A Low-Order Dynamic Model of Counterflow Heat Exchangers for the Purpose of Monitoring Transient and Steady-State Operating Phases

TL;DR

This paper introduces a low-order, real-time capable dynamic model for counterflow heat exchangers that accurately estimates thermal properties during all operating phases using a nonlinear Kalman-Filter, facilitating practical industrial monitoring.

Contribution

A novel low-order dynamic model that simplifies the reference equations for real-time thermal monitoring of heat exchangers, including real gas effects, with an efficient estimation method.

Findings

Effective real-time monitoring of heat exchanger performance.

Model accurately tracks thermal properties during transient and steady states.

Low computational burden enables industrial deployment.

Abstract

We present a model-based real-time method to monitor a counterflow heat exchanger's thermal performance for all operating conditions. A first principle reference model that describes the reference counterflow process in an accurate manner is derived first. Real gas behavior is taken into account. Without simplifications, the respective equations must be solved in an iterative, computationally expensive manner, which prohibits their use for real-time monitoring purposes. Therefore, we propose one-step-solvable model equations, resulting in an approximate but quick model, which is able to track an important thermal property reliably. The monitoring, i.e., the online estimation of the thermal properties, is achieved via a nonlinear Kalman-Filter. Due to the low-order dynamic model formulation, the overall monitoring scheme is accompanied by an acceptable computational burden. Moreover, it is easy to deploy and to adapt in industrial practice. Monitoring results, where the reference model replaces a real process with supercritical carbon dioxide, are given and discussed herein.