Study on design optimization of snow melting system in Light Rail Transit (LRT) system

초록

In these days, metropolitan city demands a new public transportation system which can be applied to a branch line that lacks passengers and operation profit. Light Rail Transit (LRT) system (in Fig.1) is considered as an alternative for this case. LRT has advantages such as the reduction of noise and CO2 emissions compared with public bus system as well as quickness and punctuality of subway. LRT has different components from typical train in system. For example, as a power supply system, power supply rail is installed on the side of a neighboring rail track instead of a pantograph on a train roof. This system has an advantage of reduction in infrastructure cost compared with a typical pantograph system. On the other hand, it is so susceptible to weather condition that its operation must be stopped. It is due to the phenomenon that the snow or ice pieces on a rail track spread during train operation to the power supply rail, and they are accumulated and frozen to make a gap between power supply rail and power collector shoe in a cold weather.(in Fig.2) Therefore, as a solution, snow melting system is installed on rail track and power supply rail also. In LRT system, the electrical heating system is most suitable considering the characteristics of infrastructure. In the operation of heating system, it is also considered the operation heating time concerning a maintenance cost of LRT operator. And the standard of proper heating time should be created based on the weather forecast in order to prevent the excessive electric consumption. In this study, design of snow melting system (or heating system) is optimized by numerical analysis. The number, heating capacity, pitch and depth of heating cables are considered as design parameters. The objective of optimization is to minimize the time to reach the snow melting point anywhere in snow-contact surface of the structures of rail-track and power supply rail. For a heat transfer analysis, temperature, wind speed, humidity and the amount of snowfall are considered as climate factors. From these factors, convective coefficient is determined consequently.