Numerical simulation of glass doors fogging and defogging in refrigerated display cabinets

A numerical procedure for the simulation of fogging and defogging phenomena is presented and is applied to the prediction of the demisting process on the glass door of a refrigerated closed display cabinet.The physical problem depends on the flow field along the glass, both inside and outside the refrigerated cabinet, on the unsteady conduction through the multi-glazed door and on the heat and mass transfer phenomena within the thin water layer on the fogged surface. Thus a suite of routines for the unsteady simulation of the water layer evolution is coupled with FVM solvers for the Navier Stokes and energy equations inside the cabinet and for the conduction problem in the glass. The convective heat transfer coefficient on the exterior side of the glass door is evaluated through empirical correlations.The codes are iterated simultaneously to reproduce the physical transient, before, during and after the door opening.Simulations are carried out for a frozen food display cabinet with an air curtain flowing along the internal side of the door. Both activated and deactivated configurations of the electric heaters inside the glass are considered. The results show a good agreement with the experimental ones and highlight the importance of taking into account the shape and the distribution of the dew droplets.