Análise energética de um sistema de refrigeração compacto: desenvolvimento de uma metodologia experimental didática, avaliação e primeiros resultados.

Abstract

A simple refrigeration system is designed to remove heat from a space or product, generally using a vapor compression cycle. Given the high ambient temperatures in the metropolitan region of Recife, there is a notable demand for air-conditioned environments. However, this activity entails high costs due to electricity tariffs. This study presents a case analysis using a cascade-type refrigeration bench, aiming to develop an experimental methodology through result analysis focused on improving energy efficiency under different operating conditions. For this purpose, a single-stage vapor compression refrigeration prototype was used, employing a 50% ethylene glycol solution as the secondary fluid. The prototype, intended for research purposes, uses R404A as the refrigerant, with a nominal cooling capacity of approximately 1 kW. The thermal load applied to the system is simulated using an electric resistance submerged in a heating tank containing the ethylene glycol solution, which is connected to the prototype's evaporator. The condensing unit uses a hermetic compressor coupled to a finned-tube heat exchanger, operating under forced convection. An experimental methodology was developed to assess the refrigeration system's performance under different expansion valve openings and levels of superheating. The valve opening was adjusted to 60%, 80%, and 100%, and superheating levels were set at 5 °C and 8 °C. To ensure result reliability, each configuration was tested three times, totaling eighteen measurements that allowed observation of the system's behavior. A standardized, didactic methodology was established, offering greater data collection accuracy and validated through practical application by technical course students. The experimental analysis identified two operating conditions with the best performance: superheating at 5 °C with a valve opening of 60%, and superheating at 8 °C with a valve opening of 100%. These results validated the applied methodology and confirmed the study's success in exploring different operational conditions.