Optimization of heat transfer in electric heating snow melting systems for turnout

To address the issues of high energy consumption, low thermal efficiency, and incomplete snow melting in electric heating elements of turnout, No. 18 turnout of a 60 kg·m^-1 steel rail was selected as the research subject. Based on finite element analysis and physical field analysis methods of solid-fluid heat transfer, a physical model of "turnout-heating element-snow accumulation-air" was constructed. The model surface was defined as an open boundary, with the bottom defined as thermally insulated. Under identical initial conditions, the simulation results of heating methods of rail web, rail slope, and combined rail web and slope heating were compared. An optimized method involving the installation of heat-conducting plates on the sides of the slide bed was proposed. Simulation analyses were conducted under varying temperatures, wind speeds, and directions. Analysis results show that, under constant total power, a more pronounced rise in the slide bed temperature is observed when the rail slope heating method is employed, as compared with the other two heating methods. After installing heat-conducting plates, heat generated by the heating element transfers faster to the sliding bed due to their higher thermal response speed. Under the temperatures of -5 ℃ and -15 ℃ and in the absence of snow accumulation, the time required for the heating element to reach the corresponding temperature is shortened by 40% when a heat-conducting plate is used, compared with the general condition without such a plate. With an additional 20 mm of snow accumulation, a lead time of over 20% is achieved compared with the general condition. Snow-melting rate at the near end of the stock rail is initially lower than under general conditions. Later, the rate increases. As a result, the snow at the far end melts faster and more completely. Different wind directions act on different positions of the turnout and produce different effects in suppressing temperature rise. Higher wind speed makes the temperature rise more slowly. It also causes the system to reach a balance between heat absorption and heat loss more quickly. The established heat transfer model of the heat-conducting plate in the switch rail provides a theoretical basis for power optimization in different regions. It can also guide the selection of heating element power and the precise control of heating time.