Counter-current tubular heat exchanger: Modeling and adaptive predictive functional control

The control of the outlet temperature of a counter-current tubular heat exchanger in heater configuration with the predictive functional control is presented in this paper. The outlet temperature of the cold fluid is controlled by variation of the flow of the hot fluid while the inlet temperatures corresponding to the principal inputs are maintained constant. An approximated first order model, corresponding to the response of the heat exchanger to a step change of the flow rate is used to apply the functional predictive control. The gain and the time-constant of this model depend on the initial and final steady state temperatures according to the flow rates. This nonlinear dynamic model, obtained from the partial differential equations (PDE) is taken into account to apply the functional predictive control, which was validated experimentally in various configurations. The robustness of this controller is also examined when the system is subjected to the sudden change of the flow rate of the cold fluid.