Refrigeration systems are one of the largest consumers in supermarkets. In order to evaluate different refrigeration system conditions and to properly monitor the hazardous nature of the stored food, we have developed and presented a hybrid model of the display case. The model considers the main discrete display case events and also the identified temperature dynamics of the stored food and display case. The model was used to analyse how the defrosting strategy, the frequency of food loading and the frequency of door openings influence the total operational cost and the product quality.
The paper introduces the hybrid model of the display case. The model consists of the dynamical and discrete event model part. The dynamical part describes the main energy flows and temperature dynamics within display case. The discrete event model part consists of the main discrete activities that influence the system performance. The model was developed within the discrete event modelling environment – AnyLogic. The model was applied to find the optimal timing for defrosting the evaporators coil and what would be the optimal threshold when refrigerator has to be refilled.
Heating and air conditioning of buildings (HVAC systems) consume nearly 40 % of global energy production. Sensor failure or fault of any component in the control loop can increase the energy consumption and shorten lifespan of the equipment. For reducing energy consumption, fault-tolerant control of HVAC systems is required. In this paper an innovative fault-tolerant algorithm for maintaining high control performance, when sensor failure occurs is proposed, based on the correlations between valves openings, ratios of the valves openings in adjacent rooms are calculated. When sensor failure occurs, the proposed system calculates the control signal from the valves openings of the adjacent rooms. The proposed algorithm was evaluated by using real weather data, while the model of a building was developed in MATLAB/Simulink. The results of the experiment showed that the proposed algorithm maintained constant actual temperature in the room even if the temperature sensor fails.