Simplified modeling of liquid-liquid heat exchangers for use in control systems

For last decades various models of heat exchange processes have been developed to capture their specific dynamic nature. These models have different degrees of complexity depending on modeling assumptions and simplifications. Complexity of mathematical model can be very critical when the model is to be a basis for deriving the control law because it directly affects the complexity of mathematical transformations and complexity of final control algorithm. In this paper, the simplified cross convection model for wide class of heat exchangers is suggested. Apart from very few reports so far, the properties of this modeling approach have never been investigated in detail. The concept for this model is derived from the fundamental principle of energy conservation and combined with a simple dynamical approximation in the form of ordinary differential equations. Within this framework, the simplified tuning procedure of the proposed model is suggested and verified for plate and spiral tube heat exchangers based on experimental data. The dynamical properties and stability of the suggested model are addressed and sensitivity analysis is also presented. It is shown that such a modeling approach preserves high modeling accuracy at very low numerical complexity. The validation results show that the suggested modeling and tuning method is useful for practical applications.