Journal: Engineering Heritage Journal (GWK)

Dead time is a major source of instability and performance loss in process control systems, requiring effective compensation strategies. This study investigates temperature regulation in a two-tank thermal system with transport delay using two control configurations: PID with Smith Predictor (PID-SP) and PID with Internal Model Control (PID-IMC). A 10 L laboratory-scale stirred-tank heater was modeled as a first-order-plus-dead￾time (FOPDT) process, and controller parameters were tuned using the Process Reaction Curve (PRC) method. Closed-loop simulations in Scilab/XCOS were performed for both regulatory and servo control cases under various delay conditions. The results show that PID-IMC achieves faster settling, smaller integral absolute error (IAE), and smoother manipulated-variable responses, while PID-SP offers better robustness to delay variations. The key finding highlights that PID-IMC provides higher precision for well-modeled processes, whereas PID-SP ensures stable performance under model uncertainty. These insights are valuable for improving process control design and implementation in industrial thermal systems with significant dead time.