Investigation on the choking flow characteristics in electronic expansion valves

A one-dimensional model, in which the evaporation wave theory is employed, is developed to investigate the choking flow characteristics in Electronic Expansion Valves (EEV). The results predicted by the model are validated by the experimental data presented by Zhang. The results show that the choking mass flow rate of EEVs calculated by the model, with R22 as working fluid, agrees well with the tested data. The relative deviation between the predictions and Zhang's tested data is in the range from −5% to 6%. Compared with the tested data, the choking mass flow rate of EEVs with the mixture R407c is over-predicted by the model. The pressure at the EEV exit under which choking just occurs is decreased as the flow area is decreased. The trend is consistent with Zhang's experimental results.