Análise termodinâmica de eficiência energética de um sistema de refrigeração aplicado em uma sala de aula

Abstract

The cooling of an installation in thermodynamic terms does not occur spontaneously, it is necessary that an inverted thermal machine (air conditioning) expend energy to cool an environment. For the installation of an air conditioning system, it is necessary to carry out a survey of the environment to be conditioned in order to discover the thermal loads incident on the system, so that it is possible to size the refrigeration equipment to be used, thus allowing to obtain the real value of system energy efficiency. The study application environment was a classroom of the Educational Institution Association of Dom Bosco, located in the city of Resende-RJ, whose objective thermal comfort conditions were established by current Brazilian standards and referenced in the project. The assessment methodology involved dimensions and measurements at the location of the room, followed by the creation of a 3D model in software to facilitate visualization and summation of surface areas. In addition, the listing of materials that make up the construction and other factors such as people's physical activity level, number of students, bioclimatic characteristics of the region, geographic orientation of the construction, exposure or not to sunlight, presence of electrical equipment, artificial lighting and air renewal were also considered. The calculations were divided by type of thermal load, each with its respective formula, in order to obtain a value of total thermal load later on. After performing the study and applying the appropriate calculations, it was possible to reach a total thermal load value of 13406.68 Watts, which is equivalent to 45745.49 BTU/h, this value made it possible to choose the appropriate air conditioning device, that when compared to an ideal Carnot refrigerator showed an efficiency of 7.24%. It is noteworthy that in this project we chose to use the split system vapor compression refrigeration system. With this, it was also possible to present a projection of the energy expenditure of the device based on the use proposed by the study, so that the faculty can analyze the project's feasibility, as well as suggestions for structural improvements in order to reduce expenditure on refrigeration.