CONTROLLABILITY AND OBSERVABILITY OF HEAT-EXCHANGER NETWORKS IN THE TIME-VARYING PARAMETER CASE

In this paper the structural controllability and observability of heat exchanger networks are determined from qualitative information about the heat exchangers and their network topology. The heat exchanger net work is modelled as a time-varying linear system based on first engine ering principles where the effect of the flowrate variations is descri bed by unknown time-varying parameters, inlet temperature variations a re regarded as disturbances and external heaters/coolers are considere d as input variables. Necessary and sufficient conditions for structur al controllability and observability of heat exchanger networks are de rived, based on an extended Kalman-type rank criterion for linear syst ems with time-varying parameters. Determining the structural controlla bility and observability of heat exchanger networks needs only checks for the input and output connectability of the network in both constan t and time-varying parameter cases. The results are extended to the mo re-practical case where bypass ratios are also used as control variabl es and where more than one time-varying parameter enters into the stat e-space matrices.