Optimisation des dégivrages par gaz chauds en chambre à basse température

Abstract

An investigation into energy expenses related to frosting and defrosting is very useful as it reveals all the technological strategies for minimizing energy expenses. In the case of cooling coils for ambient conditioning at very low temperature, certain solutions need to be changed when other expenses are involved or when they do not satisfy industrial safety standards. Nevertheless, hot gas defrosting gives significant advantages with the use of a heat pump. If ρ is the coefficient of performance of the refrigerating plant, all the expenses linked to hot gas defrosting benefit from the minor coefficient 1 (2ρ+1) . All the terms of the general expression of the expenses are considered in this case and take on a particular relative importance. It is sometimes possible and more efficient to ‘fight’ the causes rather than to seek elaborate remedies. Management and automation systems are one way to solve this problem, and the different sensors able to control both the extent of frosting and the entire defrosting process are considered in this paper. Differential thermometers and manometers are most often used for frosting control; the ice capsule is a very efficient means of controlling the final steps of defrosting. It is certain that technologies are sufficiently developed to be used on an industrial scale; the common applications are only under development, and their practical advantages remain to be estimated even if their reliability and theoretical advantages are proven. For large cold rooms, frost entrapment is the solution proposed; it is more interesting from the point of view of air quality than from energy savings.