# Study of Heat Distribution in Railway Switch Using Resistive Heater in Cold Climate Conditions
## 3 Results
### Lab Experiments  
The lab experiments were carried out under two different sets of operation conditions, specified in Table 1. An infrared camera was used to measure the surface temperature variation, and IR results were compared with the thermocouple temperature values. The aim of this comparison study was to investigate the possibility of using IR cameras in the actual railway field to monitor the temperatures while heaters are operating. Temperatures were recorded using the data logger system. Tables 3 and 4 show the average temperatures in these locations at t = 20 min after the heater was switched on.  
IR images were further processed and analyzed. For each part of the rail, known as the foot, web, and head of the rail, lines of interest (LOI) were defined to observe the temperature on the line. As the heating process is not symmetrical on the rail, it was not expected to have a smooth temperature distribution on each LOI. Results show that the temperature measurements from IR camera are in good agreement with values from the thermocouples. This highlights the possibility of reliable use of IR cameras for observing the temperatures in actual field conditions of railways.  
Figures 6 and 7 show the IR images of temperature distribution along the rail switch cross-section at two different room temperatures. It is observed that the temperature distribution along each section is not constant, and the temperature values fluctuate along each LOI. IR imaging provides more in-depth information along the surface as thermocouples are point devices and can only give the temperature value at one particular point.  
According to Figures 6 and 7, most of the heat is transferred to the foot section, especially on the right side where the heater is installed; this means most of the heat generated by the heater is vulnerable to being transferred through the foot into the ballasts under the rail, while the web and head of the rail have a small share of this heat so that the head cannot reach a temperature over 273 K (0 \({}^{\circ}\)C). It should be considered that the head has a connection with the switch rail, and it is important for the head to have a higher temperature than 273 K (0 \({}^{\circ}\)C).  
This pattern is clearly observed in Figure 8 over time; from IR images, the heat transfer over time for a total duration of 20 min was recorded. In this picture, four time sections are shown. The sequence of pictures (1-4) shows how the heat is transferred from the resistive heater to the rail section over time. These pictures also confirm that the heat is mostly transferred to the foot rather than two other sections, which is normal according to the location of the heater. The point is, that this heat transfer cannot be preferable as it is not efficient. While the stock rail needed to be heated in the sections in contact with the moving rail, the heater's energy is mostly consumed to heat up the foot rail and is lost through the foot.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Scenario** & **Foot (K)** & **Web (K)** & **Head (K)** \\ \hline IR & 272.12 & 264.84 & 258.95 \\ Thermocouples & 270.13 & 263.47 & 256.62 \\ Difference (\%) & 0.73 & 0.52 & 0.90 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Average rail temperatures at different locations for atmospheric temperature, T = 253 K (\(-\)20 \({}^{\circ}\)C).  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Scenario** & **Foot (K)** & **Web (K)** & **Head (K)** \\ \hline IR & 284.15 & 277.95 & 272.95 \\ Thermocoouples & 284.25 & 276.85 & 272.05 \\ Difference (\%) & 0.03 & 0.39 & 0.33 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Average rail temperatures at different locations for atmospheric temperature, T = 268 K (\(-\)5 \({}^{\circ}\)C).  
Figure 6: Temperature distribution on LOIs for the temperature of 268.15 K (\(-5\)\({}^{\circ}\)C) at t = 20 min.  
Figure 7: Temperature distribution on LOIs for the temperature of 253.15 K (\(-20\)\({}^{\circ}\)C) at t = 20 min.