Electronic expansion valves (EEVs) in air conditioner systems may induce serious flow noise when the refrigerant flows into them with unstable two-phase flow patterns. The addition of a flow pattern regulator in the flow path of an EEV is expected to stabilize the refrigerant flow pattern

thereby reducing flow noise. Therefore

determining the influence of flow pattern regulators on the flow noise of EEVs is essential for optimizing their structural parameters. In this study

a method for flow pattern simulation was verified through experiments. Then

the influence of the structural parameters of the flow pattern regulator

including the hole interval

thickness

and hole diameter

on the flow noise of the EEV under the typical unstable slug flow pattern was determined. Finally

the structure of the flow pattern regulator was optimized by reasonably combining the parameters to minimize the flow noise of the EEV. The results showed that the flow noise increased as the hole interval increased

whereas it initially decreased and subsequently increased as the thickness or hole diameter increased. The hole diameter is the most important factor affecting flow pattern regulation

and flow noise can be significantly reduced by appropriately designing the hole diameter. Under the working conditions of this study

noise was reduced by 6.88 dB.