Abstract
The paper presents an approach for robust PI controller design for a system affected by parametric uncertainty. The method is based on plotting the stability boundary locus in the plane of controller parameters that is called (kp, ki)-plane. Designed robust PI controller is implemented for control of two counter-current tubular heat exchangers in series with uncertain parameters, in which kerosene as a product of distillation in a refinery has to be cooled by water. The controlled variable is the temperature of the outlet stream of the kerosene from the second heat exchanger and the control input is the volumetric flow rate of the inlet stream of the cold water in the second heat exchanger. Simulation results of robust PI control of heat exchangers are also presented.
Abstract
Possibilities of using robust controllers for a shell-and-tube heat exchanger control were studied, tested and compared by simulations and obtained results are presented in this paper. The heat exchanger was used to pre-heat petroleum by hot water; the controlled output was the measured output temperature of the heated fluid — petroleum, and the control input was the volumetric flow rate of the heating fluid — water. Robust controllers were designed using ℋ2, ℋ∞, ℋ2/ℋ∞ strategies and μ-synthesis. A comparison with the classical PID control demonstrated the superiority of the proposed robust control especially in case when the controlled process is affected by disturbances.
A new approach to modeling counterflow heat exchangers is presented which takes into account variations of the heat transfer coefficients with respect to fluid flow rates and temperatures. The approach involves the derivation of a transcendental transfer matrix based on linearization of a set of four nonlinear partial differential equations which describe the heat exchange processes. An approximate rational transfer matrix is derived from the transcendental transfer matrix using a parametrical identification program. The rational model is directly useful in optimal controller design. Results of an experimental study on a pilot heat exchanger are presented to validate the theoretical results.
Process Systems Engineering. Application of Finite Integral Transform to Controller Design for a Double-pipe Heat Exchanger.
