Fumio Matsuoka

Water adsorption–desorption isotherms of two-dimensional hexagonal mesoporous silica around freezing point

Zr-doped mesoporous silica with a diameter of approximately 3.8 nm was synthesized via an evaporation-induced self-assembly process, and the adsorption-desorption isotherms of water vapor were measured in the temperature range of 263-298 K. The measured adsorption-desorption isotherms below 273 K indicated that water confined in the mesopores did not freeze at any relative pressure. All isotherms had a steep curve, resulting from capillary condensation/evaporation, and a pronounced hysteresis. The hysteresis loop, which is associated with a delayed adsorption process, increased with a decrease in temperature. Furthermore, the curvature radius where capillary evaporation/condensation occurs was evaluated by the combined Kelvin and Gibbs-Tolman-Koening-Buff (GTKB) equations for the modification of the interfacial tension due to the interfacial curvature. The thickness of the water adsorption layer for capillary condensation was slightly larger, whereas that for capillary evaporation was slightly smaller than 0.7 nm.

Cogeneration System Dynamic Simulation for Snow-Melting Plant.

In this paper we describe an alternative snow-melting system for the Joetsu Shinkansen Line which runs through a heavy snowfall district. This system consists of a cogeneration system, heat pumps and thermal storage tanks. In order to verify its performance and to establish a control procedure, a dynamic simulation of the system based on the actual equipment data, was carried out under actual load conditions. As a result, the thermal storage tanks were found to play the important role of reducing the start/stop frequency of the heat generation equipment for unpredictable intermit-tent snow load. It contributes to reduce the total energy consumption. This alternative system concludes about 30% less primary fuel than the conventional plant.