Vertical display cabinets are widespread in food stores, because they have a large
display area and an ease access for customers. Recently, open cabinets has been
replaced with closed ones in order to reduce energy consumptions for refrigeration.
However, the presence of the glass doors can have an effect on product visibility
because of mist formation on the glass, particularly for low temperature display
cabinets. This effect appears when the temperature at the external surface of the
glass falls below the ambient dew temperature, which is a quite common situation in
humid climate in the mid-season, when neither indoor air heating nor cooling is
performed. Today the mist formation is prevented increasing the surface
temperature at external side of the glass doors by means of electrical resistances
embedded in the doors frame. The glass door surface temperature can be raised
enhancing the heat transfer coefficient driving the supply air towards the display
cabinet doors. This paper investigates the behaviour of different air ceiling diffusers
(vortex diffusers and linear diffusers) in order to reduce the risk of mist formation
and the energy consumption of electrical resistances. Initially, 3D numerical
simulations of isothermal airflow field has been performed and, later, summer and
winter conditions were considered.
The air flow field in the display zone, the temperature distribution on the glass
surfaces and the influence of different diffusers on customers comfort condition are
investigated.
