Kazuhisa Sawase

Energy Conservation in Snow-Melting System on Railway Tracks Using Feed Forward Control

The Joetsu Shinkansen line, which runs through a heavy snowfall district is installed with snow-melting systems whose function is to melt snow deposit on the track by sprinkling heated water over a total distance of 74 km. Because of its long water path in these systems, delivery and return of the water takes a very long time, resulting in a time lag of the feedback control. In order to lessen this time lag, a control system using a feed forward algorithm has been developed and a system operation test has been carried out. It is found to be very promising as a snow-melting device from a view point of energy saving.

CHARACTERISTICS OF A WATER SPRINKLER SYSTEM WITH VARIABLE FLOW RATES TO MELT SNOW ON RAILWAY TRACKS

This chapter discusses the construction, experiments, and the characteristics of a water sprinkler system with variable flow rates in response to weather conditions for snow-melting in railway tracks. It is indispensable for high-speed railway lines running through snowy areas to eliminate the snow deposit from railway tracks. It is important from a standpoint of system performance and economy to provide a variable sprinkling water flow in response to snowfall intensity and atmospheric temperature. To construct such a system, two things must be done: one is to develop a sprinkler that maintains a constant water droplet flying distance even in variable water flow and the other is to develop a variable-flow water sprinkling model to be controlled by water pressure. The chapter describes an experiment that was done to study the sprinkled water distribution and the heat loss of sprinkled water. The sprinkled water distribution and the heat loss of sprinkled water were measured by a conventional method, and photographic method was used to measure the diameter and the velocity of water droplets flying through the air. Unsteady state analysis was carried out by a numerical technique for both motion loss and heat loss in flying water droplets. A performance test following the construction of an experimental model was carried out by inverter pump-controlled operation. The sprinkling distances of flying water droplets after leaving the sprinkler nozzle were affected by sprinkling water pressure, levitation angle, sprinkled from nozzle, diameter of flying water droplet, and wind velocity.

Characteristics of a water sprinkler system with variable flow rates for melting snow in railway tracks.

For a snow-melting system for railway tracks, from an economical point of view, it is necessary to manufacture a water sprinkler with variable flow rates in response to snowfall intensity and atmospheric temperature. A newly developed sprinkler was constructed and operated to control water flow rates by water pressure, using either a module valve or an inverter pump installed in the pipe line. The experiment confirmed that the snow-melting system with the proposed sprinklers is technically and economically promising in terms of energy conservation.

Development of an air source heat pump driven by a diesel engine for melting snow on railroad tracks

To save the running costs of melting snow by sprinkling heated water, a heat pump was conceived and constructed. Various kinds of performance experiments were conducted in winter at the Maibara station precincts on the Tokaido Shinkansen railroad. The TCOP of the heat pump was found to be 2.73 in a mild climate of about 2 degrees C. When the coil surface of the air heat exchanger is frosted, the TCOP drops to 1.71 on account of the thermal output consumed for the defrost operation. Thus it is demonstrated that the hear pump can cut energy expenses as compared with a conventional boiler heating system.<<ETX>>

Characteristics of a sprinkler operating with variable flow to melt snow on the track under all weather conditions.

The experimental study was conducted to investigate the performance of a prototype sprinkler for melting snow or railway tracks at various pressures. The heat loss in flying water droplets and the performance of the sprinkler were theoretically obtained. The mean diameters of water droplets were measured at different water flow rates by photography : they were 5∼6 mmφat the initial speed of 11.5∼16.0 m/s. The temperature drop of the droplet is about 0.2°C/m in flight through air at 0°C. In this sprinkler, the distribution of sprinkled water is kept uniform regardless of the water flow rate.