Predictive functional control of a counter current heat exchanger using convexity property

This paper deals with the global modelling and the predictive functional co ntrol (PFC) of a tubular counter current heat exchanger. The hot product fl owing through the inner tube is cooled and its outlet temperature is monito red under varying the flow rate of cold fluid circulating in the annular du ct. A global model representing the response to inlet temperature variation s is used to implement the PFC algorithm. The control law takes into accoun t the convexity property of the heat exchanger, which distinguishes the lin ear effects of state perturbations from the non-linear effects of structure disturbances. The control equation corresponds to a generic algebraic solv er, which enables to assess the inlet temperature or the flow rate of cold fluid. In this study, the manipulated variable used to control the heat exc hanger is the flow rate of cold fluid corresponding to a parameter of the d ynamic model while the inlet temperature, which is the principal input, is kept constant. The PFC algorithm is then 'parametric' and the manipulated p arameter is derived from the control equation. The robustness of this contr oller has also been studied when inlet temperatures and flow rate of produc t are subjected to sudden fluctuations. (C) 2001 Elsevier Science B.V. All rights reserved.