Salinity and growth rate of ice formed by sea spray

Abstract

A model of salt entrapment in ice grown by sea spray is developed. It is pointed out that during wet growth spray icing the ice/water interface always assumes a dendritic growth morphology, and that consequently liquid water is trapped in the spray ice matrix. A result of the proposed theory is that the salinity of spray ice depends mainly on the accretion fraction. The ratio k of the salinity of accreted ice to the salinity of sea spray is k = k∗ [1 - (1 - k∗) n] , where k∗ is the interfacial distribution coefficient (ratio of the ice salinity to the salinity of water at the ice/water interface) and n is the accretion fraction (ratio of the accretion rate to the water impingement rate). The mechanisms controlling K∗) are discussed, and it is concluded that a constant value of k∗ can be used, as a first approximation, in modelling salt entrapment in spray ice. To calculate n, the proposed theory is incorporated into a cylinder icing model so that the accretion fraction and the salinities of ice and the liquid film on the icing surface are solved simultaneously by an interative procedure. This makes it possible to calculate both the salinity and the growth rate of spray ice. At temperatures typical to marine icing the growth rate of saline water spray ice is lower than that of fresh water spray ice.