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A theoretical study of the ice accretion process
Author(s) -
Macklin W. C.,
Payne G. S.
Publication year - 1967
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.49709339606
Subject(s) - supercooling , radius , materials science , clear ice , mechanics , thermodynamics , convection , latent heat , enthalpy of fusion , meteorology , melting point , physics , composite material , sea ice , computer security , antarctic sea ice , arctic ice pack , computer science
Abstract A theoretical study has been made of the assumptions underlying the simple heat balance relations which have been used so far to predict the surface temperatures of ice deposits being formed by the accretion of supercooled water droplets. Calculations have been made of the freezing and subsequent cooling times of a thin water film on the surface of a ventilated sphere initially at a uniform temperature. It is demonstrated that this effectively simulates hailstone growth. The calculations show that both the freezing and cooling processes are dominated by the sphere temperature although, during freezing, the temperature of the water film may rise to a value close to 0°C. They also show that, except at sphere temperatures within a few degrees of 0°C, the freezing time of the water film is short compared with the total time taken to remove the latent heat of fusion by the forced convection process. The reason for this is that the heat of fusion is first conducted rapidly into the sphere, and then more slowly dissipated through the air boundary layer on the surface of the sphere to the environment. Values of the freezing and subsequent cooling times of the water film are presented for various values of the ambient temperature, sphere radius and film thickness. Film thicknesses have been related to the radii of the cloud droplets by a semi‐empirical relation. The liquid water concentrations required to maintain a sphere at a steady temperature have been computed and found to compare well with those given by the simple heat balance relation for a spherical hailstone. Thus, although the simple heat balance relations completely ignore the physical processes involved in the accretion of individual droplets, they are useful for predicting values for the mean temperatures of an accreting surface in a steady state situation.