A simplified physical model-based fault detection and diagnosis strategy and its customized tool for centrifugal chillers

This article presents a new fault detection and diagnosis strategy for centrifugal chillers of building air-conditioning systems. The strategy adopts a simplified physical chiller model calibrated using chiller operation data, which is convenient for practical application. Four schemes are developed to identify chiller model parameters based on available information and data from tests or manufacturers. A new semi-physical subcooling model is adopted by the chiller model. The overall heat transfer coefficient of the condenser is assumed to consist of two parts: one presenting the condensing section and the other presenting the subcooling section. By analyzing the changing trends of two proposed performance indexes (i.e., the normalized heat transfer coefficient and the fictitious subcooling temperature), the patterns in fault conditions can be obtained. The proposed method could therefore be used without the need of any fault data. It provides good applicability and convenience for actual applications. A comparison is also made with four typical existing fault detection and diagnosis methods. The results show that the proposed method has much higher detection and diagnosis ratios.