DEVELOPMENT OF THREE DEGREE OF FREEDOM CONTROLLER FOR SHELL AND TUBE HEAT EXCHANGER USING NON-DOMINATED SORTING GENETIC ALGORITHM II

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Department of Engineering

ABSTRACT
This thesis presents the development of a Three Degree of Freedom (3DoF) based outlet fluid temperature controller for Shell and Tube Heat Exchanger (STHX). Shell and Tube Heat Exchangers are classes of heat exchangers being used in industries for heat transfer between fluids. Tracking a setpoint by the STHX is usually a challenging problem, especially when subjected to noise and disturbance. Addressing this challenge, an existing STHX experimental data was employed to develop a three degree of freedom Proportional Integral Derivative (PID) controller. The parameters of the controller were optimized using the Non-Dominated Sorting Genetic Algorithm II (NSGA) while subjecting the system to noise. A Multi-objective Optimization Problem (MOP) of setpoint tracking, disturbance rejection, and noise suppression was formulated using Integral Absolute Error (IAE), Integral of Squared Error (ISE), and Integral of Time-weighted Absolute Error (ITAE) as cost function. Simulations were performed using MATLAB/SIMULINK R2018a. From the obtained results, the percentage overshoot under IAE using 3DoF controller, were slightly higher than that of 2DoF controller in setpoint tracking, the trend was reversed under the ISE criterion. The research found that the flow and temperature disturbance responses were optimally reduced to the range of 90% to 99% in all three criterions as compared to 2DoF controller which was in the range of 25% to 78%. The results also proved great suppression of noise with the developed 3DoF controller.