雪氷，融雪工学

It is well known that the ice heat storage system is an attractive way of using night-time electric power energy, of saving thermal energy and an effective use of narrow building space. There are numerous ice heat storage systems on the market although there has been no good evaluation of these systems. This review deals with the ice formation mechanism for ice-making methods based on the previous literature. Particular attention is paid to the way the appearance of the ice nucleus and the growth of the ice front are strongly influenced by the water supercooling phenomenon. Moreover, ice crystal growth is explained from the standpoint of molecular and heat transfer theory.

Ice storage is becoming popular due to the peak electricity demand problem and for other reasons of technical interests. This paper overviews the state of the art from the viewpoint of feasibility compared to water thermal storage. Developments in HVAC application technologies and correct evalution methods of the thermal characteristics in the tank are required.

Following the preceding review, this review examines the influence of heat transfer models on the freezing of water and the melting of ice. The phenomenon of the freezing of flowing water in a river is discussed. In particular, the effects on freezing and melting of natural convection, forced convection and thermal radiation heat transfers under various conditions are clarified.

Physical structures and properties of ice are discussed in relation to ice heat-storage technology. Ice polymorphs including Ices I, II, III, ..., IX, are mentioned, and varieties of ice growth modes in supercooled and other conditions are discussed. Physical properties of ice discussed include structures, mechanical, electrical, and thermal characteristics and others.

A numerical model of powder snow avalanches is developed based the tllermal model in the field of fluid mechanics. The model consists of theconservative equation of fluid phase, the conservative equation of the solid phase, the momentum equation and the equation of the kinetic energy of turbulence. Some constitution relationships, i. e. the entrainment coefficients of ambient fluid, the entrainment coefficient of snow particles on the bed and the shape facotors are expressed by the functions of the slope angle. This model is examined by the experimental data of inclined thermals using the mixture of water and solid particles in the laboratory. The numerical calculations are carried out to simulate the powder snow avalanche occurring at the Yokokura, Katsuyama city in Fukui Prefecture. The reasonable numerical results are obtained. It can explain the longitudinal variations of the height, the speed, the concentration of snow particles, the kinetic energy of turbulence and the distructive power of the avalanche.

The technology of snow-utilization is consisted with (i)gathering snow and transportation, (ii) storing and (iii) snow using such as cold heat source. In the field of the gathering and the transportation of the snow(i) , the heavy equipment machine such as the rotary type snowplow that have already used it in the snow-removal work is diverted and used. Because energy density of snow to be low, and, therefore, it has low economical value. Even if it is not too big power, the snow is easily transformed into a clod. Therefore, the use of transportation snow with air (solid-air two-phase flow) has been limited to the minimum in the popular snow machines of such as the rotary type snowplow. Therefore, there is few case to use the solid-air two-phase flow in the field of the gathering and transporting the snow (i) and (ii). However, the multi-phase flow plays an important role in the use of the snow like the extraction of cold heat from the snow in the fields of (iii). It is because a lot of movements of vapor and droplets of water are used at the same time in the heat exchanging between the snow and air. In this paper, the author described an introduction of the snow utilization technology necessary to talk about the multi-phase flow related to the snow utilization, the example of the multi-phase flow in the field of the snow utilization, and described the views of them.