Análise da eficiência energética de câmaras frigoríficas com diferentes isolantes térmicos

Abstract

Cold rooms are storage spaces conditioned by a mechanical refrigeration system for the temporary preservation of food. The most common types are: cold and frozen chambers. One of the requirements in the design of cold rooms is the search for an economical thickness of insulating materials that involves important factors, namely: the cost of installation (i.e. acquisition of insulating plates) and the cost of operation (i.e. energy losses measured monthly on invoices issued by the electric company). Good thermal insulation is essential to reduce undesirable thermal changes and to avoid temperatures close to the dew point on the surrounding walls, avoiding condensation problems. Thus, materials of high thermal resistance must form the thermal insulation. Currently, in the construction of cold rooms, prefabricated insulating panels of the "sandwich" type are applied, which consist of two metallic coatings interconnected by an insulating core. The most common materials for the panels are: injected polyurethane foams (PUR), extruded polystyrene (XPS), polyisocyanurate (PIR) and polystyrene (EPS). In this context, this work presents a study aimed at analyzing the energy efficiency of cold rooms equipped with different thermal insulators. Several simulations are carried out to survey the refrigeration load and analyze the efficiency of the aforementioned insulators. The analyzes also include some real case studies with determination of operating, installation and total costs. Interesting results stand out, valuing a new parameter that emerged from a different concept for “Thickness of Operation Excellence” (EEO) for the various types of insulators studied. As a result, theoretical and practical graphs of the real costs for operation and installation in the city of Natal-RN / Brazil are presented. The conclusions emphasize the importance of the correct dimensioning and specification of the insulating materials, with emphasis on the PUR and PIR panels. Clearly, theoretical and practical graphs exhibit similar behaviors. However, in the current economic situation, it was found that operating costs are more relevant compared to installation costs. In practice, it was concluded that the EEO stood out in terms of “theoretical economic thickness” in all the cases studied. This conclusion regarding the thickness of excellence proved to be valid even admitting a previous choice of insulating material with high thermal resistance.