New Results in Modeling Heat Exchanger Dynamics

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.