Icing Rate on Stationary Structures Under Marine Conditions

Abstract

Abstract Icing on stationary structures is an increasingly serious problem as off-shore drilling operations in the sub-polar regions becomes more popular. Since this problem is less complicated than icing on a ship, an attempt was made to calculate accretion rate using existing data. The rate of ice accumulation R can be calculated from R = C f C c F where F is the mass flux of the water drops and C f and Cc are the proportions of spray frozen on the surface and coefficient of capture of drops, respectively. Cc can be close to unity for larger drops such as sea spray. Although many other factors may contribute, C f seems to be a strong function of the air temperature. Mass flux can be written as Vr3 dr where n(r) is the number of drops of radius r in unit volume, V is the wind velocity, ρ is the density of water; n(r) is a function of wind velocity and height of observation. For a stationary structure, the mass flux is primarily dependent upon the wind speed. The ice accretion rate R, calculated using published data on the size distribution of sea spray and using a capture efficiency Cc of I agrees surprisingly well with the diagrams given by previous authors for icing on ships.