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This paper deals with the global modelling and the predictive functional control (PFC) of a tubular counter current heat exchanger. The hot product flowing through the inner tube is cooled and its outlet temperature is monitored under varying the flow rate of cold fluid circulating in the annular duct. A global model representing the response to inlet temperature variations is used to implement the PFC algorithm. The control law takes into account the convexity property of the heat exchanger, which distinguishes the linear effects of state perturbations from the non-linear effects of structure disturbances. The control equation corresponds to a generic algebraic solver, 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 exchanger is the flow rate of cold fluid corresponding to a parameter of the dynamic model while the inlet temperature, which is the principal input, is kept constant. The PFC algorithm is then ‘parametric’ and the manipulated parameter is derived from the control equation. The robustness of this controller has also been studied when inlet temperatures and flow rate of product are subjected to sudden fluctuations.

This paper deals with the control of a counter current heat exchanger using the predictive functional control. The outlet temperature of cold fluid is monitored under varying hot fluid flow rate while the inlet temperatures corresponding to the principal inputs are maintained constant. A simple model of first order corresponding to the system response to flow rate steps is used to implement the predictive functional control. The gain and the time constant of this model depend on initial and final steady states temperatures according to the flow rate. This dynamic model derived from the partial differential equations (PDE) is taken into account to implement the predictive functional control and tested in various configurations. The robustness of this controller has been also tested when the system is submitted to unexpected sudden change of cold fluid flow rate.