雪の水力輸送に関する研究-6-雪水2相流のエルボにおける圧力損失

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The pressure drop of a snow/water mixture in commercial elbows (90° bend pipe with sharp curvature) connecting two straight pipes of circular cross section was measured and the influences of the pipe diameter D (40 mm and 77 mm), the setting direction of the elbow, flow velocity Um, snow volume fraction C at discharge and the property of the snow were investigated. From the experimental results for granulated snow and fresh snow in the regions Um=0.3 2.5 m/s, C=030% and Fr=3200 =Fr=Um2/ (|1-sgD) (Froude number, S : the density ratio of ice to pure water, g : acceleration of gravity) the following conclusions were obtained. When the pressure drop between two points upstream and downstream of an elbow was expressed as the sum of the pressure loss he due to change of flow direction and the friction loss hs in the straight pipe, he was usually far greater than hs. Mixing of snow increased he at a low value of Fr, although this pressure loss increasing effect was lower than for the flow in a straight pipe. The increment of he due to snow mixing decreased with increasing Um and when Fr 100 he is virtually equal to that for water irrespective of C. In this case the equivalent length of the bend loss he was 4050 times the pipe diameter. The influences of the setting direction of the elbow and the snow properties on he were found to be negligible. Through the whole experimental runs no choke phenomenon was observed at the elbows, which, together with above results on the pressure drop, confirmed that a bend in a pipeline was not a cause of difficulty for the hydraulic conveying of snow.

雪の水力輸送に関する研究-6-雪水2相流のエルボにおける圧力損失

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