A switched system model for heat exchangers using a moving boundary method

This paper presents a new switching scheme for moving boundary thermo-fluid models of heat exchangers. Pseudo state variables are introduced to accommodate the changing roles of dynamic variables as the number of different zones is changing. As a result, the number of states is conserved throughout the switches, but the forcing functions of the state derivatives change. A unique switching criteria based on void fraction is introduced and shown to be critical for mass conservation. Simulation results verify both the validity of the switched moving boundary model as well as its usefulness in a system simulation environment.