Fault Diagnosis Of Heat Exchanger And Temperature Control Performance Assessment In Waste-heat Utilization System

Waste-heat utilization is a major subject for further development of energy conservation and emission reduction. As the core component of waste heat utilization, the heat exchanger is critical for the safe and stability of system. It is necessary to monitor the performance of heat exchangers in the system and diagnose fault in time. This paper has conducted a series of research in temperature control performance assessment and fault diagnosis of heat exchanger system.To address fouling and sensor fault which are two typical failures in the heat exchanger control system, in this paper, a bilinear model-based parameter estimation method is presented for detecting fault of heat exchangers. In order to facilitate the analysis and simulation, bilinear model of heat exchanger is established. An recursive least-squares estimator with forgetting factor is utilized to identify the model parameters which are related to the unmeasurable physical parameters. Simulation results demonstrate that the proposed method can detect fault occurred in heat exchangers at early stage. To evaluate the healthy degree of the heat exchanger control system, performance assessment is essential. Considering the limitations of the conventional performance assessment for the cascade control system and the actual situation with non-Guassian disturbances in the industry production, in this paper, a general and effective index of the performance assessment based on minimum entropy of the cascade control system is proposed. Unlike the minimum variance based performance assessment index, the innovative control performance index can be used in the cascade control system with non-Gaussian disturbances. In this paper, an system identification method based information entroy is applied toidentify the cascade control system. To elucidate wide applicability and effectiveness of the minimum entropy cascade control index, a simulation and a cascade control case of an oil refinery are applied. The comparison with minimum variance based cascade control is also included.