Lumped heat and mass transfer model of the frost formation process.

Abstract

An important problem in the refrigeration industry is the formation of frost layers on sub-freezing surfaces of air coolers. The frost growth process is described by a set of partial differential equations that combines both the latent and sensible heat and mass transfer. A direct method to predict the heat transfer coefficient from the frosted surface would be desirable for system design engineers. We present a framework to determine the heat transfer coefficient from a frosted surface. The sensible and latent heat transfer coefficients are lumped into a single term, which is convenient for calculating the total heat transfer from the surface. The sensible portion of the heat transfer is calculated from common heat transfer correlation for flow over a surface, while the latent heat term is proportional to the growth in frost thickness. Any frost thickness growth model can be used with the described method, which has the added benefit of calculating the ratio of sensible to latent heat transfer. The results of the model are compared to measurement and show excellent agreement.