CFD simulation of anti-fogging coatings performance in refrigerated display cabinets

A numerical procedure for the simulation of both fogging and the defogging process on the glass door of a vertical refrigeration display cabinet for chilled food is presented. The large scale problem within the cabinet (convective air flow and heat transfer, moisture mass transport, unsteady conduction through a multi-glazed door) is modelled via a commercial CFD code, whereas the water layer is modelled, via in-house user defined routines, as a collection of tiny droplets in order to take into account the surface wetting properties, the latent heat contributions and the area effective wet fraction. Local water layer equivalent thickness and time needed for the complete defogging are evaluated for different indoor conditions. The influence of anti-fog coatings is investigated comparing different droplets contact angle, from 30° to 90°.