and Discussion

Table 3: Relevant parameters. larger, the main heat exchange between the droplet and the outside was the heat exchange between the droplet and the wall. When the contact area between the droplet and the wall was larger, the more heat transfer of the droplet and the contact area of the hydrophilic wall surface was the largest, the hydrophobic area was small, and the superhydrophobic area was the smallest. Looking at the droplets with different wall contact angles, the droplet height of the hydrophilic wall surface was the smallest, and the droplet height of the superhydrophobic wall surface was the largest. Hence, the heat transfer process of the superhydrophobic wall surface was longer, the ice front surface growth process was longer, and the freezing time was longer. Figure 8 shows the complete freezing time \(T_{t}\) of the droplet under different contact angles \(\theta\), different wall temperatures \(T_{w}\), and different salinity levels S. An analysis and summary of the numerical simulation results were carried out. For the same volume of droplets, the complete freezing time increased with the increase in the contact angle, and the freezing time of the hydrophobic wall increased by about 70% compared to the hydrophilic wall. The freezing time of the superhydrophobic wall increased by about 100% compared to the hydrophobic wall. Changing the wall  
Figure 7: Temperature field distribution and growth peak change of droplet freezing on the wall at \(-5\)\({}^{\circ}\)C at different contact angles. characteristics and increasing the wall contact angle can effectively prevent or delay the occurrence of icing. The freezing time of the droplets varied with the changes in the wall temperature. The lower the wall temperature, the faster the freezing process of the droplet. The wall temperature dropped from \(-5\)\({}^{\circ}\)C to \(-10\)\({}^{\circ}\)C, and the icing time decreased by about 50-70% for the droplets with different saline concentrations and wall contact angles. The wall temperature dropped from \(-10\)\({}^{\circ}\)C to \(-15\)\({}^{\circ}\)C, and the icing time decreased by about 30\(-\)40%. For salt-containing droplets, the increase in the droplet salinity decreased the droplet solidification temperature, so unlike changing the contact angle, changing the wall temperature had slightly different effects on the droplets with different salinities. Increasing the wall temperature can effectively prevent or delay the occurrence of icing. With different wall contact angles and different wall temperatures, the freezing times of the droplets changed with the changes in the droplet salinity, and the higher the droplet salinity, the longer the freezing process of the droplets. At a wall temperature of \(-5\)\({}^{\circ}\)C, the freezing time increased by about 25% from pure water droplets to \(S=10\) at three contact angles. From the \(S=10\) saline droplets to the \(S=20\) saline droplets, the freezing time increased by about 30%. From the saline droplets of \(S=20\) to the saline droplets of \(S=30\), the freezing time increased by about 35%. From the saline droplets of \(S=30\) to the saline droplets of \(S=40\), the freezing time increased by about 45%. At a wall temperature of \(-10\)\({}^{\circ}\)C, for every 10% increase in salinity at the three contact angles, the freezing time increased by about 20%. At a wall temperature of \(-15\)\({}^{\circ}\)C, for every 10% increase in salinity at the three contact angles, the freezing time increased by about 15%. When the wall temperature was higher, the increase in salinity was more obvious because the increase in salinity reduced the freezing point of the droplets. When the wall temperature was \(-5\)\({}^{\circ}\)C, the difference between the freezing point of the pure water droplet and the wall temperature was \(5\)\({}^{\circ}\)C, and the difference between the freezing point and the wall temperature of the \(S=40\) saline droplets was 2.68 \({}^{\circ}\)C. When the wall temperature  
Figure 8: Complete freezing time.