Performance Monitoring in Supermarket Refrigeration Systems - Synchronization of Refrigerated Display Cases

AbstractThe overall task of a supermarket refrigeration system is to maintain the quality of the foodstuff. This is done by making use of a refrigeration cycle in which a refrigerant transport heat from the refrigerated display-cases to the outdoor surroundings. Typically the system is equipped with a decentralized control system neglecting interactions between subsystems. Though these interactions are minor they from time to time lead to a synchronization of the operation of the display-cases which causes an inferior control performance and increased energy consumption. In this paper we will analyze the synchronization using bifurcation theory and show that the system has a chaos-like behavior when it is not synchronized. Therefore, it is a good choice to de-synchronize the system by making the system chaotic. The positive maximal Lyapunov exponent is usually taken as an indication that the system is chaotic, it is used in this paper as a measure of performance for the tendency of the system to synchronize.