A semi-empirical correlation for predicting the frost density on hydrophilic and hydrophobic substrates

A new semi-empirical correlation for the prediction of frost density on hydrophilic and hydrophobic surfaces is proposed. The proposed correlation is a function of the modified Jakob number and contains two correction terms, one for surface contact angle and another for relative humidity. Whereas most frost correlations exclude surface wettability as a parameter, our research has shown that the surface contact angle can be important when trying to accurately predict the properties of a growing frost layer. The correlation was developed using data from three different surfaces. On each surface, the frost was grown for three hours and then defrosted. The proposed correlation predicted more than 93% of the data to within a ±20% error band and is proposed for use on surfaces with contact angles 45° < θ < 160°, relative humidity 0.40 < ϕ < 0.80, and plate temperatures −13 °C < Tw < −5 °C under natural convection conditions.