说明：  we have considered implementation of both the methods i.e. Ziegler Nichols PID (ZNPID) and Augmented Ziegler Nichols PID (AZNPID) in MATLAB on the generic model of heat exchanger which is validated against results available in the literature and their performance is analyzed for different performance parameters, namely percentage overshoot, rise time and settling time. Ziegler Nichols auto-tune method used for tuning the decentralized PID loop is implemented in MATLAB.