Fault Detection and Diagnosis in Air Conditioners and Refrigerators

A fault detection and diagnosis (FDD) method was used to detect and diagnose faults on both a refrigerator and an air conditioner during normal cycling operation. The objective of the method is to identify a set of sensors that can detect faults reliably before they severely hinder system performance. Unlike other methods, this one depends on the accuracy of a number of small, on-line linear models, each of which is valid over a limited range of operating conditions. To detect N faults, N sensors are needed. Using M>N sensors can further reduce the risk of false positives. For both the refrigerator and air conditioner systems, about 1000 combinations of candidate sensor locations were examined. Through inspection of matrix condition numbers and each sensor's contribution to fault detection calculation, the highest quality sets of sensors were identified. The issue of detecting simultaneous multiple faults was also addressed, with varying success. Fault detection was verified using both model simulations and experimental data. The results were similar, although in practice only one of the two would probably be used. Both load-type faults (such as door gasket leaks) and system faults were simulated on the refrigerator. It was found that system faults were generally more easily detectable than load faults. Refrigerator experiments were performed on a typical household refrigerator because it was readily available in a laboratory, but the results of this project may be more immediately useful on larger commercial, industrial or transport refrigeration systems. Air conditioner experiments were performed on a 3-ton split system. Again, the economic benefits of this type of fault detection scheme may also be more feasible for larger field-assembled systems.Air Conditioning and Refrigeration Project 8

Protection of Water Distribution Networks against Cyber and Physical Threats: The STOP-IT Approach Demonstrated in a Case Study

Water critical infrastructures are undergoing a process of digital transformation that entails an increasing integration between the physical and cyber layers of the system. This integration brings efficiency and monitoring advantages, but it also exposes water systems to a new threat surface that includes cyberattacks. Formed in 2017, STOP-IT is Europe’s first project dedicated to developing cyber-physical security solutions tailored to the water sector. During the 4 years of collaboration, the STOP-IT team has codeveloped an extensive list of technologies that integrates cyber and physical layers of infrastructure, allowing water utilities to prevent, detect, assess, and treat risks, as well as simulate scenarios of attacks and explore how to react to increase preparedness. This article first introduces the overall aim and main outcomes of the STOP-IT project and then focuses on the risk management integrated framework composed of modeling solutions developed to help water utilities identify vulnerabilities and protect critical parts of their systems. The solutions are presented along with the results from the demonstration activities performed by a selected water utility concerning three risk scenarios that were assessed through the mentioned integrated framework.publishedVersio