MODELING OF FROST GROWTH AND DENSIFICATION

A one-dimensional transient formulation is derived to predict frost gr owth and densification on a cold wall submitted to a moist air flow. T he model is based on a local volume averaging technique that allows th e computation of temperature and density distributions throughout the entire frost layer according to time. It is particularly shown that th e effective vapour mass diffusivity throughout frost should reach valu es several times larger than the molecular diffusivity, so that the mo del is in agreement with experimental data. In order to represent this phenomenon, a new expression for the so-called diffusion resistance f actor is proposed. Values of an adjustable parameter appearing in this expression are correlated to heat and mass transfer boundary conditio ns, and to the global rate of densification. Two possible interpretati ons of the phenomenon are proposed. (C) 1997 Elsevier Science Ltd.