# Study of Heat Distribution in Railway Switch Using Resistive Heater in Cold Climate Conditions
## 2 Materials and Methods  
This study was carried out using lab-based experiments and numerical simulations. Experiments were carried out in a cold room chamber facility at UiT, whereas, for numerical simulations, a MATLAB-based analytical model of heat transfer was developed. For lab-based experiments, the setup was developed using the actual railway switches obtained from the railway department. The setup was developed in the cold room facility where the temperature could be controlled up to 248 K (\(-25\)\({}^{\circ}\)C). A reactive electrical heater was used for heating. This heater contained wire and element parts. The element part was attached to the rail using four clamps. These clamps were specified for the rail and heater type. Ballasts and soil were provided under the rails to make the conditions as real as possible. Temperature was recorded using thermocouples and infrared cameras. Various thermocouples were attached along the 2 m long rail track, and data were recorded using data loggers. For infrared images, an FLIR A615 IR camera was used. Figure 2 shows the lab experimental setup used in this study. For these experiments, S54 Rail was used. On the stock rail, thermocouples were installed at three points to record the temperature on the rails. The rail has three main parts, called the head, web, and foot of the rail, and each has its own specific geometry. Moreover, the contact of each part with the switch rail, ground, heater, and clamps is not the same, so it was decided to install thermocouples to observe each area separately. The locations of the thermocouples are shown in Figure 3 with red circles. A control device was designed to control the heater using a temperature controller. This device could read the power consumption by a power meter. Moreover, the temperature data from thermocouples were recorded using the data logger presented in Figure 3.  
For the experiments, an infrared-based imaging technique was used to record the dynamic variation in rail surface temperature. An IR camera is a non-contact temperature measurement device that detects the infrared energy emitted, transmitted, or reflected by all materials at temperatures above absolute zero (0\({}^{\circ}\) Kelvin) and converts the energy factor into a temperature reading or thermogram [15]. IR images are processed using IR control software V4.59. For the calibration of the IR camera during experiments, firstly, the reflected temperature was examined. To increase the emissivity, the rail surface was covered by a black coating sprayed on the rail cross-section. The reflected temperature, the emissivity of 0.92, and the distance from the object were carefully adjusted for the calibration of IR imaging. Surface temperature measurements from IR cameras were validated with the thermocouples recorded temperatures during the experiments. For the experiments, heat distribution due to resistive heating along railway switches were observed under different conditions. Experiments were carried out under two different conditions (Table 1). To explain the experimental process, we take scenario 1 as an example, where the air temperature was 268 K (\(-\)5 \({}^{\circ}\)C). To start the experiment, the room temperature was set to 268 K (\(-\)5 \({}^{\circ}\)C). It took some time until the rails' temperature reached 268 K (\(-\)5 \({}^{\circ}\)C) as well (all thermocouples on rails should have shown 268 K), then the control unit automatically switched on the heater. The heating continued until the rail surface temperature reached the target temperature of 278 K (\(+\)5 \({}^{\circ}\)C). Then, the  
Figure 3: (**a**) Location of thermocouples on the rail, (**b**) heat controller, (**c**) data logger. Figure 2: Lab experimental setup. heater tried to maintain the rail temperature and automatically switched off. Rail surface temperature and heat distribution were recorded from the start of heating for 20 min. The power consumption of the heater was also recorded during the experiments.