A modular approach to dynamic modelling of heat exchangers in vapor compression cycles

This paper describes a modular approach to the dynamic modelling of heat exchangers (condenser and evaporator) in vapor compression cycles. The model of the heat exchangers is obtained by properly connecting a small number of generic modules where a fluid flows, exchanging heat and, possibly, changing state (fromliquid to vapor and vice-versa). The dynamicmodel of the generic element is phase- independent and is valid in every working condition. Unlike other approaches described in the literature, the mass exchange rate from vapor to liquid is explicitly computed in order to comply with state-trajectories constraints which are defined according to the current phase condition and highlighting when a phase-transition is possible. This leads to an effective representation of constrained evolutions and smooth jumps among different phases. The proposed dynamic elements are characterized by dynamic-orientation of some interface variables; this crucial feature for correct modelling is treated carefully in composing them and a suitable standardized interface is defined.