水平通道制冷剂流型-阻力耦合特性与两相压降预测实验研究

The flow pattern evolution and flow mechanisms of low-dryness R3 2 and R134a refrigerants are still not fully understood,which constrains the optimal design of high-efficiency air-conditioning systems.To address this issue,a pressure drop prediction method based on flow pattern-flow resistance coupling is proposed in this study.For the purpose of the study,a visual experimental setup was established；the flow pattern distribution and pressure drop characteristics of R134a and R32 in a horizontal circular tube with 7 mm inner diameter were studied under the flowrate of 15 0 to 750 kg/(m²•s)and dryness of 0 to 0.2；then image features were extracted based on OpenCV software library to identify the evolution laws of three typical flow patterns: namely,slug flow,wave flow and annular flow；finally,a new pressure drop prediction model integrating flow pattern parameters (Ci) and dimensionless numbers (Fr,We,Re_tp) was established based on a flow pattern zoning strategy.The results show that R32 displayed a slug flow under the conditions of low flowrate and low dryness,while it was more likely for R134a to form an annular flow under the conditions of high flowrate with high dryness,with a 13% higher cross-sectional void fraction than R32 on average；the full liquid-phase friction coefficient reached the peak at a flowrate of 360 kg/(m²•s),concurring with the maximum gas-liquid-phase velocity ratio；a 25% to 50% higher friction-pressure-drop gradient was observed for R134a than that for R32；with the new model,the mean absolute deviation was reduced from 30% to 70% to 12.31%, compared with existing models,with 89% of the data locating within ±20% error band.These results may provide robust theoretical support for optimized design of efficient new and environment friendly air-conditioning systems.