Showing papers on "Glaze ice published in 1996"

Modeling power line icing in freezing precipitation

Abstract: The existing widely used models of power line icing in freezing precipitation are conceptually evaluated. The reasons for the different predictions by the models are pointed out, and it is shown that none of the models is both correct and complete in predicting design glaze ice loads. Improvements to the modeling are proposed and a new comprehensive numerical model is presented. This model includes detailed simulation of icicle growth. The results of the new model show that earlier models underestimate ice loads under certain conditions. Furthermore, the new model shows that ice loads formed close to 0°C may be much higher than those formed at lower temperatures, other conditions being the same.

A computer model of glaze accretion on wires

Abstract: The design of power transmission lines requires a knowledge of combined wind and ice loading and of the dynamic behavior of wires loaded with ice accretion. The calculation of the wind forces, in turn, imposes a need for a more detailed computer model for determining glaze accretion shape. For this purpose, a computer model of glaze accretion on wires was developed. It is based on experimental results in the area of ice accretion on wires, as well as on results in the related field of the glaze ice accretion on airfoils. The model incorporates the time dependent on feedback between the growing accretion and the air stream, the variation of the heat transfer coefficient around the cylinder, and the surface runback of water. The main components of the model are the computation of the air flow field, the computation of the impingement water at the control volume level, the solving of the heat balance equation, and the computation of the accretion shape on the wire. The surface air velocity is obtained through the solution of the potential flow around the iced wire and wake, followed by the integration on the surface of the laminar boundary layer. The water flux ismore » computed in each control volume down to the separation point. The heat balance equation derived from the energy equation is solved to determine the freezing fraction and the resulting modified ice surface geometry.« less