Fault Diagnosis Research For Centrifugal Chillers Based On Operating Data

In modern society, along with the rise and great development of science technology and industrial automation, HVAC system has been used in the sectors of the national economy and people’s life increasingly, and the energy consumption of the air conditioning system is more and more large. The energy efficiency and environmental protection are two major theme to the world attention, improving energy efficiency and reducing emissions of greenhouse gases is becoming more and more important. HVAC system often fails to satisfy performance expectations envisioned at design stage since various faults in the actual operation, resulting in a large number of energy wastage, even it often happens in the system after a period of time in operation. Fault detection and diagnosis (FDD) methods are applied to identify the faults and help put the systems back into normal operation to reduce energy consumption. Therefore, it is very necessary to carry out FDD research in HVAC systems.This paper proposes the FDD strategy based on model method for centrifugal chillers, which primarily contain data preprocessor, polynomial regression model, adaptive estimator of fault detection threshold and fault diagnostic classifier. The basic chiller FDD scheme employs six performance indexes which have strong thermophysical meaning to depict the health status of a typical centrifugal chiller. The residual for each performance index is generated by comparing the measured value with its benchmark predicted by the reference model. The fault threshold which is dependent on chiller operation is acquired using statistical analysis method based on data analysis. Once residuals of one or more preformance indexes are outside the range defined by the corresponding fault detection thresholds and have the continuous deviation tendency, the chiller will be considered to be faulty and particular faults are diagnosed by the fault diagnostic classifier. Since the influence between chiller faults and each performance index is analysed, the fault diagnostic classifier rule table is achieved based on the laboratory data and thermodynamics principle of basic refrigeration circulation and each component.The FDD strategy is validated using laboratory data provided by an ASHRAE research project and applied to a real building HVAC system in Hong Kong. The fault of condenser fouling is studied based on the chiller historical operation data. Finally, the software of chiller performance diagnosis is developed used the FDD strategy on the Visual Basic6.0in this paper.