# Model Experimental Study on De-Icing Method of Bridge Pylon Beam Based on Electric Heating
## 4 Results and Analysis of De-Icing Tests
### Anti-icing Tests
#### 4.1.3 Suggested Environment Range of Application  
The ambient temperature [23] and wind velocity [4] are crucial factors that affect the electric heating de-icing. The wind velocity on a bridge crossing a river is usually higher than in urban areas. When the environment is too harsh, the heating performance of the heating system will be greatly affected, the anti-icing for the beam may fail, and a serious icing situation may occur again. However, when the icing coverage ratio reaches a certain degree or covers the whole surface of the heating system, the heating performance of the heating system may be less affected by the wind due to the ice cover preventing the wind. Conversely, the ice layer may fall off faster due to the internal heating caused by the heating system. Because the ice-falling situation tends to occur after the ambient temperature rises, the ice does not come off easily when the outward environment of the icing is relatively stable. In contrast, if the external environment of the icing is relatively stable and the internal temperature of the component rises, the ice accumulation is likely to fall off more quickly relative to the natural shedding situation, and after the ice falls off, the surface of the heating system will freeze again due to low temperature; this process of icing and melting will be repeated. In such a case, bridge traffic safety may be threatened more quickly and more frequently. Therefore, it is necessary to find out the applicable environmental range of the heating system, beyond which it may be safer to shut down the heating system because thicker ice accumulation in the stable low-temperature environment is more strongly adsorbed to the components than that in a warmer environment [24]. Five groups of anti-icing tests were carried out by changing the ambient temperature and wind velocity. By calculating the icing coverage of each group of tests, the suggested applicable environment range is given. The test conditions and icing coverage are shown in Table 4. Figure 14a shows the effects of the five groups of anti-icing tests, and Figure 14b shows the variation of the icing coverage with the environment. When the wind velocity was 3 m/s, after 40 min of pre-heating, the heating system surface was free of ice at \(-5\)\({}^{\circ}\)C and \(-10\)\({}^{\circ}\)C (Figure 14a). At \(-15\)\({}^{\circ}\)C ambient temperature, the ice was accumulated on the leading edge of the heating system, and the shape was a long strip of ice. By calculating the area proportion of the icing area, the icing coverage ratio was obtained; it was 28.27%. When the wind velocity increased to 5 m/s, the leading edge of the heating system not only froze but also generated a few icicles outward. At \(-15\)\({}^{\circ}\)C in particular, the heating system almost lost the anti-icing performance, and the icing coverage was as high as 92.07%. Only the area within the diameter of the CFHC was free of ice. This shows that wind has a serious impact on the anti-icing performance of the heating system. When the ambient temperature is at a low level or the wind velocity is high, the heating system almost loses the anti-icing performance, and the ice will cover the surface of the heating system in a large area. In addition, since the internal heat source is still generating heat, the risk of ice falling in the heating system-equipped area may occur more quickly when the icing stops. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Group Number**} & **Ambient Temperature** & **Wind Velocity** & **Pre-Heating Time** & **Precipitation** & **Ice Coverage Ratio** \\  & **/**\(\mathrm{\SIUnitSymbolDegree}\)** & **/**\(\mathrm{\SIUnitSymbolDegree}\)** & **/**\(\mathrm{\SIUnitSymbolDegree}\)** & **Time** & **/(mm/min)** & **Ratio** \\ \hline
1 & \(-5\) & 3 & 40 & 1 & 0\% \\
2 & \(-10\) & 3 & 40 & 1 & 0\% \\
3 & \(-15\) & 3 & 40 & 1 & 28.27\% \\
4 & \(-5\) & 5 & 40 & 1 & 28.88\% \\
5 & \(-15\) & 5 & 40 & 1 & 92.07\% \\ \hline \hline \end{tabular}
\end{table}