24 June 2014

Transient Modeling of a Multi-Evaporator Air Conditioning System and Control Method Investigation

In this paper, a transient mathematical model for a multi-split variable refrigerant flow (VRF) system having six indoor units is presented. The compressor is modeled using
curve-fitted equations based on the performance map. The moving boundary method (MBM) is chosen to simulate the indoor and outdoor coils. Electronic expansion valves (EEVs) are
modeled via empirical correlations. The conditioned rooms are emulated as lumpedparameter control volumes. With the aid of this transient system model, a control strategy is proposed. The compressor frequency is used to regulate the saturated suction temperature. EEV openings are used to control the superheat degree of the indoor coils. Room temperatures are regulated by hysteresis on-off control. Controllability test is carried out to
demonstrate that the proposed control strategy is adequate to achieve individual zone control.