Abstract
In earlier works by the present authors, two systems for sustainable energy were proposed: (i) a system for urban snow removal in winter and storage for air conditioning in summer, applied to Nagaoka City, which suffers heavy snow fall every winter, and (ii) a district cooling system utilizing latent heat of ice to reduce the size of storage reservoir and transportation pipeline system. In these systems, the hydraulic conveying of snow or ice through pump-and-pipeline is the key technique to be developed, since characteristics of snow (ice)/ water slurry is largely different from those of conventional non-cohesive solid particle slurries. In this study, the blocking of pipeline of snow/water slurry is investigated experimentally. While the blocking of conventional slurry occurs due to deposition of heavy particles at low flow velocity or arching of large rigid particles, that of snow/water slurry is caused by a compressed plug of snow formed due to cohesive nature of snow particles. This is because the strength of snow plug formed at a high resistance piping element, such as an orifice, becomes higher when the compression velocity is lower, resulting in a solid-like plug filling the whole channel upstream the element.
Highlights
Many cities along the Japan Sea Coast in Honshu Island suffer heavy snow fall every winter.In contrast, during the two months in summer it is very hot and humid in these areas
The heavy snow fall requires removing of snow off the roads in the city as soon as possible, and, several times a winter from roofs of houses and buildings so as to avoid cracking of roofs and/or distortion of structures
It is well known that the mechanical properties of natural snow on the ground, e.g., the bulk density, shear, and compression strengths, largely depend on the size and shape of snow particles, as well as the temperature
Summary
Many cities along the Japan Sea Coast in Honshu Island suffer heavy snow fall every winter. The understanding on the characteristics of snow/water slurry and techniques for its treatment, obtained through these projects, were transferred to later NUT-TDC projects for the development of district cooling system utilizing ice/water mixture [11]. In this system, it is expected that the diameter of the cold energy delivery pipeline can be reduced to a half of the conventional cold water system by mixing ice with a concentration of up to 20%. The term “snow” will be used both for snow and ice, in this paper
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