Monitoramento e controle de câmaras de refrigeração via velocidade variável do compressor

Abstract

The conventional on-off control system, commonly used in refrigeration chambers, presents a low performance and a high energy consumption. This work presents a control scheme of temperature for refrigeration chambers based on the variable speed of the compressor. For this purpose an experimental platform has been developed. It consists basically of three parts: a continuous monitoring and control system (CMUF®), a refrigeration chamber and a variable-frequency drive capable of accurately changing the speed of the compressor. This work describes the features of each part of this experiment platform. The control developed incorporates information about the dynamics of the system and most influential variables in the process and operates the compressor at a speed that results in greater efficiency and better temperature stabilization in the desired reference value. To accomplish this, the controller can operate on three modes: Continuous, Hybrid and Efficient On-Off. In order to characterize the dynamics of the system with mathematical models, step response tests were performed for two different loading thermal conditions, and each obtained model was properly validated. The capacity and potential of the developed strategy are demonstrated and evaluated by applying a PI controller, suitably designed for two different tunings that have been obtained with the known method of direct synthesis. Finally, the experimental results with both the conventional and the elaborate control are presented. Also presented are the analysis and comparisons between controllers and tunings. The results indicate advantages such as better temperature stabilization and operational efficiency improvement of the chamber.