6. Air curtains

Opening a refrigeration unit represents a technical challenge. How do you maintain an interior temperature in an open refrigerated volume, with a temperature difference of up to 50 K with the outside?

In the case of horizontal gondola-type units open at the top and featuring a deep tray, it is conceivable that the air inside the unit has a higher density than the air outside (+10 to 20%), and will tend to remain contained in the refrigerated volume under the effect of gravity ("bathtub" effect). This precarious equilibrium can only be envisaged if the cabinet is not full of food. The slightest draught or handling of the products on display will disrupt this idealistic vision. What's more, the partial pressure of ambient water vapour, which is higher than that inside the cabinet, constantly causes vapour to migrate from the outside to the inside of the cabinet through...