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...

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Air curtains

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Evaporator and refrigerant

References

(1) - RIGOT (G.) - Meubles et vitrines frigorifiques pour la distribution alimentaire. - 350 p. Pyc Édition France (1990). (Remerciements à l'Éditeur PYC Livres pour son autorisation d'en publier de larges extraits).
(2) - RIGOT (G.) - Load variations for...

Regulations

Order of May 9, 1995 (JO of May 16, 1995) published by AFNOR in the Maîtrise de la chaîne du froid (Cold chain control) compendium.

Standardization

Various technical standards apply to refrigerated display units:

international standards ISO series 5160..., ISO series 1992...
European standards EN 441 series...
French standards series D74...

These various standards can be obtained from AFNOR

Simulation software

Sales refrigeration units installed in food retail outlets are complex thermal and aeraulic machines, operating under variable ambient conditions. They constantly exchange air, heat and humidity with the store's internal environment. The cold production needed to maintain their temperature is cyclically interrupted by defrosting operations. The temperature of the goods on display will be strongly affected by these...