9. Icing and defrosting

The frost that forms and the snow that settles on the cold parts of a refrigeration appliance come from the humidity of the ambient air introduced through the opening, and in some cases result from the loss of water from unpackaged foodstuffs.

This moisture transforms into ice, with a density ranging from 0.2 (light snow) to 0.9 (pure ice), on contact with surfaces at temperatures below 0°C. This frost settles preferentially on the evaporator, which is the coldest part of the unit, in the supply and return air ducts, reducing the evaporator's cooling capacity.

This decline is due to the interaction of several factors:

increase in the pressure drop across the air flow (known as pressure drop) caused by the reduction in the free cross-sectional area of the air flow between the frost-covered fins;...

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Icing and defrosting

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Opening protection

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...